Influence of micro-blasting on the microstructure and residual stresses of CVD κ-Al2O3 coatings

Cemented carbides coated with CVD multilayers are commonly used in metal cutting turning and milling operations. For many applications, a micro-blasting finishing procedure based on an impact treatment of the surfaces is carried out in order to smooth the coated surface and reduce sharp cutting edges. In this work, micro-blasting with corundum in aqueous solution at pressures between 0.05 and 0.3 MPa was applied to CVD TiN/Ti(C,N)/κ-Al2O3 multilayer coatings deposited onto cemented carbides in order to investigate its influence on the micro-topography, microstructure and residual stresses. The results showed that the micro-blasting reduces the surface roughness and affects the coating thickness. TEM investigations revealed no significant changes on the microstructure of the κ-Al2O3 top layer. Synchrotron X-ray investigations showed that the residual stress state of the as-deposited κ-Al2O3 top layer is not affected by the micro-blasting treatment under the conditions investigated.