Effect of Cryogenic Treatment on Microstructural Evolution and Tribological Properties of Ni-Co-Cr/SiC Nanocomposite Coatings

To address the demands of modern high-speed and high-quality continuous casting production, depositing high-performance coatings on the surface of mold copper plates is critically important for extending the service life of continuous casting molds. To this end, a Ni-Co-Cr/SiC nanocomposite coating was developed, and cryogenic treatment was applied to further improve its hardness and wear resistance. This work systematically investigates the microstructural evolution and performance enhancement of the Ni-Co-Cr/SiC nanocomposite coating under different cryogenic treatment parameters, with special emphasis on the effects of treatment temperature on the coating’s microstructure, hardness, wear resistance, and adhesion to the substrate. The results demonstrate that decreasing the cryogenic treatment temperature and extending the holding time effectively refine the grains of the coating while simultaneously promoting the accumulation of microstrain and dislocation density. These changes lead to significant improvements in hardness, wear resistance, and interfacial bonding performance. Specifically, after direct immersion at −196 °C for 16 h, the coating reached a hardness value of 946.5 HV, and the wear rate was reduced to 0.032 mm3·(N·m)−1, representing only 54.6% of that of the untreated coating. The dominant wear mechanism transitioned to a mixed mode of abrasive wear and oxidative wear. Moreover, the cryogenic treatment enhanced the stability of the coating-substrate adhesion.