Effect of WC particle size on the microstructure and tribological properties of high-speed laser cladding Ni/WC composite coatings

Ni/WC composite coatings with WC particle sizes of 30-65, 65-100, and 100-145 mu m were prepared on 304 steel using high-speed laser -cladding (HSLC). The phase composition, microstructure, and wear mechanism of the composite coatings were studied. The dendrite -growth mechanism around WC with different particle sizes and the effects of WC with different particle sizes on the microhardness and tribological properties of the composite coatings were analyzed. The results demonstrated that the composite coating consisted of intermetallic compound Ni3Fe and secondary carbides W2C and (Cr, Fe)7C3. The composite coating exhibited good macroscopic morphology and uniform microstructure. The WC particle size obviously influenced the columnar and cellular dendrites in the coating. The microhardness values of the three groups of composite coatings were 419.35, 314.64, and 331.65 HV. The average friction coefficients were 0.4876, 0.5693, and 0.5439. The wear volumes were 0.001, 0.0015, and 0.002 mm3. The wear mechanisms included adhesive, abrasive, and oxidation wear mechanisms. The results verified that the WC coating with a small particle size possessed the best microhardness and tribological properties.