To further improve the high-temperature dry sliding performance of Si₃N₄ ceramics, a CrAlN transition layer was introduced to improve interfacial stability, while Ag was incorporated as a solid lubricant into the CrAlN matrix. The effects of Ag content on the microstructure and mechanical properties of the coatings were systematically examined, and the tribological performance was evaluated from 25 °C to 550 °C under dry sliding conditions. The Ag concentration increased with increasing Ag target power and affected the morphology, nanoparticle distribution, surface roughness, and mechanical properties of the coatings. Among the tested samples, the coating containing 9.6 at.% Ag exhibited a comparatively favorable combination of mechanical properties within the investigated composition range, with a hardness of 11.5 GPa, an H/E ratio of 0.0913, and an H³/E² value of 0.096 GPa. Tribological tests showed that the average coefficient of friction decreased from 0.32 at 25 °C to 0.12 at 550 °C. This reduction may be associated with temperature-assisted Ag redistribution toward the worn surface and the possible development of Ag-rich surface features at elevated temperatures. However, the wear rate increased with temperature, reaching 3.6 × 10⁻⁵ mm³/(N·m) at 550 °C, suggesting that friction reduction was accompanied by increased material removal and possible near-surface weakening. These results indicate that controlling Ag content is important for balancing friction reduction and wear resistance in ceramic-based self-lubricating coatings.

This paper investigates the contact stress induced by a rigid sphere sliding on a coating-ceramic system. A discrete element model incorporating a ceramic substrate, a surface coating, and a rigid sphere is developed. The influences of the coating grain elastic modulus, coating surface friction coefficient, coating thickness, and interface microcrack defects on the stress distribution within the system are analyzed. The results indicate that a higher coating-to-substrate elastic modulus ratio increases the overall stress but reduces the interfacial shear stress. A lower surface friction coefficient is more beneficial for hard coatings. The relatively optimal coating thickness (h/a) is approximately 0.5. When interface microcrack defects are present, stress concentrations occur at their locations. Longer interface microcracks lead to greater stress concentration, and the interfacial concentrated stress increases with crack length.

For irregularly shaped 820CrMnTi carburizing and nitriding parts, the challenges of high reflectivity-induced overexposure, low surface contrast, and interference from minute burrs in industrial online inspection are addressed in this paper. An innovative precision detection method integrating adaptive imaging and a dual-drive heterogeneous coupling model (RGFCN) is proposed. Such parts, due to surface photovoltaic characteristic changes caused by carburizing and nitriding heat treatment and the complex on-site lighting environment, are prone to local overexposure and “false out-of-tolerance” measurements caused by outlier sensitivity in traditional inspections. First, an innovative programmatic adaptive exposure control algorithm based on grayscale histogram feedback is introduced, which dynamically adjusts imaging parameters in real time to effectively suppress high-brightness overexposure under specific working conditions. Second, a novel adaptive main-axis scanning strategy is designed to construct a dynamic follow-up coordinate system, eliminating projection errors introduced by random positioning from a geometric perspective. Additionally, Gaussian gradient energy fields are combined with the Huber M-estimation robust fitting mechanism to suppress thermal noise while automatically reducing the weight of burrs and oil stains, achieving “immunity” to non-functional defects. Meanwhile, a data-driven innovative compensation approach is introduced. Based on sample training, gradient boosting decision trees (GBDTs) are integrated to explore the nonlinear mapping relationship between multidimensional feature spaces and system residuals, achieving implicit calibration of lens distortion and environmental coupling errors. By simulating factory conditions with drastic 24 h day–night lighting fluctuations and strong oil stain interference, statistical analysis of over 1000 mass-produced parts shows that this method exhibits excellent robustness in complex environments. It reduces the false out-of-tolerance rate caused by burrs by over 90%, and the standard deviation of repeated measurements converges to the micrometer level. This effectively addresses the visual inspection challenges of irregular, highly reflective parts on dynamic production lines.