Effect Of Tempering Temperature Research Articles

In depth analysis of the passive film on martensitic tool alloy: Effect of tempering temperature

Effect of tempering temperature on the composition of the passive film of a martensitic tool alloy was studied by synchrotron-based hard/soft X-ray photoelectron spectroscopy and electrochemical analyses. The contents of Cr and Mo in the passive film are affected by precipitation of tempering carbides. Increase of tempering temperature from 200 to 525°C leads to enhanced formation of Cr/Mo-rich tempering carbides and Cr depletion. Tempering at 525°C results in a Cr content < 11 at% in the underlying metallic layer and formation of a Cr-deficient defective passive film, and thus loss of passivity for the tool alloy in corrosive conditions.

Effect of tempering temperature on microstructure and mechanical properties of 4Cr13VTi steel

To optimize the tempering process of 40Cr13VTi steel containing V and Ti, the effect of tempering temperature on microstructure, precipitation, and properties of 40Cr13VTi stainless steel has been studied. Optical microscope (OM), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS) were used to analyze microstructure and precipitates. Tensile, impact, and hardness testing tests were performed to test the mechanical properties of 40Cr13VTi martensitic stainless steel. The research results indicate that as the increase of tempering temperature, the carbides precipitated gradually increase, and the shape gradually changes from particle to flake, which is consistent with the direction of the original martensite flat surface, and most of them concentrate at the martensite boundary. When the tempering temperature is 350°C, 40Cr13VTi martensitic stainless steel obtains the best comprehensive properties, strength, impact toughness (IT), and hardness which are 1360 MPa, 1717 MPa, 8.5 J/cm2, and 45.1 HRC respectively.

The Effect of Tempering Temperature on Microstructure and Wear Behavior of Tungsten and Boron Alloyed Ni-Hard 4 White Cast Irons

AbstractThis study investigates the effect of tempering temperature on the microstructure and wear resistance of high-alloy white cast iron (Ni-Hard 4) with 1.15% W and 0.5% B additions. Specimens were austenitized at 850 °C for 5 h, quenched in air, and tempered at temperatures between 250 and 650 °C for 4 h. Equilibrium and non-equilibrium thermodynamic calculations were performed using Thermo-Calc software. After the microstructural investigations, hardness testing was carried out. A pin-on-disk tribometer was used to conduct wear tests under dry sliding conditions. Microstructure and worn surfaces were examined using light and scanning electron microscopes. The results showed that increasing tempering temperature resulted in a higher volume fraction of carbides. It was found that tempering at 550 °C for four hours increases resistance to wear giving the lowest measured values of weight loss and wear rate. Accordingly, tempering allows the precipitation of fine carbides in the martensitic matrix which may increase wear resistance.

Effect of tempering temperature on stress corrosion resistance of a low alloy high strength steel with high vanadium content

The stress corrosion resistance of a low alloy high strength steel with high vanadium content, tempered at different temperatures, was examined by electrochemical measurements and slow strain rate tensile test under different environments. Combined with scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), the results show that three different tempering temperatures had an influence on the microstructure of this steel as well as its electrochemical behavior and stress corrosion sensitivity. With the increase of tempering temperature, the ferrite grains coarsened, the average dislocation density lowered as well as the number of vanadium carbide also decreased, though the size of vanadium carbide increased. However, the interface distortion between vanadium carbide and matrix exacerbated, resulting in the increase of the local dislocation density. Therefore, the corrosion potential and impedance decreased, meantime, the stress corrosion sensitivity aggravated.

Effect of tempering temperature on the precipitation behavior of B-containing carbides and mechanical properties of heat-resistant steel

The precipitation behavior of B-containing carbides during tempering at 300–700 °C has here been studied. With an increase in the tempering temperature, the variation of mechanical properties of the heat-resistant steel was then revealed. It was found that the BN inclusion, which had been formed during solidification, disappeared and a fine (Nb,V)(C,N) precipitation was observed by SEM analysis after isothermal quenching. The carbides were acicular M7(C,B)3, with a dominant brittle fracture morphology, when the tempering temperature was lower than, or equal to, 550 °C. Also, the carbides were block M23(C,B)6, with a dominant ductile fracture morphology, when the temperature was higher than 550 °C. It was also found that the lath boundaries of the martensite and the phase boundaries of M7(C,B)3 were favorable conditions for a preferential nucleation of M23(C,B)6.

On the effect of tempering temperature on the long-term creep behavior of a 10% Cr steel with low nitrogen and high boron contents

The effect of a decrease in the tempering temperature from 770 to 750 °C on the long-term creep behavior of a 10% Cr martensitic steel with 0.008 wt % B and 0.003 wt % N was studied. The evolution of microstructure and precipitation distribution during creep was examined using the interrupted tests under an applied stress of 120 MPa at 650 °C. It was found that a higher dislocation density, a finer lath structure and finer carbides after tempering at 750 °C did not provide higher long-term creep strength than after tempering at 770 °C. The creep rupture time was about 30% shorter. Effect of changes in the dislocation density, lath width, sizes of M23C6 carbides and Laves phase particles, and precipitation of V-rich MX phase on the strengthening contribution at the onset of creep and at the transient, apparent steady-state and tertiary stages was analyzed. The higher dislocation density formed by the tempering at a lower temperature provided a higher climb velocity at the transient creep stage. The higher driving force for recovery was not fully compensated by the higher strength exerted by smaller M23C6 carbides. This led to faster annihilation of the lath boundaries and a decrease in internal stress and, consequently, to an order of magnitude higher minimum creep rate of the steel after tempering at 750 °C as compared to tempering at 770 °C.

Effects of tempering temperature on the precipitation behaviors of nanoparticles and their influences on the susceptibility to hydrogen embrittlement of a Cr–Mo–V steel

This paper presents an experimental study of tempering treatment to optimize the precipitation behavior of nano-sized particles for improving the resistance to hydrogen embrittlement (HE) of an AISI 4330-type low-alloy high-strength steel. The precipitates and dislocations in the microstructure, which serve as irreversible and reversible hydrogen traps, were quantitatively investigated using TEM, X-ray diffraction and hydrogen permeation techniques. It was found that V-rich M2C precipitates of less than 2 nm size appeared when tempered at 610 °C, a tempering temperature associated with the lowest HE susceptibility of the tempered steel. Furthermore, the hydrogen could promote movement of the multiple dislocation at the low-temperature tempering process but pin the separated dislocation at higher temperature tempering process. The interaction of the dislocations (i.e., multiple dislocation or separated dislocation) with nanoprecipitates and hydrogen atoms produced the hydrogen-induced hardening/softening behavior in a hydrogen-charging environment.

Effect of heat treatment on the performance of 30MnB4 steel for being used as grade 10.9 bolt material

Due to technological advancements, alloy steels are now widely used in producing high-strength bolts through various heat treatments. One of the essential features desired in bolts is their strength, as they are subject to heavy loads. This strength is referred to as bolt quality, and interest in heat treatment methods applied to increase the strength of alloy steels is increasing. The mechanical properties achieved from different heat treatment methods and chemical compositions vary. This study aimed to impart the mechanical properties of grade 10.9 steel bolts onto 30MnB4 steel by applying different heat treatments. The effects of tempering temperature on tensile strength, yield strength, elongation at break, reduction in cross-sectional area at break, hardness, and notch impact values at -20°C were examined by passing the prepared samples through five different tempering processes after preheating, annealing and quenching processes. The results revealed that the mechanical properties of grade 10.9 steel bolts were imparted to 30MnB4 steel at all tempering temperatures applied within the scope of the study. Yield strength, tensile strength, hardness, and -20°C notch impact values increased as tempering temperature decreased, while elongation at break decreased. This study adds 30MnB4 steel to the literature as an alternative material that can be used to produce grade 10.9 steel bolts. In addition, mechanical properties obtained depending on tempering temperatures have also revealed the usability of 30MnB4 steel for different applications requiring high strength and toughness values.

Effect of Tempering Temperature on Hydrogen Embrittlement of SCM440 Tempered Martensitic Steel.

The effect of tempering temperature on the hydrogen embrittlement characteristics of SCM440 tempered martensitic steels was investigated in terms of their microstructure and hydrogen desorption behavior. The microstructures were characterized using scanning and transmission electron microscopy, as well as X-ray diffraction and electron backscattered diffraction analysis. Thermal desorption analysis (TDA) was performed to examine the amount and trapping behavior of hydrogen. The cementite morphology of the SCM440 tempered martensitic steels gradually changed from a long lamellar shape to a segmented short-rod shape with an increasing tempering temperature. A slow strain rate tensile test was conducted after electrochemical hydrogen charging to evaluate the hydrogen embrittlement resistance. The hydrogen embrittlement resistance of the SCM440 tempered martensitic steels increased with an increasing tempering temperature because of the decrease in the fraction of the low-angle grain boundaries and dislocation density. The low-angle grain boundaries and dislocations, which acted as reversible hydrogen trap sites, were critical factors in determining the hydrogen embrittlement resistance, and this was supported by the decreased diffusible hydrogen content as measured by TDA. Fine carbides formed in the steel tempered at a relatively higher temperature acted as irreversible hydrogen trap sites and contributed to improving the hydrogen embrittlement resistance. Our findings can suggest that the tempering temperature of SCM440 tempered martensitic steel plays an important role in determining its hydrogen embrittlement resistance.

The effect of microstructure evolution on fatigue property of SA508Gr.4N steel for nuclear reactor pressure vessels

The effect of tempering temperature on the microstructure evolution of SA508Gr.4N steel as well as the subsequent effect on the low cycle fatigue property were studied. The tempering temperature was carried out from 595 °C to 675 °C. The experimental results showed that more M/A islands were decomposed at 630 °C, and carbides were dissolved when the tempering temperature increased to 640 °C. The intercritical tempering temperature of the steel reached at a higher temperature (675 °C). After the intercritical range cooling, the granular bainite transformed into martensite, quasi-polygonal ferrite and a small number of undissolved carbides. Subsequently, the tempered specimens at 595 °C, 630 °C and 675 °C were subjected to low cycle fatigue tests under the strain amplitudes of ±0.45% and ±0.6% at 300 °C, respectively. The fatigue life of the steel increased first and then decreased with the increase of tempering temperature. The fatigue stripes separation exhibited a contrary trend to the fatigue life with the increase of tempering temperature. Moreover, the fatigue crack initiation points were transferred from around the M/A islands to the grain boundaries triple point with the increase of tempering temperature from 595 °C to 630 °C. Subsequently, the fatigue crack initiation points were transferred from the grain boundaries triple point to the ferrite phase and the boundary between martensite and ferrite when the tempering temperature increased to 675 °C. The obtained results can provide meaningful reference for improving the fatigue life of nuclear reactor pressure vessels.

Effects of tempering temperature on the microstructure evolution and mechanical properties of 16%Cr–5%Ni super martensitic stainless steel

The effects of tempering temperature on the microstructure evolution and mechanical properties of 16%Cr–5%Ni super martensitic stainless steel (SMSS) were investigated in the present study. Reversed austenite was detected via X-ray diffraction when the as-quenched samples with full martensite were tempered above 500 °C, and its volume fraction attained a maximum of ∼17% at 620 °C. When tempered below 620 °C, all the reversed austenite formed was able to keep stable at room temperature, while partial or even entire reversed austenite formed above 640 °C with Ni content less than 8 wt% transformed back into fresh martensite during cooling, demonstrating that the enrichment of Ni determined the thermal stability of reversed austenite. EDS results revealed that the precipitation of M23C6 carbides caused Ni enrichment in the adjacent regions, promoting the nucleation of reversed austenite, and the growth of reversed austenite was mainly controlled by Ni diffusion. The results of tensile tests and instrumented impact tests indicated that stable reversed austenite effectively improved the ductility and toughness, and offset the deterioration of toughness caused by the M23C6 precipitating at grain boundaries. Tempering at 540 °C achieved an excellent combination of strength and toughness, while the best plasticity of samples was obtained by tempering at 620 °C.

Effect of tempering temperature and subzero treatment on microstructures, retained austenite, and hardness of AISI D2 tool steel

The presence of retained austenite in the hardening process of tool steel often causes the lower hardness compared to the hardness requirements and poor dimensional stability in the tool steel. The purpose of the present research is to determine the relationships between the tempering process with and without cryogenic treatment to the hardness and retained austenite amount of as-hardened D2 tool steel. The austenitizing temperature was 1020 °C, the tempering temperatures have variations of 180 °C, 280 °C, 380 °C, 480 °C, and 580 °C, and the subzero treatment has a temperature of −172 °C, followed by tempering at 180 °C, 380 °C, and 580 °C. This study aims to determine the appropriate treatment to obtain a minimum retained austenite percentage to prevent and mitigate the failure of AISI D2 tool steel in the industrial application process. An optical microscope with image processing software (Image-J analysis), as well as Brinell and Vickers hardness testing, is the characterization method used in this work. In general, plate martensite, bainite, retained austenite, and primary and secondary carbides are the phases contained in the microstructure. Tempering temperatures have the effect of increasing the secondary carbide precipitation and decreasing the retained austenite content (γr 3,671%–2,769%). However, the cryogenic treatment can provide a more efficient martensitic phase transformation process and minimal retained austenite content (γr 2,257%–1,199%). The increase in tempering temperature causes a decrease in hardness at a temperature of 180 °C–380 °C. On the other hand, the secondary hardening and phase transformation phenomena cause an increase in the hardness of the as-tempered sample at a temperature of 480 °C, before the sample reexperiences a significant decrease in hardness at a temperature of 580 °C due to diffusion that decreases the carbon content.

Effect of tempering temperature on stress-assisted hydrogen diffusion and hydrogen-induced embrittlement in a high strength low alloy steel

Hydrogen can be used as a probe to detect defects created during tensile tests. Through hydrogen diffusion behavior investigated under two loading ways in a high strength low alloy steel tempered at three different temperatures, the mechanism of embrittlement resulted from dynamic hydrogen charging was elaborated. Before yielding, the stress has no significant effect on the hydrogen diffusivity. However, near yield stress, the hydrogen diffusion varies with sustaining the loaded time, while at the plastic region, the hydrogen diffusivity returns to a relative lower and stable value. In addition, hydrogen solubility monotonously increases with elastic stress in all samples tempered at different temperatures, whereas the plastic stress can differently alter the steady state hydrogen permeation flux from sample to sample depending on the tempering temperature. Hence, all samples tempered at different temperatures can be damaged in advance by dynamic hydrogen charging but the sensitivity to hydrogen embrittlement can still be alleviated by raising tempering temperature.

Effect of Tempering Temperature on the Microstructure, Deformation and Fracture Properties of an Ultrahigh Strength Medium‐Mn Steel Processed by Quenching and Tempering

Herein, a medium‐Mn steel containing 4 wt% Mn is designed to achieve ultrahigh tensile strength and good ductility by the quenching and tempering process. The effects of tempering temperature on the microstructure, tensile behavior, and fracture properties under different stress states are explored. It is observed that tempering temperature influences the fracture mechanisms of the ultrahigh‐strength steels. Both ductile fracture strain and cleavage fracture strength of the investigated medium‐Mn steel are affected by the tempering temperature. The impacts of tempering temperature on volume fraction, carbon content of retained austenite (RA), and tensile properties are quantitatively analyzed. Detailed microstructure analysis reveals that both volume fraction and carbon content of the RA are increased in the tempered steels, accompanied by improved tensile properties than in quenched conditions. The superior tensile properties are achieved after tempering at 250 °C, with the ultrahigh yield strength of 1590 MPa, ultrahigh tensile strength of 1963 MPa, and total elongation of 12%. The corresponding relationship between microstructure and mechanical properties is investigated, with a focus on the change of residual stress, the occurrence of carbon redistribution/carbide precipitation, the decrease of dislocation density of martensite, and the presence of transformation‐induced plasticity effect during deformation.

Effect of Tempering Temperature on the Structure, Morphology and Electrochemical Performance of LiNi0.5Mn1.5O4

LiNi0.5Mn1.5O4, the cathode material for 5V lithium ion batteries, was synthesized through the coprecipitation-combustion process in air. The effect of tempering temperature on the structure, morphology and electrochemical performances were investigated. The phase and electrochemical properties of the samples were characterized by powder X-ray diffraction, scanning electron microscopy and constant current charge-discharge tests. The experimental results indicate that the samples tempered at 800°C-900°C all have spinel structure, with the increase of tempering temperature, the crystallinity and grain size of the sample increase.The sample tempering at 850°C has well-developed crystals, moderate crystal size and the best electrochemical performance.

Effect of Tempering Temperature on the Microstructure and Mechanical Properties of 42CrMo4 Steel

This paper investigated the effects of tempering temperature (200°C, 400°C, 600°C or 800°C) on microstructures, mechanical properties, and residual stress of 42CrMo4 steel. Microstructures were characterized by OM and SEM techniques. The results show that the change in tempering temperature leads to a change in austenite, resulting in a change in hardness and toughness. The specimen showed the best combination of mechanical properties under the heat treatment condition of a tempering temperature of 600°C. The hardness, yield strength, tensile strength, area shrinkage, and elongation reached 312.74HV, 759MPa, 898MPa, 60%, and 18%, respectively. The experimental results provide a reference for the selection of the heat treatment process of 42CrMo4 steel.

Effect of tempering temperature on plasma-welded joint of martensitic heat-resistant steel

The effect of tempering temperature on microstructure and mechanical properties of plasma welded martensitic heat-resistant steel P92 was investigated by tempering heat treatment process (tempering temperature range was 550–750°C, temperature interval was 100°C). The results show that with the increase of tempering temperature, the microstructure of welded joint coarsens, the tensile strength and hardness decrease, and the toughness is improved.In the tempering process, M23C6 and Laves phases are produced in the welded joint. A certain amount of M23C6 precipitates can strengthen the mechanical properties of the welded joint. Excessive M23C6 carbides lead to the softening of martensite and the decrease of hardness; the formation of Laves phase can inhibit the excessive precipitation of M23C6, but the excessive precipitation of the Laves phase will lead to coarsening at the grain boundary and the formation of voids at the grain boundary. When the welded joint temperature is 650°C, the comprehensive mechanical properties of the welded joint are the best.

Effect of Subcritical Treatment (Tempering) on Hardness and Wear of High Chromium White Cast Iron

High chromium white cast iron (HCWCI) is used in mining, crushing plants, as mill liners, and in the manufacture of grinding balls. The grinding ball is the essential element in fine fragmentation. It must have an excellent life to counter extreme wear and impact conditions that it undergoes. Hence it is important to improve its mechanical properties. This study aims to find the effect of tempering temperature on microstructure, hardness, and abrasive wear of High Chromium White Cast Iron used in the manufacture of grinding balls. In this study, the balls in high chromium white cast iron with 12 to 17% Cr, of 50mm and 70mm in diameter were austenitized at 950°C for 45 min and 55 min for the balls of 50 and 70mm then were quenched in forced air. The balls were tempered at 250°C, 400°C, and 600°C for 120 min and 180 min for both diameters 50 and 70mm respectively, and cooled in the furnace. The results showed that tempering practiced at 250°C and 400°C gives an excellent hardness than balls austenitized at 950°C. It is about 60 HRC and it drops to less than 50 HRC for the tempering at 600°C. This tempering causes a significant mass loss (short life) but tempering at 250°C and 400°C decreases this loss by up to 1.6%. The results of XRD showed the presence of the martensite and carbides type M7C3 after tempering at 250°C and a ferritic matrix after tempering at 600°C.

Effect of tempering temperature and grain refinement induced by severe shot peening on the corrosion behavior of a low alloy steel

In this study, the effect of tempering temperature on the corrosion behavior of a low carbon steel (F1272) was analyzed by means of electrochemical tests: linear polarization resistance, potentyodinamic polarization and electrochemical impedance spectroscopy (EIS) in freely aerated 3.5% NaCl solution, at room temperature. The results show that corrosion resistance of the steel increases with elevating tempering temperature from 200 to 500 °C and finally, to 680 °C. Additionally, a severe shot peening (SSP) treatment was applied in the sample with the best corrosion behavior (TT680), in order to modify the grain structure. Results evidence that corrosion resistance of the TT680 sample decreases after the applied SSP treatment (10A and 5000% coverage). Corrosion behavior is discussed through the different microstructural singularities induced both the heat treatments and the SSP.

Effect of tempering temperature on microstructure and mechanical properties of a low carbon bainitic steel treated by quenching-partitioning-tempering (QPT) process

The quenching-partitioning-tempering (QPT) treatment was carried out on a low carbon bainitic steel, and the effect of tempering temperature on the microstructure and mechanical properties of the QPT processed steel was investigated. The findings demonstrate that as the tempering temperature increases, the yield strength decreases gradually, while the tensile strength decreases first and then increases. However, the elongation exhibits a trend of increasing first and then decreasing with increasing the tempering temperature. When the tempering temperature is 340 °C, the best mechanical properties can be obtained with the yield strength of 1495 MPa, tensile strength of 1806 MPa, elongation of 17.7%, and product of strength and elongation up to 32.92 GPa%. Such excellent mechanical properties are related to the synergistic combination of tempered martensite, low carbon bainite, retained austenite and carbides.