Microstructure and Friction Properties of WC/Co-Cr Composite Coatings Prepared by Laser Cladding

A WC/Co-Cr coating was fabricated via laser cladding onto W18Cr4V high speed steel and its macroscopic morphology, phase composition, microstructure, microhardness and wear resistance were examined. The findings indicate that when the laser power is 1500 W, the powder feed rate is 20 g/min and the scanning velocity is 1.5 mm/s the laser clad layer is primarily composed of WC and WCo compounds, exhibiting minimal pores and cracks. The resulting microstructure is complex and characterized by a regional gradient distribution, containing WC, W2C, Fe2W2C, Fe3W3C, Co3W3C, Mo2V4C5, (Cr, Fe)(7)C-3, and other complex phases. The hardness and wear resistance of the laser clad layer are significantly superior to those of high speed steel. The maximum hardness is exhibited within 0.3 mm from the surface of the laser clad layer, reaching 1361HV0.2 which is approximately 1.6 times that of the W18Cr4V high speed steel substate and the average wear amount is 70% of the W18Cr4V substate. After subjecting the laser clad layer to heat treatment at 450 degrees C for 1 hour its wear resistance is further improved. The average wear of the laser clad layer is effectively reduced from 57.6 to 28.1 mg, which accounts for only 35% of the wear rate observed in the substrate.