Improving High-Temperature Wear Resistance of Ti-6Al-4V alloy via Si-B-Y Co-Deposited Coatings

Si-deposited and Si-B-Y co-deposited coatings were prepared on the Ti-6Al-4V alloy using the pack cementation technique. The microstructures of the coatings, as well as their high-temperature wear performance and mechanisms, were comparatively investigated. The results illustrated that the Si-B-Y co-deposited coating had a similar structure with the Si-deposited coating, both of them possessed three-layer structures: an outer layer of TiSi2 matrix, a middle layer of TiSi, and an inner layer of Ti5Si4 and Ti5Si3 mixtures. However, numerous TiB2 and Y2O3 phases formed in the superficial zones of the Si-B-Y co-deposited coating. The micro-hardness of the Si-deposited and Si-B-Y co-deposited coatings was significantly higher than that of the Ti-6Al-4V substrate, and displayed a gradual decrease tendency from the coating surface to the interior. Compared to the Si-deposited coating, the Si-B-Y co-deposited coating possessed a more compact structure and higher surface hardness, and offered better anti-wear performance for the Ti-6Al-4V substrate at 600 degree celsius. Worn against the GCr15 ball, the average friction coefficient of the Si-B-Y co-deposited coating (similar to 0.449) were near equal to that of the Si-deposited coating (similar to 0.474), but lower than that of the Ti-6Al-4V substrate (similar to 0.685). The wear rate of the Si-B-Y co-deposited coating was approximately 4.1 x 10(-5) mm(3)/N center dot m, lower than that of the Ti-6Al-4V substrate by about 74.6%, and the Si-deposited coating by about 37.3%, respectively. When worn against the Al2O3 ball, the average friction coefficient of the Si-B-Y co-deposited coating (similar to 0.742) was lower than that of the Si-deposited coating (similar to 0.811), but higher than that of the Ti-6Al-4V substrate (similar to 0.551). The wear rate of the coating was approximately 1.22 x 10(-4) mm(3)/N center dot m, lower than that of the Ti-6Al-4V substrate by about 72.2%, and the Si-deposited coating by about 35%.