Laser modification of the microstructure and mechanical properties of (Cr3C2-25(Ni20Cr))-5(Ni25C) cermet coatings containing a solid lubricant

Abstract

This paper presents a study on the effect of laser surface treatment on the microstructure and mechanical characteristics of cold sprayed Cr3C2-25(Ni20Cr)-(Ni-graphite) cermet coatings. The as-sprayed deposits retained the initial powder phase composition. The Cr3C2 particles were homogeneously distributed within the deformed nickel-chromium matrix phase. Moreover, the carbide particles were heavily fragmented due to a high-velocity impact on the substrate or particles already embedded. The solid lubricant (graphite) was mostly distributed between crushed Cr3C2 particles or deformed nickel-chromium matrix. The surface of the as-deposited coatings was laser-treated using a CO2 laser. With the higher applied power of the laser beam, the changes in the coating microstructure and surface topography were more significant. The refinement of the deposit structure and formation of new phases such as Cr7C3 and Cr2O3 were observed. All coatings, both those cold sprayed and those laser-treated, revealed compressive residual stresses, which increased with higher laser power. The post-deposition laser modification of the coating surfaces improved their mechanical properties by almost half.