Microstructure and tribological properties of CrB2-enhanced NiCrBSi composite coatings prepared by high-velocity oxygen-fuel under different kerosene flow rates

CrB 2 -enhanced NiCrBSi composite powder and coatings were prepared using a spray granulation method and high-velocity oxygen-fuel (HVOF) spraying, respectively. The enhancement mechanism of CrB 2 on NiCrBSi and the effects of different kerosene flow rates on the phase structure, microstructure, and tribological properties of the coatings were investigated. The results showed that the composite powder was mainly composed of γ-Ni, CrB, CrB 2 , Ni 2 B, and CrSi 2 phases. The content of CrB phase in the composite coatings increased, while Ni 2 B and CrSi 2 phases disappeared or decreased due to dissolution. The hardness and fracture toughness of the composite coatings increased, then decreased with increasing kerosene flow rate, while the wear rate (WR) showed the opposite trend. When the kerosene flow rate was 28 L/h, the coating had the highest hardness and toughness (888.5 HV 0.3 and 3.46 MPa·m 1/2 , respectively). The coating had the lowest WR of 1.04 × 10 −13 m 3 /(N·m), which was 55 % lower than that of the NiCrBSi coating. The excellent wear resistance was attributed to the rigid backbone structure provided by the CrB 2 and CrB phases. The refinement and diffuse distribution of the grains improved the microhardness and fracture toughness of the coating, allowing it to exhibit the best tribological properties. Furthermore, the formation of Cr 2 O 3 and NiCr 2 O 4 during the wear process further improved the wear resistance. • NiCrBSi-CrB 2 powder and coatings were prepared successfully. • The ceramic phase provides a rigid skeletal structure for the composite coating. • The best mechanical and tribological properties of the composite coatings were obtained at a kerosene flow rate of 28 L/h. • The K-28 coating has the lowest wear rate, which is attributed to the grain refinement of the coating.