Research On Tribology Characteristic Of Micro-arc Oxidation Of Titanium Alloys

With high strength, corrosion resistance, heat resistance and high efficient structure performance, titanium alloys are widely used in aviation, aerospace, shipbuilding,bio-medical and other fields. However, because of low hardness and poor wear resistance,especially the sensitivity to wear, fretting when contacted with other metals, it is limited for further applications.Micro-arc oxidation, as also named micro-plasma oxidation, is a technology by which ceramic coatings situ-grew on the surfaces of Ti、A1、Mg and their alloys. It creates spark discharge by employing electrochemical methods. And with the combined effects of heat chemistry, plasma chemistry and electrochemistry, the ceramic coating forms.The formula of silicate-sodium fluoride, phosphate-sodium citrate and sodium phosphate-sodium aluminate were optimized. The effects of electrolyte systems on the color, uniformity, hardness, structure and tribological properties were investigated. The best electrolyteformula and output parameters of power source were obtained A micro-arc oxidation ceramic coating with certain wear properties was formed. The conclusions are summarized as followed.1. The micro-arc oxidation coating has uniform microstructure in sodium fluoride electrolyte. As the termination voltage increases, a certain thickness of loose film is formed.The coefficient of the film and the 45# steel discs increases and then decreases with the increasing termination voltage, which agrees with the results that the micro hardness increases and then decreases with the increasing termination voltage.2. The micro-arc oxidation coating has less uniform microstructure in phosphate-sodium citrateelectrolyte. The coating is prolate and uneven distributed.The coefficient of the film and the 45#steel discs also increases and then decreases with the increasing termination voltage. But it has higher wear coefficient of 0.35~0.40.3. The micro-arc oxidation coating has highlyuniform microstructure in sodium-sodium aluminate electrolyte. The pore on the surface is uniform distributed and a little loose because of the double main salt effects of sodium and sodium aluminate as the termination voltage increases, and the coefficient of the film and the 45# steel discs increases and then decreases, with a value range of 0.11~0.13.4. The wear coefficients of the micro-arc oxidation coating prepared by the threeelectrolyte systems are better than that of TC4. Based on the coefficient values of coatings to 45#steel, the coating performance prepared by sodium-sodium aluminum silicate system is superior to sodium fluoride system, and the coating in phosphate-sodium citrate system has highest coefficient, which is agreed with the results of microhardness.