Augmentation of wear-protective coatings for non-ferrous alloys by the addition of Cr and Ni Elements

Abstract

A number of Al-, Mg- and Ti-base alloys were preconditioned by oxidation via Plasma-electrolytic oxidation (PEO) followed by the addition of Cr and Ni elements in the coating pores by chemical precipitation and a final stage of mechanical treatment. The overall effect was a combination of hardness and resistance to wear. PEO voltage level was found to be a factor decisive for the oxide layer thickness and level of porosity. In turn the latter two factors appeared to act upon the degree of hardening corundum to alumina fraction in the layer and the degree of Cr/Ni penetration into the oxide layer itself. The optimum condition of increased micro-hardness and high resistance to wear was achieved for an AlCu4Mg2 alloy of extended oxide layer thickness and intermediate levels of open porosity. Similarly good wear results were obtained for a Be60AlMg2 alloy of particularly low microhardness but of sufficiently high porosity in order to accommodate the Cr/Ni intake.