Surface Modification Of Titanium Alloy By Micro-arc Oxidation

By adding SiC micro-particles with different sizes to the electrolyte, micro-arc oxidation (MAO) technique was employed to fabricate oxide ceramic layer embedded with SiC of both pure Ti and Ti-6A1-4V alloys. The scanning electron microscope、 X-ray diffractometer and ball-on-disk tribometer were used to analyze surface topography, phase composition and tribological properties, respectively.Various kinds of parameters were adjusted to analyze the effect of adding different sizes of SiC to the oxide ceramic layer. By using optimal parameters, Ti-6A1-4V alloys oxide ceramic layer embedded with SiC microparticles by using MAO technique was prepared. Then, its tribological behaviors were incestigated by using ball-on-disk tribometer.For micro-arc oxidation on pure Ti, it showed that different kinds of electrolyte have significant impact on the surface topography and the reaction. With the increase of the voltage and experimental time, the electric spark becomes stronger. In addition, the intensity of micro-arc discharge improves dramatically. Thus, the oxide ceramic layer damages more seriously. It is found that it is feasible to get ceramic layer embedded with SiC by adding SiC to the electrolyte. SiC has no impact on the process of the micro-arc reaction, but could change the inner structure which include the porosity and the diameter of the pores. The result shows that adding SiC particles with smaller sizes would reduce the porosity and the diameter of the pores. Adding SiC to the layer could influence the hardness of the layer, but the influence level depends on the size of SiC. Small SiC(0.4 μ m) has small impact on the hardness of the layer. However, the big SiC(8 μ m) has no impact on the hardness of the layer for its oversize diameter. The SiC with proper size(1-2 μ m) could diffuse into the pore of the oxide layer and for its larger size it could strengthen the oxide layer structure, so that it could improve the hardness of the layer dramatically.For Ti-6A1-4V alloy, it showed that SiC micro-particles have significant effects on the surface topography and tribological properties of the strengthened layer. SiC particles with smaller sizes would reduce the porosity and improve the density and tribological property of Ti-6A1-4V alloys dramatically, especially for SiC particles with 1-2 u m diameter. By contrast, larger SiC particle can not go through the pores in the oxide layer for its larger size, so that the wear resistance property of the oxidation layer is improved slightly.