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In this study, a new hybrid surface modification process, fine particle peening (FPP) treatment prior to nitriding, was proposed. In order to clarify the effects of FPP treatment prior to nitriding on the fatigue strength of notched AISI 4135 steel with a stress concentration factor Kt of 2.36, fatigue tests were conducted at room temperature using...
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Context 1
... nitriding process was performed at 823 K for 6 h in nitrogen and ammonia atmospheres. The FPP treatment conditions are given in Table 2. The shot particles used in this study were made from a high-speed tool steel and were 55 µm in diameter with a Vickers hardness of 876HV. ...
Context 2
... analysis was performed for 2θ angles ranging between 20° and 90°, although only the diffraction peaks produced between 30° and 60° are shown in (Table 2) Machining ( Fig.1 diffraction patterns were produced between the N and FN series, but the intensities of ε(002), γ'(111) and ε(112) were different. This indicates that the crystal structure of the compound layer in the FPP-treated specimen prior to nitriding is different to that of the nitrided specimen. ...
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Citations
... Furthermore, Podgornik and Hogmark [11] also suggest that the combined process of nitriding-polishing-DLC (diamond-like coating) is the best for the formation of austenitic stainless steel. The effect of surface layer modification of AISI 4135 steel by fine particle peening prior to nitriding was investigated by Kikuchi and Komotori [12]. Such studies involve for example a titanium alloy [13]. ...
Wear is the most serious problem in service of moving steel parts. To mitigate it, we have studied phase transformations in the surface layer of Vanadis 6 tool steel obtained after several treatment routes. Changes in wear resistance were examined in particular. There are various ways to improve the quality of surfaces of tool steels for cold working - including mechanical, chemical or physical vapour deposition (PVD) coatings. Several multistage processes of surface layer modification were applied: turning-burnishing, turning-burnishing-PVD, grinding-nitriding, turning-burnishing-nitriding, turning-nitriding-polishing, turning-burnishing-nitriding-polishing, and turning only used as a reference. To provide comparability, samples were subjected to heat treatments in vacuum furnaces with gas quenching until a hardness of ≈62 ± 1 HRC was achieved. Scanning electron microscopy observations, X-ray diffraction analysis, and finally ball-on-disc tribological tests against Al2O3 balls as counterparts provide information about wear and friction values. The best wear resistance – more than ten times higher than after turning only - was achieved for a sample following the turning-burnishing-PVD sequence. The turning-burnishing (130 N)-nitriding sequence may act as an alternative to the grinding-nitriding treatment. Wear rate values for the two latter variants are almost the same.
... In addition to the improvement in surface properties, mechanical surface treatment followed by thermo-chemical technique could also impact the fatigue strength. Kikuchi et al. 17,18 performed fine particle peening on stainless steel and subjected them to gas nitriding, resulting in an improvement of the fatigue strength. Gangaraj et al. 19 investigated the effect of a combination of severe shot peening and nitriding on the fatigue behavior of low alloy steel. ...
... However, the USDR series presented a single fatigue crack initiation site at strain amplitudes of 0.8%, while the AN series showed the characteristics of several fatigue crack sources at high strain amplitude. That shows that the refined grains and the high compressive residual stress after the USDR process inhibited the fatigue crack initiation, contributing to the fatigue life improvement in USDR series 17,18 . www.nature.com/scientificreports/ ...
Ultrasonic surface deep rolling (USDR), oxygen boost diffusion (OBD), and their combination (USDR-OBD) were all used to improve the surface hardening of pure titanium. The microstructure, microhardness, and fatigue life of pure titanium treated by USDR, OBD, and USDR-OBD methods were analyzed. USDR treatment induced a severe deformation area, while OBD treatment produced a brittle oxygen diffusion zone. The USDR-OBD treated samples approached the highest hardness in comparison with other treated samples. The fatigue lives of USDR treated samples were improved, which was due to the high compressive residual stress and refined grains. However, the fatigue lives of both OBD treated samples and USDR-OBD treated samples were decreased due to premature crack initiation and rapid propagation in the oxygen diffusion zone. Finally, the fatigue fracture mechanisms of different samples were proposed.
... This decrease in corrosion loss has been reported to be related to the application of compressive residual stress, among other factors [14]. In addition to cavitation processing, other technologies for applying compressive residual stress to material surfaces include shot peening [15,16,17,18]. When compressive residual stress is applied to the material surface, it suppresses cracking that is likely to occur because of thermal stress induced by high-temperature corrosion. ...
In this paper, long-term high-temperature corrosion at 500 °C and high-temperature corrosion at the melting temperature of a corrosive ash mixture were examined because the use of high-temperature equipment such as boilers and gas turbines increases year over year. To investigate the optimum cavitation processing conditions for the specimens used in high-temperature corrosion tests, the surface properties of each processed specimen were examined. In specimens processed using multifunction cavitation (MFC), the compressive residual stress was high when the processing time was 10 min and the Cr content on the surface was greater than on the surface of an unprocessed specimen. On the other hands, in specimens subjected to water-jet peening (WJP), the compressive residual stress was high when the processing time was 10 min. In the present study, the processing time was selected to be 10 min and all high-temperature corrosion tests were conducted by the coating method. In the case of long-term high-temperature corrosion at 500 °C, the corrosion loss of the MFC-processed and WJP-processed specimens was small, whereas the corrosion loss of the unprocessed specimen was large.
... In addition, the presence of a compound layer also affects the fatigue strength. Hence, the compound layer thickness [1], phase distribution [2,3], and porosity [4] were investigated to improve rotating bending fatigue strength. ...
... Also, K N 0.35 had a lot of voids compared to K N 0.25 (Fig. 9). As mentioned in section 3.4, voids in a porous layer became a crack initiation site and also it was known as decreasing the rotating bending fatigue strength [4]. However, the fatigue strength in K N 0.35 (490 MPa) was higher than that of K N 0.25 (450 MPa). ...
The rotating bending fatigue strength of JIS-SCM415 steels after austenitic nitriding was evaluated to find the surface phase that gave the highest strength. Nitriding was performed at 903 K under conditions of KN = 0.15, 0.25 and 0.35 atm−1/2. In addition, specimens which were tempered at 523 K for 7.2 ks after nitridings with KN = 0.15 and 0.25 atm−1/2 were prepared. A specimen prepared by nitrocarburizing at 853 K was also evaluated as a comparison. Specimens nitrided at 903 K at KN = 0.15 atm−1/2 showed the highest fatigue limit because the 10 μm thick surface layer was a dual phase of austenite and martensite that might have a fine microstructure which inhibited initial crack generation and growth. Specimens nitrided at 903 K at KN = 0.35 atm−1/2 showed the second highest fatigue limit because the ε compound layer that was 20 μm thick had a high compressive residual stress. Specimens nitrides at 903 K at KN = 0.25 atm−1/2 showed the third highest fatigue limit because of the formation of a 6 μm thick compound layer which was a dual phase of ε and γ’ that had few voids and a high toughness (low hardness) in addition to its compressive residual stress. Tempered specimens showed a lower fatigue limit than that of non-tempered specimens. This was because the surface layer became brittle in tempered specimens. Specimens other than the tempered specimen in KN = 0.25 atm−1/2 showed a fatigue strength higher than that of a sample nitrocarburized at 853 K.
... The microstructure, phase analysis and also residual stress determination in nitrided materials are reported in [28][29][30][31][32][33][34]. To investigate the surface hardening mechanism of H13 steel, Cho et al. [28] carried out a shot peening process as a pre-treatment of ion-nitriding. ...
... They concluded that refined grains and higher nitrogen concentration acted as main factors for the surface hardening of shot peened and ionnitrided specimens. Kikuchi and Komotori [29,30] reported that nitrided specimens, pre-treated with fine particle peening had a lower friction coefficient and less wear loss. Such surface modification improves the tribological properties of AISI 4135 steel due to the presence of a thick and hard compound layer without cracks and pores. ...
The effects of plastic deformation, by slide diamond burnishing as a pre-nitriding treatment, of the surface layers of a conventional, Sverker 21, and a powder metallurgy, Vanadis 6, tool steel were examined by metallography and X-ray diffraction for phase and internal stress analyses. Two sequential processes: turning-nitriding and turning-burnishing-nitriding were compared in the affected nitrided regions: surface (compound layer) and sub-surface (diffusion zone). Compared to nitriding only, prior burnishing leads to an increase in the thickness of the affected region, containing Fe3N, Fe4N, CrN nitrides, by 60% from ~36 μm for Sverker 21 and by more than 300% from ~3 μm for Vanadis 6 steels. A homogenization of the stress state to isotropic compression was found in the surface layers of both prior burnished tool steels.
... Enhanced grain boundary area and dislocation density promote nitrogen diffusion by enhancing the nitriding kinetics indicated by reduced activation energy for nitrogen diffusion in steel surface [23][24][25][26][27][28][29][30][31]. ...
... Severe plastic deformation by shot peening forms ultrafine grained structure (in nanometer range) and high defect density at the surface of specimens. As pointed out by number of researchers [25][26][27][28][29][30][31][32][33][34], the large grain boundary area and the high defect density particularly dislocation density provide alternative and shot paths for diffusion of nitrogen. This substantially lowers the activation energy for the diffusion of nitrogen and enhances the nitriding kinetics. ...
Shot peening is a simple but effective severe plastic deformation process to synthesize ultrafine grains in micro- to nanometer range on metallic surfaces. In this work, shot peening on AISI 4140 steel specimens was done in a novel centrifugal air blast shot peening reactor with shot velocity of 5.8 m/s for 3 h. Characterization of the shot peened surface (XRD, micro-hardness, SEM, and TEM) showed that surface undergoes significant plastic deformation with marked increase in microstrain of lattice, dislocation density, and surface hardness. XRD profiles and TEM analysis confirmed formation of ultrafine grain structure in the nanometer range. These specimens were then subjected to austenitic nitriding at 610°C for 4 h followed by cryo-treatment at − 185°C for 32 h. Characterization of pre-shot peened nitrided and cryo-treated surfaces showed that there was marked improvement in surface hardness (from 695 to 797 HV0.05) and effective case depth (from 19 to 54 µm) in comparison with un-shot peened nitrided and cryo-treated specimens. It was demonstrated that presence of ultrafine grain structure and austenitic phase during nitriding plays synergetic role to improve content and diffusion kinetics of nitrogen in AISI 4140 steel surface. 2017
... There is a need for non-destructive analysis of the surface layer quality after complicated processes of surface treatment, especially the plastic surface treatment, in particular in high volume production environments or storage. Treatment consisting of cold work deformation of the surface introduces compressive stresses which, as confirmed by numerous, independently carried out research of national and international centers [14,[23][24][25], have a very beneficial effect on the performance of products. The level of stress and a way of their distribution may, however, be subjected to significant changes due to the existence of variable, random conditions of the manufacturing process, giving a large scatter of the performance of products. ...
Modern production technology requires new ways of surface examination and a special kind of surface profile parameters. Industrial quality inspection needs to be fast, reliable and inexpensive. In this paper it is shown how stochastic surface examination and its proper parameters could be a solution for many industrial problems not necessarily related with smoothing out a manufactured surface. Burnishing is a modern technology widely used in aircraft and automotive industries to the products as well as to process tools. It gives to the machined surface high smoothness, and good fatigue and wear resistance. Every burnished material behaves in a different manner. Process conditions strongly influence the final properties of any specific product. Optimum burnishing conditions should be preserved for any manufactured product. In this paper we deal with samples made of conventional tool steel – Sverker 21 (X153CrMoV12) and powder metallurgy (P/M) tool steel – Vanadis 6. Complete investigations of product properties are impossible to perform (because of constraints related to their cost, time, or lack of suitable equipment). Looking for a global, all-embracing quality indicator it was found that the correlation function and the frequency analysis of burnished surface give useful information for controlling the manufacturing process and evaluating the product quality. We propose three new indicators of burnishing surface quality. Their properties and usefulness are verified with the laboratory measurement of material samples made of the two mentioned kinds of tool steel.
... The surface-modified layer created by the nitriding process generally consists of two types of layers; a compound layer on the top surface and a diffusion layer beneath it. The compound layer especially improves the tribological properties of a material due to its high hardness; 4,8) however, in some cases, it also reduces the fatigue strength of the material 2,5,9) due to its brittleness and the presence of cracks and pores. Therefore, the compound layer is removed by grinding and blasting processes to prevent the nitrided products from decreasing the fatigue strength, although it exhibits high wear resistance. ...
... 23) We have reported that the fatigue strength of nitrided AISI 4135 chromium-molybdenum steel pre-treated with FPP was improved due to the formation of a dense compound layer. 5) This dense compound layer is also expected to improve the wear resistance of steel; however, the mechanism for the formation of this dense compound layer and the effect of the layer on the tribological properties have not yet been investigated. ...
The effect of fine particle peening (FPP) on the gas nitriding of AISI 4135 chromium-molybdenum steel was investigated. Surface microstructures of nitrided specimens pre-treated with FPP were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). The nitrided layer formed on the fine grained specimen treated with FPP was thicker than that on the nitrided-only specimen, because the fine grains created by FPP accelerate the formation of iron nitride during the nitriding process. Furthermore, FPP reduces the concentration of chromium near the nitrided surface, which suppresses the formation of cracks and pores in the compound layer. Therefore, a nitrided specimen pre-treated with FPP has higher hardness than a nitrided-only specimen. Reciprocating ball-on-disk friction tests were performed at room temperature to investigate the tribological properties of the nitrided AISI 4135 steel. The nitrided specimen pre-treated with FPP had a lower friction coefficient and exhibited less wear loss due to the presence of a thick compound layer without cracks and pores. Therefore, a hybrid surface modification that employs FPP as a processing step prior to gas nitriding is effective for improving the tribological properties of AISI 4135 steel.
... Pomimo wielu zalet nagniatania, w dążeniu do uzyskania jeszcze lepszych właściwości WW części maszyn ze stopów metali lub celem zwiększenia dokładności i wydajności obróbki, poszukiwane były w Instytucie i innych ośrodkach badawczych metody hybrydowe lub sekwencyjne łączące obróbkę nagniataniem z innymi rodzajami obróbek, takimi jak np. laserowa [4][5][6][7], kriogeniczna [8][9][10][11][12] i cieplno-chemiczna [13][14][15] opisane w artykule, a także rozwijane było wspomaganie nagniatania ultradźwiękami [16] lub wibracyjnie [17], pozwalające na wytworzenie dużych korzystnych naprężeń ściskających (rzędu 1000 MPa) i zgniotu na większej głębokości [1]; oraz łączenie nagniatania z obróbką elektrochemiczną w celu zwiększenia wydajności obróbki i polepszenia gładkości powierzchni [7,18]. Podejmowane były również próby poprawy struktury geometrycznej powierzchni (SGP) i właściwości WW uzyskiwanej po obróbce elektroerozyjnej przez stosowanie po niej procesu nagniatania [19,20]. ...
... It is well known that dislocation densities and grain size are important factors that enhance the elemental diffusion behavior [2]. In this study, in order to create fine grains which could accelerate the nitrogen diffusion into titanium, cold rolling is introduced as pre-processing step to plasma niriding [3][4][5][6]. The microstructure created by cold rolling is expected to accelerate the nitrogen diffusion into CP titanium during the nitriding process and form a thick nitrided layer at low temperature. ...
In order to improve both of the fatigue and tribological properties of commercially pure (CP) titanium, a low temperature nitriding process was developed. Cold rolling was introduced as pre-processing step to plasma nitriding to create fine grains which could accelerate the diffusion of nitrogen into the material. Surface microstructures of nitrided specimens pre-treated with cold rolling were characterized using a micro-Vickers hardness tester, an optical microscope, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron backscatter diffraction technique (EBSD). Titanium-nitrides (TiN and Ti2N) were formed on the surface nitrided at the temperature higher than 600 inverted perpendicular C. Moreover, the compound layer formed on the nitrided CP titanium pre-treated with cold rolling was thicker than that on the nitrided-only one, resulting in showing higher hardness. 4-points bending fatigue tests were performed for the specimens treated with low temperature nitriding (600 degrees C), which could suppress the grain-coarsening, under the stress ratio R= 0.1 at room temperature. In addition, fatigue fracture mechanism of nitrided CP titanium was discussed based on the observations of microstructure and fracture surface.
