Laser glazing of FeCr-TiC-composite coatings

FeCr-TiC powder, manufactured with a self-propagating high temperature synt hesis, was deposited using atmospheric plasma spraying onto mild steel subs trates. The sprayed composite coatings were very porous and a treatment wit h a high power CO, 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 foun d to melt the steel matrix of the composite without melting the TIC reinfor cement. The temperature of coatings surface at these parameters was determi ned with a CCD camera to be about 2000 degrees 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 po res near the coatings' surface. This investigations also revealed a formati on of dendrites on laser treatment. X-ray diffraction studies enabled us to confirm that the TiC phase was present in the composite coatings before an d after laser glazing. Finally, oscillating wear resistance tests showed th at the laser glazing improves the performances of the composites. (C) 2000 Elsevier Science S.A. All rights reserved.