Papers by Author: Zhong Xu

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Authors: Wen Ping Liang, Zhong Xu, Qiang Miao, Xiao Ping Liu, Zhi Yong He
Abstract: Ti2AlNb orthorhombic alloy is a promising high temperature structural material for aero-industries due to its advantageous properties. However, insufficient wear-resistance is a major drawback that has restricted the actual uses of this alloy in many circumstances. A treatment of double glow plasma surface chromizing on Ti2AlNb alloy has been carried out as an attempt to resolve this problem. This paper mainly investigated the electrochemical corrosion behaviors of this alloy after chromizing. The microstructure of the chromized layer was analyzed by X-ray diffraction (XRD). The sectional morphology of chromized layer was surveyed through scanning electronic microscopy (SEM).The polarization curves of specimens in three corrosive media, 5% H2SO4, 5% HCl and 3.5% NaCl, were measured. The eroded surface morphologies were also surveyed by SEM. The results indicate that surface chromizing treatment slightly decrease the alloy’s corrosion resistance, but still exhibit good performance.
1753
Authors: Wen Ping Liang, Zhong Xu, Qiang Miao, Zhi Yong He
Abstract: Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries, but insufficient wear-resistance is a major drawback which restricts the actual uses of this alloy in many circumstances. A double glow plasma surface molybdenizing on Ti2AlNb alloy had been carried out to resolve this problem. This paper investigated the electrochemical corrosion behaviors of the alloy after molybdenizing. The polarization curves of specimens in three corrosive media, 5% H2SO4, 5% HCl and 3.5% NaCl, were measured. The eroded surface morphologies were surveyed by SEM. The results indicate that surface molybdenizing decreased the alloy’s corrosion resistance slightly, but still exhibit good performance.
1793
Authors: Yan Mei Zhang, Xiao Hua Jie, Zhong Hou Li, Zhong Xu
1817
Authors: Yan Mei Zhang, Xiao Hua Jie, Zhong Hou Li, Zhong Xu
Abstract: In this paper, cobalt, tungsten and molybdenum were co-diffused into the surface of T8 steel by double glow discharge technique. A carbide layer with M6C+MC was formed on T8 steel. Under the carbide layer was a diffusion layer of W,Mo,Co. Hardness of carbide layer is high over 1200~1400 HV0.025 and can improve to 1400~1600 HV0.025 after solution and ageing treatment. Hardness of the diffusion layer is only 400~550 HV0.025, but it can improve to 800~1000 HV0.025 after solution and ageing treatment. The carbide layer combides with the substrate in metallurgy and can not peel off from the substrate. The carbide layer on T8 steel possess same good tribological properties of M2 steel.
1071
Authors: Xiao Ping Liu, Wen Huai Tian, Chao Li Guo, Dong Dong Chen, Zhi Yong He, Zhong Xu
Abstract: In this study, plasma niobium alloying of the TiAl based alloys has been carried out at 1050, 1100 and 1150°C. The effect of the alloying temperature on the characteristic of the alloyed layer was investigated by optical microscopy, scanning electronic microscopy (SEM), glow discharge spectrum (GDS) and energy dispersive spectrum (EDS). The results show that the surface roughness, chemical composition and thickness of the alloyed layer increased with the alloying temperature which is dependent on the sheath potential. A deposition layer formed on the TiAl surface at 1150 °C was resulted from the larger sheath potential or the stronger sputtering of source electrode.
1854
Authors: Xiu Yan Li, Ying Zhang, Bin Tang, Zhong Xu
Abstract: Ti6Al4V alloy is promising biology material with outstanding properties of low density, high specific strength, and exceptional corrosion resistance. However, one of its disadvantages is the poor tribological property. In this paper Mo-N hard surface modification layers were formed on Ti6Al4V at 900°C substrate temperature by plasma reactive sputtering. The flux ratio N2/Ar is an important parameter and its influence on the composition, structure and hardness of the Mo-N layers is studied. The Mo-N layers are duplex layers, composed of diffusing layer and surface coating. The component of Mo and N elements in the diffusing layer changes gradually which can enhance the load-bearing capacity to the coating and ensure the durability of the coating. With the increase of the flux ratio N2/Ar, the content of N element in the Mo-N layers increases. The Mo-N layers were polycrystalline γ- Mo2N with (200) plane oriented parallel to the substrate surface. The surface hardness of the formed layers is in the range HK1330-1430. The hardness of the Mo-N layers increases with the increase of the flux ratio N2/Ar and the reason is that the content of N element in the Mo-N layers increases.
1128
Authors: Wen Bo Wang, Zhong Xu, Zhi Yong He, Zhen Xia Wang, Ping Ze Zhang
Abstract: A niobium modified layer on Ti-6Al-4V surface was obtained by means of the plasma surface alloying technique. The oxidation behavior of the modified layer was investigated and compared with Ti-6Al-4V at 700°C~900°C for 100h. Composition and microstructure of Ti-6Al-4V and the modified layer after oxidation at 900°C for 100h were analyzed using XRD and SEM respectively. The experimental results showed the oxidation behavior of Ti-6Al-4V at 900°C for 100h was obviously improved after the niobium alloying process.
1818
Authors: Yuan Gao, Jin Yong Xu, Zhong Xu
Abstract: This research tries to improve the plasma surface W, Mo alloying process by adding inlet methane aside from the original inert gas argon. The carbon and hydrogen particles are incorporated into the ion sputtering, ionization, surface activation and diffusion processes. The W, Mo atoms sputtered from the target diffuse into the surface of the substrate at the same time with the diffusion of carbon atoms. So the synergism of the alloying process and the carburizing process is established in this way. The hydrogen atoms participate the reduction and activation process on the surface of the target and the substrate. The surface HSS combines with substrate via metallurgical bonding and the carbides are all secondary carbides formed at lower temperature during solid state diffusion. These carbides are very soluble to the austenite. This makes the alloy elements fully functional. The carbides with granular shape and distributes homogeneously on the matrix are very fine. No coarse ledeburite eutectic carbide exists. After the co-alloying process of W, Mo, C, direct quench or quench at lower temperature can be applied.
1798
Authors: Zhi Yong He, Xiao Feng Wang, Ying Fan, Zhen Xia Wang, Xiao Ping Liu, Zhong Xu
Abstract: Sputtering rate Sr was proposed as an alternative parameter instead of sputtering yield Y to calibrate the sputtering ability of the target, defined as the mass loss of the target per unit time and sputtering current. The approach is more reliable for glow discharge processes since the intense backscattering effect was taken into consideration. The effects of processing parameters on Sr were investigated through orthogonal test, the results indicated that target temperature affects Sr obviously, and among the discharge parameters, the target voltage and discharge pressure were the governing factors. Through regression analysis, the sputtering rate Sr was expressed as a function of sputtering voltage and discharge pressure which could be used to evaluate or predict the real output of the sputtering target.
1891
Authors: Jin Yong Xu, Yuan Gao, Mei Fa Huang, Jun Cheng, Zhong Xu
Abstract: Mo-Cr diffusion layer on carbon steels are prepared by double glow plasma surface metallurgy and then treated by ultra-saturated carbonization, quenching and tempering. The content of component is roughly that of high-speed steels (HSS). The results showed that the depth of coating is over 100μm and the content of Mo, Cr alloyed layer is about 20% and 10% respectively. Surface carbon content is over 2.0% after ultra-saturated carbonization. The carbides of the alloyed layer are fine and dispersed, without coarse eutectic ledeburite. X-ray diffraction showed that the carbides are M6C, M2C, M23C6 etc. SEM analyse indicated that the dimension of surface carbide is less 1μm. The abrasion experimental results showed that the relative wear resistance of the treated sample was 2.38 times as that of quenched GCr15.
1708
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