Wide-temperature-range tribological behavior and control mechanism of SnAg/ZrW₂O₈-incorporated Ni-based adaptive composite coatings

To realize the adaptive regulation of friction performance for core mechanical components over a wide temperature range, an integrated antifriction and wear-resistant composite structure combining coating, texture, and lubricant was proposed and prepared. Arrayed circular micropore textures were fabricated on CSS-42 L high-temperature bearing steel with a nickel-based hard coating, and SnAg soft metal lubricant doped with the negative thermal expansion agent ZrW₂O₈ was filled into the textures. Cellular automaton models were established to simulate the diffusion process of the lubricant, and combined with systematic tribological experiments, the frictional behavior and adaptive regulatory mechanism at different temperatures were systematically analyzed. Simulation results based on cellular automata models show that with increasing temperature, the proportion of medium- and high-concentration regions of SnAg lubricant increases gradually and reaches 75.28% at 350 °C, confirming the favorable diffusion behavior at elevated temperatures. Tribological tests reveal that the 95Sn5Ag-filled coating and the 95Sn5Ag–10 wt% ZrW₂O₈-filled coating exhibit significantly superior tribological properties compared with the pure Ni-based coating across a wide temperature range. At 350 °C, the average friction coefficients of the 95Sn5Ag-filled coating and the 95Sn5Ag–10 wt% ZrW₂O₈-filled coating are 0.42 and 0.44, respectively, reduced by 35.4% and 39.7% compared with room temperature, and the wear rates decrease to 1.3×10⁻⁷ and 2.0×10⁻⁷ mm³·N⁻¹·m⁻¹. The lubricating layer thicknesses reach 4.48 and 4.18 μm, increasing by 164% and 80%, respectively. The 95Sn5Ag–10 wt% ZrW₂O₈-filled coating presents a more stable adaptive lubrication performance. The unique “inhibition at high temperatures and promotion at low temperatures” regulatory mechanism of ZrW₂O₈ effectively enhances the wide-temperature adaptability. The synergistic effect of coating, texture, and lubricant enables excellent antifriction and self-lubrication, which provides an efficient and feasible strategy for the active design and performance optimization of wear-resistant and lubricating functions of mechanical components.