Oxidation protection of Ti–6Al–4V alloy using a novel glass–amorphous silica composite coating

Abstract A novel glass–amorphous silica composite coating was prepared by the slurry method in order to improve the oxidation resistance of Ti–6Al–4V alloy at high temperatures. The microstructure of the as-prepared composite coating was analyzed by SEM, XRD and EDS techniques. The oxidation resistance and the microstructure evolution of the composite coating at 800 °C for 50 h were also studied. The results show that mass gains of the specimens coated with the composite coating were far less than that of the uncoated ones after oxidation of 50 h. Thick oxide scales composed of plate-like rutile TiO 2 and some granular α-Al 2 O 3 formed on bare Ti–6Al–4V alloy, while quartz, cristobalite and diopside were observed in the composite coating, which are useful crystals for slowing the inward diffusion of oxygen to the substrate. The cross-sectional EDS line scanning images show that inward diffusion of oxygen and outward diffusion of Ti through the composite coating were insignificant. The microhardness profile reveals that the solid solution oxygen in Ti–6Al–4V alloy with composite coating was limited.