Effects of Cr₃C₂ Nanoparticle Content on Microstructure and Property of Plasma Surfacing Co40 Alloy Coating

The Co40 alloy coatings with different Cr₃C₂ nanoparticle content (0, 20wt%, 30wt%, 40wt%) were obtained by plasma surfacing on low-carbon steel Q890, and then the effects of the Cr₃C₂ nanoparticle content on the microstructure and wear resistance of the alloy coating were studied. The results show that the Co40 alloy coating was composed of developed columnar crystals and netlike eutectic crystals among them. With the addition of Cr₃C₂ nanoparticle, the microstructure was refined and the solidification characteristic changed from the hypoeutectic crystallization to the hypereutectic crystallization. Moreover, the hardness and wear resistance of the alloy coating were significantly improved. When the Cr₃C₂ nanoparticle addition was 30wt%, the wear mass loss of the alloy coating was the lowest, which decreased by 55.8% comparing to that without Cr₃C₂; the wear surface was relatively smooth with only little slight furrows and almost no peeling phenomenon was observed.