Effect of laser power on the microstructure and wear resistance of TiO2-SiO2 ceramic coating by laser-assisted micro-arc oxidation on Ti6Al4V alloy

In this study, laser-assisted micro-arc oxidation (LMAO) processing was carried out on Ti6Al4V alloy under laser powers of 30, 45, and 60 W, and the influence of the laser power on the microstructure and wear resistance of the coating was further investigated. The breakdown voltage and termination voltages of LMAO processing decrease gradually as the laser power increases. At the same time, micro-discharges increase in quantity. Within the suitable laser power range (30–45 W), the obtained coating continuously enhances uniformity, thickness, and density with rising power, contributing to higher hardness and adhesion strength . However, raising laser power to 60 W will damage the obtained coating due to the violent micro-discharges, which generate interconnected larger pores in the local area. Laser power also affects the coating's reaction process and phase transition. More electrolyte ions dope into the coating as a consequence of increasing laser power. The Si concentration of the LMAO-45 coating is the highest, whereas that of the LMAO-60 coating comparatively reduces due to localized coating detachment. Moreover, enhancing laser power is more conducive to forming SiO 2 and rutile-TiO 2 phases. Compared with the traditional MAO or other LMAO coatings, the LMAO-45 coating significantly improves wear protection, evidenced by the lowest COF value , the minimum wear rate, and the least peeling during the wear test . Low porosity, surface roughness , high thickness, and increased incorporation of the SiO 2 phase are responsible for the same. However, under 60 W of laser irradiation , the wear resistance of the resultant LMAO coating decreased due to the formation of local damaged areas.