| Titanium alloy has been applied in aerospace, biomedical, chemical, transportation, sports and electronics industries due to its excellent properties, such as high specific strength, low temperature stability, excellent corrosion resistance and good biocompatibility. However, its disadvantages of low carrying capacity of the surface, poor wear resistance, high temperature oxidation embrittlement and low corrosion resistance at specific environment significantly influence the structure safety. Because the performance of wear and corrosion are mainly determined by the surface, so many processing technologies to improve wear resistance of titanium alloy have developed, including electroplating, chemical heat treatment, PVD, CVD, laser strengthening and plasma surface alloying and so on at home and abroad. But these processes have some poor performance, like exist thin films, partly improve the wear resistance, brittle wear-resistant layer, and so on. To satisfy the request of surface wear-resistant of titanium alloys, Mo surface modified layer was prepared on titanium gear using plasma surface alloying technique, consisted of a external coating, which can completely modify the surface content, and a gradient diffusion layer, which can improve the coordination deformation capacity between the modified layer and the substrate. For overcoming the disvantage of hard coatings on soft substrate, like titanium, that was easily peeled off under high loadings condition, Mo-base surface modified layers were prepared on Titanium Gear, which can obviously improve its wear resistance and simultaneously increase anti-burning properties due to weak adhesion tendency of molybdenum element with other elements. Without severe loss of the performance of substrate, the wear resistance of titanium alloy can be effectively improved, which will largely improve the life of titanium alloy parts in industrial applications and expansion of its applications.This article originates from the 863 projects "The preparation and properties of high-performance surface titanium alloy" (2007AA03Z521). By taking Ti6Al4V alloy as research target, this paper discusses process of Mo surface modified layer prepared on Titanium Gear and its effect on wear resistance at the field of theoretically and experimentally, so as to provide beneficial experiences for researches on the preparation of high-performance surface titanium alloy. Major work accomplished in this paper is as follows:Mo surface modified layer was prepared on titanium gear using plasma surface alloying technique to increase the surface hardness and adhesion strength which can effectively improve the wear resistance of titanium alloy gear. The micro structure of the modified layer was investigated by XRD, GDOES and SEM. The sliding friction and rolling friction test were performed to evaluate wear resistance of Mo modified layer by the wear test machine, the sliding friction and rolling friction characteristics were also investigated, and the rolling contact fatigue was performed to investigate the rolling contact fatigue performance of Mo modified layer. By simulating the actual working conditions, through the gear running-in tests and actual running test to evaluate the actual operation of the Ti6Al4V alloy gear and explore the performance of modified titanium gear.Based on the theoretical and experimental analysis, the results as follows:(1) Mo surface modified layer was prepared on titanium gear using plasma surface alloying technique, Mo surface modified layer is consisted of a pure Mo surface layer and a diffusion layer and its depth is no less than 18μm.;(2) The micro-hardness changes gradually from surface to Ti6Al4V matrix, and Mo modified layer reach up to 1050HK, which is nearly three times higher than that of Ti6A14V matrix.(3) The samples of Ti6A14V alloy with Mo modified layer and tempered 40Cr carried on ground sliding and rolling friction, the friction condition was significantly improved, the wear resistance and load carrying capacity had been significantly strengthened.(4) The failure characterizes of Ti6A14V alloy by rolling contact fatigue were adhesion pitting and corrosion pits, Mo surface modified layer can significantly improve performance of rolling contact fatigue of the Ti6A14V alloy;(5) The gear running-in tests and actual running tests were carried on. The performances of the molybdnized Ti6Al4V alloy gears gears were successful applied.Researches done in this paper enrich methods of the preparation of high-performance surface titanium alloy, and provide beneficial research fruits for surface alloying technology in the application of the surface of Ti6A14V alloy gears.
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