SPUTTER-COATING OF WEAR-RESISTIVE ALUMINA FILMS ON CEMENTED CARBIDE TOOLS

Wear-resistant alumina films were coated on cemented carbide tools and the following results were obtained from a cutting test using S 45 C as a work material. 1) The optimum film thickness obtained in this experiment is 5-8 mu m. Films thinner than this range are rapidly worn by friction, while those thicker are stripped off by the stress caused by the friction of chips and the deformation of the tools resulting from the cutting. 2) The wear resistance of the films is increased with elevation of the substrate temperature during the initial stage of sputtering up to 500 degree C and is assumed to be further increased above 500 degree C. 3) The wear resistance of the films depends on the apparent angle of incidence of the sputtered molecules: the highest resistance is obtained from an arrangement where the substrate surface is directly opposite the target surface. 4) The tools manufactured have wear resistances comparable to available CVD coated tools.