Microstructure and performance of laser cladding Co+Cr₃C_{2 composite coating}

Laser cladding Co-based alloy coating(Co50) and Co-based alloy composite coating(Co+Cr₃C₂) with different Cr₃C₂ addition(20%,40%,60%,mass fraction) on low carbon steel substrates has been obtained.Microstructure and performance of the coatings have been comparatively discussed in the same test conditions.It is shown that the Co50 coating consisted of many dendritic solid solution γ-Co and eutectic structure(γ-Co and Cr₂₃C₆) between the dendrites.The Co+Cr₃C₂ composite coating consisted of un-dissolved Cr₃C₂ particles,bacilliform or nubbly rich-chromium carbides(M₇C₃) and very finer dendrite structure(γ-Co and Cr₂₃C₆) between the carbides.Cr₃C₂ particles remodeled the solidification characteristic of the composite coating,and fined the dendrite structure.With the increase of Cr₃C₂,Cr₃C₂ particles un-dissolved and the rich-chromium carbides were also increased.Surface hardness,wear resistance,high temperature oxidation resistance at 1300℃ and corrosive resistance in 30% vitriol of the composite coatings are obviously better than that of the Co50 coatings.With the increase of Cr₃C₂,oxidation resistance and corrosive resistance were increased,but wear resistance of the Co+40% Cr₃C₂ composite coatings was the best.Laser cladding Co+40% Cr₃C₂ composite coating had the best integrative performance.