75Cr3C2-25NiCr and 86WC-10Co-4Cr High Wear- and Corrosion-Resistant Cermet Coatings Deposited on A356 Substrate by High-Velocity Oxy-Fuel Technique

In this research, Cr3C2-NiCr and WC-Co-Cr cermet coatings were developed on A356 aluminum-based alloy substrate by the high-velocity oxy-fuel (HVOF) technique for use in wear and corrosion applications. The substrate and coatings were characterized using a field emission scanning electron microscope (FESEM) equipped with the energy dispersive spectroscope (EDS), microhardness, wear, and corrosion test instruments. Microstructural observations revealed that the coatings with an average thickness of about 250 mu m were well bonded with the substrate. The microhardness of the Cr3C2-NiCr (similar to 930 HV) and WC-Co-Cr (similar to 1300 HV) coatings were about eleven and sixteen times higher than that of the A356 substrate (similar to 80 HV), respectively. Cermet coatings showed significantly lower mass losses, wear rates, and friction coefficients in comparison with the A356 substrate. WC-Co-Cr coating illustrated higher tribological performance in comparison with Cr3C2-NiCr coating. The mass loss and friction coefficient of the WC-Co-Cr coating under an applied load of 10 N was about 0.2 mg and 0.13 (about 99.5% and 79.7% lower than that of the A356 substrate, e.g., 41.5 mg and 0.64), respectively. Rising applied load increased the wear characteristics of the A356 substrate with the more pronounced degrees. FESEM observations on wear test specimens illustrated the different wear mechanisms on the surfaces. The results illustrated significant improvements in the corrosion performances of the coated samples.