20 September 2018, Volume 42 Issue 9
    

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  • Research Progress on Preparation of Antibacterial Stainless Steel by Plasma Surface Technology
    LIU Yang, XU Jinyong, GAO Bo, GAO Cheng
    Materials For Mechanical Engineering. 2018, 42(9): 1-5. https://doi.org/10.11973/jxgccl201809001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Antibacterial stainless steel is a new antibacterial material, and has a big difference in antibacterial properties because of the difference in antibacterial mechanism and preparation method. Research progress on the preparation of antibacterial stainless steel by plasma surface technology, such as ion implantation technique, magnetron sputtering coating technique and double-layer glow plasma surface metallurgy technique, is reviewed. The antibacterial mechanism of antibacterial stainless steel is described. The future development direction is prospected.
  • Effect of CaCO3 Content on Slag Detachability of Self-shielded Flux-Cored Wire
    LI Jihong, CHENG Kangkang, SHU Shaoyan, HE Xiaoyu, LI Le, ZHANG Min
    Materials For Mechanical Engineering. 2018, 42(9): 6-10. https://doi.org/10.11973/jxgccl201809002
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    Self-shielded flux-cored wires with 1wt%, 3wt%, 5wt% and 7wt% CaCO3 were prepared, and then used to weld ultra-low carbon bainitic steels. The effects of CaCO3 content on the micromorphology, phase composition and slag detachability of slag after welding were studied. The results show that with the increase of CaCO3 content, the micromorphology of internal surface of slag changed from massive to rod-like, then to dendritic, and finally to granular. When CaCO3 content was 1wt% and 3wt%, the slag was composed of composite oxide of BaO and TiO2 (BaTiO3), spinel compound (MgMn2O4 or MnAl2O4) and BaMg3Al2Si2O10F2 composite oxyfluoride. When CaCO3 content was improved to 5% and 7%, respectively, the BaMg3Al2Si2O10F2 phase disappeared and Ca2SiO4 phase formed. With the increase of CaCO3 content in the flux-cored wire, the slag detachability decreased.
  • Aging Behavior of Glass Fiber Reinforced Epoxy Resin Composite in Warm-Wet and Ultraviolet Irradiation Environment
    WANG Guojian, SUN Yaoning, JIANG Wanle
    Materials For Mechanical Engineering. 2018, 42(9): 11-15,20. https://doi.org/10.11973/jxgccl201809003
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    Accelerated aging test was conducted on glass fiber reinforced epoxy resin composite in warm-wet and ultraviolet irradiation environment. The chemical structure, surface element content, surface morphology, glass transition temperature, and bending and tensile properties of the composite were studied by infrared spectrometer, X-ray photoelectron spectrometer, scanning electron microscope, thermal gravimetric analyzer and mechanical testing machine. The results show that in the warm-wet and ultraviolet irradiation environment, the rupture of chemical bond occurred in the resin of composite after aging for 1 440 h, the chemical structure changed and the resin went through the photo-oxidation reactions. With aging time increasing, the surface of composite showed discoloration, cracking and warping deformation features. After aging for 1 440 h, a laminar wave pattern was observed on the surface. With the increase of aging time, the strength and modulus of the composite both increased first and then decreased, and reached the maximum values after aging for 160 h. After aging for 1 440 h, the initial decomposition temperature of the composite was lower than that before aging, the glass transition temperature was about 113.4 ℃, which was 8 ℃ higher than that before aging.
  • Thermal Stability of Plasma-Nitrided Layer on Surface of GH2132 Fe-Based Superalloy
    SONG Weixiu, XU Xiaolei, YU Zhiwei
    Materials For Mechanical Engineering. 2018, 42(9): 16-20. https://doi.org/10.11973/jxgccl201809004
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    Low temperature plasma nitriding was conducted on the surface of GH2132 Fe-based superalloy at 723 K, and then the nitrided tested alloy was treated at different temperatures (673,873,973 K) for 5 h. The sectional morphology, phase composition, hardness and corrosion resistance of the nitrided layer before and after treatment were analyzed. The results show that the nitrided layer on the surface of GH2132 Fe-based superalloy was mainly composed of supersaturated solid solution of nitrogen in austenite, namely expanded austenite γN phase. The thickness of nitrided layer increased with increasing heating temperature. The γN phase was undecomposed during heating at 673 K. During heating at 873, 973 K, the γN phase was decomposed to γN phase with lower lattice expansion and CrN phase. The lattice expansion rate of γN phase decreased with the increase of heating temperature. The hardness of nitrided layer was firstly increased then decreased with increasing heating temperature, and reached to the largest of 926 HV during heating at 873 K. The corrosion resistance of nitrided layer after heating at different temperatures for 5 h all decreased.
  • Uniaxial Ratcheting Behavior of 7075 Aluminum Alloy
    ZHAO Luyuan, HUANG Jun, CHEN Tao, DA Ling, WU Yucheng
    Materials For Mechanical Engineering. 2018, 42(9): 21-25. https://doi.org/10.11973/jxgccl201809005
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    The ratcheting behavior of 7075 aluminum alloy in the T651 heat treatment state was studied by uniaxial tension-compression cyclic tests under different mean stresses and stress amplitudes. The microstructure of the aluminum alloy before and after tests was observed and analyzed. The results show that the 7075 aluminum alloy presented apparent ratcheting strain accumulation characteristics under different cyclic loads. At the beginning of the cycle, the plastic deformation was obvious and the ratcheting strain rate was high, due to the increase of dislocation density, strengthening of dislocation elastic stress field and appearance of a large amount of dislocation tangle in the aluminum alloy. With the increase of the number of cycles, the plastic deformation accumulation decreased obviously and the ratcheting strain rate increased slowly in a near linear trend. The ratcheting strain accumulation increased with the increase of stress amplitude or mean stress.
  • Microstructure and Corrosion Resistance of Zr-Mo Micro-alloying 310S Stainless Steel after Solution and Stabilization Treatment
    LIU Guiliang, WU Tianyang, LI Minghao, PAN Qianfu, TANG Rui, CHEN Guoqing, WANG Qing
    Materials For Mechanical Engineering. 2018, 42(9): 26-32,40. https://doi.org/10.11973/jxgccl201809006
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    Zr-Mo micro-alloyed 310S stainless steel was prepared and treated by solution at different temperatures (1 050-1 150 ℃), and by solution at 1 150 ℃+stabilization at different temperatures (950-1 050 ℃). The microstructure and corrosion resistance of the test steel treated with different heat treatment were studied. The results show that the microstructure of the tested steel after solution was uniform austenite equiaxed grains, and there were a large number of annealing twins in the grains; strip-shaped or clumpy (Zr, Mo) C phase and massive Zr(C,N) phase precipitated from the grain boundaries or grains. The microstructure of the tested steel after solution treatment at 1 150 ℃ and stabilization treatment at different temperatures was similar to that after solution treatment, but the number of precipitated phases increased; a large number of hammer-like M23 C6 phase precipitated from the grain boundaries after stabilization treatment at 950 ℃. Stabilization treatment at 950-1 050 ℃ had little effect on the uniform corrosion resistance of tested steel. With the increase of stabilization temperature, the inter-granular corrosion sensitivity of the tested steel decreased, and inter-granular corrosion resistance was improved.
  • Oxidation Kinetics Behavior at High Temperature of TC4 Titanium Alloy
    XU Xiang, GENG Luyang, GONG Jianming
    Materials For Mechanical Engineering. 2018, 42(9): 33-36,46. https://doi.org/10.11973/jxgccl201809007
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    Oxidation tests at 600-850 ℃ for 0.3-80 h were conducted on TC4 titanium alloy, and then the effects of oxidation on the macro morphology, cross section micro-hardness and cross section morphology of the alloy were studied. The oxidation behavior at high temperature was analyzed. The results show that with the increase of temperature and oxidation time, the surface oxide film of TC4 titanium alloy experienced the process of completion, cracking, spalling, severe spalling, peeling off completely. The thickness of oxygen diffusion layer formed on the near surface increased with the increase of temperature and oxidation time. The oxidation kinetics curve complied with parabolic law when the oxidation temperature was 600-650 ℃, linear law when the oxidation temperature was 750-850 ℃, parabolic law in the first 8 h oxidation and linear law with the oxidation time of more than 8 h when the oxidation temperature was 700 ℃. The hardness decreased with the distance from surface increasing at different oxidation temperatures for different times.
  • Process and Property of TiO2 Coating cBN Composite Powder Prepared by Sol-Gel Method
    LIANG Lixing, WANG Hailong, LI Jian, HU Biyong, SHAO Gang, XU Hongliang, LU Hongxia, FAN Bingbing, ZHANG Rui
    Materials For Mechanical Engineering. 2018, 42(9): 37-40. https://doi.org/10.11973/jxgccl201809008
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    A layer of TiO2 was coated on the surface of cubic boron nitride (cBN) particles by sol-gel method with anhydrous ethanol and water as dispersion medium and with tetrabutyl titanate as titanium source, and then cBN-TiO2 composite powders were obtained. The effects of the molar ratio of anhydrous ethanol to butyl titanate and the molar ratio of cBN to butyl titanate on the coating effect were investigated. The preparation process was optimized. The oxidation resistance of cBN-TiO2 composite powder under optimal process was studied. The results show that the surface of cBN particles was coated with a layer of dense TiO2 uniformly when the molar ratio of anhydrous ethanol to butyl titanate was 10∶1 and the molar ratio of cubic boron nitride to butyl titanate was 1∶1, indicating the best coating effect. The initial oxidation temperature of cBN-TiO composite powder prepared under optimal process was 900 ℃, and was 220 ℃ higher than that of cBN micro powder before coating with TiO2.
  • Preparation and Photocatalytic Properties of Ordered Mesoporous ZnS Nanorods Loading on Graphene Composite
    ZENG Bin, LIU Wanfeng, ZENG Wujun
    Materials For Mechanical Engineering. 2018, 42(9): 41-46. https://doi.org/10.11973/jxgccl201809009
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    The composite of ordered mesoporous ZnS nanorods loading on graphene was prepared by microwave-assisted heating. The microscopic morphology and phase composition of the composite were studied; the effect of graphene oxide content (0-15wt%) and microwave heating power (320-800 W) and time (0-80 min) on microscopic morphology and photocatalytic performance was analyzed; the formation mechanism of the composite, and the relation between micromorphology and photocatalytic performance were discussed. The results show that the composite consisted of flake graphene and rodlike ZnS, and ordered mesoporus ZnS nanorods distributed on the surface of graphene evenly. The increase of graphene oxide content was favorable for dispersion of ZnS nanorods. The formation of ZnS nanorods was promoted with the increase of microwave heating power and time. The photocatalytic performance of the composite was the best when the microwave heating time was 60 min, microwave heating power was 640 W, and the content of graphene oxide was 10wt%.
  • Preparation and Properties of Vacuum High-Frequency Induction Cladding Wear-Resistant Coating on Inner Surface of Sand Blasting Nozzle
    WANG Qingchun, LIN Chen, ZHANG Juanjuan, ZHOU Changhuan, DU Sheng
    Materials For Mechanical Engineering. 2018, 42(9): 47-50,54. https://doi.org/10.11973/jxgccl201809010
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    Ni60A alloy coating containing 20wt% WC was cladded on the inner surface of 45 steel sand blasting nozzle by vacuum high-frequency induction cladding technique, and then the sand blasting nozzle was reamed by lathe and electric discharge shaped machine, respectively. The microstructure and hardness distribution of the coating and substrate were analyzed, and the friction and wear properties of the coating were studied. The results show that the coating had an excellent cladding quality. The coating was smooth and crack-free with a small number of holes. The coating was metallurgical bonding with substrate. After reaming by electric discharge shaped machine, the porosity of the outer layer of the coating decreased and structure was finer compared with that after reaming by lathe. The hardness of the coating was much higher than that of substrate, and the hardness of the outer layer of the coating after reaming by electric discharge shaped machine was higher than that after reaming by lathe. After erosion wear testing for 150 min, the wear loss of the sand blasting nozzle with coating was 11% of that without coating, the friction coefficients of the sand blasting nozzle with and without coating were 0.16 and 0.22, respectively, indicating significantly improved the wear resistance of the sand blasting nozzle cladding with coating.
  • Preparation and Visible Photocatalytic Properties of Spinel-Type CuAl2O4
    ZHANG Xuguang, MA Yunfei
    Materials For Mechanical Engineering. 2018, 42(9): 51-54. https://doi.org/10.11973/jxgccl201809011
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    Spinel-type CuAl2O4 powder was prepared by sol-gel method with copper nitrate, copper chloride, and copper sulfate as raw materials, respectively. The phase composition, photocatalytic property and microstructure of the powder were studied by X-ray diffractometer, photocatalytic reactor, infrared spectroscope and X-ray photoelectron spectrometer. The results show that the CuAl2O4 powder, prepared at 700 ℃ with copper sulfate raw material added with 20 mL ammonia, had the best photocatalytic property, and the degradation rate of methyl orange was 90%. There was Cu2O(SO4) phase in the CuAl2O4 powder prepared with raw material of copper sulfate. The Cu2O(SO4) phase improved the photocatalytic property of CuAl2O4 powder.
  • Electrochemical Corrosion Resistance of 304 Stainless Steel after Sensitization
    HUANG Zidong, LIN Junming, JIANG Yikui, YE Lifang, WEI Minsheng, XIE Chunyu, ZHENG Ruisheng
    Materials For Mechanical Engineering. 2018, 42(9): 55-60,64. https://doi.org/10.11973/jxgccl201809012
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    The sensitization degree of 304 stainless steel after heating at 600 ℃ for different times was evaluated by electrochemical potentiodynamic reactivation. The electrochemical corrosion behavior of tested steel with different sensitization degrees in 4vol% acetic acid solution, 5wt% NaCl solution and the two solution mixture with volume ratio of 1∶1, respectively, and the influence of immersion time and solution temperature on the electrochemical corrosion resistance of tested steel with the same degree of sensitization were studied. The results show that with the increase of holding time, the reactivation current of tested steel increased, and the sensitization degree increased. With the increase of sensitization degree, the self-corrosion potential of tested steel in NaCl solution and NaCl/acetic acid mixed solution shifted negatively, and the corrosion resistance decreased; the self-corrosion potential in acetic acid solution shifted positively, and the corrosion resistance was improved. With the extension of immersion time, the self-corrosion potential of tested steel in NaCl solution shifted negatively, and the corrosion resistance decreased; the self-corrosion potential in acetic acid solution shifted positively, and the corrosion resistance was improved; the self-corrosion potential in NaCl/acetic acid mixed solution changed little, and the corrosion resistance was basically unchanged. With the increase of solution temperature, the self-corrosion current densities of tested steel in different solutions all increased.
  • High Strain-Rate Shear Behavior of TiB2/2024Al Composite at Different Temperatures
    ZHOU Ping, GUO Weiguo, LI Yanping
    Materials For Mechanical Engineering. 2018, 42(9): 61-64. https://doi.org/10.11973/jxgccl201809013
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    High strain-rate (dynamic) shear behavior at different temperatures (25, 150, 300, 450 ℃) of TiB2/2024Al composite prepared by mixed salts method was investigated with a newly designed hat-shaped shear specimen by the improved split Hopkinson tension bar testing, and the shear fracture morphology of the composite was analyzed. The results show that the dynamic nominal shear stress-shear strain curves of the composite at different temperatures were similar. At the initial stage of deformation, the shear strength increased with the increase of shear strain, and when the shear strain was larger than a certain value, the curve showed steady-state rheological features. The shear strength of the composite decreased while the fracture strain increased with the increase of temperature. The fracture of the composite mainly showed features of metal tear ridge and dimples, melted aluminum zones appeared in some local regions, and cracks existed in some TiB2 particles. The size and quantity of voids on facture both increased with the increasing testing temperature.
  • Effects of Aging Time on Microstructure and Mechanical Properties of 20Cr32Ni1Nb Steel
    JIA Xiankai, TANG Jianqun, GUO Xiaofeng, GONG Jianming
    Materials For Mechanical Engineering. 2018, 42(9): 65-68. https://doi.org/10.11973/jxgccl201809014
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    20Cr32Ni1Nb steel was aged at 950 ℃ for different time (200-5 000 h), and the effects of aging time on microstructure and mechanical properties of the steel were studied. The results show that with the increase of aging time, the lamellar structure of eutectic carbides on grain boundaries of the 20Cr32Ni1Nb steel disappeared, and then the structure changed from short rod shape to granular shape gradually. The secondary carbides precipitated from the austenite matrix and diffusely distributed, and the number of secondary carbides was the largest after aging for 500 h. G phase precipitated from 20Cr32Ni1Nb steel when the aging time was 5 000 h. With the increase of aging time, the tensile strength and yield strength of 20Cr32Ni1Nb steel both increased first and then decreased, the elongation decreased, and the impact toughness decreased first, then increased and then decreased. The impact toughness was 40 J·cm-2 after aging for 5 000 h.
  • Effect of Deposition Speed on Microstructure and Properties of Double-Wire and Plasma Arc Additive Manufactured Carbon Steel Stacking Layer
    LIU Siyu, FENG Yuehai, ZHAN Bin, LUO Zhenjiao, FANG Lele
    Materials For Mechanical Engineering. 2018, 42(9): 69-72. https://doi.org/10.11973/jxgccl201809015
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    Multi-layer stacking layer samples were prepared by double-wire and plasma arc additive manufacturing process on Q235 steel plate at different deposition speeds with H08Mn2Si low alloy carbon steel welding wire as wire. The effects of deposition speed on the macro size, microstructure and mechanical properties of stacking layer were investigated. The results show that with the deposition speed increasing, the surface formation quality of stacking layer became better, the interlayer lines became clearer, and the macro size decreased. At a relatively high deposition speed, the ferrite grains in the stacking layer were relatively small, the content of pearlite was relatively high, and the microstructure was relatively uniform. With the increase of deposition speed, the tensile strength of stacking layer in both vertical direction and horizontal direction increased, the elongation decreased slightly, and the average microhardness inside increased. The tensile fracture was fiber-like and had a lot of dimples, indicating that the ductile fracture occurred.
  • Effect of Tempering Temperature on Microstructure and Mechanical Properties of 35CrMo Steel
    DAI Faming, JIANG Xin, WANG Lingxu, ZHANG Renqi, FAN Lei, HE Jinhang, XU Pingwei, LIANG Yu
    Materials For Mechanical Engineering. 2018, 42(9): 73-77. https://doi.org/10.11973/jxgccl201809016
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    35CrMo steel was quenched at 860 ℃ and then tempered at different temperatures (450, 500, 550, 600 ℃). The effect of tempering temperature on microstructure, tensile properties and fracture toughness was studied by universal testing machine and scanning electron microscope. The results show that with the increase of tempering temperature, the carbides precipitated from supersaturated α phase and were sphericized, and the lath feature of martensite disappeared gradually. The tensile strength and yield strength of the tested steel both decreased,while the elongation increased with the increase of tempering temperature. The tensile strength, yield strength and elongation of the tested steel tempered at 600 ℃ were 1 014 MPa, 933 MPa and 16.8%, respectively. With the increase of tempering temperature, the fracture toughness of the tested steel increased, and the fracture initiation zone changed from rapid crack initiation and propagation characteristics to more obvious plastic deformation characteristics.
  • Residual Stress in Cast Iron Brake Disc Measured by Laser-Generated Surface Wave Technique
    FENG Wanwan, PAN Yongdong, RU Dongheng, WU Hao, YAN Yunfeng
    Materials For Mechanical Engineering. 2018, 42(9): 78-82. https://doi.org/10.11973/jxgccl201809017
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    The relationship between surface stress and laser-generated surface wave velocity of Q235 steel was studied by self-developed laser ultrasonic detector based on piezoelectric sensor with the help of the acoustoelasticity theory, and was compared with experiment results tested by surface wave piezoelectric probe. The relationship between surface stress and laser-generated surface wave velocity of cast iron brake disc was obtained by the detector. The residual stresses at different positions of the cast iron brake disc were detected by laser-generated surface wave technique and compared with that measured by X-ray stress analyzer. The results show that the acoustoelasticity coefficient of Q235 steel detected by laser-generated surface wave technique was 1.02×10-5 MPa-1, and was very close to that measured by surface wave piezoelectric probe. The stresses at different positions of the cast iron brake disc measured by laser-generated surface wave technique and X-ray stress technique were all compressive stress. The values of the stesses by the two techniques were different, but the stresses had the same trend.
  • Reason for Surface Corrosion of 304H Spring Steel Wire and Spring
    SHI Xi, JIN Weiqiang, FENG Huiwei, DU Wenwen, DING Shufang, SHEN Xu, CHEN Chen, CHEN Genbao, MI Zhenli
    Materials For Mechanical Engineering. 2018, 42(9): 83-86. https://doi.org/10.11973/jxgccl201809018
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    After placement for a certain time in the room, the partial surface of 304H spring steel wire and spring rusted. The microscopic morphology of rusty part and unrusty part was observed, and the chemical composition was analyzed. The rusty cause of 304H spring steel wire and spring was discussed. The results show that the rusty part of 304H spring steel wire and spring had the normal microscopic morphology, but copper or zinc elements existed on the surface of the rusty part. The wire rod was polluted by copper element from baler shaft during finishing packaging, and was polluted by zinc element from drawing wheel surface during wire drawing. The potential difference was formed between copper or zinc elements and matrix solid solution, and electrochemical corrosion occurred on the surface of 304H spring steel wire and spring when a water film existed on the surface, resulting in the occurrence of partial rust.
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