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Influence of WC content on microstructure and wear resistance of AlCrFe₂Ni₂Mo_0.9 high-entropy alloy coatings

Wang Qingtian, Man Jiao, Wang Juncheng, Liu Genggen, Yang Bin

Heat Treatment of Metals 2025, 50 (2): 282-291. doi:10.13251/j.issn.0254-6051.2025.02.046

Abstract （12）

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By adding spherical WC particles with mass fraction of 10% to 30% to AlCrFe₂Ni₂Mo_0.9 high-entropy alloy powder, the coatings with various WC contents were prepared on 316L stainless steel by using high-velocity laser cladding technology. The effect of WC content on the phase composition, microstructure, element distribution, hardness, and wear resistance of the coatings was systematically evaluated by means of X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, microhardness tester, and friction wear tester. The results indicate that, without WC addition, the coating mainly consists of FCC phase, BCC phase and σ phase. As the WC content increases, the diffraction peak intensities of the BCC and σ phases gradually weaken, while that of the FCC phase strengthens. When the WC content reaches 30%, the phase composition is in a state where FCC phase and Fe₃W₃C phase coexist. With the increase of WC content, the microstructure of the coating transitions from dendritic to a more uniform equiaxed crystal morphology, significantly enhancing the fine grain strengthening effect. Simultaneously, partial dissolution of WC particles promotes the formation of an alloyed reaction layer and fishbone-like structures. As the WC content increases from 0% to 30%, the microhardness and wear resistance of the coating show a trend of first decrease and then increase, ultimately reaching the highest hardness of 567.22 HV at 30% WC content, along with the best wear resistance, reducing the wear rate to 0.68×10^-5 mm³·N^-1·m^-1, with a friction coefficient of 0.386.

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Effects of activators and surface laser-quenching on low-temperature pack aluminizing of TC4 titanium alloy

Lu Jiacheng, Tian Xiaodong

Heat Treatment of Metals 2025, 50 (2): 292-297. doi:10.13251/j.issn.0254-6051.2025.02.047

Abstract （13）

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Effects of activators and surface laser-quenching pretreatment on low-temperature aluminizing of TC4 titanium alloy were studied. The solid powder pack cementation aluminizing of TC4 alloy was conducted between 550-700 ℃ for 4 h with three different activators of NH₄Cl, NH₄F and NaF, respectively, in the pack mixture, and the aluminizing of TC4 alloy substrate after surface laser-quenching was carried out. The cross-sectional morphology, element content and surface phase of the aluminized layers were analyzed by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-Ray diffractometer (XRD). The results reveal that the three activators, NaF, NH₄F and NH₄Cl, can make Al content increase from 10.04% to 11.56%, 15.66% and 16.96%, respectively, of the surface layer of TC4 alloy after 700 ℃×4 h pack aluminizing. Compared with the Al content of the substrate, it is increased by 15.1%, 56.0% and 68.9%, respectively. The catalytic permeation effect of NH₄Cl is the best, followed by NH₄F, and the effect of NaF is the worst. The experiment results and the thermodynamic analysis are coincident. When the holding temperature drops to 600 ℃, there is almost no change in the surface Al content of the specimen after aluminizing. However, surface laser-quenching pretreatment of TC4 alloy substrate can refine the surface grain size and promote low-temperature aluminizing. After surface laser-quenching of TC4 alloy, the surface average grain size of α-Ti phase decreases continuously with the increase of laser power. When surface laser-quenched under 240 W, the average grain size of α-Ti phase is reduced by 47.9% compared with that without laser-quenching, and after four times laser-quenching at this power, the average grain size of α-Ti phase can be reduced by 68.6% than that without laser-quenching. The reduction of grain size of α-Ti phase on surface layer can promote the diffusion of aluminum in the surface layer, of which the content increases from 10.04% to 15.54% after 600 ℃×4 h aluminizing.

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Influence of PIP/LQ composite process on properties of gun steel

Luo Yisong, Wang Fangzhou, Zhu Wei, Chen Shengyi, Luo Defu

Heat Treatment of Metals 2025, 50 (2): 298-303. doi:10.13251/j.issn.0254-6051.2025.02.048

Abstract （11）

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A composite treatment combining the advantages of two processes, PIP (Programable ion permeation) and laser quenching (LQ) for the gun steel material 25Cr3Mo3NiNbZr steel was performed to enhance its surface properties. After pretreatment of quenching and tempering, the tested steel was treated with PIP followed by laser quenching at different scanning speeds. Properties of the specimens were characterized by metallographic observation, XRD analysis, microhardness test, electrochemical corrosion and neutral salt spray test. The results show that scanned at the laser energy density of 2.31-3.00 J/mm², part of the compound layer decomposes, reducing the surface hardness, nitrogen-containing martensite generates in the diffusion layer, and the peak hardness of the subsurface layer is improved. Laser scanning speed of 39 mm/s (laser energy density of 2.31 J/mm²) is determined for the optimum process, when scanned at this speed, the microstructure is refined, more nitrogen-containing martensite transforms, less nitrides lose in the surface layer, and the eggshell effect is effectively alleviated. The corrosion resistance of the PIP/LQ composite process treated specimens is lower than that of the PIP treated specimens but still higher than that of the untreated specimens. It is concluded that the PIP/LQ composite process is feasible to improve the surface properties of gun steel.

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Microstructure and properties of ion nitriding/PVD composite modified layer on 316L stainless steel

Cao Chi, Zhang Xiang, Chen Zhilin, Chen Dongsheng, Zhang Zhuo

Heat Treatment of Metals 2025, 50 (1): 299-307. doi:10.13251/j.issn.0254-6051.2025.01.046

Abstract （36）

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To improve the surface hardness, wear resistance, and corrosion resistance of stainless steel, the effects of single ion nitriding and ion nitriding/physical vapor deposition (PVD) composite treatments on the microstructure, hardness and tribological and corrosion properties of 316L austenitic stainless steel were studied. The results show that the specimen treated by single ion nitriding forms a high-nitrogen hardened layer with a thickness of about 20 μm and hardness of about 802 HV0.05. The specimen treated by nitriding/PVD composite treatment forms a modified layer with a thickness of about 25 μm and nanohardness of about 29 GPa. Both processes form the γ_N phase, and the amorphous film formed on the surface of the nitriding/PVD composite treated specimen does not affect the phase of the intermediate layer. Compared to that of the substrate steel, the friction coefficients of the single nitrided specimen decrease to 0.520 and 0.311 under dry friction and corrosive friction conditions, respectively, while that of the nitriding/PVD composite treated specimen decrease to 0.074 and 0.119, respectively. The self-corrosion current density of the single nitrided and the nitriding/PVD composite treated specimens decrease from 4.602×10^-8 A/cm² to 4.084×10^-8 A/cm² and 3.318×10^-8 A/cm², respectively, and the self-corrosion potentials increase from -0.213 V to -0.195 V and -0.182 V, respectively. Comprehensively, the composite treatment can significantly improve the surface hardness, wear resistance, and corrosion resistance of the 316L austenitic stainless steel.

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Development of induction heat treatment technology and equipment for key components of machine tool

Li Xianjun, Jiang Chao, Zhang Minghao, Zhang Wenliang, Sun Lizhuang

Heat Treatment of Metals 2025, 50 (1): 308-316. doi:10.13251/j.issn.0254-6051.2025.01.047

Abstract （27）

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Induction heat treatment technology and its application in key components of machine tool were summarized from the two aspects of induction heat treatment technology and equipment, the specific induction heat treatment process and equipment design for spindle, ball screw and guideway of the machine tool were introduced, and the prospects for future promotion were prospected.

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Effect of centrifugal barrel finishing/QPQ combined treatment on wear resistance of titanium alloy

YanYuan, Li Xiuhong, Li Qihang, Wang Delong, Li Wenhui

Heat Treatment of Metals 2025, 50 (1): 317-324. doi:10.13251/j.issn.0254-6051.2025.01.048

Abstract （16）

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Aiming at the high surface requirement when applying QPQ treatment to improve titanium alloy surface properties, centrifugal barrel finishing before QPQ treatment was carried out. The effect of centrifugal barrel finishing/QPQ combined treatment on the surface morphology, phase composition, microhardness and wear resistance of TC4 titanium alloy were studied by means of XRD, SEM, ultra-depth of field optical microscope, white light interferometer, roughness meter, micro-Vickers hardness tester and friction and wear tester. The results show that more uniform titanium nitrides and oxides are formed on the surface of TC4 titanium alloy after centrifugal barrel finishing composite QPQ treatment, and the surface quality is improved as the surface roughness Ra decreases by 35.7% than that of only grinding, the microhardness increases by 42.74%, the average friction coefficient decreases by 6.56%, the wear rate decreases by 38.89%, and the wear scar depth decreases by 49.81%, indicating that the wear resistance increased significantly.

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Friction properties of H13 steel nitrocarburizing-modified by hollow cathode plasma source

Liao Yongfa, Shang Yong, Li Yang, Liu Zhongli, Jiang Mingquan, Zhou Zelong, Gao Yue

Heat Treatment of Metals 2025, 50 (1): 325-331. doi:10.13251/j.issn.0254-6051.2025.01.049

Abstract （24）

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To improve the hardness and wear resistance of H13 steel, surface treatment of H13 steel was carried out by hollow cathode ion discharge nitrocarburizing (520, 530 and 540 ℃ for 5 h), and the microstructure, hardness and friction and wear properties of the H13 after nitrocarburizing were analyzed. The results show that an iron-nitride compound diffusion layer is formed on the surface of the H13 steel after nitrocarburizing, which results in significantly improvement of the hardness and wear resistance. The surface hardness of the specimen after nitrocarburizing at 530 ℃ is the highest, which is 999.3 HV0.1, 120% higher than that of the specimen after quenching and tempering, and the depth of the hardening layer is about 175 μm based on the measurement of hardness gradient. The friction and wear test under oil lubrication condition shows that the wear volume of the specimen after nitrocarburizing at 540 ℃ is 83% lower than that of the specimen after quenching and tempering.

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Influence of diffusion regimes on duplex platinum-aluminum coating on nickel based superalloy

Si Yan, Wu Yeqiong, Chao Guotao, Li Jie, Huang Xuanxuan, Guo Shuangquan, Li Shuguang

Heat Treatment of Metals 2025, 50 (1): 332-336. doi:10.13251/j.issn.0254-6051.2025.01.050

Abstract （23）

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The duplex platinum-aluminum coatings were prepared by electroplating platinum, vacuum diffusion and embedded aluminization. Effects of different diffusion and annealing treatments on the thickness, element content and hardness of the duplex platinum-aluminum coatings were studied. The results show that the Pt content of the outer layer decreases with the increase of diffusion temperature, the Al content slowly increases with the increase of diffusion temperature, the hardness of the outer layer of the coatings slowly decreases with the increase of diffusion temperature, and the hardness of the middle layer does not change much. At the same time, adding annealing treatment after coating preparation can reduce the hardness of the outer layer of the duplex platinum-aluminum coatings and decrease the brittleness of the coatings.

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Effect of holding temperature on wear resistance and corrosion resistance of powder sherardized layer containing Mg

Gu Jian, Li Dongqing, Liu Shengchun, Qi Yi

Heat Treatment of Metals 2024, 49 (12): 221-228. doi:10.13251/j.issn.0254-6051.2024.12.036

Abstract （35）

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In order to investigate the effect of holding temperature on the properties of sherardized layer, sherardized layer containing Mg was prepared on the surface of Q345R steel by using powder sherardizing at three holding temperatures (410, 430 and 450 ℃). The thickness, elemental distribution, wear resistance and corrosion resistance of the sherardized layer were characterized by using analytical methods such as scanning electron microscope, wear tester and electrochemical workstation. The results show that a continuous sherardized layer can be formed when the holding temperature is between 410-450 ℃. The sherardized layer becomes thicker as the holding temperature increases and reaches the maximum thickness of 110 μm at 450 ℃. The wear resistance of the sherardized layer decreases with the increase of holding temperature, and the main wear mechanisms of the sherardized layer are abrasive, adhesive and oxidative wear. The corrosion resistance of the sherardized layer increases first and then decreases with the increase of holding time, and the sherardized layer has the best corrosion resistance when held at 430 ℃.

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Comparison of laser surface hardening ability between nodular cast iron and gray cast iron

Zhou Xianmin, Zeng Daxin, Yang Wei, Shi Qiuyue, Guo Dazhi

Heat Treatment of Metals 2024, 49 (12): 229-236. doi:10.13251/j.issn.0254-6051.2024.12.037

Abstract （25）

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Laserline-LDF3000 fiber-coupled semiconductor lase was used to harden the surface of nodular cast iron and gray cast iron. Effect of laser processing parameters on microstructure, depth and hardness of hardened layer was studied, and the hardening ability of the two types of cast irons was compared. The results show that at the same energy density, the hardened layer depth of the nodular cast iron is higher than that of the gray cast iron, and the depth of the hardened layer of the two types of cast irons with only slight melting on the surface is basically the same, around 0.8 mm. The main factors affecting the hardened layer depth of the tested cast irons are process parameters and material thermal conductivity. The hardened layer depth of the nodular cast iron has an approximate linear correlation with the energy density, but no linear relationship exists between them for gray cast iron because of its higher thermal conductivity. The surface hardness of the nodular cast iron (55-60 HRC) is higher than that of the gray cast iron (45-50 HRC) after laser hardening, and the influence of process parameters on the surface hardness is relatively small. The laser hardening ability of the nodular cast iron is higher than that of the gray cast iron.

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Fatigue properties and fracture behavior of shot peened 55Si2MnMoV spring steel

Jia Jinke, Li Xing, Zhang Jiwang

Heat Treatment of Metals 2024, 49 (12): 237-242. doi:10.13251/j.issn.0254-6051.2024.12.038

Abstract （26）

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Shot peening and shot peening-polishing treatments were applied to the 55Si2MnMoV spring steel. The surface roughness, hardness, and residual stress were characterized by using laser confocal microscopy, microhardness tester and X-ray residual stress analyzer. Fatigue tests were conducted to plot S-N curves and observe fatigue fracture morphology, thereby investigating the fatigue property of the 55Si2MnMoV spring steel subjected to shot peening. The results indicate that shot peening improves the fatigue property of the spring steel specimens. Compared to the untreated specimen, the fatigue strength of the both shot peened and shot peened-polished specimens is increased by 16.7%. Although the surface roughness of the shot peened-polished specimens is lower than that of the shot peened specimens, their fatigue strength remain the same. Shot peening treatments do not change the fatigue fracture mechanism, as all the specimens exhibit a fracture mode initiated by surface cracks. The residual compressive stress in the hardened layer of the shot peened specimens is the primary factor contributing to the enhanced fatigue strength.

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Tribological properties of shot peening/bionic clam shell micro-texture composite modified layer of 65Mn steel plow surface

Liu Chengzhou, Wu Keyang, Wang Yingdong, Zhao Deyong, Wang Yuan

Heat Treatment of Metals 2024, 49 (12): 243-248. doi:10.13251/j.issn.0254-6051.2024.12.039

Abstract （26）

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Ultrasonic shot peening was first applied to strengthen the plow surface of 65Mn steel, followed by laser processing to create bionic clam shell micro-texture for reducing adhesion and drag. A shot-peening/bionic clam shell micro-texture composite modified layers with texture ratios of 19%, 23% and 37% were formed, and tribological properties tests were conducted under lubrication with artificially prepared earthworm fluid by using the HSR-2M reciprocating friction and wear tester. The hardness and surface roughness of the specimens were measured by using HV-1000D Vickers hardness tester and TR200 roughness tester, respectively. Surface structure and wear scar morphology were observed by using M330BD-HK830 metallurgical microscope and S-4800FE scanning electron microscope. The results show that ultrasonic shot peening alone increases the surface roughness of the 65Mn steel plow, which leads to an increase in the friction coefficient, while the improved hardness enhances wear resistance. The single bionic clam shell micro-texture with a texture ratio of 23%, without shot peening, provides limited improvement in the friction-reducing and wear-resistance of the 65Mn steel plow, reducing the friction coefficient and wear rate by 4.83% and 29.18%, respectively, compared to the unpeened and untextured specimen. Both shot peening and bionic clam shell micro-texture improve the friction-reducing and wear-resistant properties of the 65Mn steel plow to varying degrees. The specimen with texture ratio of 37% exhibits the best friction-reducing and wear-resistant properties, with maximum reductions in the friction coefficient and wear rate of 23.45% and 86.77%, respectively, compared to the unpeened and untextured specimen.

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Effect of programable ion permeation (PIP) treatment on mechanical properties of 25Cr2Ni4WA steel thin-walled parts

Yang Junxia, Luo Defu, Chen Yunxin, Xie Zhousheng

Heat Treatment of Metals 2024, 49 (12): 249-253. doi:10.13251/j.issn.0254-6051.2024.12.040

Abstract （30）

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Surface modification of the 25Cr2Ni4WA steel specimens with thickness of 2 mm was carried out with programable ion permeation (PIP) technology. The main processes were nitriding temperature of 530 ℃, cyanate concentration of 32%, nitriding time of 20, 40, 60 and 90 min, respectively, and after nitriding, oxygenation treatment was carried out, with oxygenation temperature of 450 ℃ and oxygenation time of 15 min. The microstructure, surface hardness, cross section hardness, tensile properties and fracture morphologies of the specimens treated by different PIP processes were analyzed. The results show that the structure of the permeation layer is composed of oxide film, loose layer, bright white layer and diffusion layer. The thickness of permeation layer increases with the extension of nitriding time, but the growth rate of infiltration layer decreases. PIP treatment can significantly improve the hardness of the specimens, in which the hardness of the specimens with nitriding time of 60 min is the highest and 2.3 times of the substrate one. After PIP treatment, the tensile properties of the specimens decrease, and the deeper the penetration layer, the more the decrease, and the specimens as a whole show ductile-brittle mixed fracture.

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Surface oxygenation technology and hardness of pure tantalum used as artificial joints

Yang Guang, Xie Xiaodong, Luo Yong, Xu Zhentao, Sun Xiaolei, Qi Yang, Ma Xian

Heat Treatment of Metals 2024, 49 (11): 284-289. doi:10.13251/j.issn.0254-6051.2024.11.044

Abstract （34）

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Surface oxygen infiltration products and hardness of the pure tantalum used as artificial joints under different processes were studied by means of low pressure vacuum surface oxygenation technology, scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and nanoindentation technology. The results show that surface oxygen infiltrated layer with thickness of about 3.6 μm, which contains the phase of tantalum oxide Ta₄O, can be prepared under the condition of 500 ℃×2 h/273 mL(oxygen flow volume, the same below). The δ-(Ta, O) compounds can be prepared under the conditions of 550 ℃×2 h/273 mL, 550 ℃×5 h/1.3 mL, 550 ℃×10 h/0.013 mL and 650 ℃×3 h/0.013 mL. The thickness of surface oxygen infiltrated layer with δ-(Ta, O) compounds varies according to the parameters of oxygen infiltration temperature, time and oxygen flow volume. The surface oxygen infiltrated layer with the average thickness of nearly 60 μm is prepared under the condition of 550 ℃×1 h/273 mL, and the surface phase is tantalum oxides with polyvalent tantalum, the Vickers hardness and maximum nanoindentation hardness of the specimen are (160.27±2.80) HV5 and 7.92 GPa, respectively, which are significantly higher than those of the pure tantalum. This technology can be used to increase the abrasion resistance and lifespan of the Ta-based artificial joints.

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Microstructure and properties of TiC-Fe₃Al-Ni clad layer prepared by mechanical vibration

Guo Jun, Zhou Junjie, Liang Guoxing, Huang Yonggui

Heat Treatment of Metals 2024, 49 (11): 290-295. doi:10.13251/j.issn.0254-6051.2024.11.045

Abstract （26）

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In order to enhance the wear resistance of 42CrMo steel surface and improve the porosity and crack defects frequently generated in the clad layers, as well as the performance of the clad layer, TiC-Fe₃Al-Ni clad layer was prepared on the surface of 42CrMo steel via laser cladding, and mechanical vibration carrying different modes was introduced. The phase composition, microstructure and properties of the clad layer under different vibration directions were analyzed by means of SEM, XRD, microhardness tester and friction and wear tester. The results show that the porosities and cracks in the clad layer are significantly restrained due to the mechanical vibration. Furthermore, part of crystal arms of dendrites is broken by the mechanical energy coming from the vibration during the process of grain growth, and the dendrite growth is reduced. Therefore, the condition of equiaxial crystal growth is developed, and the compactness of the clad layer is strengthened. The clad layer primarily contains the phases of TiC, Ti₈C₅, Fe₃Al, FeO, as well as AlNi. Mechanical vibration has a little effect on changing the phase constituent of the clad layer. Vertical vibration significantly improves the microstructure of the clad layer. The mean hardness of the clad layer at vertical vibration reaches up to 1891.78 HV0.2, which is obviously higher than that without mechanical vibration, the wear resistance of the clad layer is optimal, with wear loss of 1.57 mg, and the wear process has small fluctuation.

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Effect of austenitizing process on structure and cracks of galvanized layer on 22MnB5 hot stamped steel

Zhao Jingxuan, Liang Jian, Zhang Lingling, Dong Yikang, Wang Lihui, Miao Bin, Shen Chunguang, Zheng Shijian

Heat Treatment of Metals 2024, 49 (11): 296-301. doi:10.13251/j.issn.0254-6051.2024.11.046

Abstract （52）

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22MnB5 hot-dip galvanized hot stamped steel was heated to different austenitizing temperatures for different time for hot stamping. The effect of austenitizing process for hot stamping on the microstructure and cracks of the galvanized layer on hot stamped steel was investigated through characterization of the microstructure, surface oxides and cracking of the galvanized layer by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) analysis. The results indicate that the galvanized layer is primarily composed of α-Fe (Zn) and a small amount of brittle Fe₃Zn₁₀ after austenitizing. With an increase in heating temperature from 870 ℃ to 890 ℃, the galvanized layer thickness reaches the maximum, and there is a noticeable decrease in the presence of Fe₃Zn₁₀, leading to a reduction of cracks after hot stamping. However, the galvanized layer thickness slightly decreases at 910 ℃ due to Zn volatilization, resulting in the formation of a large amount of Mn, Zn and other elemental oxides on the surface, and the content of Fe₃Zn₁₀ in the galvanized layer significantly increases, leading to a large number of cracks after hot stamping. When the holding time at 890 ℃ is extended from 370 s to 400 s, the Fe-Zn reaction is promoted, more α-Fe(Zn) phases are formed, resulting in an increase of the galvanized layer thickness, but with no significant change of the surface oxidation degree.

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Effect of laser cladding power on quality and microstructure of FeCoCrNiAl_0.3Mo_0.1 alloy coating

Zhao Yongtao, Hu Yuqing, Hu Shuai, Wu Yinhu, Yang Zehua, Wang Rui

Heat Treatment of Metals 2024, 49 (10): 246-250. doi:10.13251/j.issn.0254-6051.2024.10.040

Abstract （35）

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FeCoCrNiAl_0.3Mo_0.1 alloy coating was prepared on the surface of 304 stainless steel, and the effect of laser power (800, 1000, 1200 W) on the coating quality and microstructure was studied. The results show that the coating prepared at 800 W and 1000 W laser power has cracks and stoma defects, and no obvious defect is found at 1200 W. The coating structure at different laser powers is columnar, but after comparative analysis, the microstructure of the coating at 1200 W is finer and more uniform. The composition analysis of the coating finds that the Fe content is much higher than the nominal value, but the Al content is far lower than the nominal value. From bottom to top, the average content of Fe and Cr gradually decreases, and the content of other elements gradually increases. It is also found that the content of Mo and Cr in intergranular is higher than that in intragranular.

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Microstructure and properties of nitrided layer on austenitic gray cast iron by glow ion nitriding

Cao Chi, Zhang Zhuo, Chen Zhilin, Song Xiangyu

Heat Treatment of Metals 2024, 49 (10): 251-257. doi:10.13251/j.issn.0254-6051.2024.10.041

Abstract （38）

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Nitrided layer was prepared on the surface of Ni15Cu6Cr2 austenitic gray cast iron by glow plasma nitriding at different temperatures (380, 540 ℃). The cross-section structure, element distribution and phase composition of the nitrided layer were analyzed by Zeiss optical microscope, scanning electron microscope, electron probe and X-ray diffractometer. The tribological properties of the nitrided layer were analyzed by wear scar morphology and three-dimensional profile. The corrosion resistance of the austenitic gray cast iron before and after nitriding was investigated by electrochemical test. The results show that after nitriding at 380 ℃ for 10 h, a compound layer composed of ε phase and a small amount of γ′ phase with a thickness of about 2 μm is obtained on the surface of the austenitic gray cast iron, and the surface hardness is about 330 HV0.05. When the nitriding temperature rises to 540 ℃, the surface hardness increases to about 900 HV0.05, the thickness of the compound layer reaches about 10 μm, the ε phase gradually transforms into the γ′ phase, and the thickness of the whole nitrided layer is about 45 μm. The wear mechanism of the austenitic gray cast iron matrix is abrasive wear, which gradually transforms into adhesive wear after nitriding. The width of the wear scar gradually narrows and the depth gradually becomes shallower, and the wear resistance is significantly improved. After nitriding at 540 ℃, the corrosion resistance is significantly improved. Compared with the matrix, the self-corrosion potential increases from -0.337 V to -0.217 V, the self-corrosion current density decreases from 1.51×10^-6 A/cm² to 3.07×10^-7 A/cm².

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Effect of boronizing temperature on properties of boronized layer on 45 steel

Wang Lan, Xie Yuanna, Weng Chenhao, Song Jianfeng

Heat Treatment of Metals 2024, 49 (10): 258-263. doi:10.13251/j.issn.0254-6051.2024.10.042

Abstract （45）

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Effect of different boronizing temperatures (800, 850, 900 ℃) on thickness, hardness, fracture toughness, brittleness and corrosion resistance of boronized layer on 45 steel was studied. The hardness, crack morphology of indentation and elastic modulus of boronized layer were tested by Vickers hardness tester. The elastic modulus of boronized layer was measured by nanohardness tester, and the fracture toughness and brittleness of boronized layer were characterized quantitatively. The corrosion resistance of boronized layer was characterized by electrochemical workstation. The results show that after boriding at different temperatures, as the boronizing temperature increases, the thickness and hardness of the boronized layer increase, the fracture toughness decreases and the brittleness increases. After boronizing at 800 ℃, the self-corrosion potential of the boronized layer is the highest, the self-corrosion current density is the lowest and the corrosion resistance is the best. Comprehensively, the optimal boronizing process for 45 steel is boronizing at 800 ℃ for 4 h.

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Microstructure and properties of Stellite12 alloy surfacing welded on multi-stage step-down control valve spool

Chen Lin, Cao Yongmin, Jiang Yongbing, Hao Jiaoshan, Tang Fanshun, Ma Shichuan, Fei Qinnan

Heat Treatment of Metals 2024, 49 (10): 264-271. doi:10.13251/j.issn.0254-6051.2024.10.043

Abstract （37）

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In order to improve the abrasion resistance and corrosion resistance of multi-stage step-down control valve spool, and shorten the manufacturing cycle of such parts, Stellite12 alloy was prepared on the surface of valve spool by laser cladding and gas tungsten arc welding(GTAW). The microstructure, microhardness, friction and wear properties, uniform corrosion properties of the surfacing welded Stellite12 alloy layer were compared and studied. The results show that the surfacing welded alloy layer prepared by both methods forms a good metallurgical bond with the substrate, and the microstructure is mainly composed of dendrite structures of plane crystal, coarse columnar dendrites, fine and dense equiaxed dendrites. Compared with that of GTAW, the laser clad alloy layer has more dense and fine dendrite structure, and more uniform distribution of dendrite composition. At the same time, the laser clad alloy layer has higher microhardness and better abrasion resistance. In addition, the laser clad alloy layer has lower uniform corrosion rate and more uniform corrosion behavior than the GTAW alloy layer.

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