Effect of auxiliary laser irradiation on characteristics and properties of micro-arc oxidation coating on Ti6Al4V alloy

Abstract

In this study, auxiliary laser irradiation was introduced into MAO processing (L-MAO), and its influence on the microstructure and properties of MAO coating was investigated. The results show that laser irradiation causes a reduction in the breakdown and working voltage of MAO processing while the number and brightness of discharge channels increase. Generating more discharge channels promotes a uniform energy distribution on each discharge channel and avoids the formation of high-intensity discharges. Therefore, after introducing laser irradiation, the obtained coating improves in terms of homogeneity, density, thickness, and bonding strength. Compared with MAO processing, the thickness of coating prepared by L-MAO processing increases by 33.8%, while the porosity decreases from 11.94% to 9.77%. The compositions and phase of coating are also impacted after introducing laser irradiation. More electrolyte ions (SiO32−) enter the coating under laser irradiation, raising the Si content from 18.804 to 21.309 at. %. Besides, more rutile TiO2 phases are detected in L-MAO coating. Based on the above microstructural improvements by laser irradiation, the wear and corrosion resistance of the resultant coating are enhanced correspondingly relative to the MAO processing without laser irradiation.