Laser glazing of FeCr–TiC composite coatings

Abstract

FeCr–TiC powder, manufactured with a self-propagating high temperature synthesis, was deposited using atmospheric plasma spraying onto mild steel substrates. The sprayed composite coatings were very porous and a treatment with a high power CO 2 laser was applied to improve their wear properties. The laser power density of 8 kW cm −2 and a scan speed of 3 mm s −1 were found to melt the steel matrix of the composite without melting the TiC reinforcement. The temperature of coatings surface at these parameters was determined with a CCD camera to be about 2000°C. The porous nature of the sprayed coatings was evidenced with a scanning electron microscope. Optical microscope investigations of the glazed coatings shown a sealing of the pores near the coatings' surface. This investigations also revealed a formation of dendrites on laser treatment. X-ray diffraction studies enabled us to confirm that the TiC phase was present in the composite coatings before and after laser glazing. Finally, oscillating wear resistance tests showed that the laser glazing improves the performances of the composites.