Microstructure and wear resistance behavior of Ti-C-B4C-reinforced composite coating

Poor wear resistance and microhardness of nickel (Ni)-based alloy pose major concern and challenges in industrial applications. To enhance mechanical properties, composites reinforced with different contents of titanium (Ti), carbon (C), and boron carbide (B4C) particles were prepared on the 45# die steel by laser cladding. Microstructure characteristics and evolution mechanisms were investigated by scanning electron microscopy and X-ray diffraction. Hardness and wear testers were used to measure microhardness distribution and wear resistance of composite coating. Results indicated that in situ synthesized TiC, TiB2, carbides, and borides in the coating significantly refined microstructure, which were uniformly distributed. Diffusion of Ti and C in the matrix contributed to obvious dispersion strengthening, improved bonding strength among ceramic particles through ring phase and multiphase, and increased holding force of matrix, which are responsible for the good wear resistance. Coatings with 9:1:5 and 11.5:1:2.5 mass fraction ratios of Ti/C/B4C exhibited the highest microhardness and the lowest friction coefficient (low speed wear), which are 4.98-5.1 times higher and 4.75 times smaller than those of original Ni204 coating, respectively. All samples show a small value of friction coefficient (< 0.3) under high frequency wear conditions, and the wear resistance is closely related to the bonding strength of matrix and ceramics.