| Titanium and its alloys are advanced structure materials and known as "almighty metal" due to their high specific strength, light weight, good corrosion resistance and excellent comprehensive performance. Thus, titanium and its alloys are widely applied in many industries, such as aerospace, military, biological medicine, automobile industry and chemical industry etc. However, their weaknesses are also prominent, including low hardness, poor thermal conductivity and wear resistance.In recent years, as a promising wear resistant material,much attention had been paid to TiNi alloy for its good toughness, unique hyper elasticity and superb tribological performance. In this study, TiNi alloy was prepared on the surface of widely used Ti6A14V alloy to improve its wear resistance. The surface alloy would have moderate hardness similar to TiNi alloy but superb wear resistance due to the unique pseudo elastic deformation mechanism. Ti-Ni/Ni modified layers were prepared on surface of the Ti6A14V substrate by plasma surface alloying technology. The Ti-Ni/Ni alloying processes, micro-structure, composition distribution, phase structure, and micro-hardness of alloying layer were investigated. Tribological performance of the Ti-Ni/Ni modified layers and Ti6A14V substrates were investigated by pin-on-disc tribometer with GCrl5 and Si3N4 counterbody. The influences of loads and rotation speed on wear processes of Ni alloyed layers were analyzed. Corrosive wear performance of Ni alloyed layers and substrates were tested in 3.5%NaCl solution,5%HCl solution, distilled water and dry air. Corrosion resistance of Ni alloyed layers and substrates in 3.5%NaCl solution,5%H2SO4 solution and 5%HCl solution were alos researched by electrochemical corrosion method.From the experimental results, the following conclusions were obtained:1. The optimum process parameters for the preparation of Ti-Ni and Ni alloyed layers are:distance between source and cathode 18mm, processing temperature 900℃, working pressures 35Pa/45Pa, holding time 3h, the voltage difference between cathode voltage and workpiece voltages 250V-300V/350V-450V.2.Ti-Ni and Ni alloyed layers obtained under optimum condition have Ni content up to 16.58at% and 94.62at%, depth to 18.69μm and 59.24μm and micro-hardness up to 625HV and 677HV. The alloyed layers were dense, uniform, and the composition changes gradually from surface to substrate. The substrate remained the fine equiaxial grains. The X ray diffraction revealed the formation of Ti2Ni, TiNi, Ti within the Ti-Ni and Ni alloyed layers.3. Coupled with GCrl5 ball, the results indicated that the friction coefficient of Ti-Ni alloyed layer was higher than that of substrate, but width of wear rate was much lower. With Si3N4 ball, friction coefficient and wear rate of Ti-Ni alloyed layer were all lower than that of substrates. Coupled with GCr15 ball, the friction coefficient of Ni alloyed layer was higher than that of substrate, the wear rate was lower. With Si3N4 ball,the friction coefficient of the Ni alloyed layer was higher than that of substrate, the wear rate was lower than that of substrate.4.Under different loads, friction coefficients were basically unchanged. With the increase of loads, wear rates were gradually increased. As rotating speed changed, there were an optimum moderate value.5.The corrosion wear properties of Ni alloyed layers in 3.5%NaCl solution, 5%HCl solution, distilled water and dry air were improved. The wear mechanism for the alloyed surface is mainly adhesive wear, but the wear mechanism of substrates is mainly abrasive wear.6.Electrochemical corrosion were tested in 3.5%NaCl solution,5%H2SO4 solution and 5%HCl solution. Analysis results showed that corrosion resistance of Ni alloyed layers were worse than that of substrates. This Phenomenon is maybe relevant to the surface condition of alloyed layers and the precipitation of nickel ions during electrochemical process.
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