Reciprocating Wear of Ti-TiB In Situ Composites Synthesized via Vacuum Arc Melting

TiB-reinforced titanium matrix composites were synthesized using vacuum arc melting to enhance the hardness and wear resistance of pure (Ti). The microstructure showed a macroscopically uniform distribution of TiB whiskers in the Ti matrix. The hardness of the composite increased from 799 (with TiB content 50 vol.%) to 895 HV (with TiB content 85 vol.%) compared to the 236 HV hardness of pure Ti. Dry sliding reciprocating wear tests under four different loads of 10, 15, 20, and 25 N were carried out against a steel ball as a counterface at a constant frequency of 4 Hz. The coefficient of friction and wear rate decreased with increasing TiB content. The observed behavior has been explained based on the hardness of the composites, the presence of loose wear particles over the worn surface, formation of a transfer layer of wear debris over the surface and its degree of compaction, extent of coverage, and presence of lubricious oxides (TiO₂, B₂O₃ and H₃BO₃). The operative mechanism of wear is a mix of ploughing, adhesion and oxidation for pure Ti, whereas the same for composites is adhesion, oxidation, delamination, and abrasion. The composite having 80 vol.% TiB has shown the lowest coefficient of friction among all the composites.