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.
Reliable and highly accurate Cu/glass structures are indispensable for the development of electronic device packaging technology. Nevertheless, adhesion between Cu and glass is well known to be poor. Atomic level interfacial bonding can be achieved using the interfacial reaction. This report describes the fabrication process of a high adhesion Cu/glass structure in which metal is doped onto the glass surface and a noble metal catalyst is applied to form a mixed layer before Cu deposition at room temperature. Different glasses were used as substrates, with ZnO as a metal doping source. Considerable adhesion improvement was confirmed for all test pieces, although the lack of alkaline components led to lowered adhesion strength. Metal oxides other than ZnO（In2O3, CuO, Fe2O3, and NiO）were used as dope sources for borosicilate glass substrates, all of which improved adhesion effectively.
Diamond coating on cemented tungsten carbide（WC-Co）is quite difficult. Generally, to reduce the reactivity of cobalt（Co）, which is the binder of WC-Co, an acid pretreatment is applied. Recent reports have described that the adhesion of nanostructured diamond coating was improved using diborane（B2H6）to reduce the reactivity of Co as a catalyst. To obtain boron-doped diamond（BDD）, B2H6 and trimethyl boron（B（CH3）3）are often used as boron sources. However, special apparatus must be prepared because of the toxicity, flammability, and explosiveness of these sources.
This study was conducted to deposit BDD directly on WC-Co using microwave chemical vapor deposition with trimethyl borate（B（OCH3）3）as a boron source. B（OCH3）3, a mixture of boric acid（H3BO3）and methanol（CH3OH）, was introduced into the vacuum chamber with hydrogen（H2）carrier gas. The WC-Co substrate was scratched with diamond powders and was cleaned with ultrasonic cleaner before loading into the chamber. Boride was formed on the substrate to reduce the reactivity of Co. BDD was formed continuously using reactive gases of methane（CH4）and H2, after forming borides. The presence of BDD was evaluated using SEM, Raman spectroscopy, and XPS. Evaluation using Rockwell hardness testing confirmed that the adhesion strength was secured through adhesion. Results suggest that the use of boride is important to secure adhesion strength and deposition of BDD, which can be done continuously with good adhesion and without Co removal as a pretreatment.