2017 年 68 巻 12 号 p. 718-722
Because of its excellent hardness and tribology properties, diamond films have been applied not only to molds for plastic working but also to cutting tools. Nevertheless, for the application of diamond film to the die for plastic working, difficulties remain such as peeling off of the film and breakdown of the die because of repeated deformation under heavy loads. Accordingly, the evaluation of diamond film fatigue properties is necessary to assure diamond-coated mold quality.
This study assessed the pre-treatment conditions of the surface of tungsten carbide substrate to improve bonding force of the diamond film and examined fatigue properties of a diamond film coated substrate. We evaluated the properties of diamond film coated substrate using a custom-made four-point bending tester and a plane bending fatigue tester. The experimentally obtained results demonstrated that a substrate with boron-doped diamond film has(1)bending strength higher than that of a substrate with no diamond film,(2)greatly improved fatigue strength, and(3)a diamond film fatigue limit equal to or greater than that of a WC-Co alloy substrate.