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Effect of ultrasonic surface rolling process on corrosion resistance of 304 stainless steel

Chen Xinjian, Sui Rongjuan, Wang Yanfei, Cheng Yanhai, Gao Linhao

Heat Treatment of Metals 2024, 49 (9): 268-274. doi:10.13251/j.issn.0254-6051.2024.09.045

Abstract （58）

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Effect of ultrasonic surface rolling process (USRP) on the corrosion resistance of 304 stainless steel surface was investigated. The surface morphology, microstructure, residual stress and surface roughness were analyzed by means of scanning electron microscopy, X-ray diffraction analysis, and metal surface roughness meter, respectively. The corrosion resistance and integrity of the oxide film was assessed using electrochemical tests and o-phenanthroline color development experiments. The results indicate that the value of R_a for the 304 stainless steel is reduced from 0.60 μm to 0.28 μm after USRP treatment. The surface grain size is reduced from 23.13 μm to 20.80 nm, and the surface residual stress is changed from 20 MPa to -329 MPa. Compared with the untreated specimen, the minimum corrosion current density I_corr of the USRP treated specimen is 0.94×10^-5 A/cm², which is reduced by 71%. The oxide film resistance R_p is 2.59×10⁶ Ω·cm², increased by 2 times. The range of color rendering value of phenanthroline is narrowed and the color rendering area is decreased, indicating that the surface defects are reduced and the quality of the surface oxide film is improved. For the 304 stainless steel, USRP treatment promotes the grain refinement near the surface layer, produces residual compressive stress, reduces surface defects, denseres oxide film, and then blocks the electrochemical reaction process, and improves the corrosion resistance.

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Electrochemical corrosion behavior of FeCoCrNiMoBSi high-entropy alloy coating prepared by laser cladding

Du Xinyu, Zhai Changsheng, Rong Haisong, Xie Fang, Zheng Hongxing, Zhang Xi, Zhang Xin, Liu Gang

Heat Treatment of Metals 2024, 49 (8): 261-267. doi:10.13251/j.issn.0254-6051.2024.08.044

Abstract （55）

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FeCoCrNiMoBSi high-entropy alloy (HEA) coating was fabricated on the 316L stainless steel substrate via laser cladding. The microstructure, electrochemical corrosion and immersion corrosion properties of the HEA coating in H₂SO₄ solution were investigated. The results show that the laser clad HEA coating exhibits a bilayer structure, consisting of a columnar crystal at the bottom and an equiaxed crystal at the top. In the 0.3 mol/L H₂SO₄ solution, the self-corrosion potential, self-corrosion current density and polarization resistance of the HEA coating are 0.091 V, 11.499 μA/cm² and 9839.90 Ω, which are 2.12 times, 6.17% and 12.2 times, respectively, of the 316L stainless steel substrate. The HEA coating exhibits larger capacitance arc radius and impedance modulus value. Additionally, in the 50% H₂SO₄ solution, the corrosion rate of the HEA coating is lower, approximately 0.098 mg/(dm²·d), 316L stainless steel substrate shows conspicuous heterogeneous corrosion, whereas the corrosion surface of the HEA coating remains uniformly flat, showing homogeneous corrosion rate. The comprehensive results show that the corrosion resistance of the FeCoCrNiMoBSi high-entropy alloy coating on the 316L stainless steel substrate is significantly better than that of the substrate itself.

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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 B₄C addition on morphology and properties of Stellite6+B₄C laser clad layers on 42CrMo steel surface

Zhang Zejiang, Li Xinmei, Zhu Chunjin, Li Hang, Yang Dingli

Heat Treatment of Metals 2024, 49 (7): 200-207. doi:10.13251/j.issn.0254-6051.2024.07.031

Abstract （49）

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In view of the surface modification of shearer picks, effect of B₄C addition (3%, 5% and 7%) on the cross-section morphology, microhardness, wear resistance and corrosion resistance of the Stellite6+B₄C laser clad layers on 42CrMo steel was studied by means of X-ray diffractometer, scanning electron microscope, Vickers microhardness tester, multifunctional friction and wear testing machine and electrochemical workstation. The results show that the cross-section morphology of the clad layer is good when the B₄C addition is 3% and 5%, however, when the B₄C addition is 7%, there are many defects on the surface of the clad layer. With the increase of B₄C addition, the microhardness of the clad layer increases from 781.04 HV to 1044.72 HV, the average friction coefficient decreases and the wear loss decreases first and then increases. When the B₄C addition is 7%, the average friction coefficient of the clad layer is 0.42, but due to the poor forming quality, the wear loss is the highest as 1.9 mg. When the B₄C addition is 5%, the wear loss is the least as 0.6 mg. The corrosion resistance of the clad layer first increases and then decreases with the increase of B₄C addition. When the B₄C addition is 5%, the self-corrosion potential of the clad layer is the highest, the self-corrosion current density is the smallest, and the charge transfer resistance R_ct is the largest, the best corrosion resistance of the clad layer is obtained.

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Effect of TiC content on microstructure and wear resistance of AlCoCrFeNi high-entropy alloy clad layer

Zhang Hongliang, Wang Mingxin, Zhang Jingbing, Li Yutao, Jin Tounan

Heat Treatment of Metals 2024, 49 (9): 275-279. doi:10.13251/j.issn.0254-6051.2024.09.046

Abstract （48）

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AlCoCrFeNi-2xMo-xTiC (x=0, 0.1, 0.25, 0.4) high entropy alloy clad layer was prepared on 40CrNiMo steel surface by laser cladding method. The effect of TiC and Mo content on the microstructure and wear resistance of the AlCoCrFeNi-2xMo-xTiC alloy clad layer was studied through XRD, SEM, EBSD, TEM, and wear resistance tests. The results show that after in-situ formation of TiC, the microstructure of the clad layer consists of BCC and TiC phases. As the atom fraction of TiC increases, the size of carbide precipitates gradually increases, and the grain size of the clad layer is significantly refined, decreasing from 109 μm to 15 μm. The AlCoCrFeNi-0.8Mo-0.4TiC clad layer has the highest hardness of 750 HV0.3, which is 300 HV0.3 higher than the AlCoCrFeNi alloy clad layer. The hardness and wear resistance of the clad layer increase with the increase of atom fraction of TiC. The wear surface of the AlCoCrFeNi alloy clad layer has more debris, and the wear mechanism is adhesive wear. The wear mechanism of the AlCoCrFeNi-0.2Mo-0.1TiC, AlCoCrFeNi-0.5Mo-0.25TiC, and AlCoCrFeNi-0.8Mo-0.4TiC alloy clad layers are abrasive wear.

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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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Optimization of carburizing and quenching process for 20MnCr5 steel inner star wheel

Ding Zhong, Meng Xianggang, Li Xiaotian, Gu Jiacheng, Xu Jie

Heat Treatment of Metals 2024, 49 (7): 208-211. doi:10.13251/j.issn.0254-6051.2024.07.032

Abstract （44）

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In order to improve the surface hardness and wear resistance of inner star wheel and ensure the toughness of the core, the carburizing and quenching process of 20MnCr5 steel inner star wheel was optimized. The results show that the hardness and the depth of effective hardening layer of the 20MnCr5 steel inner star wheel meet the technical requirements after (935±10) ℃×295 min+830 ℃×30 min carburizing and quenching with diffusion carbon potential of 0.75%, quenching carbon potential of 0.65%, and the oil cooling stirring speed of 1100 r/min. After 400 cycles life test, wear and peeling appear on the surface of the inner star wheel treated by the original carburizing and quenching, while only slight scratches appear on the surface of the inner star wheel treated by optimized carburizing and quenching. The wear resistance is significantly improved compared to the original carburizing and quenching.

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Effect of substrate surface rust on hot-dip galvanized and galvannealed coatings

Li Shanshan, Jin Xinyan

Heat Treatment of Metals 2024, 49 (8): 268-274. doi:10.13251/j.issn.0254-6051.2024.08.045

Abstract （44）

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Annealing and hot-dip galvanizing simulations were conducted on the cold-rolled IF steel sheet with localized surfacerust by using IWATANI hot-dip galvanizing simulator. Effects of substrate surface rust on annealed, hot-dip galvanized (GI) and galvannealed (GA) coatings were studied. The results show that after continuous annealing in an atmosphere of N₂+5% H₂ at 800 ℃, the rust is reduced to reduced iron with small grains, loose structure and numerous micropores between each other. During hot-dip galvanizing, the reduced iron rapidly diffuses with the molten zinc, causing the appearance of a zinc iron alloy phase in the coating and reducing the fluidity of the molten zinc, which further affects the control of the coating thickness when the specimen passes through the air knife, resulting in localized thickening of the GI coating at the rust location. After coating alloying, the morphology of the GA coating at the rust position is completely different from that of the normal coating, that is, the coating is flat and thick, and ultimately shows as white spot defects on the surface of the GA coating.

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High-temperature oxidation resistance of bi-electrodes micro-arc oxidation ceramic coating on tantalum

Cai Mingliang, Tian Xue, Chen Xinxin, Zhang Daiyue, Hao Guodong

Heat Treatment of Metals 2024, 49 (5): 267-271. doi:10.13251/j.issn.0254-6051.2024.05.045

Abstract （41）

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Under silicate system and dual pulse constant pressure mode, the bi-electrodes micro-arc oxidation and traditional micro-arc oxidation techniques were used to grow ceramic coating in situ on the surface of tantalum metal. The thickness of the coating was tested by using thickness gauge. The phase composition, surface morphology and element content of the coating were analyzed by using X-ray diffractometor, scanning electron microscope and energy dispersive spectrometer. The high-temperature oxidation resistance of the coating was studied by using high-temperature oxidation mass gain test. The results indicate that the phase composition of the coating formed by traditional micro-arc oxidation and bi-electrodes micro-arc oxidation reactions is Ta₂O₅ phase. The coating thickness generated under traditional micro-arc oxidation mode is greater than that under bi-electrodes micro-arc oxidation mode. After high-temperature oxidation, the surface of the coating is smoother compared to that before oxidation, indicating that the oxides melt and collapse after oxidation, and there are obvious sintering traces, with some remained volcanic crater-like small pores. High temperature oxidation causes the oxide to extrude and expand, resulting in microcracks. Compared with the matrix, the specimens subjected to micro-arc oxidation have better resistance to high-temperature oxidation. The ceramic coating generated in situ by bi-electrodes micro-arc oxidation technology has less high-temperature oxidation mass gain and better resistance to high-temperature oxidation compared to that of traditional micro-arc oxidation technology.

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Effect of medium-low temperature annealing on morphology, structure and electrical properties of MoS₂ nano films

Liu Chunquan, Xiong Fen, Ma Jiayi, Zhou Jintian, Liang Zexun, Huang Jianping

Heat Treatment of Metals 2024, 49 (7): 186-194. doi:10.13251/j.issn.0254-6051.2024.07.029

Abstract （40）

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MoS₂ nano films with different thicknesses were prepared by radio frequency (RF) magnetron sputtering via deposition at room temperature, and then annealed by different processes in 95%Ar+5%H₂ mixed atmosphere. The structure, surface morphology and electrical properties of the MoS₂ films were studied by means of atomic force microscope(AFM), Raman spectrum, four-probe and Hall tester. The results show that the MoS₂ films grown on the silicon substrate are uniform and continuous. The annealing process can effectively remove the impurity oxygen in MoS₂ films and improve its crystallinity, stability and structural integrity. The comprehensive properties of the MoS₂ films are better when the deposition time is 40 min (the thickness is about 300 nm), while the crystallinity and electrical properties of the films after annealing at 500 ℃ for 60 min are all better.

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Preparation and high-temperature friction behavior of TiN coating on valve disc cone surface based on dual glow technology

Luo Changzeng, Zeng Xiaoxiao, Wei Dongbo, Li Xucong, Chen Yuechun, Lin Muyao, Zhang Pingze

Heat Treatment of Metals 2024, 49 (7): 195-199. doi:10.13251/j.issn.0254-6051.2024.07.030

Abstract （39）

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TiN coatings were prepared on NCF3015 valve alloy steel using double-layer glow plasma surface metallurgy technology. The microstructure, hardness and high-temperature wear resistance of the coatings were studied by SEM, EDS, XRD, microhardness tester and high-temperature friction and wear tester. The results show that the TiN coating grows uniformly in an island-like manner and has a dense surface structure. The average surface hardness of the coating can reach 1265.2 HV0.05. Under 5 N and 10 N loads, the specific wear rate of the coating is reduced by 79.3% and 79.7% compared to the valve substrate, respectively. It is an ideal material for valve surface protection under high temperature and harsh conditions, and can significantly improve the service life of valves in engines.

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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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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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Effect of laser clad Stellite6+WC composite coating on water erosion resistance of stainless steel blades

Deng Dewei, Wan Hongming, Wang Hongsuo, Chen Wenbo, Lian Shiwei

Heat Treatment of Metals 2024, 49 (5): 243-251. doi:10.13251/j.issn.0254-6051.2024.05.042

Abstract （37）

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Stellite6+WC composite coating was deposited on the surface of 17-4PH stainless steel by using laser cladding method. The optimal cladding parameters suitable for Stellite6 alloy were obtained through orthogonal experiments, and then different contents of WC powder were added to the coating under these cladding parameters. By using optical microscope, microhardness tester and salt spray corrosion test chamber, the effects of WC addition and laser quenching technology on the microstructure, Vickers hardness, and salt spray corrosion resistance of the clad coating were compared and studied. The results indicate that the optimal cladding parameters are laser power of 1500 W, laser scanning speed of 18 mm/s, and focal distance of 13 mm. When the mass fraction of WC is within 30%, the microhardness and salt spray corrosion resistance of the Stellite6+WC clad coating gradually increase with the increase of WC content. However, when the mass fraction of WC is higher than 30%, the microhardness and salt spray corrosion resistance of the clad coating are not significantly improved compared to that of the cladding with 30%WC. Although the laser quenching process improves the microhardness and salt spray corrosion resistance of the cladding to some extent, the salt spray corrosion resistance of the coating after laser quenching at 3000 W is not further improved compared to that after laser quenching at 1000 W.

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Influence of Y₂O₃ addition on microstructure and wear resistance of ultra-high-speed laser-clad IN718 alloy coatings

Li Rui

Heat Treatment of Metals 2024, 49 (7): 173-180. doi:10.13251/j.issn.0254-6051.2024.07.027

Abstract （36）

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IN718 alloy composite coatings with Y₂O₃ addition were prepared by ultra-high-speed laser-cladding technology. The effect of Y₂O₃ addition on coating microstructure and morphology, phase composition, hardness and wear resistance was analyzed. The results show that the addition of Y₂O₃ reduces the pore defects in the coating and forms a dense and refined grain. The hardness of the coatings is the highest when Y₂O₃ content is 1.0% which average value is 380.2 HV0.1, meanwhile, it has superior wear resistance with the friction coefficient of 0.66 and the wear rate of 5.03×10^-4 mm³/(N·m), and the wear mechanism is combined of abrasive wear, adhesive wear and oxidative wear. The dispersed Y₂O₃ in the coatings forms nucleation point, resulting in the refinement of grains and improvement of hardness and wear resistance.

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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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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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Effect of heat treatment process on microstructure and surface oxides of zinc coating galvanized on 22MnB5 hot formed steel

Zhao Jingxuan, Liang Jian, Zhang Lingling, Fan Longlong, Xiong Ziliu, Shen Chunguang, Miao Bin, Zheng Shijian

Heat Treatment of Metals 2024, 49 (8): 275-280. doi:10.13251/j.issn.0254-6051.2024.08.046

Abstract （35）

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Microstructure and surface oxide distribution of the galvanized layer of 22MnB5 hot formed steel were systematically characterized by scanning electron microscope (SEM) and energy dispersive spectroscope (EDS) at different austenitizing temperatures and holding time. The results show that when the austenitization temperature exceeds 850 ℃, the thickness of the galvanized layer increases, and a microstructure transformation occurs from pure Zn phase to α-Fe(Zn), and the interface with the matrix is blurred. As the austenitizing temperature rises from 850 ℃ to 900 ℃, the thickness of the zinc layer grows with the increase of temperature, and the zinc oxide particles become denser, interconnecting and agglomerating. When the austenitization temperature exceeds 900 ℃, large-sized Mn-rich oxides begin to emerge within the galvanized layer. When the austenitization time extends from 4 min to 8 min (austenitization temperature of 920 ℃), the degree of surface oxidation increases, the oxides increase in size and connect to each other in layers, resulting the α-Fe(Zn) layer being exposed and reducing the protective effect on the zinc layer, causing oxygen atoms to diffuse into the interior of the zinc layer to form Mn-rich oxides.

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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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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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