Effect of laser irradiation on high-velocity oxy-fuel Cr3C2-Ni-Cr coating micro structure

In the thermal spraying technique, the process includes some problems such as insufficient cohesive strength between particles in the coating. It is considered that the laser treatment of thermal spray coating will be effective method to improve the coating properties. In this study, an yttrium aluminum garnet (YAG) laser treatment was carried out on the sprayed coating in order to examine the effect of laser beam on the coating properties. The Cr3C2-Ni-Cr powder was used as the spray material, and stainless steel (SUS304) was used as the substrate. Irradiation laser power conditions were 1.5 kW, 2.0 kW and 2.5 kW, and defocus distance conditions were +/-0 mm, +30 mm, +60 mm, + 90 mm, changing the energy density and the traverse speed conditions were 100 mm/s, 200 mm/s, 300 mm/s. The cross section of coating structure was observed by optical microscopy and was analyzed by EPMA and XRD. The hardness of the coatings was measured by micro vickers hardness tester. The coating structure varied from the laser irradiation condition. In the conditions of defocus distance 0 mm, traverses speed 100 mm/s, the sprayed coatings were melted. The coating structure was different even in the identical processing condition by the place. The micro vickers hardness of melted area of coatings was lower and heat affected area of coatings was higher than no laser treatment coating.