Tribological behavior and thermal stability of sputtered WSTi nanocomposite films from room temperature to 400 °C

Based on enthalpy-induced amorphization strategy, magnetron sputtered WSTi nanocomposite films achieved ultralow coefficients of friction (CoF) and enhanced wear resistance at high temperatures up to 400 °C. The effects of Ti doping concentration, tribo-testing temperature, and thermal stability on the microstructure and tribological properties of WSTi films were systematically investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the microstructure and surfaces of the composite films after tribo-sliding, while the first-principle calculations elucidated the superior lubrication mechanism. Results indicated that the WSTi film with 19.4 at.% Ti exhibited the lowest CoF (0.07) and wear rate (W_R, 4.1 × 10⁻⁵ mm³/N·m) at room temperature. Furthermore, the film maintained stable lubrication performance at 400 °C, with a low CoF of 0.2. High-temperature annealing (400 °C and 600 °C) induced partial oxidation of WSTi film to WO₃ and TiO₂, yet the residual WS₂ phase preserved advanced self-lubricity through dynamic reorganization into lubricous layered structure. Density functional theory (DFT) calculations revealed that Ti incorporation increases interlayer spacing and reduces shear strength, facilitating ultralow CoF. This study provided a promising strategy for developing high-temperature adaptive solid lubricants for aerospace industrial applications.