Effect of laser surface melting pretreatment on wear and corrosion properties of micro-arc oxidation coatings on magnesium alloys

This study aimed to examine the impact of laser surface melting (LSM) pretreatment on the wear and corrosion resistance of micro-arc oxidation (MAO) ceramic coatings on AZ31B magnesium alloy. LSM pretreatment was conducted using laser beams with energy densities of 30 J mm-2 , 90 J mm-2 , and 150 J mm-2 , followed by the preparation of MAO ceramic coatings using a bipolar pulse mode. The electrical signals during the MAO process were measured using Hall sensors, while the morphology, structure, elemental composition, and phase composition of the samples were assessed using field emission scanning electron microscopy and other characterization methods. The frictional properties of the coatings were determined using a Multi-Functional Tribometer, and electrochemical tests were conducted in a 3.5 % NaCl solution. The results indicated that the main phase grains of the substrate were significantly refined after LSM pretreatment. The primary phase composition of the ceramic coatings comprised MgO and SiO2. In comparison to untreated samples, the samples pretreated with 150 J mm-2 energy density exhibited the weakest capacitance effect during the MAO growth process, resulting in the highest quality MAO ceramic coatings. Specifically, these samples displayed a reduction in average pore area to 0.84 mu m2, a decrease in porosity of 7.14 %, a 50 % reduction in wear rate, a two orders of magnitude decrease in corrosion current density, and a one order of magnitude increase in polarization resistance.