Comparison of wear properties of HVOF sprayed WC-Co and WC-CoCr coatings on Al alloys

Coating is applied onto aluminum alloys to improve their surface properties. Cermet coatings applied especially by thermal spraying techniques give high mechanical and corrosion resistance to the surface of alloys. In this study, the WC-Co and WC-CoCr coatings were applied onto three different substrates, Al-2024, Al-6082, and Al-7075 alloys, using High Velocity Oxy-Fuel (HVOF) method. The properties of coatings were investigated according to the coating and substrate type, considering microstructures, tribological properties and sliding wear resistance of the sprayed coatings. It was found that the WC-CoCr coatings exhibited higher hardness while giving a thinner coating than the WC-Co coatings. Besides, the presence of Cr in the coating enhanced the binding of carbide grains. Depending on all these, the WC-CoCr coatings showed better wear resistance for all Al-alloy substrates compared to the WC-Co coatings. Slight decomposition of WC phase was taken place during coating process and this contributed to the wear resistance. The highest wear resistance was obtained in the WC-CoCr coating on Al-7075 alloy.