Microstructural characterization and microscopy analysis of laser cladding Stellite12 and tungsten carbide

Stellite12 cobalt base alloys with different WC content were deposited on SK3-carbon tool steel by laser cladding. The behavior of WC particulates, including the dissolution, distribution, and microstructures of WC–Co–Cr–C composite coatings with rapidly solidifying were investigated using scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Several significantly different solidified microstructures were characterized by dendrites, interdendritic eutectics, faceted dendrites (third phase) and the retaining of WC particles in the laser clads of Stellite12 + WC, under different laser energy densities. When WC was completely melted and fully dissolved into the Stellite12 melt pool, the basic solidification, characterized by the matrix and faceted dendrites (third phase) in various shapes, and the compositional evolution of the clad layers remained nearly identical, no matter the added WC was increased to 10%, 20% or 40% (wt.%). The faceted dendrites (third phase) contained the majority of W as well as some Cr, Co while more Cr and Co were located in the matrix. The X-ray diffraction analyses indicated the existence of σ-Co, M23C6, M6C and M7C3 (M = W, Cr, Co) in the Stellite12 alloys with different WC contents when deposited on substrates by laser cladding.