Song Ni, Jianhui Yan, Lixia Ma, Tong Wei, Jiwen Wu, Hongyu Yang
In this study, near-spherical CoCrFeNiMo(B 4 C) x (x = 0, 0.1, 0.2, 0.3, and 0.4) feedstocks and their corresponding coatings were successfully fabricated on Q235 substrate via spray granulation and laser cladding. The precipitation behavior, phase composition, microstructure, mechanical, and tribological properties were systematically investigated. The results indicated that the precipitation behavior was significantly influenced by Marangoni convection, resulting in macroscopic segregation. The BC0 coating (x = 0) consists of FCC, σ, and μ phases, exhibiting an interdendritic eutectic structure. The addition of B 4 C promoted various carbides and borides precipitation, such as Mo 2 FeB 2 , (Mo, Cr)(B, C) 2 , M 2 B, Fe 3 C, MoC, and M 23 (B, C) 6 , effectively refining the grain. The hardness gradually increased with B 4 C content and essentially reached saturation at x = 0.2 (599.1 HV 0.2 ), which was mainly attributed to the transformation of the reinforcing phases caused by the depletion of Mo. Furthermore, no cracks were observed around the indentations in all coatings, demonstrating high resistance to deformation. The BC0.2 coating showed the best tribological properties, manifesting as a low friction coefficient (0.46 ± 0.01) and wear rate (3.50 ± 0.03 × 10 −6 mm 3 ·N −1 ·m −1 ). This was attributed to the support of hard precipitates and the lubrication of the oxide layer, effectively inhibiting spalling and tearing caused by adhesive wear. However, excessive B 4 C caused the localized agglomeration of precipitates, leading to stress concentration and particle detachment, ultimately resulting in severe wear. This work provides valuable insights for developing wear-resistant HEA composite coatings by optimizing the incorporation method and content of ceramic particles.