Interface adhesion enhancement of V-coatings deposited by high power impulse magnetron sputtering on Al-alloy substrate

The V-coatings were synthesized by high power impulse magnetron sputtering on the substrate of Al-alloy covered with transition layers of Cu and Cr. The influence of the type and phase-structure of the transition layers on the interfacial adhesion was investigated with X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy and mechanical probes. The results show that the Cu/Cr transition layers with an optimized thermal expansion coefficient gradient significantly increased the adhesion at the interface of the compact smooth V-coatings. To be specific, the transition layers, Cu/(Cu-Cr)/Cr/(Cr-V), significantly increased the adhesion at the interface of the Al-alloy and V-coating from the original 12 up to 30 N, because of the inter-diffusion between the Cu/Cr and Cr/V layers. Preferential growth of V(111) and Cr(111) was observed. In addition, the transition layers considerably reduced the length and surface density of indentation micro-cracks.