Study on the WC structural evolution and wear behavior of the cemented carbide coatings by laser directed energy deposition

Abstract

At present, laser directed energy deposition (LDED) of cemented carbide faces critical problems, such as WC melting, porosity, and cracks, which severely affect the mechanical properties of cemented carbide. In this study, WC-NiFeCr cemented carbide coatings were prepared using the LDED technique at various laser powers (1800 W, 2100 W, 2400 W, and 2700 W) to investigate the evolution of the WC particles, crack formation, and wear behavior. The results show that the WC particles gradually melted (unmelted WC → slightly melted WC → completely melted WC) through two erosive effects: edge melting and internal infiltration of the nickel-based solvent. Microcracks initiate in the edge melting and internal infiltration regions of the WC particles, whereas fine eutectic carbides help prevent crack extension. When the laser power increased from 1800 W to 2400 W, the microhardness and wear resistance of the cemented carbide coating gradually increased. The maximum microhardness of the coating is 1457.19 HV_0.5, and the minimum wear-profile area is 2801.48 μm². When the power is further increased to 2700 W, owing to the increase in internal pore defects, the microhardness and wear resistance decrease slightly. The main wear mechanisms are three-body abrasive wear and brittle spalling, as well as a small amount of adhesive wear. The results provide a new method for optimizing the wear resistance of cemented carbide coatings by changing the process parameters to regulate the evolution of the WC structure.