Laser forming of Zr-based coatings on AZ91D magnesium alloy substrates □ for wear and corrosion resistance improvement

To improve the wear and corrosion resistance of AZ9ID magnesium alloy, Zr-based coatings were fabricated on the alloy substrate using laser forming. They were prepared from (i) Zr+Mg powders (5 : 1 mass%), and (ii) an undercoating of Zr+Mg powders (5 : 1 mass%) with a top layer of Zr powder. The Zr+Mg powder coating was found to consist primarily of Zr particles with some Zr-based intermetallic compounds in a Mg-Al matrix; while that with an extra top coating of Zr powder had an outer layer composed of Zr oxides and Zr aluminides. With regard to wear and corrosion resistance, the highest improvement was obtained for the specimen that was clad with a top layer of Zr powder. Compared to the AZ91D specimen without a laser formed coating, a fivefold decrease in weight loss and around three orders of magnitude decrease in corrosion current density respectively were obtamed.