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This study examines the design and numerical analysis of induction hardened of Inconel 718 superalloys on the tensile properties. The two tensile specimens (IHT1 & IHT2)'s outside surfaces are heated to temperatures of 850 and 1000 °C. The heated samples are then quenched in oil. The samples are evaluated utilizing a 250kN capacity servo hydraulic universal test at ambient temperature and an enhanced temperature of 800 °C. At both room temperature and a raised temperature of 800 °C, the metrics yield strength (YS), ultimate tensile strength (UTS), and elongation of induction hardened sample have risen. Induction-hardened materials have better mechanical characteristics than non-induction-hardened samples, according to numerical results from ANSYS Workbench that are corroborated with experimental data. The results of the tensile test's cracked surfaces under a scanning electron microscope (SEM) show that the presence of shallow dimple structure at 800 °C caused transgranular cleavage and intergranular dimple rupture as the modes of failure. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effect of grain size of an initial microstructure (pearlite + ferrite) on a resulting microstructure of induction-hardened microalloyed steel 38MnVS6, which is one topical medium carbon vanadium microalloyed non-quenched and tempered steel used in manufacturing crankshafts for high-power engines. The results show that a coarse initial microstructure could contribute to the incomplete transformation of pearlite + ferrite into austenite in reaustenitization transformation by rapid heating, and the undissolved ferrite remains and locates between the neighboring prior austenite grains after the induction-hardening process. As the coarseness level of the initial microstructure increases from 102 μm to 156 μm, the morphology of undissolved ferrite varies as granule, film, semi-network, and network, in sequence. The undissolved ferrite structures have a thickness of 250–500 nm and appear dark under an optical metallographic view field. To achieve better engineering applications, it is not recommended to eliminate the undissolved ferrite by increasing much heating time for samples with coarser initial microstructures. It is better to achieve a fine original microstructure before the induction-hardening process. For example, microalloying addition of vanadium and titanium plays a role of metallurgical grain refinement via intragranular ferrite nucleation on more sites, and the heating temperature and time of the forging process should be strictly controlled to ensure the existence of fine prior austenite grains before subsequent isothermal phase transformation to pearlite + ferrite. [ABSTRACT FROM AUTHOR]

The research was aimed at investigating effective methods of surface strengthening of the working bodies of agricultural machines to increase their wear resistance and extend their service life. The study used surface hardening methods such as heat treatment, chemical and thermal processes, coatings, and mechanical methods. It has been shown that various methods of surface hardening significantly increase the wear resistance of working parts of agricultural machinery. The use of such heat treatment as induction hardening increased the resistance to wear due to localised heating and rapid cooling, which led to an increase in the hardness of the material. Chemical and heat treatment, including carburisation, nitrocementation and nitration, showed a significant improvement in surface layer hardness and increased corrosion resistance. Mechanical methods such as shot blasting and roller hardening have increased hardness and wear resistance by 30-50% due to plastic surface deformation. It has been proven that the use of surfacing and coatings of physical vapour deposition/chemical vapour deposition increases the durability of parts by 20-40%, which reduces operating costs and increases the productivity of agricultural machinery. The study examined approaches to enhancing the wear resistance of agricultural machinery’s working parts, highlighting a notable issue: Ukrainian agricultural machinery often exhibits a shorter service life (1.2-2 times less) compared to imported counterparts. The analysis focuses on the reasons behind the wear and deterioration of cultivator teeth, with particular emphasis on how wear affects the size and shape of the working parts, resulting in decreased efficiency. The surface strengthening methods under study can be directly implemented in production to increase the durability and reliability of working parts of agricultural machinery, which would help to increase their efficiency and reduce operating costs

The article considers combined methods of restoration and hardening of massive metalworking and tillage tools, which involve both induction hardening or surfacing and plasma surface treatment. The methods increase not only the hardness and wear resistance of the tool material, but also its toughness and crack resistance, which is not achieved by traditional methods of surface hardening. [ABSTRACT FROM AUTHOR]

Progressive induction hardening is an in-line steel heat treatment method commonly used to surface harden powertrain components. It produces a martensitic case layer with a sharp transition zone to the base material. This rapid process will induce large residual stresses, where a compressive state in the case layer will shift to a tensile state in the transition zone. For fatigue performance, it is important to quantify the magnitude and distribution of these stresses, and moreover how they depend on material and processing parameters. In this work, x-ray diffraction in combination with a layer removal method is used for efficient and robust quantification of the subsurface stress state, which combines electropolishing with either turning or milling. Characterization is done on C45E steel samples that were progressively induction hardened using either a fast or slow (27.5 or 5 mm/s, respectively) scanning speed. The results show that although the hardening procedures will meet arbitrary requirements on surface hardness, case depth and microstructure, the subsurface tensile stress peak magnitude is doubled when using a fast scanning speed. However, the near-surface compressive residual stresses are comparable. In addition, the subsurface tensile residual stress peak is compared with the on-surface tensile stresses in the fade-out zone. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Historically, steels with carbon contents above about 0.45% C that are quenched to attain hardness above about 53 HRC (560 HV) are prone to brittle intergranular fracture when stressed in uniaxial or cyclic tension. In this study, five laboratory-melted steels containing nominally higher 0.56% C, additions of Mn, Mo, Ni, or W, and no grain refining additions (Ti, Al, V, or Nb) were heat treated on a Gleeble 3500® simulator to emulate thermal heating and quenching cycles for both induction surface hardening and conventional through thickness heat treatment. Rapid heating at 50 °C/s and limiting the peak heating temperatures and times to 950 °C and 10 s produced a very fine austenite grain size (AGS) as small as 10 µm with a final hardness above 60HRC (700HV) and additions of Mo. Ni or W further refined the AGS to as small as 5 µm for the rapid heating. Fracture resistance measured by the peak breaking load (PBL) in notched bend tests increased by up to threefold for the short low-temperature heating cycles as compared to longer time (1000 s) higher-temperature (1050 °C) cycles. Fracture surfaces showed transgranular crack propagation for the short low-temperature cycles as compared to intergranular fracture for the longer higher-temperature cycles. The addition of 0.56 wt. pct W was especially effective for reducing AGS and PBL, and the addition of 2.12 wt. pct Ni increased the PBL for most of the heat treatment conditions. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The research was aimed at investigating effective methods of surface strengthening of the working bodies of agricultural machines to increase their wear resistance and extend their service life. The study used surface hardening methods such as heat treatment, chemical and thermal processes, coatings, and mechanical methods. It has been shown that various methods of surface hardening significantly increase the wear resistance of working parts of agricultural machinery. The use of such heat treatment as induction hardening increased the resistance to wear due to localised heating and rapid cooling, which led to an increase in the hardness of the material. Chemical and heat treatment, including carburisation, nitrocementation and nitration, showed a significant improvement in surface layer hardness and increased corrosion resistance. Mechanical methods such as shot blasting and roller hardening have increased hardness and wear resistance by 30-50% due to plastic surface deformation. It has been proven that the use of surfacing and coatings of physical vapour deposition/chemical vapour deposition increases the durability of parts by 20-40%, which reduces operating costs and increases the productivity of agricultural machinery. The study examined approaches to enhancing the wear resistance of agricultural machinery's working parts, highlighting a notable issue: Ukrainian agricultural machinery often exhibits a shorter service life (1.2-2 times less) compared to imported counterparts. The analysis focuses on the reasons behind the wear and deterioration of cultivator teeth, with particular emphasis on how wear affects the size and shape of the working parts, resulting in decreased efficiency. The surface strengthening methods under study can be directly implemented in production to increase the durability and reliability of working parts of agricultural machinery, which would help to increase their efficiency and reduce operating costs. [ABSTRACT FROM AUTHOR]

Axle shafts, which are an important part of the vehicle's powertrain system, transfer the torque to the wheels and enable the vehicle to move. In this respect, the design of the axle shaft to be used in a new vehicle is of great importance for vehicle manufacturers. When a cylindrical shaft is torsionally loaded, the shear stress is highest at the surface of component and zero at the center. Therefore, these axle shafts are exposed to an induction hardening process that enables only this superficial case to have its properties changed, remaining the core zone with its material original characteristics. Current study presents the results of a project aimed at developing and evaluating the fatigue life of axle shaft that belongs to a commercial vehicle. Developments were made on the existing axle and the results were examined using experimental tests and finite element analysis method. In line with the improvements made, the developed axle shaft has 331.7% more fatigue life than the existing axle, while the cost is 24% lower. According to these results, more attention must be paid to material selection, induction hardening process, stress concentration and surface condition of axle shaft in the design. This study involves many disciplines such as design, manufacturing, analysis, testing, etc. It is very important to ensure communication between all these disciplines in the production of the product. The output obtained from one discipline becomes the input of another discipline. In the cumulative sum of all these inputs, the optimum level of parts is obtained. For this reason, this study, which processes all these disciplines together, is very valuable. [ABSTRACT FROM AUTHOR]

Higher carbon 1060 steel can be completely transformed to austenite at 850, a 100 °C lower temperature than that for conventionally used 1045 steel, allowing development of very small austenite grains during induction hardening. Torsion fatigue test specimens were machined from quenched and tempered martensite and as hot-rolled pearlitic bars of 1060 steel. Specimens from both initial conditions were induction hardened to a 3 mm case depth with peak surface temperatures of 1050 and 850 °C followed by tempering at 176 °C. Specimens were fatigue tested in torsion at R = 0.1 and peak stresses of 1222 to 1444 MPa, corresponding to 49 to 58% of the estimated shear ultimate strength and fatigue lives of 104 to 106 cycles. The fractures for all conditions except three of the 1050 °C pearlite specimens were initiated as small longitudinal cracks in shear (Mode III) at the surface and showed a Mode I (tensile) fatigue zone on a 45-degree spiral plane followed by rapid fracture. Microstructures were evaluated by light optical and scanning electron microscopy and by Mossbauer spectroscopy. Surface residual stresses were determined by x-ray measurements and found to be lower for the 850 °C cycle. The pearlitic as-rolled microstructure resulted in a higher case hardness and a more abrupt case to core hardness transition, but lower fatigue life as compared to the quenched and tempered martensitic microstructure. The initial martensitic microstructure and higher peak induction hardening temperature resulted in a higher surface compressive residual stress and the longest low cycle torsional fatigue life. The 850 °C peak induction temperature for the QT 850 condition produced a very small prior austenite grain size (3 µm) that contributed to a long fatigue life, but a lower compressive residual stress that partially offset the benefit of the small austenite grain size. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effect of grain size of an initial microstructure (pearlite + ferrite) on a resulting microstructure of induction-hardened microalloyed steel 38MnVS6, which is one topical medium carbon vanadium microalloyed non-quenched and tempered steel used in manufacturing crankshafts for high-power engines. The results show that a coarse initial microstructure could contribute to the incomplete transformation of pearlite + ferrite into austenite in reaustenitization transformation by rapid heating, and the undissolved ferrite remains and locates between the neighboring prior austenite grains after the induction-hardening process. As the coarseness level of the initial microstructure increases from 102 μm to 156 μm, the morphology of undissolved ferrite varies as granule, film, semi-network, and network, in sequence. The undissolved ferrite structures have a thickness of 250–500 nm and appear dark under an optical metallographic view field. To achieve better engineering applications, it is not recommended to eliminate the undissolved ferrite by increasing much heating time for samples with coarser initial microstructures. It is better to achieve a fine original microstructure before the induction-hardening process. For example, microalloying addition of vanadium and titanium plays a role of metallurgical grain refinement via intragranular ferrite nucleation on more sites, and the heating temperature and time of the forging process should be strictly controlled to ensure the existence of fine prior austenite grains before subsequent isothermal phase transformation to pearlite + ferrite.

JIS SUJ2 steel is most widely used in bearing steel. The advantages are good hardenability, excellent fatigue, wear resistance and comprehensive mechanical properties. The wear resistance and fatigue resistance of this steel are attracting more attention, and the residual stress state and its distribution on the surface of the heat affected zone are critical factors affecting the fatigue life and wear resistance of the parts. In this study, SUJ2 is used as a material by which to study the surface residual stress and retained austenite distribution of induction-hardened steel. Quenching and tempering treatments were used to obtain different microstructures and an induction method was used to re-quench the case region. After the heat treatment, the residual stress and retained austenite volume on the surface were analyzed by X-ray diffraction and analyses of the microstructure and the hardness were also conducted. The results show that the microstructure after heat treatment contains unsolved carbides, tempered martensite and retained austenite. In the induction-hardened area, the residual stress is all compressive, and the values are more than −750 MPa. In conclusion, the microstructures of the specimens before induction hardening have a significant impact on the effective case depth for the same output power condition and the surface residual stress changes from a tensile to a compressive state. In the induction-hardened area, the maximum of the residual compressive stress was increased as the austenitized temperature of quenching increased. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Straightening has to be carried out in order to ensure the straightness of a shaft, as distortions exceed the tolerance limit. Since the straightening load is typically large enough to produce plastic and residual deformation, repeated straightening loading cycles are very likely to induce cracks or fractures on the case-hardened shaft surface. In this study, in order to minimize repeated straightening cycles, an analytical straightening model is developed which calculates optimum stroke displacements corresponding to measured straightness errors so as to achieve the desired residual deflections and eliminate straightness errors. First, the hardness variation in the shaft radial direction is considered in the analytical model. Then, the proposed theoretical model is validated by numerical simulations. The results suggest that the analytically predicted stroke displacements and residual deflections agree very well with the numerical results when using induction-hardened SAE 4140 steel, and this signifies that the analytical straightening model developed in this study is capable of providing predictions of straightening stokes.

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the service behavior of gears, surface heat treatments such as nitriding or induction hardening can be performed. Since these processes are limited in their achievable maximum hardness or depth of hardness, a combination treatment could allow benefits from the advantages of both processes. The aim of this work was to show the correlation between the microstructure resulting from combination treatment and the performance of the surface layer using the example of wear behavior. The investigations focused on the impact of different nitrided states, in the combination treatment of the material EN31CrMoV9, on wear resistance. The wear was evaluated after running the two-disc test gravimetrically and optically. Nitrided-only specimens showed better wear resistance compared to those subjected to induction hardening after nitriding. Substantial differences in weight loss indicate that induction hardening worsens the wear behavior. The variants with the compound layer removed in the nitride-only state as well as in the induction hardened state showed a better wear behavior compared to the respective conditions with a compound layer. This was attributed to the lower surface roughness and the higher hardness due to less retained austenite after combination treatment. [ABSTRACT FROM AUTHOR]

This paper presents the development of a piece of induction hardening equipment based on the foundations of the design, starting from zero. It was intended for steels in general, and was tested on unalloyed low- and medium-carbon steels, whereas the results for EN 1C60 steel are shown in this study. The EN 1C60 steel showed average results, and was chosen as a representative of a wider group of engineering steels. The main objective of this work was to develop a flexible system for mild steel hardening that can be used for various hardening depths and steel types. The system design's priorities were the use of standard electronic components to avoid supply chain disruptions and to achieve high energy efficiency. The construction of the prototype in full detail is also presented. The optimal process parameters are listed, as well as the procedure of their obtaining by using the appropriate simulation method. The key parameters were adjusted in consecutive steps. This study resulted in high matching between the model predictions and experimental results. The basic goal of this research was achieved, with the system having a minimum energy efficiency of 75.3%, a most frequent energy efficiency of 90% and a maximum energy efficiency of 95.1%. [ABSTRACT FROM AUTHOR]

Conditions of industrial production introduce additional complexities while attempting to solve optimization problems of material technology processes. The complexity of the physics of such processes and the uncertainties arising from the natural variability of material parameters and the occurrence of disturbances make modeling based on first principles and modern computational methods difficult and even impossible. In particular, this applies to designing material processes considering their quality criteria. This paper shows the optimization of the rack bar induction hardening operation using the response surface methodology approach and the desirability function. The industrial conditions impose additional constraints on time, cost and implementation of experimental plans, so constructing empirical models is more complicated than in laboratory conditions. The empirical models of nine system responses were identified and used to construct a desirability function using expert knowledge to describe the quality requirements of the hardening operation. An analysis of the hypersurface of the desirability function is presented, and the impossibility of using classical gradient algorithms during optimization is empirically established. An evolutionary strategy in the form of a floating-point encoded genetic algorithm was used, which exhibits a non-zero probability of obtaining a global extremum and is a gradient-free method. Confirmation experiments show the improvement of the process quality using introduced measures. [ABSTRACT FROM AUTHOR]

This work presents an interpretability study with XAI tools to explain an XGBoost model for hardness prediction in the simultaneous double-frequency induction hardening. Experiments were carried out on C45 steel spur-gear. In order to explain the model, firstly, the built-in tool of the XGBoost library was used to interpret the feature importance. Then, a more advanced approach with the SHAP library was employed to highlight local and global explanations. Finally, the implementation of an interpretable surrogate model allowed to illustrate rules for prediction, making the explanation, although approximate, clear. This study proposes a relevant approach of AI to explain the results obtained by black box models which is currently a major element for the industry allowing to justify the quality of the results in a clear way. It is concluded that the model is consistent with physical principles. [ABSTRACT FROM AUTHOR]

This research was carried out with the aim of obtaining appropriate principles for describing the influence of working parameters and the aggressive action of an acidic medium on the wear and corrosion resistance of martensitic stainless steels. Tribological tests were performed on induction-hardened surfaces of stainless steels X20Cr13 and X17CrNi16-2 under combined wear conditions at a load of 100 to 300 N and a rotation speed of 382 to 754 min−1. The wear test was carried out on a tribometer with the use of an aggressive medium in the chamber. After each wear cycle on the tribometer, the samples were exposed to corrosion action in a corrosion test bath. Analysis of variance revealed a significant influence of rotation speed and load due to wear on the tribometer. Testing the difference in the mass loss values of the samples due to corrosion using the Mann–Whitney U test did not show a significant effect of corrosion. Steel X20Cr13 showed greater resistance to combined wear, which had a 27% lower wear intensity compared to steel X17CrNi16-2. The increase in wear resistance of X20Cr13 steel can be attributed to the higher surface hardness achieved and the effective depth of hardening. The mentioned resistance is the result of the creation of a martensitic surface layer with dispersed carbides, which increases the resistance to abrasion, dynamic durability, and fatigue of the surface of the protective layer. [ABSTRACT FROM AUTHOR]

Straightening has to be carried out in order to ensure the straightness of a shaft, as distortions exceed the tolerance limit. Since the straightening load is typically large enough to produce plastic and residual deformation, repeated straightening loading cycles are very likely to induce cracks or fractures on the case-hardened shaft surface. In this study, in order to minimize repeated straightening cycles, an analytical straightening model is developed which calculates optimum stroke displacements corresponding to measured straightness errors so as to achieve the desired residual deflections and eliminate straightness errors. First, the hardness variation in the shaft radial direction is considered in the analytical model. Then, the proposed theoretical model is validated by numerical simulations. The results suggest that the analytically predicted stroke displacements and residual deflections agree very well with the numerical results when using induction-hardened SAE 4140 steel, and this signifies that the analytical straightening model developed in this study is capable of providing predictions of straightening stokes. [ABSTRACT FROM AUTHOR]

The experiment was focused on comparison of mass loss exhibited by induction-hardened and gas-nitrided samples made of 42CrMo4 steel. The mass loss was caused by abrasive wear, i.e. by motion of the abrasive particles. Wear testing was performed with different input parameters (sample velocity and impact angle of abrasive particles and the tested surface). This experiment proceeded with metallographic analysis performed by an optical microscope and by imaging of wear path done by scanning electron microscopy (SEM), to conclude with the statistical analysis of obtained data. The conducted experiment determined that the gas-nitrided samples lost less mass at all levels of input parameters than the induction-hardened samples.

The effects of induction quenching with different current frequency on the surface hardness， tooth root hardness， tooth core hardness， hardness gradient and metallography of gear shafts are analyzed and discussed by carburizing， tempering and induction quenching experiments of heavy-duty gear shafts. The results show that carburizing， quenching and tempering and induction quenching of 18Cr2Ni4WA steel gear shafts can effectively improve the surface hardness of the workpiece to more than 58 HRC， and improve the hardness gradient value of hardened layer. Improve the metallographic structure of hardened layer， and ensure the best hardness of the tooth core， so as to increase the bending fatigue strength of gear shafts. Therefore， a heat treatment method is provided for the low carbon alloy steel gear material containing more Cr， Ni， W and Mo after carburizing， which can improve the product quality.

Inverse problems can be challenging and interesting to study in the context of metallurgical processes. This work aims to carry out a method for inverse modeling for simultaneous double-frequency induction hardening process. In this investigation, the experimental measured hardness profiles were considered as input data, while the output data were the process parameters. For this purpose experiments were carried out on C45 steel spur-gear. The method is based on machine learning algorithms and data treatment for dealing with inverse approach issues. In addition to the inverse modeling, a forward problem-based verification completes the study. It was found that according to promising results that this method is suitable and applicable for inverse problem of hardness modeling. [ABSTRACT FROM AUTHOR]

Induction hardening is a heat surface treatment technique widely employed for steel components in order to improve their fatigue life without affecting the metallurgy of the bulk material. The control of the treated components goes through the prediction and the optimization of the induction hardening process parameters. The aim of this work is to propose an approach based on artificial intelligence technique to predict the in-depth hardness profile. For this purpose, experimental tests were first carried out on 300M steel bar and C45 steel spur-gear under single and double frequencies, respectively. Intermediate variables were then generated to be used as input data. Data-driven model based on XGBoost library was finally developed. It was found that the proposed approach predicts with good agreement the hardness profiles and can be used in induction treatment process optimization. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The experiment was focused on comparison of mass loss exhibited by induction-hardened and gas-nitrided samples made of 42CrMo4 steel. The mass loss was caused by abrasive wear, i.e. by motion of the abrasive particles. Wear testing was performed with different input parameters (sample velocity and impact angle of abrasive particles and the tested surface). This experiment proceeded with metallographic analysis performed by an optical microscope and by imaging of wear path done by scanning electron microscopy (SEM), to conclude with the statistical analysis of obtained data. The conducted experiment determined that the gas-nitrided samples lost less mass at all levels of input parameters than the induction-hardened samples. [ABSTRACT FROM AUTHOR]

High-speed steels (HSS) such as AISI M2 are generally used for cutting and forming tools or broaches with the highest demands on load bearability and hot-hardness. The requirements for high-speed steels are, on the one hand, extremely high hardnesses of over 800–900 HV and, on the other hand, the thermal stability of the microstructure up to 500 °C. This combination is achieved by complex precipitation-hardenable iron-based alloys. Common heat treatment practices for high-speed steels use salt baths or vacuum ovens, which are energetically unfavorable and require subsequent cleaning. The study consists of short-time hardening and short-time tempering on a laboratory scale by means of dilatometry and thereupon an implementation in an industrial induction hardening machine. The laboratory scale experiments demonstrate the feasibility of bringing sufficient alloying elements into solution by means of several heat treatment cycles despite short holding times of 1 s and less. Combined tests of short time hardening and tempering show a hardness of up to 850 HV10 that are competitive with the conventional heat treatment route. First attempts to transfer the process to an industrial setup exhibit some peculiarities in the process control, but reveal promising results with a surface hardness of up to 750 HV10.

JIS SUJ2 steel is most widely used in bearing steel. The advantages are good hardenability, excellent fatigue, wear resistance and comprehensive mechanical properties. The wear resistance and fatigue resistance of this steel are attracting more attention, and the residual stress state and its distribution on the surface of the heat affected zone are critical factors affecting the fatigue life and wear resistance of the parts. In this study, SUJ2 is used as a material by which to study the surface residual stress and retained austenite distribution of induction-hardened steel. Quenching and tempering treatments were used to obtain different microstructures and an induction method was used to re-quench the case region. After the heat treatment, the residual stress and retained austenite volume on the surface were analyzed by X-ray diffraction and analyses of the microstructure and the hardness were also conducted. The results show that the microstructure after heat treatment contains unsolved carbides, tempered martensite and retained austenite. In the induction-hardened area, the residual stress is all compressive, and the values are more than −750 MPa. In conclusion, the microstructures of the specimens before induction hardening have a significant impact on the effective case depth for the same output power condition and the surface residual stress changes from a tensile to a compressive state. In the induction-hardened area, the maximum of the residual compressive stress was increased as the austenitized temperature of quenching increased.

Dimensional distortions can manifest themselves significantly in carbon steel components, such as SAE 1050 steel, after quenching heat treatment, due to their low hardenability. The cooling rate is a quenching process parameter that can be controlled to minimize this inconvenience. Solutions containing PAG (polyalkylene glycol) can be used for cooling in the quenching process, allowing to control the severity of the cooling as a function of the amount of PAG in the solution. The studied automotive component is located at one end of the CV joint, which is mounted next to the vehicle's wheel hub. The assembly region on the wheel hub has extremely tight dimensional specifications, which makes it even more challenging to meet the design requirements, when it is a carbon steel without the addition of alloying elements. The present study target to evaluate the different concentrations of PAG as a cooling means, and the influence on the dimensional distortions of an induction-hardened SAE 1050 steel shaft end. For this, concentrations of 5%, 10% and 15% of PAG were used, and dimensional distortions were evaluated by measuring the diameter at three points of the piece aligned in the longitudinal direction after induction hardening, as well as measurements of the hardened case depth (Vickers hardness) and microstructure. [ABSTRACT FROM AUTHOR]

A non-destructive verification method was explored in this work using the Barkhausen noise (BN) method for induction hardening depth measurements. The motive was to investigate the correlation between the hardness depth, microstructure, and the Barkhausen noise signal for an induction hardening process. Steel samples of grade C45 were induction-hardened to generate different hardness depths. Two sets of samples were produced in two different induction hardening equipment for generating the model and verification. The produced samples were evaluated by BN measurements followed by destructive verification of the material properties. The results show great potential for the several BN parameters, especially the magnetic voltage sweep slope signal, which has strong correlation with the hardening depth to depth of 4.5 mm. These results were further used to develop a multivariate predictive model to assess the hardness depth to 7 mm, which was validated on an additional dataset that was holdout from the model training. [ABSTRACT FROM AUTHOR]

• Specimens were induction hardened under three types of processing parameters and their microstructural characters were analyzed. • Electrical discharge machined (EDM) notches and impact craters were introduced on specimens to simulate actual defects on railway axles. • Failure mechanisms of specimens under different heat treatments were analyzed in both macro and micro aspects. • Influence of heat treatments on fatigue behavior of specimens was analyzed considering damage type, defect size and residual stress. The safety of heavy-duty freight railway axles is threatened by defects, including inclusions, corrosion pits, fretting cracks and foreign object impact damages. Accordingly, surface strengthening techniques are applied to reduce the detrimental effect of defects on the structural integrity of railway axles. This work studied the effectiveness of heat treatment, in which the specimens machined from a heavy-duty freight railway axle were induction hardened under three types of processing parameters and tempered. The fatigue strengths of specimens with electrical discharge machined (EDM) notches and impact craters on their surfaces were tested. The fatigue behavior of induction-hardened (IH) specimens was compared with that of as-received (AR) specimens and fully-quenched (FH) specimens. The fatigue limit of smooth IH specimens is close to that of FH specimens while almost twice as much as that of AR specimens. Inclusions were found on the crack initiation sites on the surface or subsurface of AR and FH specimens. For IH specimens, the crack initiation sites moved to the zone between the case and the core. Fatigue strengths of IH and FH specimens decline with increasing EDM notch size but remain higher than AR specimens'. The influence of impact damage on fatigue properties depends on damage size and heat treatment process. [ABSTRACT FROM AUTHOR]

To improve the service behavior of gears, surface heat treatments such as nitriding or induction hardening can be performed. Since these processes are limited in their achievable maximum hardness or depth of hardness, a combination treatment could allow benefits from the advantages of both processes. The aim of this work was to show the correlation between the microstructure resulting from combination treatment and the performance of the surface layer using the example of wear behavior. The investigations focused on the impact of different nitrided states, in the combination treatment of the material EN31CrMoV9, on wear resistance. The wear was evaluated after running the two-disc test gravimetrically and optically. Nitrided-only specimens showed better wear resistance compared to those subjected to induction hardening after nitriding. Substantial differences in weight loss indicate that induction hardening worsens the wear behavior. The variants with the compound layer removed in the nitride-only state as well as in the induction hardened state showed a better wear behavior compared to the respective conditions with a compound layer. This was attributed to the lower surface roughness and the higher hardness due to less retained austenite after combination treatment.

This paper presents the development of a piece of induction hardening equipment based on the foundations of the design, starting from zero. It was intended for steels in general, and was tested on unalloyed low- and medium-carbon steels, whereas the results for EN 1C60 steel are shown in this study. The EN 1C60 steel showed average results, and was chosen as a representative of a wider group of engineering steels. The main objective of this work was to develop a flexible system for mild steel hardening that can be used for various hardening depths and steel types. The system design’s priorities were the use of standard electronic components to avoid supply chain disruptions and to achieve high energy efficiency. The construction of the prototype in full detail is also presented. The optimal process parameters are listed, as well as the procedure of their obtaining by using the appropriate simulation method. The key parameters were adjusted in consecutive steps. This study resulted in high matching between the model predictions and experimental results. The basic goal of this research was achieved, with the system having a minimum energy efficiency of 75.3%, a most frequent energy efficiency of 90% and a maximum energy efficiency of 95.1%.

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The factors of affecting crankshaft torsional fatigue strength and the causes of various torsional failure were analyzed by torsional fatigures test of crankshafts, and the corresponding improvement measures were put forward. It was pointed out that with the increase of engine explosion pressure, the torque of crankshafts increases accordingly, which leads to the increase of crankshaft torsional fatigue failures. The main torsional failure locations include pin journal oil hole, crank arm and pin journal bottom center of the crankshafts. The causes of failure are related to structural design, raw materials, machining, heat treatment and so on. The oil holes of pin journal are the most common part of torsional fatigue failures, and the crack sources are generally about 8~10 mm from the inner walls of oil holes to the journal surfaces. The torsional fatigue strength of crankshafts is more affected by induction hardening on the journal surfaces. The torsional fatigue strength of crankshaft reduces about 30% by surface induction hardening. The torsional fatigue strength of surface hardening crank shafts is increased more than 25% by polishing the internal surfaces of the oil holes. [ABSTRACT FROM AUTHOR]

Conditions of industrial production introduce additional complexities while attempting to solve optimization problems of material technology processes. The complexity of the physics of such processes and the uncertainties arising from the natural variability of material parameters and the occurrence of disturbances make modeling based on first principles and modern computational methods difficult and even impossible. In particular, this applies to designing material processes considering their quality criteria. This paper shows the optimization of the rack bar induction hardening operation using the response surface methodology approach and the desirability function. The industrial conditions impose additional constraints on time, cost and implementation of experimental plans, so constructing empirical models is more complicated than in laboratory conditions. The empirical models of nine system responses were identified and used to construct a desirability function using expert knowledge to describe the quality requirements of the hardening operation. An analysis of the hypersurface of the desirability function is presented, and the impossibility of using classical gradient algorithms during optimization is empirically established. An evolutionary strategy in the form of a floating-point encoded genetic algorithm was used, which exhibits a non-zero probability of obtaining a global extremum and is a gradient-free method. Confirmation experiments show the improvement of the process quality using introduced measures.

This research was carried out with the aim of obtaining appropriate principles for describing the influence of working parameters and the aggressive action of an acidic medium on the wear and corrosion resistance of martensitic stainless steels. Tribological tests were performed on induction-hardened surfaces of stainless steels X20Cr13 and X17CrNi16-2 under combined wear conditions at a load of 100 to 300 N and a rotation speed of 382 to 754 min−1. The wear test was carried out on a tribometer with the use of an aggressive medium in the chamber. After each wear cycle on the tribometer, the samples were exposed to corrosion action in a corrosion test bath. Analysis of variance revealed a significant influence of rotation speed and load due to wear on the tribometer. Testing the difference in the mass loss values of the samples due to corrosion using the Mann–Whitney U test did not show a significant effect of corrosion. Steel X20Cr13 showed greater resistance to combined wear, which had a 27% lower wear intensity compared to steel X17CrNi16-2. The increase in wear resistance of X20Cr13 steel can be attributed to the higher surface hardness achieved and the effective depth of hardening. The mentioned resistance is the result of the creation of a martensitic surface layer with dispersed carbides, which increases the resistance to abrasion, dynamic durability, and fatigue of the surface of the protective layer.

Inverse problems can be challenging and interesting to study in the context of metallurgical processes. This work aims to carry out a method for inverse modeling for simultaneous double-frequency induction hardening process. In this investigation, the experimental measured hardness profiles were considered as input data, while the output data were the process parameters. For this purpose experiments were carried out on C45 steel spur-gear. The method is based on machine learning algorithms and data treatment for dealing with inverse approach issues. In addition to the inverse modeling, a forward problem-based verification completes the study. It was found that according to promising results that this method is suitable and applicable for inverse problem of hardness modeling.

Induction hardening is widely used in the industry as a surface heat treatment that improves the surface and the subsurface hardness of components greatly. The hardened case, which usually is a few mm, highly impacts the surface and structural integrity of the component. In this work, we simulate the scanning induction hardening process by means of finite element modeling. The computed hardness, microstructure, and residual stress profile are compared with experimentally measured data using several surface and subsurface characterization techniques. A very good agreement is found between the simulated and experimentally measured residual stresses, which were characterized by the incremental hole drilling technique. [ABSTRACT FROM AUTHOR]

Induction Hardening (IH) process contributes to the improvement of the mechanical properties of the steel. In this application, the inverter operates at resonant frequency for high operating performances. However, this is usually accompanied by steel characteristics variation under temperature effect especially the magnetic permeability. This paper proposes two approaches for resonance frequency adaptation. The first is based on maximum efficiency tracking (MET) scheme. In this context, simulation with an algorithm for control is developed to find in real-time the adequate frequency based on current and voltage sensor. This approach is found effective but requires a constant determination of the input and the output power. Hence, it makes it difficult for implementation. To alleviate this drawback, advanced technique based on deep learning (DL) algorithm is proposed. Thus, an experimental prototype is built to determine the experimental Temperature-Frequency data profiles up to the hardening for two metal bars. Hence, a neural network (NN) based model control is elaborated. After a careful selection of NN parameters, a trained model is obtained with satisfactory accuracy leading to the predict model. This was easily implemented in real time on raspberry pi 3 + and allows the system to perform continuously under high efficiency for hardening purposes.

The paper presents methods to increase the service life of some subassemblies of the heat exchangers of thermal power plants. The phenomenon of cavitation, wear or corrosion are effects of the operating conditions of these subassemblies (pipes, valves, valves, elbows, connections, cooling systems). With a set of properly applied heat treatments, the service life can be increased by 70-80%. Simple or Duplex heat treatments were applied to samples taken from such obsolete subassemblies, after which wear tests were performed, the results being significant. [ABSTRACT FROM AUTHOR]

A non-destructive verification method was explored in this work using the Barkhausen noise (BN) method for induction hardening depth measurements. The motive was to investigate the correlation between the hardness depth, microstructure, and the Barkhausen noise signal for an induction hardening process. Steel samples of grade C45 were induction-hardened to generate different hardness depths. Two sets of samples were produced in two different induction hardening equipment for generating the model and verification. The produced samples were evaluated by BN measurements followed by destructive verification of the material properties. The results show great potential for the several BN parameters, especially the magnetic voltage sweep slope signal, which has strong correlation with the hardening depth to depth of 4.5 mm. These results were further used to develop a multivariate predictive model to assess the hardness depth to 7 mm, which was validated on an additional dataset that was holdout from the model training.

Gears of module 2.5 from steel EN24 are studied after induction hardening at different powers (30 – 55 W). The effect of the hardening on the microstructure, microhardness, residual stresses and distortion of the geometry of the gears is determined. The hardening mode providing minimum distortion of the gear size is suggested. [ABSTRACT FROM AUTHOR]