Influence of laser heating on adhesion of CVD coatings to cutting edges

Laser heating with different power densities was applied for the CVD coatings: TiC, TiC + TiN, TiC + Al2O3 + TiN in order to improve the adhesion force to sintered carbide substrate. The adhesion has been defined by critical load Lc in the scratch test at which coating has been removed from the substrate. Scanning electron microscopy, 3D profilographometry and X-ray mapping were used to verify the coating state after laser heating and the scratch test. The results indicate that essential increase of Lc can be achieved up to laser beam power of 4140 W/cm2 especially for single and double coatings. The higher beam power leads to cracking of substrate. Alumina layer in the coating is not recommended for rapid laser heating due to its low heat impact resistance. Despite an increase of roughness observed after laser heating such treatment of coatings should promote their better wear-resistance during machining.