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 ℃. Worn against the GCr15 ball, the average friction coefficient of the Si–B–Y co-deposited coating (~ 0.449) were near equal to that of the Si-deposited coating (~ 0.474), but lower than that of the Ti–6Al–4V substrate (~ 0.685). The wear rate of the Si–B–Y co-deposited coating was approximately 4.1 × 10⁻⁵ mm³/N·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 (~ 0.742) was lower than that of the Si-deposited coating (~ 0.811), but higher than that of the Ti–6Al–4V substrate (~ 0.551). The wear rate of the coating was approximately 1.22 × 10⁻⁴ mm³/N·m, lower than that of the Ti–6Al–4V substrate by about 72.2%, and the Si-deposited coating by about 35%.