Characterisation and tribological properties of Stellite-coated magnesium alloy by high-velocity oxy-fuel

In the present study, the surface of AZ91D magnesium (Mg) alloy was coated with Stellite-1 powder by using the high-velocity oxy-fuel method and surface coatings were carried out at different heat inputs and spray distances. The cross-sections of the coating layers were examined by optical microscopy and scanning electron microscopy. The phase compositions and phases formed on the coating layers were determined by energy-dispersive X-ray spectroscopy and X-ray diffraction, respectively. Surface roughness, porosity percentages and microhardness were measured. The dry sliding wear and friction behaviour of the AZ91D and coated samples at 5.0, 7.5 and 10.0 N normal loads were determined by using a disc-on-disc wear test device. In the coating layers, hard oxide and carbide phases were detected. The surface roughness and porosity increased with decreasing heat input and increasing spray distance. The surface roughness of the coated samples was higher than the substrate. The microhardness values of coating layers were varied between 982 and 1449 HV_0.1, and the sample with the highest hardness was the sample coated at high heat input and low spray distance. The wear resistance of coating layers reduced with decreasing microhardness, and it was much higher than that of AZ91D.