Microstructures and properties of Ni based composite coatings prepared by plasma spray welding with mixed powders

The Ni based composite coatings have been obtained by using the plasma spray welding process and mixed powders (NiCrBSi + NiCr-Cr3C2 + WC). Their microstructures and properties were studied. The results showed that the coatings consist mainly of γ-Ni, WC, Cr23C6, Cr7C3, Ni3Si, Cr5B3, CrB and FeNi3 phases, and the Ni3Si, Cr5B3, CrB and FeNi3 phases mainly segregated between the carbide grains. The carbide contents in the coatings increased with increasing the mass fractions of NiCr-Cr3C2 and WC powders in the mixed powders, which results in enhancing the coating hardness. The abrasive wear resistance of the coatings depends on their hardness. The higher the coating hardness, the stronger the wear resistance is. When the mixed powder (15wt%WC + 30 wt% NiCr-Cr3C2 + 55wt%NiCrBSi) was used, the composite coating has higher hardness and more excellent wear resistance, and the coating hardness and weight loss after wear tests are 991 HV and 8.6 mg, respectively.