Growth kinetics and morphology of microarc oxidation coating on titanium

Growth kinetics and discharge behavior of micro-arc oxidation (MAO) coatings on commercially pure titanium in aluminate-silicate based electrolyte were studied using scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), and surface roughness tester, focusing on kinetics of micro-arc oxidation discharges and morphology of the oxide layer. The effect of the coating duration on morphology, roughness parameters, weight variation, and quantitative characters of the discharge channels and thickness was studied elaborately. Incorporation of alumina nanoparticles into the oxide layer and their effect on the geometry of discharge channels were also investigated in the present study. Results revealed that, during the coating process, the nanoparticles are driven to discharge channels due to sparking, filling the pores and smoothening the coating surface, which leads to a drop in the increasing rate of Rv and Rlo roughness parameters. Moreover, it was found that nanoparticles' adsorption reduces the volume of discharge channels. Eventually, a 106% reduction in the eruption of oxides led to a reduction of 70% in the coating's growth rate in similar coating durations.