Effects of Li2SO4 Content in the Electrolyte on Characteristics of Coating on Ti6Al4V by Micro-Arc Oxidation

Abstract:

The oxide coatings were obtained on Ti6Al4V alloy in Na2SiO3 electrolyte system containing Li2SO4 by micro-arc oxidation (MAO). The thickness of coatings was measured and their surface micromorphology and roughness were analyzed by SEM and AFM, respectively. The results show that the thickness of coatings decreases from 87 μm to 57 μm and the roughness also decrease with the increasing of Li2SO4 content from 0 to 4.0 g/L in the electrolyte. Meantime, the diameter of cellular microholes on the surface of coatings decreases from 30 μm to 5 μm and the wall of microholes becomes smoother. The number of individual particles by melt spraying reduces from 416 to 145 but the average particle diameter increases from 350 nm to 597 nm. It is found by X-ray diffraction that the amount of rutile TiO2 in the coatings is increased and that of anatase TiO2 is reduced gradually with increasing of Li2SO4 content in the electrolyte.

Key words:Ti6Al4V; micro-arc oxidation; Li2SO4; electrolyte; oxide coating characteristic