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3D surface profile of indentation carried out for sample (1353 K/1053 K) tested at (a) 300 K and (b) 923 K.
Source publication
The effect of normalizing and tempering temperatures on mechanical properties of P92 steel has been investigated using tensile tests and ball indentation techniques (BI) at several test temperatures in the range of 300-923 K. A silicon nitride indenter having 0.762 mm diameter was used for BI testing. The material deformation behaviour underneath t...
Contexts in source publication
Context 1
... pile-up height around the indentation increased from 11 μm to 25 μm with increase in the test temperature. This pile up resulted in the increased diameter of the indentation although the depth of penetration was kept constant (24% indenter radius). The 3D views of the indentation surface profile for samples tested at 300 and 923 K are shown in Fig. 9. The different colour contours in Fig. 9 represent the relative height from the deepest portion of the indentation. It was observed that, the diameter of the indentation as well as height of pile-up increased with increase in test temperature. This strengthens the previous discussion on ...
Context 2
... increased from 11 μm to 25 μm with increase in the test temperature. This pile up resulted in the increased diameter of the indentation although the depth of penetration was kept constant (24% indenter radius). The 3D views of the indentation surface profile for samples tested at 300 and 923 K are shown in Fig. 9. The different colour contours in Fig. 9 represent the relative height from the deepest portion of the indentation. It was observed that, the diameter of the indentation as well as height of pile-up increased with increase in test temperature. This strengthens the previous discussion on ...
Citations
... Therefore, the maximum indentation damage could be further reduced. Notable researchers have used this technique to characterise the mechanical properties and flow curves of different metallic structures [1,[8][9][10][11][12][13][14][15][16][17][18][19]. As early as the 19 th century, the indentation technique was used for estimating elastic properties based on Hertz contact law [19] and Sneddon's equation [20] while Tabor [19] pointed out the relationship between the hardness (Vickers and Brinell) and yield stress for metals in a plastic state. ...
... Several studies have investigated the use of ball indentation techniques to determine mechanical properties of material which range from Young's modulus (E), yield strength, hardness (H) and fracture toughness [2,11,25,[28][29][30][31][32][33][34][35][36][37][38][39]. The indentation process requires loading and unloading of the ball indenter into the specimen's surface [38] to estimate its mechanical properties. ...
... where d p is the diameter of the indentation after unloading. Note that in this work, d p value is estimated using equation (11) [3,13,26,27]. ...
Background
Instrumented ball indentation offers a promising approach to determining mechanical properties and tensile stress–strain relationships of materials, non-destructively. Objective: Using indentation load-depth experimentation to determine mechanical properties such as Young’s modulus, yield stress, strain hardening exponent and hardness, and tensile flow curve based on conventional contact mechanics principles.Method
Nine different rail steel specimens are subjected to instrumented indentation testing (IIT) using an in-house developed ball indentation equipment that considers pile-up effect for effective estimation of the contact area and specimen’s stiffness required for mechanical characterization of the rail steels.ResultsThe mechanical property response using micro-scaled ball indentation followed a comparative outcome with tensile test outcomes. The evolution of the hardness across the depth experiences a sudden increase followed by a decrease in hardness which suggests the effect of localized hardening due to indenter size effect mechanism. In order to establish the tensile flow curve via indentation, an adjusting parameter (κ) is included as part of the parameter (ϕ) that describes the development of the plastic zone beneath the indenter tip to correct the effect of multi-axial stresses and increased stresses due to the indenter size effect.Conclusions
The flow curve via the ball indentation strongly correlates with tensile stress–strain relationship, showing a promising possibility of using non-destructive indentation to determine tensile properties and flow curve for high-strength rail steels.
... On the other hand, similar to other materials, the mechanical properties of metallic materials gradually deteriorate with the extension of time, it is necessary to evaluate the temperature-dependent UTS in service. Therefore, an intensive study of the temperature-dependent plastic instability plays an important role in the proper use of materials and the prevention of fracture accidents [6,[11][12][13][14][15]. ...
... Suggestions for improving the material properties were presented. Table 4 Material parameters of P92 [14]. ...
... However, due to the peculiarities of the indentation test method, where plastic instability (or necking phenomenon) cannot be produced in the material by indentation, the indentation method often has some limitations for the acquisition of ultimate tensile strength [18]. In the present work, the predicted UTS of 316LN [18], P91 steel [3], and P92 steel [14] (normalized 1353 K/ tempered 1013 K) were compared with indentation tests. ...
Quantitative evaluation of temperature effect on the mechanical properties of materials has always been the core issue concern. In this study, based on the Force-Heat Equivalence Energy Density Principle, a method to model the temperature-dependent ultimate tensile strength (UTS) for metallic materials was proposed. The critical plastic instability energy density related to the onset of plastic instability was put forward which is composed of the elastic-plastic strain energy and the corresponding heat energy. Subsequently, two temperature-dependent UTS models considering the effect of strain hardening behavior were theoretically derived. The models do not contain meaningless adjustable fitting parameters and each parameter has clear physical meanings. The intrinsic quantitative relationships between temperature, UTS, strain hardening exponent, strength coefficient, and specific heat capacity are revealed. Model predictions achieved good agreement with 31 groups of accessible metallic materials, including structural steels, high-strength steels, cold-formed steels, zirconium alloys, and aluminum alloys, which are commonly used in engineering. Especially, the models achieved a better agreement with the results of uniaxial tensile tests compared with the current indentation method. Furthermore, the quantitative influence of the strain hardening exponent and the strength coefficient on UTS at different temperatures was analyzed. This work will contribute to the evaluation of the properties of materials at elevated temperatures and the fire design of structures.
... It is reported [41,42] that tungsten is added to enhance the solid solution strengthening and to minimize the coarsening rate of M 23 C 6 precipitates at elevated temperatures. The W addition enhances the creep strength of the P92 steel but, at the same time, improves the tendency of laves phase Fe 2 (Mo,W) formation [5]. ...
... The precipitates such as M 23 C 6 and MX are responsible for the high strength of the martensite lath structure [41,88]. The M 23 C 6 type carbides are situated at prior austenite grain boundaries (PAGBs), subgrain boundaries, or inside the martensite laths and MX carbonitrides of type VN or Nb(C,N) is located inside martensite laths [89]. ...
In this review article, microstructure and mechanical behavior of the dissimilar welded joint (DWJ) between ferritic-martensitic steel and austenitic grade steel along with its application have been summarized in Ultra Super Critical (USC) power plant. Creep-strength enhanced ferritic-martensitic (CSEF/M) P91 steel was developed to sustain at extreme operating conditions of ultra-supercritical (USC) power plants, and later, P92 was developed to achieve better mechanical properties, higher creep-rupture strength and high operating temperature with the reduction in wall thickness as compared to P91 steel. The most common application of P91/P92 material in power plants includes high pressure and high-temperature steam piping, headers, super-heater tubing, and water-wall tubing. The other most commonly used material in the power plants is austenitic stainless steel, i.e., SS 304 L. The austenitic grade stainless steel offers high resistance to corrosion due to the high wt. % chromium and nickel content (18–20 and 8–12, respectively). Due to the low carbon content, the SS 304 L is less sensitive to the sensitization problem and offers excellent weldability. The joining of these dissimilar materials is frequently required in the power generation industry. The current review focuses on the main difficulty associated with dissimilar welding of martensitic P91/P92 and austenitic grade stainless steel. The different chemical composition, mechanical, physical and metallurgical properties of the martensitic P91/P92 and austenitic grade stainless steel leads to the problems such as hot cracking and carbon migration. The other weldability issues are the formation of a brittle intermetallic compound, the formation of soft transaction heat affected zone along with martensitic steel, δ ferrite formation in fusion zone, diffusion related problem, and residual stresses, which necessitates thorough study and qualification of welds. The effect of coarsening of various precipitates such as M23C6 carbides, MX carbonitrides, and effect of laves phase, z-phase, and sigma phase on mechanical property, and creep-rupture strength of DWJ are also discussed in detail. Based on the literature reviewed, it has been found that some of the above-stated problems can be solved by using nickel-based filler wire due to its intermediate physical and mechanical properties. The selection of the proper filler metal is another vital issue in dissimilar welds joint that is also covered in this review article. The reason behind the formation of the unmixed zone, filler deficient region, peninsula, island, beach, migrated grain boundaries, solidified grain boundaries, and solidified subgrain boundaries during DWJ of martensitic P91/P92 and austenitic grade stainless steel is also discussed. The heat treatment is required to eliminate the heterogeneous microstructure during the dissimilar welding. The effect of post-weld heat treatment (PWHT) on the microstructure and mechanical behavior of the DWJ also reviewed. The residual stress developed during the DWJ may cause the premature failure of the components under service, has also been discussed in detail. The effect associated with the residual stress deformation has been reviewed in the different conditions of the DWJ.
... Very recently, the automated ball indentation (ABI) technique is widely exploited by some scholars as a nondestructive approach to determine the materials mechanical properties including the raw material as well as those in service [12][13][14]. Lee et al. [15] firstly suggested using ABI tests on the basis of continuum damage mechanics (CDM) theory to estimate fracture toughness of ductile materials. The applicability of the ABI technique was verified by crack tip opening displacement test results. ...
Machining-induced microstructure alteration in the machined surface layer possibly tends to result in the change of mechanical properties in this area that are different from the bulk material. It is very important to evaluate quantitatively mechanical properties of machined surface layer. In the present research, the nondestructive automated ball indentation (ABI) technique equipped with stress-strain microprobe system was employed to evaluate the mechanical properties of the machined surface layer generated by hard milling of AISI H13 steel. Through performing ABI tests, the mechanical properties including the true stress-strain curve, yield strength, ultimate tensile strength (UTS), strain hardening exponent and Brinell hardness were quantitatively acquired before and after hard milling. In addition, the fracture toughness can be determined by analyzing the continuous loading and unloading curves on the basis of the continuum damage mechanics (CDM). It indicates that the ABI technique can be exploited as a nondestructive technique for mechanical property evaluation of machined surface layer.
... Like every other heat transferring components, steam pipes are affected by thermal stresses and deformations that are developed due to temperature distribution, heat accumulation or dissipation and other thermal related quantities while in operation [1]. In spite of these, the increasing demand for energy has forced the power generation companies to increase the operating parameters of their plants such as the temperature and pressure [2]. The operating cycle of the steam pipe typically consist of a start-up phase followed by continuous high temperature operation under sustained load in the form of pressure and eventually shutdown [3]. ...
The thermo-mechanical stress, strain and temperature distribution across the thickness of X20 steam pipe at region less susceptible to thermo-mechanical failure was simulated using finite element analysis software, Abaqus. The mesh convergence studies conducted showed that 10 mm mesh size was suitable for the simulation. The temperature distribution profile across the thickness of Pyrogel showed that pyrogel is an excellent insulation jacket for steam pipes. The maximum stress value obtained from the simulation shows that the pipe is operating below the yield strength of X20 steel at the region under study. Hence, the pipe’s failure at this region due to thermo-mechanical stress or strain only is practically impossible over a long period of time. A deviation of 0.5% was found to exist between the analytical and simulated stress value obtained. This indicates a strong correlation between the simulated and analytical stress results.
... This means, there are different materials with those achieved similar P-h curves. Another study has been accomplished on the effect of heat treatments (normalizing and tempering) on mechanical properties of P92 steel using spherical indentation ( Barbadikar et al., 2015 ). Pile up influence in different tem peratures has been investigated and a new equation has been proposed for the high temperatures based on contact area ( Park et al., 2016 ). ...
To determine mechanical properties, instrumented indentation is a non-destructive one where traditional methods (such as tensile test) are not accessible. However, there are several serious challenges when trying to correctly use this technique. Here, a method to predict the steel stress-strain uniaxial curve is presented accompanied by an experimental verification. A wide range of Finite Element (FE) analyses using Vickers indentation were performed in order to generate an accurate equation. The experimental validation was followed by a general new procedure to achieve material properties by maximum precision and without any insight observation. Five dimensionless parameters obtained from the load-penetration (P-h) curve were used. Error function was constituted using a linear combination by these five. Genetic Algorithm (GA) was finally employed to estimate yield stress and strain-hardening exponent. A maximum of 4 percent error was observed between the stress-strain curves obtained by the macro indentation test and those determined by the conventional tensile test.
... The applied indentation loads and associated penetration depths are continuously monitored to obtain load depth curve which is then converted to true stress-true plastic strain values from a combination of elasticity and plasticity theories, and semi-empirical relationships. [10][11][12][13][14][15] Tabor [16] could correlate the relation between indentation diameter and average applied pressure. He proposed an empirical relationship, which correlates the plastic strain corresponding to uniaxial loading with plastic indentation strain corresponding to indentation loading using spherical indenter. ...
... The details of the conversion of load-depth to stressstrain and the empirical formulae used are given elsewhere. [10] The tests were carried out for two extreme tempering temperature and various test temperatures as mentioned in earlier section. The true stress-true plastic strain curves were obtained and analyzed for compliance correction with ABI software. ...
... For room temperature, the yield offset parameter is considered as zero whereas it is the function of test temperature and varies from 7 to 42 for test temperatures of 423 K to 923 K (150°C to 650°C). [10] C. Finite Element analysis ...
Ball indentation (BI) technique has been effectively used to evaluate the tensile properties with minimal volume of material. In the present investigation, BI test carried out on P92 steel (9Cr-0.5Mo-1.8W), using 0.76 mm diameter silicon nitride ball indenter was modeled using finite element (FE) method and analyzed. The effect of test temperature [300 K and 923 K (27 °C and 650 °C)], tempering temperature [1013 K, 1033 K, and 1053 K (740 °C, 760 °C, and 780 °C)], and coefficient of friction of steel (0.0 to 0.5) on the tensile strength and material pile-up was investigated. The stress and strain distributions underneath the indenter and along the top elements of the model have been studied to understand the deformation behavior. The tensile strength was found to decrease with increase in tempering and test temperatures. The increased pile-up around the indentation was attributed to the decrease in strain hardening exponent (n) with increase in the test temperature. The pile-up height determined from profilometry studies and FE analysis as well as the load depth curve from BI and FE analysis was in agreement. The maximum strain location below the indentation changes with the test temperature. Stress-strain curves obtained by conventional tensile, BI test, and representative stress-strain concepts of FE model were found exactly matching.
The impact of various heat treatment procedures on microstructure, dislocation density, hardness, tensile characteristics, and impact toughness of P92 steel was examined in the current experiment. The martensitic microstructure and average microhardness of 463 HV 0.2±8 HV 0.2 of the normalized steel were prevalent. A tempering procedure was carried out at 760 °C for a range of 2 hours to 6 hours. Additionally, an X‐ray diffraction examination was carried out, and the results were used to determine the dislocation density. The normalized sample was characterized by a high dislocation density. The dislocation density was decreased by tempering of normalized samples. With an increase in tempering time, the effect of the treatment coarsened the grains, precipitates, and decreased the area fraction of precipitates. After tempering, MX, M 23 C 6 , and M 7 C 3 types precipitates were found to have precipitated, according to energy dispersive spectroscopy and x‐ray diffraction research. The ideal tempering period was determined to be 4 hours at a tempering temperature of 760 °C based on the microstructure and mechanical characteristics. Steel that was tempered at 760 °C for 4 hours had a yield strength of 472 MPa, an ultimate tensile strength of 668.02 MPa, and an elongation of 26.05 %, respectively.
At the KIT a hybrid manufacturing concept for nuclear fusion First Walls is developed combining aspects of conventional and Additive Manufacturing (AM) technologies. The state of the art for ITER does not cover all specifications of a DEMO relevant First Wall. Thus, additional R&D-work has been initiated in terms of manufacturing. The AM technology basis used in the presented process combination is Cold Spray metal powder deposition applied in alternation with machining including the feature of filling grooves temporarily with a water-soluble granulate for creation of closed channels and cavities. Thus, the technology provides the option to manufacture shells with a thin gas tight membrane on top of previously machined structures. This membrane is used as pressure seal and makes the joining of shells by Hot Isostatic Pressing (HIP) into one monolithic body possible. This paper describes the manufacturing process and recalls differences and common aspects with regard to conventional concepts of First Wall manufacturing. The achievement of Technology Readiness Level TRL 3 by mechanical qualification and comparison of the results to other HIP joint experiments is also demonstrated. Finally, an outlook is given concerning integration options of the technology into manufacturing of shells with cooling channel structures using Oxide Dispersion Strengthened (ODS) materials.
