Microstructure and fractural morphology of cobalt-based alloy laser cladding

Abstract

The solidification features, micro-segregation, and fracture characteristics of cobalt-based alloy on the substrate of 20 CrMo steel by laser cladding were studied by using electron microscopy. Experimental results show that the fine columnar grains and cellular dendrite grains are obtained which are perpendicular to the coating/substrate interface; the primary arms are straight while the side branches are degenerated; the microstructure consists of primary face-centered cubic (fcc) Co dendrites and a network of Cr-enriched eutectic M23 C6 (M=Cr, W, Fe) carbides; the micro-segregation is severe for the rapid heating and cooling of laser cladding; the typical brittle intergranular fracture occurs in cobalt-based laser cladding layer.