Effects of nano-TiC and B on microstructure and tribological properties of laser cladding FeCoCrNiCu composite coatings

To investigate the effects of adding nano-TiC and B elements on the FeCoCrNiCu high-entropy alloy coating, laser cladding technique was employed to prepare FeCoCrNiCuB_x and FeCoCrNiCu-x wt%TiC high-entropy alloy coatings on Q235 substrate. The best-performing coatings, FeCoCrNiCuB_0.5 and FeCoCrNiCu-15wt%TiC, were selected for discussion and analysis. The results show that the addition of nano-TiC and B both lead to grain refinement and improve metallurgical bonding properties of the coatings. The microhardness values of the FeCoCrNiCu (HEA), FeCoCrNiCuB_0.5 (B5), and FeCoCrNiCu-15wt%TiC (T15) coatings are 217.95, 343.98 and 531.65 HV_0.5, respectively. The T15 coating exhibits a low friction coefficient of only 0.549 at room temperature, with a smoother surface and wear mechanism mainly attributed to abrasive wear. At 600℃, the friction coefficient of the T15 coating is 0.279, with a wear rate of 15.28×10⁻⁵ mm³/N·m, and the wear mechanisms include abrasive wear, fatigue wear, and oxidation wear. The B5 coating exhibits the lowest friction coefficient of 0.425 at room temperature, primarily due to abrasive wear and fatigue wear. At 600℃, the friction coefficient of B5 coating is 0.255, the wear rate is 6.96×10⁻⁵ mm³/N·m, and the wear mechanism is mainly abrasive wear. The B₂O₃ self-lubricating phase is formed on the surface of the B5 coating, which melts at high temperature to form a low viscosity liquid, forming a lubricating film, isolating the contact surface, reducing direct contact and adhesion, which is the main reason for significantly improving its tribological properties.