Tribological Behavior of Ti2SC at Ambient and Elevated Temperatures

The tribological properties of Ti₂SC were investigated at ambient temperatures and 550°C against Ni-based superalloys Inconel 718 (Inc718) and alumina (Al₂O₃) counterparts. The tests were performed using a tab-on-disk method at 1 m/s and 3N (≈0.08 MPa). At room temperature, against the superalloy, the coefficient of friction, μ, was ∼0.6, and at ∼8 × 10⁻⁴ mm³·(N·m)⁻¹ the specific wear rate (SWRs), was high. However, against Al₂O₃, at ∼5 × 10⁻⁵ mm³·(N·m)⁻¹ and ∼0.3, the SWRs and μ were significantly lower, which was presumably related to more intensive tribo-oxidation at the contact points. At 550°C, the Ti₂SC/Inc718 and Al₂O₃ tribocouples demonstrated comparable μ's of ∼0.35–0.5 and SWRs of ∼7–8 × 10⁻⁵ mm³·(N·m)⁻¹. At 550°C, all tribosurfaces were covered by X-ray amorphous oxide tribofilms. At present, Ti₂SC is the only member of a family of the layered ternary carbides and nitrides (MAX phases) that can be used as a tribo-partner against Al₂O₃ in the wide temperature range from ambient to 550°C.