Papers by Keyword: CVD Diamond Coating

Abstract: Chemical vapor deposition (CVD) diamond coatings were deposited on milling cutter substrate using a hollow substrate holder. The substrate is WC–Co cemented carbide contained 6% of cobalt concentration. Structures and stress state of diamond films were analyzed by scanning electron microscopy (SEM) and Raman spectroscopy. It was found that the diamond coating is of the same quality at the same cutting tool deposited on a hollow substrate holder. Diamond (sp3) bonds are better developed with substrate temperature of ~760°C. A higher or lower substrate temperature could lead to a higher non-diamond carbon content in the films. A higher substrate temperature could lead to a higher thermal stress. The compressive stress increases when the substrate temperature is higher or lower than 760°C. The concentration of amorphous phase in the coatings is low with CH4 concentration of 1.0% and 1.5%. A higher non-diamond carbon content and defects in the diamond coatings increase with the increase of CH4 concentration, which leads to the compressive stress value does not increase significantly under a high CH4 concentration.

Abstract: Chemical vapor deposit (CVD) diamond coating layer is expected to extend the lifetime of mechanical parts that are used severely abrasive conditions. However, one of the most severe problems is that the delamination between the CVD diamond coating layer and the silicon substrate occurs frequently due to large difference in the material properties. Therefore, the nondestructive evaluation of adhesive property of CVD diamond coating layer is needed. To address such a need, back-scattered Rayleigh surface wave is currently applied. However, the interpretation of the acquired signal is not easy at all. To take care of such a difficulty, we proposed the time trace angular scan (TTAS) plot and the frequency spectrum angular scan (FSAS) plot that can make possible of the systematic interpretation of the back-scattered signals from the diamond coating layer. In this paper, the concept of the TTAS and FSAS plots and the experimental results presented to demonstrate the effectiveness of the proposed approach.

Abstract: The propagation characteristics of the back-reflected Rayleigh surface wave in chemical vapor deposit (CVD) diamond coated specimens were investigated experimentally using the ultrasonic backward radiation measurement. The deliberated delaminations produced between the coating layer and the substrate decreased Rayleigh surface wave velocity. This initial experimental result obtained in the present study demonstrates the high potential of the backward radiated ultrasound as a tool for nondestructive evaluation of very thin CVD diamond coating layer.