Wear mechanism classification and adaptive behavior of TiO₂-B₄C-Al system reactive plasma spraying coating under load-speed coupling conditions

Departing from conventional component-mixing strategies, this work adopted an in-situ reaction and self-structuring approach. The TiB₂-TiC-Al₂O₃ nanocomposite coating with high hardness, strong interfacial bonding, and good toughness was fabricated by plasma spraying TiO₂-B₄C-Al powder. Through systematic friction tests over a wide range of loads and speeds, a load-speed wear diagram was constructed, revealing the evolution of wear mechanisms with increasing energy input. At low loads (≤10 N), abrasion dominated. Under medium-high loads and speeds (≥20 N, ≥200 r/min), thermal-mechanical fatigue coupled with oxidation became prevalent. At high loads with low speeds (≥20 N, ≤200 r/min), high-stress brittle fracture governed. Notably, an anomalous wear rate drop occurred at the extreme condition of 30 N−400 r/min, where dynamic interfacial reorganization appeared to promote the formation of a protective tribofilm. This tribofilm was repeatedly generated and partially removed during sliding, suggesting a quasi-steady formation-removal mechanism rather than a permanently stable film. This in-situ synthesized multiphase architecture not only ensured a strong-tough interface between the reinforcement and substrate, but also facilitated the dynamic establishment of a tribofilm during sliding. These results offer a new design paradigm for high-performance wear-resistant coatings.