Friction and Wear Behavior of In-Situ Synthesized M₂₃C₆-WC Dual-Carbides Synergistically Reinforced Laser Cladding Coatings

Abstract: M₂₃C₆-WC (M: Cr, W, Fe) dual-carbide reinforced Fe-based coating was fabricated on the surface of a 16Mn steel by laser cladding W-Fe60-C alloy powders under the optimized parameters of laser power 1.5 kW, scanning velocity 4 mm/s and powder feeding rate 10 g/min, and microstructure and phase composition of coating were further characterized. Thermodynamic calculation was also performed with Thermo-Calc software on the basis of a commercially available Fe-based Alloys' database to explore the solidification process of the coating. In addition, a comparative study on the microhardness and wear behavior of pure Fe60 alloy coating, WC reinforced Fe-based coating and M₂₃C₆-WC dual-carbide reinforced Fe-based coating was conducted. Experimental results showed that M₂₃C₆-WC dual-carbide reinforced Fe-based coating was mainly composed of dendritic matrix α-Fe, reinforcing phases W, WC and M₂₃C₆. M₂₃C₆ carbide was distributed in the inter-dendritic region with a continuous network structure, and block-shaped WC particles grew with the residual W as a nucleation core and distributed in the coating. Combined to the microstructure and thermodynamic calculation results, the solidification process in the M₂₃C₆-WC dual-carbides reinforced Fe-based coating during laser cladding process was liquid+W→liquid+W+WC→liquid+W+WC+γ-(Fe, Ni) dendrite→WC+W+γ-(Fe, Ni) dendrite+M₂₃C₆→WC+W+α-Fe dendrite+M₂₃C₆. The average microhardness of M₂₃C₆-WC dual-carbide reinforced Fe-based coating was about 835.3 HV_0.5, which was 230 HV_0.5 and 180 HV_0.5 higher than that of pure Fe60 alloy coating (604.6 HV_0.5) and WC-reinforced Fe-based coating (658.9 HV_0.5), respectively. Furthermore, the wear rate of M₂₃C₆-WC dual-carbide reinforced Fe-based coating was about 3.44×10⁻⁶mm³/mN, which was about 24.7 and 2.3 times lower than that of pure Fe60 alloy cladding 8.51×10⁻⁵ mm³/(N·m) and WC reinforced Fe-based coating 7.98×10⁻⁶ mm³/(N·m), respectively.