Microstructure evolution and wear resistance enhancement of nano-NiCoC alloy coatings via cryogenic treatment

• Published in: Surface & coatings technology 2024-10, Vol.493, p.131294, Article 131294
• Main Authors: Du, Yizhe, Yuan, Xinyi, Hu, Hao, Tian, Pengyu, Long, Mujun, Chen, Dengfu
• Format: Article
• Language: English
• Subjects: Cryogenic treatment; Hardness; Microstructure evolution; Ni–Co–C alloy coatings; Strengthening mechanism; Wear resistance
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2024.131294

High-performance coatings are crucial for improving the overall lifetime of molds. In this study, multi-scale microstructure evolution in nano Ni–Co–C alloy coatings was induced through cryogenic treatment, and various strengthening mechanisms were employed to enhance their comprehensive properties, particularly wear resistance. Specifically, it was observed that lattice contraction occurred in the coatings due to stress during cryogenic treatment, accompanied by strain and dislocation accumulation. As the cryogenic treatment duration increased, the texture of the coatings exhibited a random distribution, and the emergence and subsequent increase of copper texture were identified as crucial for enhancing coating performance. Additionally, TEM results revealed a typical nano-polycrystalline structure in the coatings, with grain sizes becoming more refined and uniformly distributed after cryogenic treatment. Simultaneously, a significant increase in stacking faults was noted, which facilitated the formation of complex dislocation structures and hindered dislocation mobility. Moreover, cryogenic treatment was found to enhance coating hardness and improve fracture toughness, primarily due to dislocation strengthening and secondarily to grain refinement. Furthermore, the wear rate of the coatings was significantly reduced, and the dominant wear mechanism shifted from oxidation wear to abrasive wear with prolonged cryogenic treatment duration. •Cryogenic treatment significantly improved the wear resistance of nano-Ni–Co–C coatings.•Multi-scale microstructural evolution of coatings induced by cryogenic treatment•A high density of stacking faults was generated inside the coatings.•Excessive cryogenic treatment caused the coatings to transition from toughness to brittleness.•High-density dislocations make the most significant contribution to improving coating performance.