Dissolving Behaviors of WC Particles in the Laser Cladding

摘要

Ni60WC35-based alloy composite coatings were fabricated by multimode CO2 laser apparatus on medium-carbon steel substrate. The microstructure and interface shape of the cladding layer were studied through X-Ray diffraction (XRD), optical-microscope (OM), scanning electronic microscope (SEM) and energy spectrometer (EDS), and the forming mechanism of WC particle was also analyzed. The cross-section microhardness of the cladding layer was measured by Vickers hardness tester. The results show that laser scanning speed greatly influence the microstructure of Ni-based WC composite coating, WC particles have transformed in the Ni matrix during the laser cladding. The main microstructure feature is WC hard phase at the edge have transformed into needle phase,needle phase area can be enlarged through decreasing laser scanning speed, and the area of needle clusters structure expanded gradually. When the molten pool temperature rises to 1250℃,the decomposition of the reaction of WC(2WC→W2C+C) occurs,and the temperature increases continually can accelerate the dissolution of WC particles and elements diffusion.