Correlating texture evolution and residual stress with the enhanced tribological performance of TiN coatings on M50NiL steel

To improve the wear resistance of M50NiL aero-bearing steel, TiN coatings were deposited using multi-arc ion plating via the L₉ (3⁴) orthogonal design. The synergistic effects of deposition parameters on the microstructural, mechanical, and tribological properties were investigated. Increasing the substrate bias triggered a (111) to (220) texture transition and grain refinement. The optimal coating (S8) exhibited a dense microstructure (grain size: 16 nm), high hardness (22.2 GPa), good fracture toughness (K_IC = 1.26 MPa·m^1/2), and excellent adhesion (L_C2 = 48.3 N). Residual stresses of the coatings ranged from −0.38 GPa to −6.58 GPa. Tailoring the compressive stress to a moderate level (−1.49 GPa) was crucial for S8's superior overall performance. In sliding friction tests, S8 achieved a low friction coefficient of 0.288 and a wear rate of 1410 μm³/(N·m), representing an 89.3% reduction compared to the substrate. This enhanced tribological performance stems from the optimal synergy between the refined microstructure, moderate stress state, and robust mechanical integrity.