Adhesion improvement of RF-sputtered alumina coatings as determined by the scratch test

One of the most important problems to overcome in the production of coatings, a major technology in surface modification, is the maximization of coating to substrate adhesion. In spite of its limitations, the scratch technique is most used in adhesion characterization studies. In this study, the adhesion of alumina coatings deposited by RF magnetron sputtering on AISI M2 high speed steel (HSS) was evaluated by the scratch test. An attempt to improve the adhesion of the alumina coatings was investigated by the deposition of an intermediate layer of Ti or TiN. The influence of the substrate surface roughness, the intermediate layer thickness, and the sputter etch cleaning on the coating adhesion was studied.