20 May 2019, Volume 43 Issue 5

    

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  Research Status and Application Progress of Ultrasonic Shot Peening Surface Strengthening Technology

  CONG Jiahui, WANG Lei

  Materials For Mechanical Engineering. 2019, 43(5): 1-5. https://doi.org/10.11973/jxgccl201905001

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  The effects of ultrasonic shot peening on the surface integrity, fatigue strength, corrosion resistance of materials were reviewed. The application status of ultrasonic shot peening was summarized. The application prospect of ultrasonic shot peening was expected.
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  Corrosion Behavior in Sulfuric Acid Solution of Ni60A Ni-based Alloy Induction Cladding Layer on Gray Cast Iron

  YU Jing, SONG Bo

  Materials For Mechanical Engineering. 2019, 43(5): 6-11. https://doi.org/10.11973/jxgccl201905002

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  Ni-based alloy cladding layer was prepared on the surface of HT300 gray cast iron by multi-step induction cladding method. The microstructure, phase composition and corrosion behavior in H₂SO₄ solution of the cladding layer were studied. The results show that the cladding layer was metallurgically integrated with the substrate. The cladding layer mainly consisted of γ-Ni,Ni₃Si,Cr_1.12Ni_2.88,Ni₃B, Cr_15.58Fe_7.42C₆ and other phases. There was a passivated procedure in the electrochemical corrosion of the cladding layer. The free corrosion current density and corrosion rate of the cladding layer were far below those of gray cast iron. The cladding layer/H₂SO₄ solution corrosion system had a higher total resistance value. Ni₂O₃ with passivation effect was formed on the surface of cladding layer in H₂SO₄ solution, and improved the corrosion resistance of the cladding layer significantly.
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  Corrosion Behavior of Super 13Cr Tubing Steel in Cl^- Solution and Electrochemical Characteristics of Corrosion Film on Its Surface

  YAO Xiaofei, TIAN Wei, XIE Faqin

  Materials For Mechanical Engineering. 2019, 43(5): 12-16. https://doi.org/10.11973/jxgccl201905003

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  Immersion corrosion tests in NaCl solutions with different NaCl mass fractions (5%-35%) were conducted on super 13Cr tubing steel at room temperature. Corrosion morphology, corrosion rate, corrosion products of the steel and electrochemical characteristics of its surface corrosion film were studied. The results show that the tested steel had relatively good corrosion resistance in NaCl solution. The corrosion resistance decreased with increasing mass fraction of NaCl and the decline was obvious when the NaCl mass fraction increased over 25%. With increasing NaCl mass fraction, the corrosion form changed from local corrosion to general corrosion. The corrosion products were composed of Fe₃O₄,and the corrosion film was loose and not dense. The polarization curves of the corrosion film had a passivation zone, indicating that the film had passivation characteristics. The electrode process in the low-frequency zone was diffusion control, and that in the high-frequency zone was charge transfer control. The impedance of the corrosion film was determined by a time constant.
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  Effects of C₂H₂ Flow Rate on Microstructure and Property of Multi-arc Ion Plated CrCN Coating

  WANG Lu, WANG Biao, WANG Jianming, CAI Fei

  Materials For Mechanical Engineering. 2019, 43(5): 17-23. https://doi.org/10.11973/jxgccl201905004

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  CrCN coating was deposited on surface of SKD11 die steel by multi-arc ion plating technique at different C₂H₂ flow rates (75,125,200,400 mL·min^-1). The effects of C₂H₂ flow rate on microstructure, hardness, bonding property, friction and wear behavior of the coating were studied. The results show that with C₂H₂ flow rate increasing, the surface roughness and thickness of the coating increased first and then decreased, and the hardness and adhesion strength decreased. When the C₂H₂ flow rate was relatively low, the CrCN coating had good ability to remove abrasive debris. When the C₂H₂ flow rate increased to 400 mL·min^-1, layered cracks appeared in the coating. The wear mechanisms of the coatings were slight abrasive wear and adhesive wear.
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  Corrosion Behavior of 304, 316 Stainless Steels and Inconel 617 Ni-based Alloy in Molten Nitrate Salt

  ZHANG Xuewen, LI Hongchuan, LI Shengyun, XUE Weiwei, LIU Kun, TANG Jianqun, GONG Jianming

  Materials For Mechanical Engineering. 2019, 43(5): 24-29. https://doi.org/10.11973/jxgccl201905005

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  Long-time immersion corrosion experiments were conducted on 304, 316 stainless steels and Inconel 617 Ni-based alloy in molten nitrate salt (60wt%NaNO₃+40wt%KNO₃) at 565℃. The corrosion kinetic curves and corrosion morphology, phase composition and microcomposition on surface of the three materials were studied and compared. The results show that oxidation corrosion occurred on the three materials. In addition, 304 and 316 stainless steels had parabolic corrosion kinetic characteristcs, while Inconel 617 Ni-based alloy exhibited significant corrosion mass loss after a brief mass increase. The corrosion resistance of Inconel 617 alloy was the best and that of 304 stainless steel was the worst. In the initial stage of corrosion, acicular and flaky corrosion products were formed on surfaces of 304 and 316 stainless steels; with increasing corrosion time, the corrosion products changed into spinel structure. The corrosion products on surface of Inconel 617 Ni-based alloy were granular, and some particles became larger with increasing corrosion time. The corrosion product layers on surfaces of 304 and 316 stainless steels were mainly composed of Fe₂O₃ and (Fe,Cr)₃O₄, while that on surface of Inconel 617 Ni-based alloy was mainly composed of NiO and CoO.
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  High-temperature Ductility-dip Cracking Susceptibility of 52M Alloy Surfacing Layer Prepared by Different Processes

  ZENG Chunjie, LI Dong, FANG Hu

  Materials For Mechanical Engineering. 2019, 43(5): 30-33,61. https://doi.org/10.11973/jxgccl201905006

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  52M alloy surfacing layer was deposited on the substrate of S304 stainless steel by laser surfacing and TIG surfacing, respectively, with 52M alloy wire as surfacing material, and then the microstructure, phase composition and sensitivity of high-temperature ductility-dip cracking of the surfacing layers were studied. The results show that the microstructures of the two surfacing layers consisted of uniphase austenite. Compared with those of the TIG surfacing layer, the grain size of the laser surfacing layer was smaller and the grain shape was more regular. Cr₂₃C₆ was precipitated in the two surfacing layers. The amount of the precipitates in the laser surfacing layer was relatively small. The amount of cracks in the laser surfacing layer was smaller than that in the TIG surfacing layer at the same temperature and different strains. With the increase of strain, the amount of cracks in the laser surfacing layer increased faster, but the sensitivity of ductility-dip cracking was lower.
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  Effect of Niobium and Vanadium Micro-alloying on Microstructure and Property of 22MnB5 Hot Press Forming Steel

  LIU Anmin, FENG Yi, ZHAO Yan, MA Mingtu, LU Hongzhou

  Materials For Mechanical Engineering. 2019, 43(5): 34-37,53. https://doi.org/10.11973/jxgccl201905007

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  22MnB5 hot press forming steel was micro-alloyed by composite addition of 0.04wt% niobium and 0.04wt% vanadium. The microstructure, tensile properties, hardenability and extreme tip cold bending performance of the tested steel before and after micro-alloying were studied and compared. The effect mechanism of niobium and vanadium micro-alloying on the properties was analyzed. The results show that the microstructures of the tested steel before and after micro-alloying consisted of whole martensite and had obvious martensite strip. The microstructure after micro-alloying was finer, the length of the martensite strip was shorter, and the tensile properties were improved slightly. The niobium and vanadium micro-alloying improved the hardenability of the tested steel effectively, whose hardened layer depth was improved from 3-5 mm before micro-alloying to 13-14 mm. After the niobium and vanadium micro-alloying, the extreme tip cold bending angle of the tested steel was between 65°-70°, which was higher than that before micro-alloying. The synergistic effect of grain refinement of NbC and precipitation strengthening of VC was the fundamental reason for the better performance of the micro-alloyed tested steel.
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  Pulsed Laser Welding Process of SUS304 Stainless Steel Sheet and Microstructure and Mechanical Properties of Joint

  DONG Weiwei, LIN Jian, XU Hailiang, FU Hanguang, LEI Yongping, WANG Xibo

  Materials For Mechanical Engineering. 2019, 43(5): 38-42,48. https://doi.org/10.11973/jxgccl201905008

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  Pulsed laser lap welding was conducted on SUS304 stainless steel sheets (0.2 mm thick), at different laser power (140-420 W) and welding velocities (10-30 mm·s^-1), namely different heat input. The influence of heat input on the weld formation was studied, and the microstructure and mechanical properties of the joint with optimal formability were analyzed. The results show that a well-formed weld can be obtained when the heat input was in the range of 9-20 J·mm^-1; the forming performance was the best at laser power of 320 W and welding velocity of 20 mm·s^-1 (heat input of 16 J·mm^-1). The microstructure in the weld center of the joint with optimal formability consisted of equiaxed grains, in the fusion line consisted of fine columnar grains, and in the weld near fusion line of cellular dendrites. The hardness at the fusion line of the welded joint with optirnal formability was the highest, followed by the weld zone. The joints obtained at different laser power and welding velocities all fractured in the heat-affected zone. The tensile strength of the joint with optinal formability was the highest of 790.1 MPa, which was close to that of the base metal, and the tesile fracture mode was ductile.
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  Micromorphology and Tribological Behavior of TiSiCN Monolayer and TiSiCN/TiSiN Multilayer Coatings by Ion Plating

  XU Lufeng, ZHOU Kaihe, JIANG Jiong, YANG Yueping, DONG Jianda, MAO Jinming, XIE Xinming, LI Jinlong

  Materials For Mechanical Engineering. 2019, 43(5): 43-48. https://doi.org/10.11973/jxgccl201905009

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  TiSiCN monolayer and TiSiCN/TiSiN multilayer coatings were deposited on titanium alloy by multi arc ion plating. The microstructure, hardness, bonding property and friction and wear property of the two coatings were investigated comparatively. The results show that the composing structure of the two coatings were compact and homogeneous. The hardness of the TiSiCN/TiSiN multilayer coating was much higher than that of the TiSiCN monolayer coating. The bonding strength between the TiSiCN/TiSiN multilayer coating and the substrate was smaller than that between the TiSiCN monolayer coating and the substrate. The friction coefficient of the TiSiCN/TiSiN multilayer coating in atmosphere and artificial seawater were 0.32 and 0.30, respectively. The friction coefficient and wear rate of the TiSiCN monolayer coating in atmosphere or artificial seawater were lower than those of the TiSiCN/TiSiN multilayer coating. The wear resistance of the TiSiCN monolayer coating was relatively good.
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  Effect of Si Addition Amount on High Temperature Oxidation Resistance of Ni-5Al Super Alloy

  YAN Haiju, LIU Zhibin, WANG Erpeng, LI Weizhou, LIANG Tianquan, ZHANG Xiuhai

  Materials For Mechanical Engineering. 2019, 43(5): 49-53. https://doi.org/10.11973/jxgccl201905010

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  Ni-5Al-xSi (x=0, 1.5, 3.0, 4.5, mass fraction/%) superalloys were prepared by powder metallurgy technique, and then isothermally oxidized at 1 000, 1 100℃ for 100 h. The morphology of oxide film on the alloy surface was observed and the phase composition was analyzed. The high temperature oxidation resistance of the alloys was studied. The results show that the high temperature oxidation resistance of the tested alloys increased with increasing silicon addition amount; when the mass fraction of silicon reached 3.0%, increasing silicon content had little effect on high temperature oxidation resistance improvement of the alloys. The oxide film on surface of the alloy without addition of silicon was mainly composed of NiO. After addition of silicon, the oxide film mainly consisted of NiO, NiAl₂O₄ and Al₂O₃, and showed spalling features at different degrees. When the mass fraction of silicon was 4.5%, the high temperature oxidation resistance of the tested alloy was the best.
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  Effect of Temperature on Tensile Properties and Microstructure after Tensile at Different Temperatures of 2297-T87 Al-Li Alloy

  YAO Ze, ZHONG Liwei, FENG Zhaohui, ZHU Congcong, GAO Wenli

  Materials For Mechanical Engineering. 2019, 43(5): 54-57. https://doi.org/10.11973/jxgccl201905011

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  Tensile tests at 25-175℃ were carried out on 2297-T87 Al-Li alloy. The effect of temperature on tensile property of the alloy were studied and the microtructures after tensile were observed. The results show that with the increase of temperature, the tensile strength and yield strength of the alloy decreased, and the elongation increased. When the temperature rose to 175℃, the tensile strength and yield strength of the alloy were 77.72% and 82.03% of the tensile strength and yield strength at room temperature(25℃), and the alloy still had relatively high strength. The microstructures of the alloys were similar, and they were mainly composed of rolling deformed grains and a small amount of fine recrystallized grains.
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  Microstructure and Properties of Argon Arc Clad Fe-based Gradient Cladding Layer

  SHI Haifang, YANG Zhaofang, LIANG Chen, YANG Zhihua

  Materials For Mechanical Engineering. 2019, 43(5): 58-61. https://doi.org/10.11973/jxgccl201905012

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  Fe-based gradient cladding layer composed of working layer and M2 transition layer was cladded on 45 steel by tungsten argon arc cladding technique. The microstructure, thermal expansion property, microhardness, residual stress and thermal shock resistance of the gradient cladding layer were investigated, and compared with those of the single cladding layer. The results show that compared with the single cladding layer, the structure of the gradient cladding layer was compact with no hole. The cross section hardness of single cladding layer suddenly decreased when it was 2 mm from the surface, and the cross section hardness of gradient layer suddenly decreased from surface to matrix. The matching degree of thermal expansion coefficient of the gradient layer was better, and the cross section residual stress was lower; also, the thermal shock resistance was better.
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  Erosion Rate Model and Influencing Factors of Cr26 High Chromium Cast Iron for Solid-Liquid Two-Phase Flow Pump Impellers

  ZHANG Nannan, ZHOU Shaoping, XING Gailan

  Materials For Mechanical Engineering. 2019, 43(5): 62-67,74. https://doi.org/10.11973/jxgccl201905013

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  Erosion tests were conducted on Cr26 high chromium cast iron by orthogonal testing method. The erosion rate calculation model of Cr26 high chromium cast iron was obtained by multiple nonlinear regression of testing results on basis of erosion rate theory calculation model, and the accuracy of the model was verified. The rule of erosion rate vs influencing factors was described quantitatively by tests and model calculation. The results show that the erosion rate calculation formula of Cr26 high chromium cast iron had high accuracy. With the increase of erosion angel, the erosion rate increased first, then decreased and finally increased slightly, and reached the maximum value near the erosion angle of 40°. The main wear form was cutting wear at low erosion angle and deformation wear at the high erosion angle. With the increase of solid particle size, the erosion rate increased, the proportion of cutting wear increased, and the proportion of deformation wear decreased. With the erosion velocity increasing, the proportion of cutting wear decreased, and the proportion of deformation wear increased.
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  Corrosion Behavior of 304 Stainless Steel in Molten Nitrate Salt at Different Temperatures

  ZHOU Caizheng, LUO Sang, SUN Yanhu, ZHANG Xuewen, TANG Jianqun, GONG Jianming

  Materials For Mechanical Engineering. 2019, 43(5): 68-70,78. https://doi.org/10.11973/jxgccl201905014

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  Corrosion behavior of 304 stainless steel in molten salt at different temperatures (400,450,500,565℃) was studied by corrosion kinetic method, corrosion surface observation and micro area composition analysis; the molten salt was composed of 60wt%NaNO₃+40wt%KNO₃. The results show that the corrosion rate of the tested steel in the molten salt increased with the increase of temperature, and reached 99.6×10^-5 mg·cm^-2·h^-1 at 565℃. There was only few oxidation corrosion products on the surface of the tested steel at 400℃. There was a small amount of Fe₂O₃ on the surface at 450℃ and 500℃. The oxidation corrosion products mainly content of Fe₂O₃ and (Fe, Cr) ₃O₄ were formed on the surface at 565℃, with the increase of temperature, the content of Fe₂O₃ increased considerably and the oxidation corrosion degree aggravated.
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  Temperature-Dependent Cyclic Plastic Deformation Behavior of U75VG Rail Steel

  YANG Gang, LI Jian, FANG Tao, KAN Qianhua, KANG Guozheng

  Materials For Mechanical Engineering. 2019, 43(5): 71-74. https://doi.org/10.11973/jxgccl201905015

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  The uniaxial tensile property and cyclic plastic deformation behavior of U75VG rail steel were studied by uniaxial tensile tests and cyclic plastic deformation tests at different temperatures (25,300,600℃). The results show that the U75VG rail steel presented initial cyclic softening characteristics under strain-controlled cyclic load at 25℃, and initial cyclic hardening characteristics at 300℃ by the dynamic strain ageing. The dynamic strain ageing effect disappeared and the cyclic softening feature was obvious at 600℃. The U75VG rail steel exhibited obvious ratcheting behavior characteristics under stress-controlled cyclic load at different temperatures. The ratcheting strain rate increased with the increase of mean stress or stress amplitude. The ratcheting strain rate was close to the stable state at 300℃, and increased rapidly with the increase of mean stress or stress amplitude at 600℃.
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  Fracture Reason of Servo Valve Bolt of Electrohydraulic Oil of High Regulating Valve of Small Steam Turbine in Supercritical Unit

  ZHU Haibao, LI Ge, CHEN Zhuoting, LIU Ming

  Materials For Mechanical Engineering. 2019, 43(5): 75-78. https://doi.org/10.11973/jxgccl201905016

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  Servo valve bolt of electrohydraulic oil of high regulating valve of small steam turbine in supercritical unit in a power plant fractured after working for 3.5 a. The fracture cause was analyzed by methods such as chemical composition analysis, hardness testing, metallographic analysis and fracture analysis. The results show that the fracture property of the bolt was fatigue fracture, and the fracture presented multi-source characteristics. There were many serious manufacturing machining defects in the thread of the bolt. Fatigue cracks initiated in these defects and propagated under complex fatigue load. The cracks became unstable when propagated to critical size, leading to the instantaneous fracture. The static load on the other bolts increased signi ficantly after the fatigue-fracture of one bolt, leading to the instant fracture under overload of the other bolts.