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  Effect of solution temperature on mechanical properties and corrosion resistance of super duplex stainless steel 2507 Gu Guochao, Li Ruifen, Xin Zhenmin, Xiang Lixin, Xu Wenhua, Lü Yupeng Heat Treatment of Metals    2022, 47 (6): 1-6.   doi:10.13251/j.issn.0254-6051.2022.06.001 Abstract （172）      PDF （3745KB）（321）       Knowledge map    Effect of solution temperature on microstructure, mechanical properties and corrosion resistance of 2507 super duplex stainless steel was investigated by using optical microscope, scanning electron microscopy, XRD, tensile test and electrochemical analysis. The thermodynamic equilibrium phase diagram of the 2507 duplex stainless steel was calculated by Thermo-Calc thermodynamic software and compared with the test results. The results show that σ phase can be eliminated by solution treatment at temperatures higher than 1050 ℃. With the increase of solution temperature, the content of ferrite phase increases, the content of austenite phase decreases, and the volume fraction ratio of α/γ increases. The duplex stainless steel has better comprehensive mechanical properties after solution treatment at 1050-1100 ℃ for 30 min and water cooling, of which the yield strength, tensile strength and elongation are more than 600 MPa, 840 MPa and 35%, respectively. The duplex stainless steel can obtain better corrosion resistance after solution treatment at 1050 ℃ for 30 min. Reference | Related Articles | Metrics

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  New material for aerospace bearing:60NiTi alloy Zhang Jiahua, Xiao Fei, Wang Jianzhong, Xu Zhongjun, Jin Xuejun Heat Treatment of Metals    2021, 46 (6): 1-7.   doi:10.13251/j.issn.0254-6051.2021.06.001 Abstract （279）      PDF （899KB）（267）       Knowledge map    Among the large family of NiTi alloys, the NiTi alloy with equal atomic ratio have shape memory effect and super elasticity, Compared with NiTi alloy, thermoelastic martensitic transformation does not occur in the 60NiTi alloy, and it has no shape memory effect and super elasticity. However it has outstanding potential in hardness, corrosion resistance and elastic properties, showing a good application prospect in the aerospace field. The solid solution treated 60NiTi alloy also has structural stability, super corrosion resistance and excellent wear resistance, and has become a candidate new material for aerospace bearings. Reference | Related Articles | Metrics

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  Effect of tempering temperature on microstructure and mechanical properties of high nitrogen stainless bearing steel Wang Lingqi, He Yanlin, Pan Le Heat Treatment of Metals    2021, 46 (6): 8-13.   doi:10.13251/j.issn.0254-6051.2021.06.002 Abstract （277）      PDF （616KB）（226）       Knowledge map    Microstructure and mechanical properties of high nitrogen stainless bearing steel Cronidur 30 with different tempering temperature were studied and analyzed by universal tensile testing machine, impact testing machine, OM, X-ray diffraction, SEM and TEM, etc. The results show that the microstructure is tempered martensite, carbonitride and retained austenite after tempering at 150-500 ℃. When the tempering temperature exceeds 550 ℃, the microstructure is tempered sorbite, and the precipitated phase gradually gathers and grows. With the tempering temperature increase, the hardness and the tensile strength first decrease, then increase, finally decrease, the impact toughness behaves on the contrary. Secondary hardening occurs because of M23C6 and Cr2N increase when tempered at 450 ℃, and the tensile strength is 2133 MPa. After tempered at 400 ℃, the precipitated phases (σ phases) which riched in Cr-Fe-Mo is observed slightly, reduces impact toughness observably. When tempered at 500 ℃, the impact toughness slightly decreases because of the translation of retained austenite. Reference | Related Articles | Metrics

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  Heat treatment for toughening technology of cold working die steel SKD11 Yuan Zhizhong, Wang Mengfei, Zhang Bocheng, Duan Xubin, Li Biaomin, Yang Haifeng, Luo Rui, Cheng Xiaonong Heat Treatment of Metals    2023, 48 (9): 1-7.   doi:10.13251/j.issn.0254-6051.2023.09.001 Abstract （142）      PDF （5140KB）（176）       Knowledge map    SKD11 steel plate after hot rolling and spheroidizing annealing was used. Two kinds of complex phase heat treatment processes, A-Q-A (Austempering-Quenching-Austempering) and Q-T-A (Quenching-Tempering-Austempering), as well asconventional Q-T(Quenching-Tempering) heat treatment process were carried out.The effect of heat treatment process on the microstructure, hardness and impact absorbed energy was studied. The results show that the microstructure of the specimens after A-Q-A and Q-T-A is the combination of lower bainite (LB) and martensite (M). The content of retained austenite is 13.2% and 18.6% for A-Q-A and Q-T-A, respectively. After A-Q-A, Q-T-A and conventional heat treatment Q-T, the hardness of the specimens is 58.5, 58.6 and 60.5 HRC and the impact absorbed energy is 31.3, 27.6 and 15 J, respectively. The excellent combination of strength and toughness of the SKD11 steel plate is realized by the duplex-phase heat treatments, which does a beneficial exploration in improving the toughness of the cold working die steel. Reference | Related Articles | Metrics

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  Effect of vacuum low pressure carburizing on microstructure and properties of austenitic stainless steels 304 and 316L Cheng Ru, Tian Yong, Song Chaowei, Wang Haojie Heat Treatment of Metals    2022, 47 (9): 1-5.   doi:10.13251/j.issn.0254-6051.2022.09.001 Abstract （214）      PDF （660KB）（174）       Knowledge map    Surface strengthening of 304 and 316L austenitic stainless steels was processed by using vacuum low pressure carburizing process. The microstructure, phase composition and microhardness distribution of the carburized layers were analyzed by means of optical microscope, scanning electron microscope, Thermo-Calc software, X-ray diffractometer and microhardness tester. The offsets of different diffraction peaks in the carburized layers and the changes in lattice parameters before and after carburizing of the tested steels were calculated. Combined with the effects of molybdenum on carburizing process of the austenitic stainless steels, the differences in the carburized layer thickness, surface hardness and mechanism of carbides precipitation after carburizing of 304 and 316L austenitic stainless steels were compared and studied. The results show that the carburized layers produced by 750 ℃ carburizing for 2.6 h are composed of expanded austenite and Cr23C6 phases, the austenite lattice constant has increased by 1.33% and 1.14% respectively for 304 and 316L stainless steels, and Cr23C6 is mainly precipitated in strip shape on the expanded austenite grain boundaries. The surface hardness of the 304 and 316L stainless steels after carburizing at 750 ℃ for 2.6 h is over 2 times higher than that of substrate. Reference | Related Articles | Metrics

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  Effects of solution and aging treatments on mechanical properties and microstructure of Al-Cu-Mn-Er cast alloy Wu Yang, Huang Hui, Shi Wei, Wen Shengping, Wu Xiaolan, Rong Li, Wei Wu Heat Treatment of Metals    2022, 47 (6): 7-12.   doi:10.13251/j.issn.0254-6051.2022.06.002 Abstract （137）      PDF （4148KB）（167）       Knowledge map    Effects of different solution and aging treatments on microstructure and mechanical properties of Al-Cu-Mn-Er alloy were studied by optical microscope, scanning electron microscope, XRD, DSC test, hardness test and tensile test. The results show that the optimal process of solution and aging treatments of the as-cast alloy is solution treating at 540 ℃ for 12 h and aging at 185 ℃ for 6 h, under which there is no overheating or "overburning" phenomena, the solute atoms are fully diffused, and a large amount of residual phases generated during the casting process are redissolved into the matrix. Meanwhile, the alloy has the highest hardness value of 142.28 HV0.1, tensile strength of 370.37 MPa, yield strength of 300.34 MPa, and elongation of 6.50%. Reference | Related Articles | Metrics

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  Microstructure and wear resistance of AlCoCrFeMnZr near-eutectic high-entropy alloy Wang Zhixin, Yang Cheng, Ma Mingxing, Wang Bozhen, Dong Chen, Li Shangzhi, Hou Runsen Heat Treatment of Metals    2023, 48 (1): 1-5.   doi:10.13251/j.issn.0254-6051.2023.01.001 Abstract （169）      PDF （695KB）（145）       Knowledge map    AlCoCrFeMnZr near-eutectic high-entropy alloy was prepared by vacuum melting, then its crystal structure, morphology, hardness and wear resistance were tested by means of XRD, SEM, microhardness tester and friction and wear testing machine. The results show that the phase structure of the AlCoCrFeMnZr alloy is BCC+HCP dual-phase structure, composing of primary phase and fine lamellar eutectic. The primary phase consists of the HCP phase enriched in Cr, Fe, and Zr, which grows in a dendritic manner. The main elements in the dendrite region (α phase) of the lamellar eutectic structure are Co, Cr and Fe, and the main elements in the intergranular (β phase) are Al and Zr, which conforms to the structure and element distribution of high-entropy alloys. The wear model changes from adhesive wear and abrasive wear to oxidative wear, and the friction factor shows a trend of increasing first and then decreasing, and the average friction factor is 0.5432, the microhardness is 768.8 HV0.5, that means the alloy has excellent hardness and wear resistance. Reference | Related Articles | Metrics

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  Microstructure and properties of Fe-Cr-Ni gradient alloy steel by direct laser deposition Zhan Di, Chen Suiyuan, Song Xiuwen, Chen Xueting, Wang Mei Heat Treatment of Metals    2023, 48 (2): 1-9.   doi:10.13251/j.issn.0254-6051.2023.02.001 Abstract （96）      PDF （673KB）（138）       Knowledge map    An outside-strong but inside-tough 12CrNi2Y-50Cr6Ni2Y-70Cr8Ni2Y gradient alloy steel specimen was prepared by direct laser deposition technology. Then the microstructure, interfacial adhesion, hardness gradient distribution and wear resistance of the specimen were studied by means of metallographic microscope, scanning electron microscope, transmission electron microscope, hardness tester and friction testing machine. The results show that the 12CrNi2Y-50Cr6Ni2Y-70Cr8Ni2Y gradient alloy steel specimen with metallurgical bonding at the gradient transition interface and no crack inclusion defects is successfully prepared under the optimized laser deposition parameters. The microstructure of the specimen shows a change trend from (granular bainite+lath bainite+a small amount of martensite) to (lath bainite+lath martensite) to (lath martensite+plate martensite), the corresponding hardness changes as gradient distribution of 356 HV0.2 → 551 HV0.2 →712 HV0.2, and the volume wear rate as gradient distribution of 2.01×10-4 mm3·N-1·m-1 → 1.33×10-4 mm3·N-1·m-1 → 0.71×10-4 mm3·N-1·m-1. In the prepared gradient alloy steel specimen, due to the increase of C and Cr content, the hardness of the specimen shows a gradient distribution from low to high, and the wear resistance of the surface working layer is improved by nearly 2.8 times, so the outside-strong but inside-tough requirements is realized by gradient distributions of microstructure and properties. The obvious element diffusion of small-size C atoms near the transition interface of gradient alloy steel specimen promotes the metallurgical bonding of gradient interface. Reference | Related Articles | Metrics

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  Research progress on preparation technology and coating of nano-powder by plasma spraying Chen Baisen, Meng Junsheng, Wang You, Shi Xiaoping Heat Treatment of Metals    2023, 48 (7): 223-236.   doi:10.13251/j.issn.0254-6051.2023.07.039 Abstract （28）      PDF （3299KB）（138）       Knowledge map    In modern industry, plasma spraying technology has become an important method to improve the wear resistance and corrosion resistance of the surface of mechanical parts. As a spraying material, the nano-powder can effectively improve the wear resistance, corrosion resistance, oxidation resistance and other aspects of plasma spraying coating, which has research value in the application of surface protection of parts and components. It is of great significance for the energy conservation and environmental protection, and has become a research hot spot in the field of surface modification at home and abroad. Based on this, on the basis of a large number of literature, the preparation method of nano powder from three aspects as solid phase method, liquid phase method and gas phase method is introduced, research on the regranulation technology of nano-powder at home and abroad is summarized, the preparation methods of nano-powder feed, including spray drying, mechanical grinding and liquid phase precursor synthesis are described, and the preparation method of liquid phase precursor synthesis method is focused on. From the selection of nano-powder for plasma spraying to the preparation of coating, the application results of nano-coating in wear resistance, corrosion resistance, thermal barrier and self-lubrication are reviewed in detail, furthermore, the influence of plasma spraying parameters (spraying power, spraying distance, moving speed of spray gun, spraying gas parameters) on quality of the nano-coating is inductively analyzed. Finally, the problems and shortcomings in the preparation of plasma sprayed nano-powder feed are discussed, and the future research direction of plasma sprayed nano-coating is prospected. Reference | Related Articles | Metrics

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  Comparative analysis of high performance bearing steels Li Xiong, Lin Faju, Du Simin, Wu Chengchuan Heat Treatment of Metals    2021, 46 (6): 14-20.   doi:10.13251/j.issn.0254-6051.2021.06.003 Abstract （178）      PDF （614KB）（119）       Knowledge map    Several kinds of high performance bearing steels were compared and analyzed. The results show that the strengths of carburized bearing steels are lower than that of through-hardened bearing steels, but the ductility and toughness are higher. Only the hardness of CSS-42L and M62 steels reaches 68 HRC among the current steel grades, which means that it has greater dynamic load-bearing capacity. High chromium Cr-Mo-V(Co) bearing steels have better hot hardness than other steels, and hot hardness of CSS-42L and M62 steels at 500 ℃ exceed 58 HRC. The hardness profiles of P675, Ferrium C61 and M50NiL are better than CSS-42L. Although CSS-42L steel has a high surface hardness, there is “concave area” in the hardness profile of the carburized layer, which limits its use under high load conditions. Corrosion resistance is the most important index affecting bearing life. The corrosion resistances of Cronidur 30 and Pyrowear 675 are better than that of CSS-42L and M50NiL. In addition to CSS-42L steel, the volume percent of retained austenite in bearing steels used above 350 ℃ is less than 10%. There are too many retained austenite in CSS-42L steel, which will affect the dimensional stability due to the transformation of austenite under the action of temperature and load when used at high temperature, so CSS-42L steel is limited applicating in aerospace field. Now only M62 and ASP2060 steels can be used as bearing above 500 ℃. Carburizing/nitriding can generate residual compressive stress on the steel surface, which is beneficial to improve the fatigue life. The subsurface compression stresses of P675 and M50NiL steels are greater than that of CSS-42L steel. Although the fatigue life of the CSS-42L steel tested by the ball-on-rod tester is approximately twice that of the Pyrowear 675 steel, the fatigue life of the Pyrowear 675 steel is higher than that of the CSS-42L steel when the lubrication is insufficient in the high-load accelerated test of the bearings. Reference | Related Articles | Metrics

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  Austenite grain distribution law in 34CrNi3MoV steel Zheng Bing, Xu Dong, Wang Yiqun, Wang Xuexi, Zhao Hongyang, Ju Dongying Heat Treatment of Metals    2023, 48 (7): 1-7.   doi:10.13251/j.issn.0254-6051.2023.07.001 Abstract （102）      PDF （2733KB）（118）       Knowledge map    Effects of different holding temperature and holding time on austenite grain growth of 34CrNi3MoV steel were studied. The effects of holding temperature and holding time on average grain size, major axis and minor axis were analyzed by means of metallography. The results show that in the Gaussian distribution equation, the standard deviation and expectation increase with the increase of holding temperature and holding time. The size of the major axis and minor axis of grains is closely related to the average size, and the ratio has a simple linear relationship. During the grain growth, the ratio of the major axis to the minor axis basically remains unchanged. The distribution probability expressions of average grain size, major axis size and minor axis size are obtained by regression. At the same time,a new way of thinking and possible explanation for the heredity in materials science in terms of mathematical laws is provided. Reference | Related Articles | Metrics

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  Effect of pre-stretching amount on microstructure and properties of 2050 Al-Li alloy Yu Juan, Feng Zhaohui, Zhao Weiyi, Yao Yong, You Wen Heat Treatment of Metals    2022, 47 (6): 64-68.   doi:10.13251/j.issn.0254-6051.2022.06.011 Abstract （76）      PDF （2672KB）（118）       Knowledge map    Effect of pre-stretching processing after solution treatment on tensile properties, intergranular corrosion resistance and microstructure of the artificial aged 2050 Al-Li alloy were studied by means of tensile test, intergranular corrosion test and transmission electron microscope(TEM). The results show that the yield strength and ultimate tensile strength at L and LT directions of the 2050 Al-Li alloy increase gradually with the increase of pre-stretching amount, and tend to be stable when the pre-stretching amount is over 4.0%, elongation decreases rapidly at first and then finally keep stable. With the increase of pre-stretching amount, the corrosion morphology changes from intergranular corrosion to pitting, and the pitting depth decreases gradually. The pre-stretching processing promotes the T1 phase precipitation in the grains and makes its distribution more dispersive and homogeneous, while the precipitation at grain boundary is restrained during the artificial aging, which consequently improves the tensile strength and the intergranular corrosion resistance. When the pre-stretching amount is 5.0%, the optimum tensile strength and intergranular corrosion resistance is obtained for the alloy. Reference | Related Articles | Metrics

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  Effect of mechanical alloying time on microstructure and corrosion resistance of laser clad coating of Ni6Cr4W1.5Fe9Ti high-entropy alloy Sun Defu, Sun Zhicheng, Gu Zhen, Xi Shengqi, Sun Chongfeng, Li Shiliang, Su Chengming, Wang Chunchang Heat Treatment of Metals    2023, 48 (3): 1-7.   doi:10.13251/j.issn.0254-6051.2023.03.001 Abstract （118）      PDF （4952KB）（116）       Knowledge map    Clad coating of mechanical alloyed Ni6Cr4W1.5Fe9Ti high-entropy alloy powder was prepared by laser melting deposition. The effect of mechanical alloying time on microstructure and corrosion resistance of the coating was studied. The results show that the increase of mechanical alloying time can promote the homogenization of alloy powder composition, the densification of coating and the grain refinement of microstructure. After mechanical alloying rod grinding for 4 h, the components of high-entropy alloy powder are evenly distributed, and the FCC+BCC two-phase solid solution structure is formed. After laser melting deposition, the structure of two-phase solid solution is transformed into FCC single-phase solid solution, which is mainly composed of 4-6 μm equiaxed crystals and a small amount of cellular crystals. Among them, the coating prepared by powder mechanical alloying rod grinding for 4 h has the highest density, hardness and the best corrosion resistance, and its corrosion resistance is nearly two orders of magnitude higher than that of the coating prepared by powder mechanical alloying rod grinding for 0 h. Reference | Related Articles | Metrics

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  Effects of post-quenching cleaning and cold treatment process on retained austenite content of 9Cr18 steel bearing ring An Min, Fu Zhongyuan, Yuan Chao, Xia Yunzhi Heat Treatment of Metals    2021, 46 (6): 21-23.   doi:10.13251/j.issn.0254-6051.2021.06.004 Abstract （138）      PDF （613KB）（105）       Knowledge map    Effects of cleaning process after oil quenching, subzero treatment process and interval between cleaning and subzero treatment on the final retained austenite content of 9Cr18 steel bearing ring were analyzed in view of the same quenching and tempering conditions. The results show that the higher the cleaning temperature after oil quenching, and the longer the interval between cleaning and subzero treatment, the higher the retained austenite content. However, the content of retained austenite increases when the temperature of subzero treatment is much too low, so the recommended subzero treatment temperature should be between －70 ℃ and －80 ℃. Reference | Related Articles | Metrics

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  Hot deformation behavior and microstructure evolution of a novel Co-Ni-based superalloy Fu Zhiqiang, He Guoai, Wu Yunjie, He Cunxiao Heat Treatment of Metals    2024, 49 (2): 1-7.   doi:10.13251/j.issn.0254-6051.2024.02.001 Abstract （70）      PDF （7060KB）（105）       Knowledge map    Gleeble-3800 thermal simulation testing machine was used to perform hot compression tests on a novel Co-Ni-based superalloy to study its hot deformation behavior and microstructure evolution at deformation temperature of 950-1100 ℃, strain rate of 0.01-10 s-1 and true strain of 0.693. The results show that the flow stress of the alloy decreases with the increase of deformation temperature or the decrease of strain rate. The average grain size of the alloy increases with the increase of deformation temperature and the dynamic recrystallization grains can be refined by reducing the deformation temperature and increasing the strain rate. The EBSD and TEM analysis results indicate that the discontinuous dynamic recrystallization (DDRX) is the main dynamic recrystallization (DRX) mechanism and the twin nucleation is the auxiliary nucleation mechanism during the hot deformation of the alloy. Reference | Related Articles | Metrics

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  Microstructure and properties of WTaVNbMo refractory high-entropy alloy layer on W surface Huang Tianyang, Zheng Jiasheng, Tian Linhai, Lin Naiming, Wang Zhenxia, Qin Lin, Wu Yucheng Heat Treatment of Metals    2023, 48 (5): 6-11.   doi:10.13251/j.issn.0254-6051.2023.05.002 Abstract （83）      PDF （2249KB）（104）       Knowledge map    WTaVNbMo refractory high-entropy alloy layers were prepared on the surface of pure tungsten by double-glow plasma surface metallurgy technology with powder metallurgy W18Ta18V20Nb18Mo26 alloy as source target. The temperature of workpiece was 1200 ℃, and the voltage difference between the source and cathode was 300 V, 400 V and 500 V, respectively. The microstructure and phase composition of the alloy layers were examined by scanning electron microscope with attached energy dispersive spectrometer and X-ray diffractometer. The hardness and corrosion resistance of the alloy layers were tested by microhardness tester and electrochemical workstation. The irradiation resistance of the alloy layer was simulated by SRIM software. The results show that the WTaVNbMo high-entropy alloy layers with BCC structure are formed on the surface of pure tungsten under different voltage differences. When the voltage difference is 400 V, the thickness of alloy layer is more than 100 μm. The alloy layer prepared under voltage difference of 500 V has uniform surface, compact structure and the highest hardness, which can reach 1635 HV0.05. The corrosion resistance is good, and the self-corrosion current density decreases by nearly two orders of magnitude compared with that of the W substrate. The irradiation simulation results show that compared with pure tungsten, the damage range of the high-entropy alloy layer is more concentrated, the projected range is shorter, the electronic stopping power is greater, and the ionization loss rate is faster. Reference | Related Articles | Metrics

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  “Thought” of metallic materials Yuan Zhizhong, Dai Qixun, Wang Andong, Ju Yulin, Cao Fuyang, Luo Rui Heat Treatment of Metals    2023, 48 (5): 1-5.   doi:10.13251/j.issn.0254-6051.2023.05.001 Abstract （131）      PDF （1390KB）（102）       Knowledge map    “Thought” of metallic materials is refined from the systematic and comprehensive perspectives. The contradictory law of the evolution process of metallic materials properties is revealed. The complexity of the role of alloy elements is summarized. The quantitative and qualitative change law of microstructure evolution of metallic materials is expounded, and the multidirectional variability of heat treatment processes is illustrated as well. Reference | Related Articles | Metrics

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  Carbide evolution law of high chromium and high vanadium powder metallurgy tool steel M390 during austenitizing Deng Jinqiang, Zhang Qinyi, Chen Jun, Wu Dong, Liu Wei, Zhou Hongfeng Heat Treatment of Metals    2023, 48 (11): 1-7.   doi:10.13251/j.issn.0254-6051.2023.11.001 Abstract （93）      PDF （4216KB）（101）       Knowledge map    Evolution of carbides in the M390 steel during different austenitizing processes was studied using analysis methods such as SEM-EDS, TEM, and Image-Pro Plus. The results show that under the austenitizing conditions of heating at 1075-1150 ℃ and holding for 15-120 min, the volume fraction and average size of carbides in the M390 steel show a decreasing trend as the quenching temperature increases. At the same quenching temperature, with the prolongation of holding time, the amount of carbides decreases as a whole, the average size of carbides decreases first and then increases, while the amount of small carbides and hardness increase first and then decrease. The types of undissolved carbides in high temperature oil quenched steel are mainly M7C3 and M8C7. During austenitizing, the change of carbides in the M390 steel is mainly the dissolution, growth and dissolution of M7C3. Reference | Related Articles | Metrics

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  Effect of tempering temperature on microstructure and properties of particle reinforced low-alloyed wear resistant steel Huang Long, Deng Xiangtao, Wang Zhaodong Heat Treatment of Metals    2022, 47 (3): 1-6.   doi:10.13251/j.issn.0254-6051.2022.03.001 Abstract （166）      PDF （670KB）（97）       Knowledge map    Microstructure, mechanical properties and wear resistance of particle reinforced low-alloyed wear resistant steel tempered at different temperatures were studied. The results show that a large number of micron-scale and nanoscale TiC particles are uniformly dispersed in the rolled particle reinforced low-alloyed wear resistant steel. With the tempering temperature increasing, more ε-carbides are precipitated in the matrix, the yield strength of the tested steel overall increases first and then decreases, the tensile strength, hardness and impact absorbed energy gradually decrease, while the elongation gradually increases. The tested steel shows the best comprehensive mechanical properties and three-body abrasive wear properties when tempered at 200 ℃. Reference | Related Articles | Metrics

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  Effect of microstructure homogenization on mechanical properties of Cr-Ni-Mo steel Shi Changxin, Gu Guochao, Cui Shugang, Xu Wenhua, Xiao Guiyong, Lü Yupeng Heat Treatment of Metals    2023, 48 (12): 1-6.   doi:10.13251/j.issn.0254-6051.2023.12.001 Abstract （86）      PDF （5916KB）（95）       Knowledge map    Homogenization treatment of AISI 4330 steel with banding defects was carried out through a step-by-step cyclic quenching and tempering heat treatment processes. The microstructure evolution and its effect on mechanical properties was studied during homogenization process. The results show that the original specimen with banded defects consists of ferrite and pearlite, with a banded structure level of 3. The element segregation of C, Cr, and Mo is significantly revealed by means of electron probe micro-analysis (EPMA). After undergoing multiple high-temperature quenching+quenching and tempering cycles, the microstructure transforms into a homogeneous structure consisting of ferrite, carbides containing Cr, and tempered sorbite. The element segregation is improved to a certain extent. Although the diffusion of C element is evident, segregation of Cr and Mo elements still exists. The step-by-step cyclic quenching process leads to lots of phase transformation, resulting in the refinement of microstructure of the steel. Furthermore, the mechanical properties of the steel are enhanced, resulting in tensile strength exceeding 1200 MPa, hardness of about 350 HBW, and impact absorbed energy at -40 ℃ of about 70 J. The refinement of microstructure contributes to the improvement in both strength and toughness of the specimen. Additionally, the large amount of precipitated carbonitride plays a beneficial role in increasing the strength of the steel. The enhanced strength and toughness characteristics fulfill the requirements of fracturing pump products and their service life. Reference | Related Articles | Metrics