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Cutting of Hardened Steel
Abstract
Cutting of hardened steel is a topic of high interest for today's industrial production and scientific research. Machine parts consisting of hardened steel are high performance components which are often loaded near their physical limits. The functional behavior of machined parts is decisively influenced by the fine finishing process which represents the last step in the process chain and can as well be undertaken by cutting as grinding. An overview of the mechanisms of chip removal in hard cutting and the thermo-mechanical influence of the work area is presented. Furthermore, several models of chip removal in hard turning are introduced and discussed summarizing the metallurgical fundamentals and giving an overview on stress and temperature distributions in the work area. Boundary conditions for hard cutting as e.g. machine tools, cutting materials and others are subject to discussion to determine the achievable workpiece quality and economic efficiency of hard cutting processes in comparison with grinding.
... Hard turning cycles have been widely used for many decades in the real industry for the production of critical components after quenching [1]. Hard turning can be employed for surface finishing [2] or in combination with grinding [3]. ...
... WL appears white on the metallographic images as contrasted against the underlying dark HAZ (see Figure 3). WL is produced mainly by the thermal cycle when the turned surface is heated above the austenitising temperature, followed by quite rapid self-cooling [1,7,11]. HAZ is the region in which the temperatures are below the austenitising temperature, and the effect of thermal softening dominates. ...
... WL is referred to as a re-hardened matrix of hardness exceeding the hardness produced by heat treatment, whereas the hardness of the thermally softened HAZ is below the bulk [1,4,29]. Table 5 clearly confirms this information. ...
This paper investigates the influence of cutting speed and flank wear on the depth profile of residual stresses, as well as the fraction of retained austenite after hard turning of quenched bearing steel 100Cr6. Residual stress and retained austenite profiles were studied for the white layer, heat-affected zone thickness, and XRD sensing depth. It was found that the influence of flank wear on the white layer and heat-affected zone thickness predominates. On the other hand, residual stresses are affected the cutting speed and the superimposing contribution of flank wear. Moreover, these aspects also alter microhardness in the affected regions. The study also demonstrates that information concerning residual stresses and the austenite fraction is integrated into the white layer, and the heat-affected zone in the surface is produced by the insert of low flank wear since the XRD sensing depth is more than the thickness of the white layer. On the other hand, the pure contribution of the white layer or the heat-affected zone to residual stress and the austenite fraction can be investigated when the affected surface region is thick enough.
... Increasing demands on components' functionality has led to novel concepts for their manufacturing, together with the application of progressive materials [1][2][3]. The high tempered steels undergo the conventional quenching process when a component is rapidly cooled down from a high temperature, followed by tempering in the furnace at an elevated temperature. ...
... WL is produced on machined surface when the temperature in the flank wear land is above 770 • C followed by the high cooling rate. Such conditions are met when flank wear VB exceeds a certain threshold [2,4]. Thermally softened layer (dark region) lying below the near surface WL usually cannot be recognized in the case of high tempered samples due to the shadowing effect of the previous tempering in the furnace during heat treatment. ...
... For this reason, Fγc and Fγp are growing versus ap. The changes in shear instability and the corresponding shape of produced segmented chips (see Figure 5) are due to the alterations in thermal and stress state in the tool-chip interface as a result of altered tool rake geometry [2,7,28]. It can be seen that the more developed crater wear increases the distance between the neighbouring segments, their size, and degree of chip segmentation [7], as well as the corresponding segmentation frequency [3]. ...
This paper investigates surface state after turning of the high tempered bearing steel 100Cr6 with a hardness of 40 HRC. White layer (WL) thickness and its microhardness, as well as surface roughness, are investigated as a function of tool flank wear VB as well as cutting speed vc. The mechanical and thermal load of the machined surface were analysed in order to provide a deeper insight into their superimposing contribution. Cutting energy expressed in terms of cutting force was analyses as that consumed for chip formation Fγ and consumed in the flank wear land Fα. It was found that the mechanical energy expressed in terms of the shear components of the Fα grows with VB, converts to the heat and strongly affects the thickness of the re-hardened layer. Furthermore, the superimposing contribution of the heat generation and its duration in the VB region should also be taken into account. It was also found that the influence of VB predominates over the variable cutting speed.
... Experiments devoted to the machining of the material 16MnCr5 (case-hardened steel) were carried out by Molnar [49] in order to achieve the selection of the most favorable cutting parameters based on the DOE, correlation analysis, and relative deviation analysis. The study [50] examined the fretting and plain fatigue behavior of case-hardened steel 16MnCr5, which is comparable to AISI 5115, as reported in [51]. ...
... Molnar [49] in order to achieve the selection of the most favorable cutting parameters based on the DOE, correlation analysis, and relative deviation analysis. The study [50] examined the fretting and plain fatigue behavior of case-hardened steel 16MnCr5, which is comparable to AISI 5115, as reported in [51]. ...
Current research studies devoted to cutting forces in drilling are oriented toward predictive model development, however, in the case of mechanistic models, the material effect on the drilling process itself is mostly not considered. This research study aims to experimentally analyze how the machined material affects the feed force (Ff) during drilling, alongside developing predictive mathematical–statistical models to understand the main effects and interactions of the considered technological and tool factors on Ff. By conducting experiments involving six factors (feed, cutting speed, drill diameter, point angle, lip relief angle, and helix angle) at five levels, the drilling process of stainless steel AISI1045 and case-hardened steel 16MnCr5 is executed to validate the numerical accuracy of the established prediction models (AdjR = 99.600% for C45 and AdjR = 97.912% for 16MnCr5). The statistical evaluation (ANOVA, RSM, and Lack of Fit) of the data proves that the drilled material affects the Ff value at the level of 17.600% (p < 0.000). The effect of feed represents 44.867% in C45 and 34.087% in 16MnCr5; the cutting speed is significant when machining C45 steel only (9.109%). When machining 16MnCr5 compared to C45 steel, the influence of the point angle (lip relief angle) is lower by 49.198% (by 22.509%). The effect of the helix angle is 163.060% higher when machining 16MnCr5.
... High-tempered steel is a progressive material with an outstanding combination of mixed hardness and toughness. However, the functionality of components made of these steels especially depends on the surface state [14] expressed in terms such as RS profile, phase transformation in the near-surface layer, its phase composition, microhardness, etc. [2,12,15]. Turning operations are usually performed under constant cutting conditions. However, flank wear VB (associated with mechanical and thermal loads), as well as the corresponding stress and microstructure of the machined surface state, can vary remarkably [10,16]. ...
... The final state of RSs is very often produced during the finishing cycles, such as grinding, turning, superfinishing, etc. The development of machine tools, as well as process technology, has increased the industrial relevance of finishing turning [2], which can be used as a substitute for the grinding cycles. Hard turning can produce a very good surface state that can be expressed in terms of surface roughness [3][4][5] and the depth extent of microstructure transformations as well as RSs. ...
This study is focused on analysing residual stresses (RSs) after turning high-tempered bearing steel through the use of the X-ray diffraction (XRD) technique. Phase transformations expressed in terms of the near-surface white layer (WL) and the corresponding microhardness profiles are correlated with the RSs as well as the depth of the RS profiles. Normal and shear components of RS and FWHM (full width at half maximum) of the diffraction peaks are analysed as a function of cutting insert flank wear as well as the cutting speed. It was found that the influence of tool wear prevails over cutting speed, RSs tend to shift into the compressive region with increasing tool flank wear, and the valuable shear components of RSs can be found in the near-surface region when the cutting inserts of lower flank wear are employed. The increasing flank wear also increases the depth in which the compressive RSs can be found. Furthermore, surface RSs are affected by the phase transformation process (formation of re-hardened WL) as well as the superimposing mechanical and thermal load.
... However, hard-turning is more popular than the grinding process due to its high stock removal ability and capacity to produce complex geometries. In addition, it has been shown to be an environmentally friendly process since no cutting fluid is used in dry hard-turning [3][4][5]. ...
... Hard-turning experiments were carried out on the GoodWay GS-260Y CNC lathe using variable cutting speeds, feed, depths of cut, and tool nose radii. Since dry cutting conditions are considered an environmentally friendly process, all experiments were performed without the use of cutting fluid [2][3][4][5]. Dry cutting conditions are not only an environmentally friendly process but also economically affordable by neglecting the costs of purchasing and disposing of cutting fluids [38]. Hard-turning is usually performed with PCBN or mixed ceramic tools that are even harder than the machined material and can withstand the tribological conditions of the process [39]. ...
Citation: Özdemir, M.; Rafighi, M.; Al Awadh, M. Comparative Evaluation of Coated Carbide and CBN Inserts Performance in Dry Hard-Turning of AISI 4140 Steel Using Taguchi-Based Grey Relation Analysis. Coatings 2023, 13, 979. Abstract: Dry hard-turning is a vital manufacturing method for machining hardened steel due to its low cost, high machining efficiency, and green environmental protection. This study aims to analyze the effect of various machining parameters on cutting forces and surface roughness by employing RSM and ANOVA. In addition, multi-objective optimization (Grey Relation Analysis: GRA) is performed to determine the optimum machining parameters. Dry hard-turning tests were carried out on AISI 4140 steel (50 HRC) using coated carbide and CBN inserts with different nose radii. The results show that the cutting force components are greatly affected by the cutting depth and cutting speed for both cutting inserts. As the level of cutting depth and cutting speed rise, the cutting forces also increase. However, the feed rate was the main factor in surface roughness. A low feed rate and high cutting speed lead to good surface quality. According to the results, CBN inserts exhibited better performance compared to carbide inserts in terms of minimum cutting forces and surface roughness. The lowest radial force (Fx = 55.59 N), tangential force (Fy = 15.09 N), cutting force (Fz = 30.49 N), and best surface quality (Ra = 0.28 µm, Rz = 1.8 µm) were obtained using a CBN tool. Finally, based on the GRA, the (V = 120 m/min, f = 0.04 mm/rev, a = 0.06 mm, r = 0.8 mm) have been chosen as optimum machining parameters to minimize all responses simultaneously in the machining of AISI 4140 steel using both carbide and CBN inserts.
... As the work piece material hardness increases, selection of cutting tool material is more significant. Usually, cubic boron nitride (CBN) tipped (HRC > 60), ceramic materials (50-55 HRC) and carbide (up to 50 HRC) tools are choices for hard turning [2][3][4][5][6]. On demand of cost effectiveness and eco-friendly environment, manufacturing industries inclining towards coated carbide tools. ...
... Nevertheless, during machining of harder materials, higher temperatures are generated due to the higher cutting forces which cause higher tool wear. There are different tool wears that exists during turning, particularly, flank wear which is the major hindrance to the use of coated carbide tool as it is unfavorable to the product quality and dimensional accuracy [6,7]. ...
Selection of machining parameters and better prediction for cutting tool flank wear is indispensable in hard machining as flank wear is directly influences the quality of machined surface. In the current study, parametric optimization and predictive model were carried out for the flank wear of TiSiN-TiAlN nanolaminate cutting insert in hard turning of 58 HRC AISI 1045 medium carbon steel which is an unexplored area. Taguchi’s method was employed for parametric optimization and predictive model was established for flank wear by response surface methodology (RSM) based regression analysis. Cutting speed = 40 m/min, feed rate = 0.3 mm/rev and depth of cut = 75µm generates optimum value of flank wear 0.07 mm. In conclusion, verification test was carried out to validate the optimal set of parameters and the result was shown a great reduction of 81.42% in the flank wear. The predictive model elaborated for flank wear was dependable and helps to make better prediction to the manufacturing industries within specified range of the experimentation.
... cutting forces, Ra, MRR, flank's temperature, vibration, etc.) [2][3][4][5]. Different types of mathematical modelling (ANN, RSM, GRA) have been implemented by various researchers for turning operation to finding out the effect of process parameters, workpiece and tool characteristics on tool's performances and to get optimal machining conditions for different types of hardened steel [6][7][8]. Even many of them manage to developed internal relations between input parameters and optimize the turning process [6][7][8][9][10]. ...
... Different types of mathematical modelling (ANN, RSM, GRA) have been implemented by various researchers for turning operation to finding out the effect of process parameters, workpiece and tool characteristics on tool's performances and to get optimal machining conditions for different types of hardened steel [6][7][8]. Even many of them manage to developed internal relations between input parameters and optimize the turning process [6][7][8][9][10]. A considerable number of work has been done by different researchers on parametric optimization few of those workers have been highlighted here. ...
... Short machining time, high stock removal rate, short installation time, elimination of cutting fluids in some cases, the ability to obtain complex workpiece geometry on a machine tool, the presence of high-pressure residual stresses on the machined workpiece, and some of the advantages of hard turning in low-cost grinding. 2,3 Some studies performed hard turning using a super hard cutting tool such as polycrystalline cubic boron nitride (PCBN or CBN) and ceramic because of their high hardness and high wear resistance. [4][5][6] However, there are some concerns about the use of both tool materials. ...
... The developed model for vibration is given in Equation (2). In Supplementary Figure 12 ...
Hardened AISI 4140 steel is widely used in automotive industries due to its high strength, high hardness, and good formability. It can be subjected to cryogenic treatments to increase wear resistance, increase the toughness and decrease the residual stress. Although many studies have been performed related to the machinability of AISI 4140 steel, the number of studies that considered four responses simultaneously are limited. In this study, the effects of cutting speeds, feed rates, and depths of cut on the vibration, motor current, machining noise, and surface roughness were investigated in turning hardened AISI 4140 steel using coated carbide insert under dry cutting conditions. Besides, the attempt was made to predict surface roughness based on machining noise, motor current, and chuck vibration during the turning process. Analysis of variance and response surface methods were carried out to analyze the experimental results and the prediction models were developed. The machining test revealed that the most effective parameter on the surface roughness value was the feed rate with a 96.07% contribution. The depth of cut and the feed rate affected vibration with 57.61% and 26.44% contribution, respectively. The machining noise was dominantly affected by the depth of cut with 76.15% contribution, it was followed by feed rate with 17.67% contribution. However, feed rate and depth of cut significantly affect motor current with 54.53% and 36.64% contribution, respectively. The graphical analysis of the effect of vibration, motor current, and machining noise on the surface roughness was presented. Based on the results, there is a direct relationship between machining noise, vibration, and motor current with surface roughness. As the level of the aforementioned responses increases the quality of the machined surface deteriorates.
... In this field, the finishing of heat treated materials is still mainly used by grinding, but to meet the increasing demand for productivity, flexibility and environmental pollution problems from using coolants, hard machining technology was proposed and developed. Unlike traditional machining methods, cutting tools with geometrically defined cutting edges are used to directly cut materials with high hardness (usually 45 HRC or more) hard machining technology [1]. High dimensional accuracy, surface quality, productivity and flexibility are the outstanding characteristics of this technology [2]. ...
The work presents a comprehensive review on the influences of cutting tool material on the efficiency of hard turning process. Major trends in tool use and coating innovations are specified. The results of the hard turning process are evaluated through a number of main parameters such as surface roughness, cutting force, cutting heat, and wear mechanism. These results show that high cutting forces and cutting temperatures are still the huge challenges in choosing cutting tool materials in hard turning. This also limits the applicability of these materials and increases tooling costs due to the need to move towards using cutting tools with higher grades and hardness. The analysis results also point out the necessity of using appropriate cooling lubrication technology to support the hard turning process, helping to improve tool usage efficiency and the effectiveness of the hard turning process.
... In recent years, hard turning has emerged as a popular alternative to grinding for the final stage in the machining of hardened steel. As a form of fine finishing, hard turning allows for the elimination of rough machining and grinding [1,2]. Hard turning is the process of turning hard materials with hardness ranging from 40 HRC to 65 HRC [3]. ...
Hardened steels need special cutting tools like PCBN and ceramic to be machined. But these cutting tools aren't cost-effective and require machine tool structures that are stiff and don't let vibrations through. The current trend is to find other, less expensive ways to make these materials easier to work with. Cryo-treating cutting tools is an effective way to improve the way the tool materials work when they are cut. Cryogenically treated tungsten carbide inserts in dry turning operations were looked at in this study. For hard turning of hardened mild steel (48 HRC), the performance of cryogenically treated Tungsten Carbide (WC) inserts was compared with that of untreated inserts in terms of chip-tool interface temperature and surface roughness under dry cutting conditions. The cutting tool (Untreated and Treated), and cutting speed (375, 512, 706 rpm) were selected as experiment parameters at a constant feed rate of 0.0841mm/rev and depth of cut 1mm. The chip-tool interface temperature analysis results revealed that temperature increases with the increasing cutting velocities. A better surface finish can be found at a higher cutting speed. The lower value of Ra was found at 1.75 μm (without cryogenic treatment) and 1.05 μm (with cryogenic treatment) for cutting speed at 706 rpm.
... According to Meyer et al. [118], the effective contact dimensions at the primary cutting edge are essential to characterize the complex turning process. Adjustments in finishing, nominal process parameters, a p , and f are imperative to obtain the best results [118][119][120]. ...
Injection moulds are crucial to produce plastic and lightweight metal components. One primary associated challenge is that these may suffer from different types of failures, such as wear and/or cracking, due to the extreme temperatures (T), thermal cycles, and pressures involved in the production process. According to the intended geometry and respective needs, mould manufacturing can be performed with conventional or non-conventional processes. This work focuses on three foremost alloys: AMPCO® (CuBe alloy), INVAR-36® (Fe-Ni alloys, Fe-Ni36), and heat-treated (HT) steels. An insight into the manufacturing processes’ limitations of these kinds of materials will be made, and solutions for more effective machining will be presented by reviewing other published works from the last decade. The main objective is to provide a concise and comprehensive review of the most recent investigations of these alloys’ manufacturing processes and present the machinability challenges from other authors, discovering the prospects for future work and contributing to the endeavours of the injection mould industry. This review highlighted the imperative for more extensive research and development in targeted domains.
... Hard turning is a cost effective and higher material removal process compared to traditional grinding where the ferrous material components are hardened above 45 HRC. Reduction of manufacturing cycles, reduction of set up times and costs, achievement of surface finish nearer to grinding, elimination of use of coolant and ability to machine complex parts are some of the benefits of hard turning over conventional grinding processes reported by Konig et al. [1], Tonshoff et al. [2], Byrne et al. [3], Klocke et al. [4]. The turning of hardened components has now become possible with the advent of hard and wear resistant tool materials like ceramic and cubic boron nitride. ...
... Among other materials it is the subject of current and past investigations regarding the surface layer [1]. High forces and temperatures occur during the manufacturing process because of its high hardness [2], which can have a negative impact on the surface layer [3]. Cryogenics like CO 2 , LN 2 or sub-zero metal-working fluids (MWF) can be used to reduce the temperatures and tool wear, thus improving the tool life [4]. ...
In this study, a control concept for the simultaneous adjustment of the workpiece residual stresses and the surface roughness when cryogenic hard turning AISI 52100 is presented. The turning process is comprised by two consecutive cuts in which the process parameters vary, focusing on roughing and finishing; i.e. first a high, then a low depth of cut. On the first cut, the surface residual stress is adjusted via the cutting speed. On the second cut, the surface roughness is minimized by adjusting the feed rate while maintaining high compressive residual stresses. The surface residual stresses are determined by XRD and hole drilling measurements. For the estimation of the residual stresses the passive force is used. Based on these results, a control concept is presented which makes several assumptions that are partly validated by experiments.
... During hard turning, the main physical properties (stress, strain, and temperature) are not equally distributed in the cutting zone and need to be evaluated. One of the rough ways to describe and evaluate the process is a description of chip formation [10]. There are usually 3 types of chips during hard cutting [11]. ...
Developing predictive models at hard machining in the frame of Smart Manufacturing
... Peças constituídas por aço endurecido são geralmente componentes de alto desempenho e freqüentemente utilizadas sob cargas de trabalho elevadas. (3) Os problemas de desgaste em ferramentas de corte sempre foram motivos de preocupação, devido ao controle dimensional e à necessidade de parada no processo para troca de ferramentas, significando custos adicionais e perda de produtividade. O desgaste é definido como a destruição de uma ou de ambas as superfícies que compõem um sistema tribológico, geralmente envolvendo perda progressiva de material. ...
... It has become widely accepted that hard turning is a better alternative to grinding in terms of shorter setup time, high flexibility, lower equipment cost, environmental compatibility, high material removal rate, and ability to handle complex geometry [1][2][3][4]. In spite of this, the longer tool-chip interface contact length during HT will result in increased cutting resistance for the cutting tool. ...
Dry hard-turning is a cost-effective, efficient manufacturing method for AISI 52100 hardened bearing steel. Surface Defect Machining (SDM) is a novel approach to address surface roughness, deteriorations, residual stresses, and metallurgical changes on machined steel. SDM involves exposing workpieces to surface irregularities, reducing cutting resistance, and enhancing surface integrity and finish. In the present work, surface irregularities are formed on the surface of the workpiece in the form of indentations. Using the response surface method's central composite design (CCD), 32 experimental runs were conducted to determine the optimal process parameters by varying the cutting and tool geometry parameters while AISI52100 steel hard turning (HT). Due to its complexity, multi-objective optimization is more challenging to study.The present work aims to evaluate the effects of input parameters on maching force, surface roughness, and workpiece surface temperature. Further, machining parameters optimization is performed employing the Grey relational analysis integrated with principal component analysis (GRA-PCA). Analysis of variance (ANOVA) was used to examine the impact of cutting and tool geometry parameters on grey relational grade (GRG). ANOVA revealed that feed has the highest influence on GRG, followed by depth of cut, nose radius, cutting speed, and negative rake angle. Cutting speed of 800 rpm, feed rate of 0.04 mm/rev, depth of cut of 0.5 mm, nose radius of 1 mm, and negative rake angle of 15º are the optimum combination of process parameters.
... As turning being simple and effective it is widely accepted process in metal cutting industries because of its ability to machine different material and also can produce rotational. axisymmetric parts such as holes, grooves, taper, threads, taper, even contoured shapes and different stapes diameter [3]. However, in addition to these advantages there is always a demand to attain high material removal rate with increased tool life and high stability. ...
... Steel having a hardness greater than 55 HRC is used in several enterprises, including dies, automotive, gears, bearings, and shafts. 1 Meanwhile, as stated, precision hard turning has been considered to be the main impact on the machining industry in recent years because of the worldwide market's constant drive to minimize costs, reduce environmental and health risks, to achieve a cleaner manufacturing process. 2,3 The most significant complexity throughout the machining process is the tool wear that results in a change in shape and a rise in cutting temperature. ...
AISI 4340 hardened steel is usually used in axle shafts, main shafts, gear, and couplings. Using multi-layer physical vapor deposition a coated tool, an attempt was made to optimize the input variables on precise turning on hardened AISI 4340 grade steel. The cutting speed, feed rate, and depth of the cut were the applied process factors in the dry-cutting environment. Furthermore, surface roughness (Ra), flank wear (VBc), cutting temperature ( T), and chip morphology were considered as technological responses. The Taguchi L 27 standard orthogonal array with three levels and three factors was used in the experiment. Furthermore, scanning electron microscopy and energy dispersion spectroscopy were used to analyze tool wear and chip morphology characteristics. The relevance of the input process factors on the measured responses was determined using analysis of variance analysis. The feed rate was observed to have a dominant impact on the surface roughness in the trials. At an optimal parametric combination with 80 m/min cutting speed, 0.05 mm/rev feed rate, and 0.3 mm depth of cut obtained from the Taguchi-TOPSIS optimization method. The enhancement of the closeness coefficient was observed to be 0.2372. The generated second-order regression model was demonstrated to be of high significance. The strategy and outcomes of this research will help metal machining enterprises to augment manufacturing productivity when working with hardened steel.
... These problems stem from high cutting forces and temperatures at the contact zone. High cutting forces and temperatures can cause local plastic deformations and microstructural alterations depending on the quick heating and cooling behavior [22,23]. In addition to the condition of the workpiece, such thermal and mechanical imbalances can lead to damage at the cutting edge. ...
Sustainable technologies draw attention in the machining industry thanks to their contributions in many aspects such as ecological, economic, and technological. Minimum quantity lubrication (MQL) is one of these techniques that enable to convey of the high pressurized cutting fluid toward the cutting zone as small oil particulates. This study examines the potency of MQL technology versus dry conditions on the machining quality during the milling of structural Strenx 900 steel within the sustainability index. High strength and toughness properties make this steel a hard-to-cut material providing an important opportunity to test the performances of dry and MQL environments. The outcomes of the experimental data demonstrated that MQL is superior in enhancing the quality of significant machining characteristics namely surface roughness (up to 35%), flank wear (up to 94%), wear mechanisms, cutting energy (up to 28%), and cutting temperatures (up to 14%). Furthermore, after analyzing the main headings of the sustainable indicators, MQL provided the same (+5) desirability value with a dry (+5) medium. This experimental work presents a comparative approach for improved machinability of industrially important materials by questioning the impact of sustainable methods.
... Based on the reference parameter set, an increase in cutting speed resulted in a higher Barkhausen noise, and a further increase resulted in a slight reduction of the Barkhausen noise. Investigations of a hard turning process for steels showed that the temperature at the tool cutting edge increases with increasing cutting speed [28]. In the comparison between V1.4 and V1.5 with an increase in cutting speed, it can be assumed that thermal softening of the material had occurred. ...
In aerospace industry, safety-relevant parts are subject to strict testing guidelines to guarantee part functionality. Depending on the manufacturing process, the surface integrity of the part can be modified undesirably. In addition to common rim zone analyses, such as nital etching or X-ray diffractometry, Barkhausen noise measurement offers new potentials for a non-destructive surface integrity inspection. In this work, the influence of a 5-axis gear end milling process on the rim zone was investigated. A stable correlation between Barkhausen noise and material hardness and residual stress was determined.
... Machining Pb-free brass is associated with higher cutting forces, severe tool wear and less chip control as compared to machining leaded brass [6,7,8,9]. Since tool wear is a known contributing factor to increased sub-surface deformation [10], and more aggressive tool wear is observed when machining Pb-free brass alloys, a higher degree of sub-surface deformation is expected in Pb-free brass alloys. It is therefore of interest to investigate the influence of cutting data and tool geometry variation with wear on sub-surface deformation and its link to stress corrosion cracking (SCC). ...
New stricter regulations on lead (Pb) content in brass for use in certain applications is driving the industry from traditional leaded brass towards Pb-free alloys. However, machining induced surface integrity for such Pb-free alloys and related corrosion resistance are largely unknown. Two Pb-free brass alloys, CuZn38As and CuZn21Si3P, approved for use in drinking water applications, were machined under different cutting conditions, tool geometries and tool wear states. The resulting surface integrity and sub-surface deformation was characterized using nano-indentation, scanning electron (SEM) and ion microscopy, and electron backscatter diffraction (EBSD). The materials resistance to stress corrosion cracking (SCC) was assessed by exposing the machined samples to a corrosive substance in accordance with SIS 117102. The results show that tool wear is the most influencing parameter leading to stronger sub-surface deformation. This was especially pronounced for alloy CuZn38As, where for equivalent depth of deformation, the material exhibited higher degree of work-hardening compared to the other tested alloy. Subsequently, substantial stress corrosion cracking was registered for machined CuZn38As samples.
... The tool material properties and process parameters are crucial for enhancing the cutting performance of hard machining. Tonshoff et al (1984) established the technological and economic feasibility of machining steel in hardened condition [11]. Machining of hardened steel with economic tool life and without the need for subsequent grinding is possible by using ceramic and CBN tools. ...
Industries use heat treated steel for various components due to its strength and other mechanical properties. Usually hardening of machining is carried out by energy and cost intensive grinding process. Recently, hard machining has replaced grinding for certain specific applications. In this study, Cubic boron nitride (CBN) of specification CNMG120408is employed to machine AISI D2 steel of 46 HRC hardness. Nine machining experiments established by L9 orthogonal array were conducted. Surface roughness and cutting force were taken as response variables. From the signal to noise ratio analysis, the optimum combination of cutting process parameters for surface roughness is found out to be 80 m/min (Cutting speed) 0.109 mm/rev (Feed) and 0.1 mm (depth of cut). From Analysis of variance (ANOVA), the share made by every process parameter on the machining performance is found out for this CBN tool-work piece combination. Feed rate has the maximum contribution (56 %) for main cutting force while Cutting speed has the maximum contribution (72 %) for surface roughness. Cutting speed exerts greater influence on surface finish compared to feed rate in hard machining.
... Compressive residual stress was induced after hard machining in gentle cutting conditions in this study. The higher compressive stress can be beneficial because it was shown to increase fatigue strength [12][13][14]. Higher initial compressive residual stress after heat treatment can induce higher compressive residual stress after hard machining. Thus, initial residual stress after heat treatment needs to be studied before hard machining. ...
This paper investigates the influence of heat treatment on the surface integrity induced by a hard turning operation on a 27MnCr5 carburized steel. Two heat treatments have been investigated, leading to two residual stress profiles. After that, the steels with the two different case hardened conditions have been hard turned. Residual stress profiles induced by hard turning are analyzed for various cutting speeds and tool flank wear. As a result, it is shown that the final residual stress profiles generated after hard turning depends strongly on the original residual stress profiles.
... Both hard turning and grinding processes introduce microstructural alterations in the surface layer known as white and dark layers [13][14][15]. These layers are visible under optical microscopy after being polished and etched or featureless under scanning electron microscopy (SEM). ...
Surface integrity induced by finishing processes significantly affects the functional performance of machined components. In this work, three kinds of finishing processes, i.e., precision hard turning, conventional grinding, and sequential grinding and honing, were used for the finish machining of AISI 52100 bearing steel rings. The surface integrity induced by these finishing processes was studied via SEM investigations and residual stress measurements. To investigate rolling contact fatigue performance, contact fatigue tests were performed on a twin-disc testing machine. As the main results, the SEM observations show that precision hard turning and grinding introduce microstructural alterations. Indeed, in precision hard turning, a fine white layer (<1 μm) is observed on the top surface, followed by a thermally affected zone in the subsurface, and in grinding only, a white layer with 5 μm thickness is observed. However, no microstructural changes are found after sequential grinding and honing processes. White layers induced by precision hard turning and grinding possess compressive residual stresses. Grinding and sequential grinding and honing processes generate similar residual stress distributions, which are maximum and compressive at the machined surface and tensile at the subsurface depth of 15 μm. Precision hard turning generates a “hook”-shaped residual stress profile with maximum compressive value at the subsurface depth and thus contributes as a prenominal factor to the obtainment of the longest fatigue life with respect to other finishing processes. Due to the high quality of surface roughness (Ra = 0.05 μm), honing post grinding improves the fatigue life of bearing rings by 2.6 times in comparison with grinding. Subsurface compressive residual stresses, as well as low surface roughness, are key parameters for extending bearing fatigue life.
... HT became a widely spread cutting technology for both roughing and finishing of revolution parts made by hardened steel with a hardness higher than 55 HRC, in many industries, e.g., automotive, bearings, dies, gears, and shafts, due to the numerous advantages it takes compared to grinding from an economic, technological, and environmental point of view. Viewed as a sustainable and attractive alternative to grinding, more environmentally and human-friendly manufacturing processes such as precision hard turning are able to yield a high quality machined surface and offer many benefits to manufactures in the context of higher flexibility, material removal rate, lower setup and cycle time, and lower costs [4]. Surface quality in finishing operation is recognized as main indicator for accepting parts; therefore, reducing values of roughness in an economic way is an important task [5,6]. ...
Precision hard turning (HT) gained more and more attention in the cutting industry in the last years due to continuous pressure of the global market for reducing costs, minimizing the environmental and health issues, and achieving a cleaner production. Therefore, dry cutting and minimal quantity lubrication (MQL) became widely used in manufacturing to meet the environmental issues with respect to harmful cutting fluids (CFs). Vegetable oils, in MQL machining, are a promising solutions to petroleum-based CFs; however, the effects and performance on surface roughness and tool wear in HT with ceramic inserts remain unclear. To address this limitation, hardened AIDI D2 steel and pure corn oil, rich in saturated and monounsaturated fatty acids, cheap and widely available, have been used to conduct dry and MQL experiments at different cutting speed and feeds. Results show that corn oil is suitable as cutting lubricant in HT, creating a strong anti-wear and anti-friction lubricating film which improves the roughness with 10–15% and tool life with 15–20%, therefore reducing costs. Best surface roughness values (Ra = 0.151 μm, Rz = 0.887 μm, Rpk = 0.261 μm) were obtained at 180 m/min and 0.1 mm/rev. The analysis of variance shows that corn oil has statistical significance on roughness, validating the results.
... Hard turning is used in the production of many parts, especially in automotive industries such as gears, bearings, and shafts. The advantages of hard turning compared to conventional machining processes are higher productivity, lower energy consumption, shorter setup time, better surface quality, and lower manufacturing costs (Yallese et al., 2009;Guo and Liu 2002;Tönshoff et al., 2000). Cutting tools play a crucial role in enhancing the products' productivity and quality besides minimizing the machining process's cost. ...
The present study investigated the machinability aspects, namely, surface roughness, sound intensity, power consumption, and crater wear, during dry turning of hardened AISI 4140 steel (63 HRC) employing (TiCN/Al2O3/TiN) multilayer-coated carbide inserts under dry cutting condition. The relationship between machining parameters and output parameters was determined using the Taguchi design. The analysis of variance was employed to evaluate the contributions of input parameters on output parameters. The main effect plots illustrated the impacts of cutting speed, feed, and depth of cut on response variables. Results show that the feed was the most dominant factor that affects surface roughness. Increasing the feed value increases the surface roughness, power consumption, and sound intensity. In the other part of this study, the constant values for feed (0.3 mm/rev), depth of cut (0.7 mm), and cutting speed (150 m/min) have been selected to evaluate a tool life that has 0.3 mm crater wear criteria. The results indicated that multilayer-coated carbide inserts presented very good tool life and reached 0.3 mm in 90 min. The experimental study results showed that chipping and abrasion were found to be the significant wear mechanism during hard turning of AISI 4140 steel. The cutting speed was the most significant parameter on the tool wear, although high cutting speed results the good surface finish but adversely increases the tool crater wear.
... Konig et al (1993) discussed the characteristics of hard machined surfaces and compared to those which ground, the hard machining is suitable for precision machining with requirements lower than tolerance class IT6 and surface qualities below Rtm 2 µm [9].The tool quality and cutting parameters set are shown to be of decisive importance.Tonshoff et al (1984) established the technological and economic feasibility of machining steel in hardened condition [10]. Machining of hardened steel with economic tool life and without the need for subsequent grinding is possible by using ceramic and CBN tools.M.A. Davies (1996) investigated the surfaces produced in finish hard turning with cubic boron nitride and correlated surface finish with tool wear [11].For finish hard turning, low carbon content ceramic binder tool gives longer lives and better surface finish than high CBN content metallic binder tools. ...
Hard machining is gaining grounds for machining hardened steels as it has several benefits over grinding. The turning of hardened steels has been applied in many cases in production. It is an important process because all manufacturers are continually seeking ways to manufacture their parts with lower cost, higher quality, rapid setups, lower investment, and smaller tooling inventory while eliminating non-value added activities. In this study, AISI D2 tool steel at a hardness of 52 HRC is being used for experimental investigation. Cutting speed, feed rate and depth of cut are the cutting parameters. Three cutting parameters each at three levels were considered in the study for the experimentation. Hard turning insert used for the experiment is CBN (Cubic Boron Nitride). of specification CNMG 120408. Cutting forces are measured using strain gauge tool Dynamometer. Surface roughness is measured using surface roughness tester. In this study, the Taguchi method, a powerful tool to design optimization for quality, is used to find the optimal cutting parameters for turning operations. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) are employed to investigate the cutting characteristics of AISI D2 Steel using CBN cutting tool. Through this study, not only can the optimal cutting parameters for turning operations be obtained, but also the main cutting parameters that affect the cutting performance in turning operations can be found. Experimental results are provided to confirm the effectiveness of this approach.
Machinability is a generalized framework that attempts to quantify the response of a workpiece material to mechanical cutting, which has been developed as one of the key factors that drive the final selection of cutting parameters, tools, and coolant applications. Over the years, there are many attempts have been made to develop a standard evaluation method of machinability. However, due to the complexity of the influence factors, i.e., from work material and cutting tool to machine tool, that can affect the materials machinability, currently there is no uniquely defined quantification of machinability. As one of the outcomes from the CIRP's Collaborative Working Group on "Integrated Machining Performance for Assessment of Cutting Tools (IMPACT)", this paper conducts an extensive study to learn interacting machinability parameters to evaluate the overall machining performance. Specifically, attention is focused on recent advances made towards the determination of the machinability through tool wear, cutting force and temperature, chip form and breakability, as well as the surface integrity. Furthermore, the advanced methods that have been developed over the years to enable the improvement of machinability have been reviewed.
Due to the challenging issues like high heat generation concerned with hardened steel machining, therefore cutting fluid has been used for removing the more higher cutting temperature. Furthermore, use of nanolubrication system makes the cutting environment more sustainable. The present work represents the impacts of cutting parameters such as cutting speed, feed rate, depth of cut and LRT 30 mineral oil-based ZrO2 nanofluid concentrations in hard turning of AISI D2 steel. The ZrO2 nanofluid was first time implemented for cooling purpose in hard turning application. The performance was examined by taking average surface roughness, tool flank wear, cutting power and cutting temperature results. Experimental results found that the 0.20% nanofluid concentration was the better choice among all adopted weight concentrations (0.05%, 0.2% and 0.5%) of nanofluid. Abrasion, cutting edge chipping and adhesion were found to be the principal wear mode. Also, acceptable range of surface roughness (0.498–0.665 micron) was seen in the entire investigations.KeywordsHard turningZrO2CVDNanofluidCutting power
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Titanium alloys are frequently utilised in applications that call for high strength at high temperatures as well as excellent mechanical resistance. This alloy has excellent mechanical properties that enable improved performance from titanium alloys. In the current research, Taguchi L25 orthogonal array of experiments were conducted first, and MCDM techniques and ANNOVA were utilised to forecast the influencing machining factors. From MCDM three methods (SAW, VIKOR & TOPSIS) prediction algorithms which rank one for experiment no. 2. Experiment results shows that experiment no. 02 gives optimum/best results in terms of Tool life and surface roughness. While the process parameter has values cutting speed = 80 rpm, Feed rate = 018 rev/mm, Depth of cut = 0.12 mm, and Rake angle = 14 degrees. From ANOVA outcome for surface finish it is noticed that the process parameter rake angle is having Rank 01 for all levels. Thus rake angle is major influencing parameter to achieve a better quality of surface roughness. While in case of flank wear it is crystal clear that the process parameter DOC is having Rank 01 for all levels. Thus DOC is most influencing parameter to achieve lesser flank wear and better quality of tool life.
Purpose – This study aims to investigate the effect of vibration on ceramic tools under dry cutting conditions and find the optimum cutting condition for the hardened steel machining process in a computer numerical control (CNC) lathe machine.
Design and methodology - In this research, an integrated fuzzy TOPSIS-based Taguchi L9 optimization model has been applied for the multi-objective optimization (MOO) of the hard-turning responses. Additionally, the effect of vibration on the ceramic tool wear was investigated using Analysis of Variance (ANOVA) and Fast Fourier Transform (FFT).
Findings - The optimum cutting conditions for the multi-objective responses were obtained at 98 m/min cutting speed, 0.1 mm/rev feed rate, and 0.2 mm depth of cut. According to the ANOVA of the input cutting parameters with respect to response variables, feed rate has the most significant impact (53.79%) on the control of response variables. From the vibration analysis, the feed rate, with a contribution of 34.74%, was shown to be the most significant process parameter influencing excessive vibration and consequent tool wear.
Research Implications - The MOO of response parameters at the optimum cutting parameter settings can significantly improve productivity in the dry turning of hardened steel and control over the input process parameters during machining.
Originality – Most studies on optimizing responses in dry hard-turning performed in CNC lathe machines are based on single-objective optimization. Additionally, the effect of vibration on the ceramic tool during multi-objective optimization of hard-turning has not been studied yet.
In this work, initially, the raw AISI 52100 bearing steel was heat-treated to obtain 40 HRC and 45 HRC workpiece hardness. Further, dry hard turning tests were carried out to study the impact of workpiece hardness ([Formula: see text]), cutting speed ([Formula: see text]), feed ([Formula: see text]), and depth of cut ([Formula: see text]) on cutting force (Fy), surface roughness (Ra), and sound intensity (SI). An economically viable PVD-coated carbide turning tool was implemented for the experiments. The Taguchi L[Formula: see text] (2–3 mixed level) design of experiments was employed to establish the experimental plan in order to save the experimental time, energy, and cost of manufacturing. The results disclosed that the feed has the prevailing consequence on surface roughness with a 96.3% contribution, while it also significantly affects the cutting force with a contribution of 13.8%. The contribution of cutting speed and workpiece hardness on the cutting force was reported as 48.3% and 35.1%, respectively. Higher workpiece hardness required more energy for plastic deformation as a result the cutting force increases with leading hardness. The sound intensity was dominantly influenced by depth of cut (53.3%) and cutting speed (40%). Finally, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was performed to determine the optimum machining parameters. According to the TOPSIS, the optimum level of cutting parameters was predicted as 40 HRC hardness ([Formula: see text]), 150[Formula: see text]m/min cutting speed ([Formula: see text]), 0.15[Formula: see text]mm/rev feed ([Formula: see text]), and 0.1[Formula: see text]mm depth of cut ([Formula: see text]) while the optimal result of Fy, SI, and Ra were noted as 27.66[Formula: see text]N, 70.7[Formula: see text]dB, and 0.86[Formula: see text][Formula: see text]m individually.
A drilling test was carried out for a 6 mm diameter carbide twist drill with CrAlCN coating and an uncoated carbide twist drill to grasp the effect of CrAlCN coating on the tool performance. Drilling and machining tests on ASTM1045 steel workpieces using CrAlCN coated and uncoated tools. Observe the pattern of variation of surface morphology and roughness of holes with the number of drilled holes using SEM and optical microscope. The effect of CrAlCN coating on carbide twist drill on drilling quality was analyzed by comparing the wear, surface roughness and chip shape of twist drill at different periods and parameters of drilling. The study concluded that using CrAlCN coated tools improved the wear resistance of the drill and significantly reduced BUE. Compared to the uncoated bit, the diameter of the drill decreased to 5.91 mm for the coated tool and 5.79 mm for the uncoated tool after 80 holes. The roughness of the coated bit was 3.324 μm at a feed rate of 0.12 mm/r and several holes of 40, which was significantly lower than that of the uncoated bit. Chip analysis showed that the coated tool maintained well-broken and tightly spiraled chips. In contrast, the uncoated tool produces tightly spiraled chips and short ribbon chips at a feed rate of 0.18 mm/rev, and the edges of the chips can appear significantly serrated. The research results improve the understanding of the drilling wear mechanism, provide new technical means to improve the analysis of working tool performance and provide a reference basis for the design of new coating tools.
In this experimental study, vibration, energy consumption, power consumption and surface roughness values that occur in the machining of AISI H11 tool steel under CO 2 , coolant and dry cutting conditions were investigated. The effects of different cutting parameters and cooling systems on machinability were investigated. Analysis of variance was done. Regression equations were obtained. Relationships between power consumption, vibration and surface roughness are explained with mathematical equations. Finally, the optimum CC were determined by the multiple optimization methods. According to the test results, while the instantaneous power consumption increases by increasing cutting parameters, energy consumption decreases as the processing time is shortened. Vibration value increases by increasing cutting parameters. The highest vibration value occurs in cutting with CO 2 . Compared to dry and CO 2 cutting, the vibration is lowest in coolant cutting. The friction decreases with the coolant and the vibration value decreases. There is a similar relationship between vibration and surface roughness value. The most effective parameter on the surface roughness value is the feed rate. It was seen that the most suitable CC for the most efficient cutting, the lowest energy consumption, vibration and surface roughness value, under coolant cutting, 0.2 mm depth of cut, 175 m/min cutting speed and 0.119 mm/rev feed rate. With optimum CC, the vibration value was reduced by 5.18%, the surface roughness value by 37.12%, energy consumption by 36.19% and the machine efficiency was increased by 7.16%.
The increasing demands concerning renewable energy have required ever-bigger projects, as seen with wind turbine cases; in these large projects, the surface contact presents high load and wear resistance requirements. The cooling and lubrication methods in machining are highlighted due to the reduction of costs and environmental impacts. In functional hardened surfaces, it is critical to understand the integrity aspects once they significantly affect the durability of the component. This work clarifies, how the machining parameters of feed, depth of cut, velocity of cut, minimum quantity of lubrication, and abundant cooling affected the machined surface in a large component, with a discussion about microstructural altered layer, residual stresses, and Sa, Sq, and Sz statistical parameters. The results indicated that the minimum quantity lubrication and abundant cooling produced highly compressive circumferential residual stresses. Both methods produced surfaces free of significant microstructure altered layers. The altered surface layer was very thin when detected, with a thickness of up to 2.35 µm. On optimal conditions, the minimum quantity lubrication, in relation to abundant cooling, presented residual stresses 37% higher, a thickness of altered layer 74% lower, and Sa and Sz roughness, respectively, 47% and 11% lower and Sz 12% higher.
The present work focusses on the hard turning of AISI H13 tool steel with PVD-TiN- and CVD-Al2O3-coated ceramic cutting tools. In this context, hard turning tests have been performed under dry cutting conditions at five different cutting speeds (120, 165, 210, 255, and 300 m/min), three different feeds (0.12, 0.18, and 0.24 mm/rev), and a constant depth of cut of 0.6 mm. The main cutting force (Fc), surface roughness (Ra), cutting power (Pc), and temperature (T), as well tool wear mechanisms, have been investigated under these subjected conditions. The outcomes of this study show that while feed plays an important role in the main cutting force and surface roughness, cutting speed also plays an important role in cutting power and temperature. The average main cutting force, surface roughness, cutting power, and temperature are 13, 15, 14, and 11% better when AISI H13 alloy is machined with the PVD-TiN-coated inserts than those in the CVD-Al2O3-coated inserts, respectively. SEM examination also revealed that the abrasion and adhesion mechanism is more effective when AISI H13 alloy is machined with the CVD-Al2O3-coated inserts compared to those in the PVD-TiN-coated inserts.
The fatigue performance of a metallic component is strongly correlated with several surface integrity features (surface roughness, residual stresses, microstructure). It is commonly characterised using ISO tests. However, conventional procedures for manufacturing fatigue samples influence all the surface integrity features simultaneously. So, standard fatigue testing procedures do not discriminate between each feature’s sensitivity. This paper aims to show how an advanced combination of various processes (finish turning, belt finishing, roller burnishing) leading to complementary process signatures determines which surface integrity features are the most sensitive and how two features can be coupled. This methodology is applied to a martensitic stainless steel 15-5 PH (precipitation-hardening). It highlights that this steel is very sensitive to the presence of a nanosized white layer and that there is a synergy effect by combining a thick compressive layer and a very low surface roughness.
The present work evaluates the turning performance of alumina (Al2O3) and titanium carbide (TiC) based mixed ceramic cutting inserts with TiAlSiN, WC/C and DLC thin-film depositions during machining of AISI 52100 steel hardened to 55 ± 2 HRC hardness. Based on the generated machining forces, coefficient of friction, geometrical characteristics of the chips, and tool wear, a comparative analysis of the performance of uncoated and coated cutting tools was carried out. The machining outcomes were interpreted in relation to the adhesion strength of coating with the substrate, surface roughness and hardness of the top surface of the coatings. It was observed that the reduction of friction and machining forces accounted to lower localized strain along the shear plane leading to lower deformation of the chips. The TiAlSiN coating exhibited superior wear-resistance at the highest cutting speed when compared to DLC and WC/C coatings owing to its higher hardness and higher coating/substrate adhesion strength. However, the DLC and WC/C coatings, although softer, accounted to significant reduction of machining forces due to their self-lubricating properties.
In the machining process, high-speed steel cutting tool is important for fabricate the any product in the manufacturing sector. However, high-speed steel is still unable to meet the requirements in some conditions. Coating is one of the methods used to enhance the cutting tool performance. Tool coating extends tool life, improves cutting quality, and increases tool durability. The deposition and properties of coated molybdenum High speed steel tools are described in this experimental investigation.
Finish turning is one of the key operations governing the residual stress of functional surfaces. The residual stress state is determined by the cutting conditions and the selected cutting tool system (macro geometry, cutting edge preparation, tool substrate, multi-layer coating…). However, this initial configuration evolves over time due to tool wear. Therefore, it seems very instructive to reproduce the wear process of the tool in order to understand the evolution of thermo-mechanical loadings applied to the machined surface. Flank wear is a parameter which can be difficult to fully control, and it is complex to reproduce experimentally. In this work, a simple, controlled and repeatable method of producing a known flank wear state is introduced and the impact of the flank wear on the surface integrity is assessed. This involves two parts, first reproducing a given flank wear state and second, evaluating experimentally the residual stress induced by the flank wear state on the workpiece. Carbide tools are used to turn 15-5PH steel under dry conditions. It is shown that the method produces consistent results. The effect of flank wear on residual stress is most notable and can generate data to validate numerical modelling. Areas for improving the method are also discussed.
Laser surface texturing (LST) followed by ultrasonic surface rolling (USR) was applied to 20CrMoH steel to improve the friction and wear behavior. In this paper, the fretting friction and wear mechanisms of the modified (USR, LST + USR) 20CrMoH steel under different loads and lubrication conditions were systematically investigated. Results indicated that the regular coupling distribution of micro-texture and gradient nanostructure (GNS) was formed on the surface layer of the combined treated material. Simultaneously, the depth of the GNS was up to 22 μm and the surface microhardness was increased from 800 HV0.2 to 860 HV0.2. Besides, the surface roughness Ra value was decreased from 0.24 μm to 0.01 μm and the maximum residual compressive stress (RCS) value was −610 MPa. Under dry friction and high load conditions, compared with the untreated specimen, the average friction coefficient and worn losses of the combined treated specimen were reduced by about 10% and 30%, respectively. In comparison with the untreated specimen, the average friction coefficient of the combined treated specimen was decreased by 26% under the conditions of low load and oil lubrication. Especially, the fretting wear resistance was obviously improved and its worn loss was significantly reduced by 92.05% compared with the untreated material. The predominant wear mechanisms of the combined treated material under dry friction and oil lubrication were oxidation wear and abrasive wear, respectively.
The wear mechanism of cubic boron nitride base cutting tool in turning was evaluated for some structural materials. It is shown that an increase in cutting speed causes a higher intensity of chemical interaction between tool and workpiece materials to form a liquid phase layer on the front face of the tool. Tool wear is accompanied by the removal of this layer, the resultant wear products arriving at non-contacting zones of the cutting insert and entering into the environment.
This paper deals with the machining of ferrous materials in their hardened condition (hardness: 50 to 70 Rc). Work materials considered include high-speed tool steels, die steels, bearing steels, alloy steels, case-hardened steels, white cast iron, and alloy cast iron.
In order to gain acceptance as an equivalent of grinding, hard turning must be able to satisfy high-quality requirements concerning surface finish and surface integrity. However, as a result of mechanical and thermal loads, the surface structure of the workpiece can be influenced by the machining process. In particular, at increased tool wear, white layers with high tensile stresses occur. These layers mainly consist of austenite and are characterized by a high hardness. Besides the mechanisms taking place on the workpiece surface, their influences on bending fatigue strength of components are discussed.
This paper considers some important findings which resulted from an investigation on the mechanism of heat generation during metal-cutting operations. It has been found that many changes during the cutting of metals are due to the change in tool-chip interface temperature through its influence on tool-chip friction. The paper is divided into two parts, the first of which pertains to the cutting forces and cutting temperatures observed during conventional turning and orthogonal cutting under otherwise identical conditions. The higher heat-dissipating capacity of the tool in orthogonal cutting operations was found to be fundamentally responsible for the observed differences. In the second part of the paper, the role of tool-chip contact area on interface temperatures is further investigated. This study has been of value in the interpretation of tool-chip interface temperature data and other phenomena heretofore inexplicable.
The mechanical state of a surface machined with a tool having flank wear is discussed in this paper, which is the second in a sequence of two papers, the first dealing with sharp tools. A technique is developed to ensure proper contact between artificially produced flank wear land and the workpiece. Mechanical state indices developed earlier, viz., apparent strain hardening index, and residual stress distribution in a semi-infinite model, were found to be governed and characterized by shear plane length, depth of cut, and flank wear length. Thermal effects due to flank wear were also observed. Depending upon the cutting speed and thus upon the temperature generated, the residual stress pattern is lightly or severely modified. It is established that the thermal effect is primarily the result of yield strength change rather than of thermally induced strain. (A)
A short overview is given about the martensitic material states, their microscopic and submicroscopic structures and their variations due to the supply of thermal energy. Then essential structure mechanical aspects are summarized which are important for the mechanical properties of hardened steels. Hardening residual stresses of quenching type, transition type and transformation type are discussed. They superimpose to loading stresses and therefore will have extensive consequences to the behavior of mechanical loaded components. Finally the materials resistances of FeC-martensites against defined mechanical loading types are described by characteristic examples.
The saw-tooth chip was the last of the major types to be identified. This occurred in 1954 during machining studies of titanium alloys which were then being considered for aerospace applications because of their large strength-to-weight ratio and corrosion resistance. This is a type of chip that forms when very hard brittle materials are machined at high speeds and feeds. Since this is an area of machining which will be of increasing interest in the future, particularly in hard turning, it is important that the mechanism and mechanics of this type of chip formation be better understood. At present, there are two theories concerning the basic origin of saw-tooth chips. The first to appear assumed they are of thermal origin while the second assumes they arise due to the periodic development of cracks in the original surface of the work. The thesis presented here is that the root cause for saw-tooth chip formations is cyclic cracking. This is followed by a discussion of extensive experimental data that supports this point of view.
Measurements of the Segmentation Frequency in the Chip Formation Process
This investigation has showed that the relationship between the chip formation process and the dynamic cutting forces in the shear zone is probably one of the most essential features of the cutting process.
In the cutting tests conventional accelerometers and a special new cutting force sensor have been used. Also metalographic samples from the chips have been studied. By comparing the information from the transducers and the metalographic samples, extended experiments and tests have showed that this method can be very useful for the basic understanding of the mechanisms of the cutting process. Also flank wear and tool damage propagation can be measured by this method. The results in this work are discussed and described in the paper. Also the possibilities of in-process measurements for adaptive control are discussed.
There are some researches on the saw-toothed chip formation, but there are many points which are uncertain. An important subject in this research is to elucidate the fracture mechanism of work material near the shear plane during cutting.
In the present study, some examples of saw-toothed chip formation were pursued experimentally and analytically. In special, a dynamic torsion test has been applied to make clear the fracture mechanism of work material under compressive stress at different temperatures and strain rates. The test temperature was ranged from room temperature to 600°C, and the maximum shear strain rate was about 100 1/s. From this study, the following two fracture mechanisms were found. The first one is “ductile fracture mechanism” caused by overstrain under compressive stress, and the other is “high speed ductile fracture mechanism”, which is caused by strain concentration due to the local weakening by heat generation. It is evident that when the stainless steel or the maraging steel is cut the saw-toothed chip is formed by latter mechanism, while the former mechanism is applicable to the cutting of a low carbon steel.
Dynamic plastic behavior of materials is influenced by internally generated temperature gradients. These gradients are a function of thermophysical properties as well as strain rate and shear strength. Criteria are presented for the prediction of catastrophic shear in materials. Catastrophic shear occurs when the local rate of change of temperature has a negative effect on strength which is equal to or greater than the positive effect of strain-hardening. Catastrophic slip is an influential deformation mechanism during high-speed machining and ballistic impact. Structural failure may occur during dynamic loading of components which are designed without regard to the specific sensitivity of certain materials to catastrophic shear.
The occurrence of catastrophic shear-type chips during metal cutting has been analyzed. A model which incorporates a simpl heat transfer analysis and material properties such as the strain-hardening rate, the temperature dependence of the flow stress and the strain rate sensitivity of the flow stress was developed in order to establish the tendency towards localized flow. Using data published in the literature, it was found that non-uniform flow in metal cutting is imminent when the ratio of the normalized flow softening rate to the strain rate sensitivity is equal to or greater than 5. This trend is identical with that found for flow localization and shear band formation during lower strain rate deformation as found in torsion and isothermal forging.
Refractory metal cutting tools exhibit an unusually high probability of edge chipping and gross fracture when suddenly unloaded after cutting a strong material at high speeds and feeds. After identifying three possible mechanisms of brittle fracture when a cutting tool exits a cut, that associated with so-called 'foot' formation is discussed in detail. This involves a sudden shift from steady state chip formation by concentrated shear to gross fracture of the workpiece as the end of the cut is approached. The other possible mechanims are discussed in a companion paper to follow.
The dynamics of chip formation during high-speed orthogonal machining (planing) is examined. Merchant's vector diagram of the forces acting upon the continuous chip free body is expanded to include inertial force components. Expressions are developed for cutting force and pressure. Energy balances are used to show that Merchant's classical equation relating shear angle to rake angle and friction angle applies, independent of cutting speed. Apparent differences between experimental observations of shear angle and Merchant's prediction are attributed to workpiece material anisotropies, tool wear, built-up edge, and inaccurate measurement of the friction coefficient at the tool-chip interface.
Shear instability was observed experimentally in machining some of the difficult-to-machine materials, such as hardened alloy steels, titanium alloys, and nickelbase superalloys yielding cyclic chips. Recht in 1964 developed a classical model of catastrophic shear instability in machining. In this investigation, based on the analysis of cyclic chip formation in machining, possible sources of heat (including preheating effects by these heat sources) contributing toward the temperature rise in the shear band were identified. The temperature rise was calculated using Jaeger's classical solutions of stationary and moving heat sources. Recht's original catastrophic shear instability model for shear localization was extended by predicting analytically the conditions for the onset of shear localization.
A presentation is given dealing with the machining of ferrous materials in their hardened condition (hardness: 50 to 70 R//c). Work materials considered include high-speed tool steels, die steels, bearing steels, alloy steels, case-hardened steels, white cast iron, and alloy cast iron. Prerequisites for the successful machining of hardened ferrous alloys include: use of an extremely rigid, high-precision machine tool system with adequate power and proper sensors and control for monitoring the cutting process; very hard ( greater than HV 1800) and tough (K//I//C greater than 6 MP m**1**/**2) tool material; negative rake ( greater than equivalent to minus 10 degree ) tool geometry with a high wedge angle ( greater than 90 degree ), strong shape (e. g. , round), and in some cases appropriate chamfer or radius, honed at the cutting edge; tool holders with high stiffness; and appropriate cutting conditions.
The hardening of steel rather lowers the cutting forces in many cases. This is the result of high shear angle and the saw-toothed chip formation due to the poor ductility of hard materials. Reinforcement of Al alloy with fiber also decreases the cutting forces. However, the hard materials wear the cutting tool rapidly and increase the forces, especially thrust force which causes size error. The profile of machined surface of hardened steel reflects the profile of cutting edge.
A major inefficiency in the manufacturing of hard, high precision parts is the number of processes, or steps, currently needed. For instance, the current method of producing the surfaces of bearing races involves annealing, rough turning, hardening, several types of grinding, and, finally, abrasive based superfinishing. There is always an additional set-up for each additional process, and an occasional inspection between processes. Therefore, there has been an economic motivation to study methods of extending one process or one machine tool's capability so that other processes in the production sequence can be eliminated, thus, reducing set-up time and the complexity of manufacturing scheduling, and gaining significant benefits for flexibility and system efficiency.The concept and feasibility of using a single step for machining hardened steel to a surface comparable to that of lapped bearing races were presented briefly with limited data (Liu and Mittal: J. Mfg Syst. 14(2): 129–133, 1995). In this paper, extensive literature review and considerable data on surface waviness, profile, finish, microstructure and residual stress confirm the feasibility of the proposed new processing concept. The cutting conditions for producing a specific surface finish ranging from 2 to 8 μin. are also presented.
Chip segmentation and the tool forces involved during cutting of hardened steel are discussed. AISI 4340 steel was machined on an engine lathe to study chip morphology, tool forces, and the surface generated. It was found that chip segmentation occurs when the hardness of the steel exceeds a certain value, and that the tool forces associated with chip segmentation are very high. A transformed layer of untempered martensite and retained austenite was produced when the cutting conditions were severe.MST/469
The temperature at the tool flank, which has an effect on the tool life and on the machined surface integrity, is measured using a two-color pyrometer with a fused fiber coupler. This pyrometer makes it possible to measure the temperature of a very small object without emissivity affecting the results. A CBN tool is used as the cutting tool. A high carbon chromium bearing steel, a chromium molybdenum steel and a quenched carbon steel are used as work materials. The temperature of the tool is highly affected by the cutting speed, but the influence of the depth of cut and the feed rate is not so great. In the cutting of the high carbon chromium bearing steel, the temperature is 800 °C at a cutting speed of 100 m/min and increases with the increase of cutting speed, reaching 950 °C at 300 m/min. There is a close relation between the tool temperature and the hardness of the work material. The influence of cutting speed on tool wear is considerable.
This paper deals with the general problem of crack extension in a combined stress field where a crack can grow in any arbitrary direction with reference to its original position. In a situation, when both of the stress-intensity factors,k 1,k 2 are present along the crack front, the crack may spread in any direction in a plane normal to the crack edge depending on the loading conditions. Preliminary results indicate that the direction of crack growth and fracture toughness for the mixed problem of Mode I and Mode II are governed by the critical value of the strain-energy-density factor,S cr. The basic assumption is that crack initiation occurs when the interior minimum ofS reaches a critical value designatedS cr. The strain-energy-density factorS represents the strength of the elastic energy field in the vicinity of the crack tip which is singular of the order of 1/r where the radial distancer is measured from the crack front. In the special case of Mode I crack extensionS cr is related tok 1c alone asS cr = (κ − 1)k 12/8μ. In general,S takes the quadratic forma 1 1k 1 + 2a 1 2k 1k 2 +a 2 2k 2 whose critical value is assumed to be a material constant. The analytical predictions are in good agreement with experimental data on the problem of an inclined crack in plexiglass and aluminum alloy specimens. The result of this investigation provides a convenient procedure for determining the critical crack size that a structure will tolerate under mixed mode conditions for a given applied stress.
The reversion of Fe-18.5 Ni-0.52 C tempered martensitic steel to austenite under shear was used to study the formation of
discontinuous chips by orthogonal cutting. For certain combinations of cutting speed, depth of cut, and tool rake angle, chips
with bands of reverted austenite along their sheared edges were formed. Tensile tests on the same material exhibited transformed
austenite on the specimen fracture surfaces for tests conducted below 200°C. Metal cutting theory predicts that continuous
plastic deformation during chip formation cannot heat the material to its reversion temperature. Analysis of the machine-sample
interaction before chip separation shows that adiabatic instability can occur, resulting in localized shearing and a temperature
rise to at leastA
s. Only those chips which are heated during continuous deformation to temperatures between 100° and 200°C undergo adiabatic
instability and reversion.
Topography of surfaces produced in finish hard turning using cubic boron nitride (CBN) tools is affected by a large number of factors including tool wear and the mechanics of the chip formation process. This paper shows first that tool wear rates are affected by interactions between the work material and the binder phase of the CBN tool. For finish hard turning, low CBN content, ceramic binder tools give longer lives and better finish than high CBN content metallic binder tools. For low CBN tools, wear rate is directly related to the microstructure of the work material and to the CBN grain size. SEM studies suggest that chip morphology is independent of work material microstructure, but varies with tool wear. Orthogonal cutting tests show that, above a critical speed, segmented chips are formed by catastrophic localized shear and that chip segmentation spacing may be reflected in a modulation of the machined surface. Segment spacing is a function of depth of cut, rake angle, and surface speed, approaching a limiting value with speed. Specific cutting energies decrease with speed, also approaching an asymptote. A simple mechanical model gives reasonable predictions of segment spacing along the original surface, although a full thermo-plastic model will be required to account for other aspects of the chip formation process.
The phenomenon of material side flow represents an important aspect of machined surface quality during hard turning. In this paper, an experimental study was performed to investigate the main features of this phenomenon. The effects of process parameters including edge preparation, nose radius, feed and tool wear on material side flow were examined. Two possible mechanisms for material side flow were investigated. In the first one, the material is squeezed between the tool flank face and the machined surface when chip thickness is less than a minimum value. In the second mechanism, the plastified material in the cutting zone flows through the worn trailing edge to the side of the tool. Both of these mechanisms can exist simultaneously. The results obtained from surface examination showed a strong correlation between edge preparation and material side flow. An increase in the tool nose radius resulted in a remarkable increase of material side flow. Feed had an indirect effect on material side flow. In addition, tool wear significantly affected the existence of material side flow on the machined surface. An increase in tool wear promoted the occurrence of material side flow.
With the availability of polycrystalline cubic boron nitride (PCBN) it is possible to machine very hard gears, etc. at speeds of (60–150 m/min = 200–500 fpm). When this is done using PCBN tools in face milling, Chip formation is of a cyclic saw toothed type. This type of chip formation is reviewed in relation to other types of cylic and noncyclic chip formation. The root cause of high frequency, saw toothed chip formation is found to be periodic gross shear fracture extending from the free surface of the chip toward the tool tip and not adiabatic shear as commonly believed.
Saw-toothed chips are formed during machining of hardened steel (HRC ∞ 60–63). This paper presents a new analytical approach for modelling the chip formation mechanism in hard-turning. It has been observed that the chip formation starts with initiation of a crack at the free surface of the workpiece which further propagates towards the cutting edge of the tool. The crack soon ceases to grow at a point where severe plastic deformation of the material exists under higher level of compressive stresses. The chip segment caught up between the tool rake face and the crack is pushed out while the material in the plastic region just below the base of the crack is displaced along the tool rake face thus forming saw-toothed chips. The direction of crack initiation and propagation are predicted using the surface layer energy/strain energy density criterion. The maximum value of surface layer energy, Yemax can be used to evaluate the angle of crack initiation while the strain energy density criterion predicts the corresponding crack propagation angle. Here, the process of chip formation is considered to be a mixed mode crack problem of Mode I and Mode II. The theoretical predictions are verified by the resultant chip contours obtained experimentally. The predictions made are shown to be in good agreement with those measured experimentally.
On the Mechanics of Chip Segmentation in Machining, Journal of Engineering for Industry
- Komanduri
Feindrehen und Bohren gehärteter Stahlwerkstoffe
- Koenig
Einfluß der Drehbearbeitung von Hartlegierungen auf die Oberflächenrandzone
- Meister
PKB-Wendeschneidplatten im Einsatz: Harte Eisenwerkstoffe wirtschaftlich zerspanen
- Steinmetz
Maschinen für die Hochund Ultrapräzision, Technica Nr. 13/14/95
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Precisjeharddraaien in de kleinseriefabricage
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Surface generation by hard machining
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Drehen von Stellite 6 mit Hartmetall und PKD
- Baik
Hartdrehen von Wälzlagerstahl mit PKD und Schneidkeramik
- Koenig
Hartbearbeitung aus der Sicht der Forschung
- Toenshoff
Schnittkraft und Temperatur beim Hartdrehen von gehärtetem Gesenkstahl
- Aspinwall
Eigenspannungen und Randzonenausbildungen beim Hartdrehen. Härterei-Technische Mitteilungen -HTM
- Toenshoff
Eigenspannung als Ergebnis von Wärmebehandlung und Umwandlungsverhalten
- A Rose
Spanende Bearbeitung verschleißbeständiger Hartlegierungen
- Biermann
Machining Characteristic of Hardened Steels
- Nakayama
Cutting mechanisms during machining of hardened steels
- Matsumoto
Einsatz moderner Schneidstoffe für die Hartbearbeitung Werkzeuge für die moderne Fertigung
- C Stanske
Hartbearbeitung mit PKB -Auf den Schneidstoff kommt es an. Industrie Diamanten Rundschau
- Koenig
Werkstückrandzonenbeeinflussung beim Hartdrehen mit PKB
- Fleming
Anwendung einschneidiger Reibwerkzeuge zur Hartfeinbearbeitung von Bohrungen
- Brinksmeier
Hartdrehen ersetzt Schleifen
- Laub