Tribological performance of PEO-WC nanocomposite coating on Mg Alloys deposited by Plasma Electrolytic Oxidation

AZ31B Mg alloy specimens were coated by PEO technique in WC nano-powder containing phosphate based electrolyte under constant current densities. Wear rate and COF diagrams were plotted in order to investigation of WC nano-particles presence and it was found that nano-particle presence can decrease wear rate and COF significantly down to 77% and 55%, respectively. Cross sectional imaging showed that coating thickness increase with coating time and in case of nano-particle containing coatings become more compact but thickness decreases slightly. Investigation of surface morphology indicated that in presence of nano-powder, porosity as well as mean diameter of pores decreased, but prolonging coating time even in presence of nano-powder, led to mean diameter of pores reached up to 8.34 µm. Presence of nano-powders, also increased hardness of coatings considerably.