Effect of Mo content on microstructure and wear resistance of Co-based coatings by laser cladding

Co-based alloy coatings with different Mo content(5.4% and 28%) on the surface of low carbon steel were prepared by laser cladding.The microstructure and phases composition of the coatings were investigated by means of optical microscope(OP), scanning electron microscope(SEM) and X-ray diffraction instrument(XRD).Microhardness and sliding wear resistance of the coatings were also tested.The results indicated that the main phases in Co-based alloy coatings with 5.4%Mo were γ-Co and Cr₂₃C₆.Another two phases of Co₃Mo₂Si and NiCoCr were identified in Co-based alloy coatings with 28% Mo.Directional dendrite was observed in Co-based alloy coatings with 5.4% Mo.Unidirectional dendrite at the interface, followed by fine dendrite at the central zone and equiaxed grain near top surface were found in Co-based alloy single coatings with 28% Mo, and almost all fine equiaxed grains appear in the multi-track coatings.The microhardness of Cobased alloy coatings with 28% Mo reaches up to 800 HV, which was 2 times of that of Co-based alloy coatings with 5.4% Mo.The sliding wear resistance was also improved.