Laser cladding of Cu_0.5NiAlCoCrFeSi high entropy alloy on AZ91D magnesium substrates for improving wear and corrosion resistance

To improve the wear and corrosion properties of AZ91D magnesium alloy, a Cu_0.5NiAlCoCrFeSi high entropy alloy (HEA) was fabricated on AZ91D magnesium substrate specimens by laser cladding using elemental powders. The laser-clad coating consists of a fine dendritic structure of a simple BBC phase with nano-size precipitates. The hardness of the coating was some ten times higher than that of the AZ91D substrate and was even higher than that of the same HEA produced by arc melting. The laser-clad coating exhibited good wear resistance, with a wear rate five times lower than that of the substrate material in dry friction wear conditions. The main wear mechanisms of the substrate and the HEA coating were different, the former dominated by both abrasive wear and adhesive wear and the latter by oxidative abrasive wear. With regard to corrosion properties, the laser-clad coating exhibited a more positive corrosion potential and a lower corrosion current density than those of the uncoated substrate material.