9Cr-1Mo Steel Research Articles

Microstructural Characteristics and Properties of Laser-Welded Diamond Saw Blade with 30CrMo Steel.

In order to enhance the quality of diamond composite materials, this work employs a Cu-Co-Fe and Ni-Cr-Cu pre-alloyed powder mixture as a transition layer, and utilizes laser-welding technology for saw blade fabrication. By adjusting the laser-welding process parameters, including welding speed and welding power, well-formed welded joints were achieved, and the microstructure and mechanical properties of the welded joints were investigated. The results demonstrate that the best welding performance was achieved at a laser power of 1600 W and a welding speed of 1400 mm/min, with a remarkable tooth engagement strength of up to 819 MPa. The fusion zone can be divided into rich Cu phase and rich Fe phase regions, characterized by coarse grains without apparent preferred orientation. The microstructure of the heat-affected zone primarily consists of high-hardness brittle quenched needle-like martensite, exhibiting a sharp increase in microhardness up to 550 HV. Fracture occurred at the boundary between the fusion zone and the heat-affected zone of the base material, where stress concentration was observed. By adjusting the welding parameters and transition layer materials, the mechanical properties of the joints were improved, thereby achieving a reliable connection between diamond composite materials and the metal substrate.

Multi-physical simulation of an inductive heat treatment process on 50CrMo4 steel rods and validation by HEXRD cross-sectional measurements

A multi-physical finite element model for the induction hardening of a 50CrMo4 steel rod was implemented in Abaqus, including an electromagnetic, thermal, mechanical, and metallurgical model describing the individual phenomena taking place during the process. For induction heating, a linearization scheme for the nonlinear permeability of steel was implemented. The model was validated by recreating a previously published experiment with the model and using the calculated residual stress data as a comparison to the measured stresses. To ensure a valid comparison, the sample preparation process and measurement methodology were considered for the simulation and a good agreement between the measured and calculated stress distributions was obtained. Thus the distribution and time evolution of several quantities such as temperature, phase fractions and plastic strain can be examined to gain insight into the formation of residual stresses.

Drilling process of indexable drill bit based on Coupled Eulerian-Lagrangian method: A simulation study

42CrMo steel has the characteristics of high strength, high wear resistance, high impact resistance, and fatigue resistance. Therefore, drilling 42CrMo steel has always been a challenging task. The indexable drill bit has the advantages of high processing efficiency and low processing cost and has been widely used in the field of aerospace hole processing. To better understand the machining mechanism of the indexable drill bit, this paper uses the Coupled Eulerian-Lagrangian method (CEL) to simulate the three-dimensional drilling model for the first time. The simulation results of the drilling force obtained by the CEL method and Lagrangian method are compared with the experimental results. It is verified that the CEL method is easy to converge and can avoid the problem of program interruption caused by mesh distortion, and the CEL simulation value is more consistent with the actual value. Secondly, the simulation results of cutting force and blade cutting edge node temperature under different process parameters are extracted. The variation of time domain cutting force, frequency domain cutting force and tool temperature with process parameters are obtained. This study provides a new method for the prediction of cutting performance and the optimization of process parameters of indexable drills.

A new method for predicting the fatigue strength at various stress ratios based on damage of metallic materials

AbstractThe prediction of fatigue strength for metallic materials in a wide range of stress ratios is a crucial engineering challenge. To pursue a more accurate method, the dependence of fatigue strength on stress ratio for 35CrMo steel and other materials was investigated in detail. It was found that as the stress ratio increases, the damage mechanism changes, and the errors of the conventional models in predicting the fatigue strength increase. The reason is that those models fail to describe the fatigue damage evolution of metallic materials under some special conditions. Based on the variational fatigue damage, a new prediction method was proposed by introducing the damage parameter. Through the validation with fatigue strength covering a variety of metallic materials and loading conditions, the method exhibits higher universality. And then the corresponding parameter of the formula is further analyzed to elucidate the influences of various loading conditions on fatigue damage of materials.

Study on the as-cast microstructure and mechanical properties of 35CrMo steel based on electric field control

Herein, the effect of current on the solidification microstructure and properties of 35CrMo structural steel has been studied. The effect of an electric field on the solidification structure of an ingot was investigated by immersing two parallel electrodes into the free surface of molten steel. Using the interaction between the current and melt as well as the Lorentz force generated by its own induced magnetic field, the whole region of the melt was covered with an eddy current. The numerical simulation of the ingot solidification process has been carried out and its influence on the inner flow field during the ingot solidification control process discussed. The results showed that an applied electric field caused turbulence inside the ingot, which drove the molten alloys to rotate and stir, refined the solidification structure, reduced the solidification defects, such as shrinkage cavity and segregation, and increased from 549.9 MPa at the top edge of the ingot and 411.4 MPa at the middle edge to 560.2 and 510.2 MPa, respectively. In addition, the electric field made the hardness and strength of each part of the ingot more uniform and improved the quality of its rigidity for the steel production process.

Microstructure and Fatigue Behavior of Cr-Mo Steel Weld Joints with Automatic TIG Welding

This research focused on how filler metal and post-weld heat treatment (PWHT) affected the microstructure and mechanical properties of 2.25Cr-1Mo steel welds, especially the fatigue behavior. Automatic TIG welding was used to fabricate the weld samples, and both AWS A5.28 ER90S-B3 (also known as B3) and AWS A5.14 ERNiCrMo-3 (commonly known as Inconel 625) were used as filler metals. The PWHT was performed at 690°C for one hour. That was the ideal condition for reducing the hardness of the heat affected zone (HAZ). The microstructure of the B3 weld metal and the HAZ was observed to alter from bainite to tempered bainite due to PWHT, resulting in a decrease in hardness (B3 WM: from 299.7 to 243.5 HV0.2 and HAZ: from 294.5 to 234.7 HV0.2). On the other hand, Inconel 625 weld metal showed an austenite microstructure: after PWHT, the formation of gamma prime increased its hardness (from 263.2 to 299.8 HV0.2). According to the tensile test results, the tensile strength of the welded samples was slightly lower than that of the original base metal, such as the UTS of the BM was 633.0 ± 3.0 MPa and that of the B3-PWHT sample was 601.4 ± 2.0 MPa. The effect of PWHT on tensile strength was negligible, but it significantly affected fatigue strength. For both filler metals, PWHT resulted in a decrease in fatigue strength. The fatigue strength of the B3 sample decreased from 290 to 120 MPa, while that of the IN625 sample reduced from 290 to 240 MPa. In comparison between two different materials, the fatigue strength of the Inconel 625 sample was greater than that of the B3 sample. Fatigue fracture surfaces can be classified into three stages: crack initiation, propagation, and fast fracture. The fatigue rupture was mostly initiated at the weld interface. The final fracture revealed a dimple appearance.

The Influence of Groove Geometry on the Creep Fracture Behavior of Dissimilar Metal Welds between Ferritic Heat-Resistant Steels and Nickel-Based Alloys

This study investigates the influence of groove geometry on the high-temperature creep life and fracture behavior of Dissimilar Metal Welds (DMWs) between low-alloy steel 2.25Cr1Mo and austenitic stainless steel 347H using Inconel 82 nickel-based filling metal. This research aims to reveal the effect of groove geometry, especially the stepped groove, on creep crack propagation path and creep life, through a combined approach of finite element simulation considering stress triaxiality and experimental validation. The study reveals that the stepped groove alters the creep crack propagation path, enhancing the endurance life by deflecting cracks away from the weld/heat-affected zone (HAZ) interface and directing them into regions with higher creep resistance. The experimental results verify the simulation findings, revealing that the stepped groove joints exhibited longer creep life with changes in failure location and mechanism compared to the V-groove joints. However, it was found that the stepped groove intensified the stress concentration at the early creep stage. Thus, a good balance should be achieved between the negative (stress concentration at interface) and positive (changing crack paths) effects of the stepped groove to extend the creep life of DMWs.

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of a low-alloyed tempered martensitic steel submitted to high internal pressure

The influence of hydrogen on the mechanical behavior of a quenched and tempered 42CrMo4 steel has been evaluated by means of high internal pressure fracture tests carried out on hydrogen precharged notched cylindrical specimens. The notched cylindrical specimens were precharged for 3 h time with 1.2 mA/cm2 in two different aqueous media: 1 M H2SO4 added with 0.25 g/l As2O3 and 3.5% of NaCl solution. Hydraulic fracture tests were performed at different ramps of pressure: 7000, 220, 80, 60 and 30 MPa/h, respectively. Hydrogen damage was more marked when the acid aqueous medium (1 M H2SO4 + 0.25 g/l As2O3) was employed. In this case, a higher hydrogen concentration was introduced, leading to hydrogen decohesion micromechanisms (HEDE) near the notched region, especially when tests were performed at 60 MPa/h. Hydrogen embrittlement susceptibility is discussed in terms of the microstructural singularities and the operative fracture micromechanisms observed in each case.

Search for high-creep-strength welding conditions considering HAZ shape factors for 2 1/4Cr–1Mo steel

The creep rupture life of ferritic heat-resistant steel weld joints is limited by Type IV cracking that occurs in the heat-affected zone (HAZ), whose shape affects creep damage accumulation. In this study, we address the inverse problem of extending the creep rupture life of weld joints by controlling HAZ shape via welding conditions. As reported separately, we have developed a workflow that predicts weld joint creep rupture life from the predicted HAZ shape from welding conditions and have implemented it in the material design system. Using this workflow, we presented a tandem Bayesian model for predicting the creep rupture life from welding conditions via the geometric features of HAZ shapes (HAZ shape factors), which are considered to determine the creep rupture life. The prediction model of a HAZ shape factor from welding conditions was formed by Gaussian process regression. The prediction model of the creep rupture life was formed by Bayesian linear regression. These models were probabilistically connected by Bayesian statistical mathematics. An algorithm to increase the creep rupture life was developed to search for welding conditions. This method was applied to a 2 1/4Cr–1Mo heat-resistant steel weld joint simulated with a plate I-bevel three-layer gas tungsten arc welding. The number of welding conditions combination reaches 78=5764801\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${7}^{8}=5764801$$\\end{document}. Start from 49 initial HAZ shape factors and 22 creep rupture life data, we performed forward calculations of 20 rupture lives to find welding conditions that can improve the creep rupture life by 12% over the initial data.

Surface Modification of 42CrMo Steels: A Review from Wear and Corrosion Resistance

This work reviews surface modification techniques for improving the wear and corrosion resistance of 42CrMo steel. The advantages and disadvantages of various methods, including thermal spraying, deposition, hardfacing, laser cladding, nitriding, and laser surface treatment, are discussed. The review elaborates on the materials commonly employed in laser cladding technology, including iron-based, cobalt-based, nickel-based, and high-entropy alloys and reinforced composite coatings. Furthermore, the mechanisms and methods of improving the wear and corrosion resistance of 42CrMo steel are summarized. Finally, this review presents research shortcomings and future opportunities of surface modification techniques. This review also provides a theoretical guide for the application of 42CrMo steel.

Thermal cracking: Clarifying the effects of phases, voids and grains through characterisation and crystal plasticity modelling

Thermally-induced cracking typically occurs during the cooling stage of various manufacturing processes, and is commonly seen in multiphase or the joints of dissimilar materials due to mismatch in their thermo-mechanical properties, such as thermal expansion, elastic-plastic deformation and, in some cases, phase transformation. However, the underlying cracking mechanism associated with local microstructure is still elusive. To improve the mechanistic understanding of thermal cracking, this work uses the diffusion-bonded 9Cr-1Mo steel as an example to study the key microstructural variables, such as interfacial phases, voids, grain boundary migration and crystallographic orientations. Meanwhile, a temperature-dependent crystal plasticity model coupled with a cohesive zone model is developed to provide more insights into the thermal-induced stress distribution at the grain scale. It is found that the stress at the void-free boundary of martensite and ferrite is dominated by shear, and its magnitude is insufficient to nucleate cracks. Whereas voids at phase boundaries can induce significant tensile stress, resulting in cracking at the phase boundaries as well as diffusion-bonded interfaces. Also, the occurrence of interfacial grain boundary migration plays an important role in local stress distribution. These microstructure features and their evolution are experimentally observed and used to verify the developed crystal plasticity models. These findings enhance the understanding of the influence of microstructure features on thermal cracking and provide a guide to designing and fabricating the microstructure with improved thermal crack resistance in various manufacturing processes.

Evaluation of effect of spheroidization heat treatment on mechanical properties via small punch test

Due to the long time high temperature thermal action, pearlite heat-resistant steel 15CrMo is prone to pearlite spheroidization, which reduces its strength and makes it difficult to meet the actual service requirements. Therefore, quantifying the effect of pearlite spheroidization is an important factor in evaluating the high temperature performance of 15CrMo steel. In this study, the mechanical properties of 15CrMo steel were tested by uniaxial tension (UT), small punch tensile (SPT) test; the microstructure of 15CrMo steel after spheroidization heat treatment (SHT) was obtained by image processing technique to obtain the geometric characteristic parameters of pearlite spheroidization phase (PSP); the influence of spheroidization characteristics and properties were analyzed by mathematical and statistical analysis, and the results showed that the PSP size had the greatest influence on the properties; based on this, the linear relationship models between the spheroidization parameters and the mechanical properties of UT and SPT results were established with high accuracy of prediction.

Degradation of a Cr-Mo steel by carbide precipitation over long-term service

Microstructure of the 40-year service-exposed 1Cr-0.5Mo steel extracted from pressure vessels through the boat sampling technique was characterized using x-ray diffraction, field-emission scanning electron microscopy, energy dispersive spectrometry, electron backscatter diffraction, focused ion beam, and transmission electron microscopy. The microstructure degradation during long-term service was identified. Statistical crystal plasticity models were developed to correlate the microstructure and mechanical properties quantitatively. The steel is found significantly strengthened but slightly embrittled. Nanoscale Mo2C carbides have nucleated within the ferrite matrix over the long-term service, resulting in significant strengthening of the matrix. The coarser grain boundary Cr23C6 carbides, on the other hand, act as the damage accumulation sites and lead to the degradation.

Effect of water jet erosion parameters on erosion rate of WC10Ni5Cr HVOF coated 35CrMo steel

Abstract This research work aims for developing the water jet erosion (WJE) prediction equation and analyzing the optimum water jet erosion parameters such as impingement angle (degree), water jet velocity (m s−1), stand-off distance (mm), and erodent discharge rate (g min−1) for minimizing the water jet erosion of 35CrMo steel coated with WC10Ni5Cr coating. The optimized high velocity oxy fuel (HVOF) process parameters were employed for developing the coating of WC10Ni5Cr on 35CrMo steel. The WJE prediction equations were checked for its validity employing analysis of variance (ANOVA). The water jet erosion was measured as the loss of mass (g) after water jet erosion testing for noncoated and coated 35CrMo steel substrates. From the results it was analyzed that the noncoated and coated 35CrMo steel substrates when subjected to the impingement angle of 60°, water jet velocity of 15 m s−1, stand-off distance of 40 mm, and erodent discharge rate of 1500 g min−1 displayed lower mass loss of 0.0177 g and 0.0079 g. The coated 35CrMo steel substrate showed 55.36 % decrement in erosion compared to noncoated 35CrMo steel substrate. These findings support the employability of WC10Ni5Cr HVOF coating for 35CrMo steel to improve its water jet erosion resistance in engineering applications.

Investigation of Dynamic Behavior and Process Stability at Turning of Thin-Walled Tubular Workpieces Made of 42CrMo4 Steel Alloy

During machining, the surface of the machined materials is damaged and tool wear occurs, sometimes even to complete failure. Machining of thin-walled parts is generally cumbersome due to their low structural rigidity. The study deals with the effect of the feed rate and the thickness of the thin-walled part on the dynamic behavior and stability of the turning process during the roughing and finishing of thin-walled tubular workpieces made of steel alloy 42CrMo4. At the same time, the cutting forces and deformations of the workpiece were also evaluated via numerical and experimental approaches. The numerical study is based on a three-dimensional (3D) finite element model (FEM) developed using the ABAQUS/Explicit frame. In the model, the workpiece material is governed by the behavior law of Johnson–Cook. Numerical and experimental results show that the cutting forces and the quality of the machined surface depend not only on the choice of cutting parameters but also on the dynamic behavior of thin-walled parts due to their low rigidity and low structural damping during the machining operation. Cutting forces are proportional to the feed rate and inversely proportional to the thickness of the part. Their variations around the average values are low for roughing tests where the wall-part thickness is higher or equal to 3.5 mm. However, these variations intensify for finishing tests where the wall thickness is less or equal to 1.5 mm. Indeed, the recorded FFT spectra for a finishing operation show several harmonics that occurred at around 550 Hz, and the amplitude of the peaks, which describes the level of power contained in the signals, shows an increase similar to that of the amplitudes of the temporal signal. The flexibility of the part generates instability in the cutting process, but the frequencies of the vibrations are higher than the frequency of rotation of the part.

Hot tensile deformation behavior and Bonora damage model of 25CrMo4 steel

In this research, hot tensile test was performed on 25CrMo4 steel in the temperature range of 1273 K to 1423 K and different strain rates in the range of 0.01 to 10 s−1.The relationship between deformation and factors such as temperature, strain rate and stress triaxiality was investigated.The results showed that decreasing the temperature and increasing the strain rate causes a significant increase in the flow stress curve of steel. Variation of the fracture behavior with temperature and strain rate was studied. The observed fracture types are all ductile fractures characterized by dimples. The maximum fracture strain was found to be 0.513 at temperature of 1273 K and strain rate of 10 s−1. At the same time, DRXed grain coarsing is observed with the decrease of strain rate and increase of tensile temperature. A fracture damage model for predicting fracture failure is proposed based on Bonora damage model. The predicted damage values obtained by the damage model have a good correlation with experimental, with only a maximum relative difference of 8.46%.

Multi-objective optimization and evolution of dissimilar welding process between Cr-Mo steel and austenitic stainless steel for power plant application

In this study, response surface methodology (RSM) was employed to optimize the welding parameters’ effects on mechanical properties of dissimilar welds between Cr-Mo steel grade (P11) and austenitic stainless steel (AISI 316LN). To determine the best welding parameters, variance analysis (ANOVA), desirability function, and perturbation analysis were used to create regression models and identify the significant parameters influencing tensile strength and hardness gaps in the weld joints. The results indicated that welding speed is the most significant parameter affecting both the austenitic hardness gap and tensile strength, while gas flow has the most significant impact on the hardness gap of Cr-Mo steel. Furthermore, welding speed positively influences the mechanical properties of dissimilar weld, whereas welding current has a slight negative effect on tensile strength. The optimum welding parameters were found to be 130 A for welding current, 70 mm min−1 for welding speed, and 13 l min−1 for welding gas flow, resulting in hardness gap values of 18.10 HV (Stainless steel side), 27.38 HV (Cr-Mo steel side), and a tensile strength of 453.90 MPa. The optimum parameter effect is concentrated at the weld interfaces between the fusion zone and the heat-affected zone. This effect led to limitations in grain coarsening, a reduction in the martensite and delta ferrite phase percentages, a slight increase in the bainite ratio, and a decrease in carbide precipitations. As a result, a homogenization of strain distribution in the optimum weld was achieved, leading to ductile fracture in Cr-Mo steel.

Optimization of the active element and reinforcement proportion for improving joint strength of brazed Si3N4/42CrMo

Micron-TiN particles and Ti powder were introduced into the AgCu powder filler to design a particle-reinforced composite filler. This TiN particle (TiNp) modified brazing material was adopted to reliably braze Si3N4 ceramics onto 42CrMo steel, and the ratio of active element Ti to TiNp reinforcement was optimized for joint strength improvement. The reaction layer’s thickness (TiN+Ti5Si3) adjacent to the ceramic decreased by introducing TiNp. Nevertheless, the reaction layer’s thickness (TiC) at the 42CrMo side did not vary too much. TiNp showed excellent wettability with Ag-Cu-Ti braze, and there was no obvious reaction at the interface. Cu-Ti intermetallic compounds were formed and randomly distributed in the brazing seam. When the TiNp content did not exceed 8 vol.%, the joints’ mechanical properties first sharply decreased and then remained basically unchanged when Ti increased. Raising the TiNp content to 10 vol.%, the joint strength showed the changing trends of first increasing and then dropping by increasing Ti content. The bending strength reached the maximum value of 396 MPa when 8 vol.% TiNp and 4 wt.% Ti were adopted.

Electro-thermal modeling of an induction heating process of 42CrMo4 steel probe

This paper describes the procedure of electromagnetic and thermal modeling of an induction hardening load of 42CrMo4 steel. In addition to the temperature and field level dependent physical properties of the material, the magnetic behavior of the load is captured by means of some kind of non-linear impedance boundary condition which simplifies the computational cost of the simulation. The numerical results show the critical behavior around Curie temperature. Finally, a comparison between several simulation results and experimental measurements are provided to assess the usefulness of the proposed electro-thermal simulation.

Corrosion resistance of VC-reinforced Fe-based SMA coatings by laser cladding

The corrosion resistance of 42CrMo steel is insufficient to meet the demands in the marine environment, despite its widespread application in bearings and other fields. Herein, Fe-Mn-Si-Cr-Ni-χ(VC) shape memory alloy (SMA) composite coatings were successfully fabricated on the surface of 42CrMo steel using laser cladding technology. The results present that the coatings are mainly composed of γ austenite (fcc) phase and ε martensite (hcp) phase. Based on research findings, the incorporation of VC has been found to promote the γ → ε martensite phase transition in shape memory alloys. Simultaneously, electrochemical tests were conducted on 42CrMo substrate and SMA coating in 3.5 wt% NaCl solution. It was found that the coatings doped with an appropriate amount of VC could effectively enhance its corrosion resistance. When the doping amount of VC reaches 1.5 wt%, the charge transfer resistance (Rct) is significantly higher than that of the 42CrMo substrate and the pure SMA coating, as well as that of the coating doped with 2.0 wt% VC, reaching 21, 2.6, and 3.3 times of them, respectively. The charge transfer resistance Rct of LS1.5 is much higher than that of 42CrMo, LS0, and LS2.0, reaching 21, 2.6, and 3.3 times, respectively. Additionally, the maximal polarization resistance (Rp) of coatings achieves 4.39 times that of 42CrMo. This study points out that VC can efficiently boost the corrosion resistance of SMA composite coatings and may have uncovered a novel approach for improving the surface corrosion resistance of medium carbon steel.