20 April 2020, Volume 44 Issue 4
    

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  • Research Progress of Cemented Carbide with Plate-Like WC Grains
    XIA Xiaoqun, GONG Manfeng, LI Meng, LIAN Haishan
    Materials For Mechanical Engineering. 2020, 44(4): 1-6,15. https://doi.org/10.11973/jxgccl202004001
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    Combined with the structure of WC grain and its panarization mechanismmechanism, The research progress of cemented carbide with plate-like WC grains is reviewed from aspects of raw materials, ball milling, sintering processes and inhomogeneous structure. The problems and future development prospect of plate-like grain cemented carbide are proposed.
  • Microbiologically Influenced Corrosion Characteristics of Marine Q235 Carbon Steel Induced by Attachment of Marine Microalgae
    ZHANG Han, BAI Xiuqin, HE Xiaoyan, YUAN Chengqing
    Materials For Mechanical Engineering. 2020, 44(4): 7-15. https://doi.org/10.11973/jxgccl202004002
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    The corrosion behavior of marine Q235 carbon steel in artificial seawater with Phaeodactylum tricornutum (seawater with algae) under cyclic light 12 h/dark 12 h, continuous light, and continuous dark conditions, and the electrochemistry performance after corrosion for 7 days were studied, compared with that in the seawater without algae. The effects of the life activity of Phaeodactylum tricornutum on the corrosion behavior of carbon steel were analyzed. The results show that in the seawater with algae, the depolarization reaction of oxygen was dominant under continuous light condition, resulting in pitting on the carbon steel surface, and the corrosion product was γ-FeOOH. Under the condition of continuous dark, carbon dioxide corrosion caused uniform corrosion of Q235 carbon steel surface, and the corrosion product was FeCO3. The two types of corrosion methods were combined under the cyclic light 12 h/dark 12 h condition, and the corrosion products consisted of γ-FeOOH, Fe3O4 and FeCO3. In the seawater with algae, the charge transfer resistance of carbon steel decreased and the self-corrosion current density increased after immersion under different light conditions for 7 days, compared with that in the seawater without algae.
  • Effect of Dual Equal Channel Lateral Extrusion of Different Routes on Microstructure and Mechanical Properties of 7003 Aluminum Alloy
    YANG Hao, LIU Zhaohua, WANG Yuan, ZHENG Jin
    Materials For Mechanical Engineering. 2020, 44(4): 16-19,24. https://doi.org/10.11973/jxgccl202004003
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    The 7003 aluminum alloy was extruded for four passes by dual equal channel lateral extrusion (DECLE) with two routes of non-rotation of samples between each pass (route A) and 90° clockwise rotation of samples between each pass (route B). The microstructure and mechanical properties of the alloy after extrusion were studied. The results show that after four-pass DECLE treatment, the grains of 7003 aluminum alloy were refined to nano scale. The parallel curved shear bands were formed in the alloy under route A. The cross shaped shear bands were formed under route B and refined the grains better due to the dislocation segmentation effect. With the increase of DECLE passes, the yield strength, tensile strength and hardness of the samples increased under the two routes. The strength and the hardness under route B were higher than those under route A, but the elongation after fracture was lower than that under route A.
  • Effect of Aging and Impact on Microstructure and Mechanical Properties of GF/EVE Composite
    LI Guo, SUN Yaoning, WANG Guojian, DAI Likui
    Materials For Mechanical Engineering. 2020, 44(4): 20-24. https://doi.org/10.11973/jxgccl202004004
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    The ultraviolet aging and low velocity impact experiments were conducted on glass fiber reinforced epoxy vinyl ester resin composite. The effect of ultraviolet aging time (0, 20, 30, 40 d) and impact energy (12.5, 25.0 J) on the surface morphology, element distribution, chemical structure and mechanical properties of the composite was studied. The results show that with the increase of ultraviolet aging time, the color of the composite surface was gradually deepened, and the fiber and the resin matrix were debonded. After aging for 40 d, the surface element content and the chemical structure of resin changed, and photo-oxidation degradation of the resin matrix occurred. When the impact energy was constant, the maximum load, tensile strength and bending strength of the composite all decreased with the increase of ultraviolet aging time. After aging for 40 d, the maximum load of the composites decreased by 5.2% and 19.5% when the impact energy was 12.5 J and 25.0 J, respectively.
  • Effect of Nitrogen Flow Rate on Properties of CrNx Coatings Prepared by Reactive Magnetron Sputtering
    GUO Jinbao, MA Fuliang, ZENG Zhixiang
    Materials For Mechanical Engineering. 2020, 44(4): 25-29,34. https://doi.org/10.11973/jxgccl202004005
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    CrNx coatings were prepared by reactive magnetron sputtering with controlled nitrogen flow rates (20-60 cm3·min-1) on stainless steel and silicon chip substrate, respectively. The influence of nitrogen flow rate on the phase composition, microstructure, nanoindentation mechanical properties, tribological properties, and electrochemical corrosion resistance in 3.5wt% NaCl solution of the coatings was investigated. The results show that the CrNx coatings all had columnar crystal structures at different nitrogen flow rates. With the increase of nitrogen flow rate, the phase composition of the coatings changed in order of Cr, Cr2N and CrN; the nanoindentation hardness and elastic modulus increased first and then decreased; the average friction coefficient and the wear rate decreased first, then increased and then decreased; the corrosion resistance got better first and then got worse. When the nitrogen flow rate was 30 cm3·min-1, the coating had a dense structure and the best mechanical properties, wear resistance and corrosion resistance.
  • Effect of Heat Input on Microstructure and Properties of Flux-cored Wire Arc Welding Joint of Duplex Stainless Steel
    ZHANG Yingying, LIU Zhengjun, JIN Meiling, LI Dongming
    Materials For Mechanical Engineering. 2020, 44(4): 30-34. https://doi.org/10.11973/jxgccl202004006
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    Flux-cored arc welding of 2205 duplex stainless steel plate was performed. The effects of different heat inputs (8.32,11.02,14.04,17.39 kJ·cm-1) on the microstructure, ferrite content, impact properties, microhardness and pitting resistance of the welded joint were studied. The results show that the welding seam, fusion zone and heat affected zone of 2205 duplex stainless steel joint were composed of austenite and ferrite, and the ferrite content gradually decreased with the heat input increasing. When the welding heat input was 14.04 kJ·cm-1, the ferrite volume fraction of the joint basically met the requirement of 40%-60%. With the increase of welding heat input, the hardness of the joint weld and the heat affected zone decreased slightly, the impact absorption energy of the weld metal increased first and then decreased, and the pitting corrosion rate of the heat affected zone changed little, while that of the weld decreased first and then increased. When the heat input was 14.04 kJ·cm-1, the resistance to pitting corrosion of 2205 duplex stainless steel was the best.
  • Microstructure and Wear Properties of High Velocity Oxygen Fuel Sprayed Cr3C2-NiCr Coating
    SHI Wei, YANG Weihua, WU Yuping
    Materials For Mechanical Engineering. 2020, 44(4): 35-39,45. https://doi.org/10.11973/jxgccl202004007
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    The Cr3C2-NiCr coating was prepared on H13 steel substrate by high velocity oxygen fuel spraying technique. The microstructure,phase composition and friction and wear properties of the coating were studied, and the wear mechanism was discussed. The results show that the Cr3C2-NiCr coating with a thickness of about 340 μm was closely combined with the H13 steel substrate. The coating was composed of Cr3C2 hard phase, NiCr bonding phase and a small amount of Cr7C3, and the structure was dense with a porosity of 0.63%. The stable friction coefficients of the Cr3C2-NiCr coating and H13 steel were 0.90 and 0.75, respectively, and the wear track depth and wear rate of the coating were only half that of H13 steel, showing that the coating had relatively good wear resistance. The main wear mechanism of the Cr3C2-NiCr coating was abrasive wear and fatigue wear.
  • Effect of Heat Treatment on Morphology and Distribution of Eutectic Silicon in AlSi10Mg Alloy Prepared by Selective Laser Melting
    MA Yao, YUE Yuan
    Materials For Mechanical Engineering. 2020, 44(4): 40-45. https://doi.org/10.11973/jxgccl202004008
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    The AlSi10Mg alloy was prepared by selective laser melting (SLM). The microstructure of the as-deposited alloy was analyzed, and effects of three heat treatment processes (T6, T2, T6+T2) on the morphology and distribution of eutectic silicon were studied. The results show that the molten pool on surface of the as-deposited alloy was divided into three areas, fine grain zone, coarse grain zone and remelting zone, in order from center to border. The eutectic siliton was in the form of short fiber with nanometer size. Before and after heat treatment, the AlSi10Mg alloy consisted of aluminum, silicon and Mg2Si phases. The eutectic silicon distributed more uniformly after heat treatment, showing that the homogeneity of the structure was improved. The silicon content of eutectic silicon of the as-deposited alloy increased after heat-treatment by T6 and T2 processes in turn, and the purity of eutectic silicon was improved.
  • Development and Application of Wire and Arc Additive Manufacturing Flux Cored Wire for Gradient Structure on Surface of 5CrNiMo Steel
    MAO Zhanzhao, YU Shengfu
    Materials For Mechanical Engineering. 2020, 44(4): 46-51. https://doi.org/10.11973/jxgccl202004009
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    The flux cored wires for gradient structure (bottom layer, transition layer and hardfacing layer) by wire and arc additive manufacturing on surface of 5CrNiMo steel were developed, and the microstructure, tensile properties, wear properties and bonding properties of the substrate and gradient layers were analyzed. Moreover, the wire and arc additive manufacturing of gradient die for engine superalloy disk was carried out. The results show that the three flux cored wires had good formability. The interface between the metal layers were well bonded, and the bonding strength was all over 1 000 MPa. Fine carbides were dispersed in the structure of the transition layer and hardfacing layer. The tensile strength, yield strength and hardness of the 5CrNiMo steel, bottom layer, transition layer and hardfacing layer increased in turn, while the elongation and area shrinkage after fracture of the gradient layer decreased in turn. At 700 ℃, the wear rate of the hardfacing layer was reduced by 35.29% compared with that of 5CrNiMo steel, showing that the hardfacing layer had good high temperature wear resistance. The service life of the gradient die by wire and arc additive manufacturing with the designed flux cored wire materials for superalloy disk was more than four times that of 5CrNiMo steel die.
  • Fatigue Properties of Different Parts of New Fe-C-Cu Powder-Forged Bimaterial Connecting Rod
    ZHANG Guangwei, ZHANG Guangming, MAO Minjie, SHAO Jingjing, LI Jian
    Materials For Mechanical Engineering. 2020, 44(4): 52-56. https://doi.org/10.11973/jxgccl202004010
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    Based on the requirements of high fatigue strength of connecting rod and fracture splitting process, a powder-forged bimaterial connecting rod was proposed. The microstructure and fatigue properties of the big end, rod of the powder-forged bimaterial connecting rod were analyzed by metallographic examination, scanning electron microscope and fatigue test. The results show that the microstructure of the big end and the rod were composed of pearlite, ferrite and nano copper rich phase, and the rod material had more and larger nano copper rich phases. The average fatigue strength and fatigue limit of the rod material were greater than that of the big end material, and the fatigue performance of the rod was further improved after shot peening. The MnS in big end material promoted fatigue crack expansion, which could reduce the fatigue strength, while shot peening could strengthen the surface layer of the rod material and improve its fatigue resistance.
  • Structure and Properties of Bionic Biporous-Oriented Pore Capillary Wicks Prepared by Ice-Templating Method
    GAN Tian, LIN Tao, QUAN Xiaojun
    Materials For Mechanical Engineering. 2020, 44(4): 57-61. https://doi.org/10.11973/jxgccl202004011
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    By using water-based nickel powder slurry with different solid content, the capillary wick containing the xylem-like pore structure was prepared by the ice-templating method at different freezing temperatures and different sintering temperatures. The micro-pore structure of the capillary wick was observed and the effect of solid content and freezing temperature on the pore structure and property of the capillary wick was studied. The results show that the new capillary wick prepared by the ice-templating method had oriented pores specific to the xylem of plants, and the pore had dual-aperture and showed a well-ordered honeycomb shape. With the increase of solid content, the pore wall thickness of the capillary wick increased, while the pore diameter, porosity and permeability decreased. With the freezing temperature decreasing, the porosity was basically unchanged, while the pore diameter and permeability were reduced. Compared with the capillary wick prepared by traditional sintering methods, the capillary wick by the ice-templating method had greater porosity and permeability.
  • Microstructure and High Temperature Tensile Properties of New Single Crystal Superalloy after Long Term Aging at High Temperature
    SHI Zhenxue, LIU Shizhong
    Materials For Mechanical Engineering. 2020, 44(4): 62-66. https://doi.org/10.11973/jxgccl202004012
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    A new single crystal superalloy was aged at high temperature (1 100 ℃), and the effect of different aging times (0, 200, 400, 600, 800, 1 000 h) on the microstructure and high temperature (1 100 ℃) tensile properties of the superalloy was investigated. The results show that the microstructure of the new single crystal superalloy before and after aging was composed of γ matrix phase and γ' phase. The space of γ matrix channel and the size of γ' phase increased with increasing aging time. The needle shaped TCP phase with obvious orientation to matrix was precipitated in the alloy after aging for 600 h, and the volume fraction increased with the increase of aging time. With the aging time increasing, the yield strength and tensile strength of the single crystal superalloy at high temperature decreased, while the elongation and reduction of area after fracture increased first and then decreased. The tensile fracture surface of the single crystal superalloy all had features of necking and dimples before and after aging, and the fracture mechanism was dimple fracture.
  • Microstructure and Mechanical Properties of Cold Metal Transfer Wire-Arc Additive Manufactured H13 Steel Block
    BAI Tao, LIN Jian, CHENG Sihua, LEI Yongping, FU Hanguang, GE Jinguo
    Materials For Mechanical Engineering. 2020, 44(4): 67-71. https://doi.org/10.11973/jxgccl202004013
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    H13 steel blocks with a 5-layer and 15-pass structure were prepared by robotic cold metal transfer wire-arc additive manufacturing technique. The surface quality, microstructure and mechanical properties of the deposited block were investigated. The results show that there was no macro-crack on the surface of H13 steel block. The structure of the body-zone of the block was acicular martensite with uniform grain orientation, and the structure of the lap-zone was composed of acicular martensite with irregular grain orientation and irregular ferrite. The average micro-hardness of the body-zone of the block was 479 HV, which was much higher than that of annealed H13 steel (254 HV), while the hardness of the lap-zone significantly decreased due to the presence of ferrite, with the average value of 381 HV. The overall tensile properties of the cold metal transfer wire-arc additive manufactured H13 steel block were better than those of annealed H13 steel.
  • Microstructure and Properties of Reactive Plasma Sprayed TiN Composite Coating on ZL104 Alloy
    SHI Ying, WANG Zehua, ZHANG Yu, SHAO Yanfan, GU Chenyu
    Materials For Mechanical Engineering. 2020, 44(4): 72-77. https://doi.org/10.11973/jxgccl202004014
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    NiCrAl alloy adhisive coating and TiN composite coating were in turn deposited by reactive plasma spraying on ZL104 alloy substrate. The phase composition, microstructure, bonding strength, micro-hardness and wear resistance of the coating were studied by X-ray diffraction, structure observation, hardness test and tensile and wear test, and the wear mechanism was also discussed. The results show that the composite coating consisted of TiN, TiN0.3 and a small amount of TiO2 phases, and its structure was dense with a few cavities and microcracks. The coating and ZL104 alloy was well bonded, and the bonding strength was 17.7 MPa. The average hardness of the TiN composite coating was 1 330 HV, which was about 22 times of the substrate; the wear mass loss of the TiN composite coating increased with the load, and was much smaller than that of the substrate. The wear mechanism of ZL104 alloy was micro-cutting abrasive wear and micro-fatigue wear, while that of the TiN composite coating was micro-cutting abrasive wear.
  • Creep Behavior of Silicone Rubber at Different Temperatures and Establishment of Viscoelastic Parameter Model with Variable Temperature
    LIU Huiying, LI Weiwei
    Materials For Mechanical Engineering. 2020, 44(4): 78-82. https://doi.org/10.11973/jxgccl202004015
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    Creep tests of silicone rubber at different temperatures (-20,-5,10,25,40 ℃) were carried out. The test results were fitted and analyzed through the three-parameter solid model and the Burgers model, and viscoelastic parameters at different temperatures were obtained. The prediction model of silicone rubber viscoelastic parameters at variable temperatures was established based on the three-parameter solid model and dimensionless analysis method. The results show that the creep behavior of silicone rubber had obvious correlation with the temperature; its creep strain and creep rate increased gradually with temperature. The three-parameter solid model described the static creep characteristics of silicone rubber at different temperatures more accurately than Burgers model did. The viscoelastic parameter prediction model based on three-parameter solid model and dimensionless analysis method had high prediction accuracy, and the prediction results were in good agreement with the test results.
  • Cracking Reason of Automobile Hub Bearing Flange Inner Ring
    CAO Longfei
    Materials For Mechanical Engineering. 2020, 44(4): 83-86. https://doi.org/10.11973/jxgccl202004016
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    A batch of automobile hub bearing flanges produced by a factory cracked in the radius area of the large plate during the production. The cracking reasons were analyzed by means of macroscopic examination, chemical composition analysis, hardness test, metallographic examination, scanning electron microscope and energy spectrum analysis. The results show that the cracking of the hub bearing flange inner ring was mainly due to the residual shrinkage defects in raw materials caused by insufficient cutting volume at head and end area of the continuous casting slab. In the process of forging, the crack initiated from the shrinkage cavity and propagated along the deformation direction of the material, eventually leading to the cracking of the flange inner ring. It was recommended to strengthen the incoming quality inspection of raw materials, focusing on its macrostructure and shrinkage defects.
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