An investigation into low-temperature HFCVD and derivative techniques for the enhancement of diamond-coated cemented carbide tool performance

The performance of diamond -coated cemented carbide tools manufactured via the conventional hot filament chemical vapor deposition (HFCVD) technique exhibits certain limitations, including issues with poor toughness and reduced adhesive strength of film-substrate systems, primarily attributed to the cobalt diffusion at elevated temperatures (> 800 C). In this study, a pioneering exploration of a low-temperature diamond film deposition technique on cemented carbide is developed, and a comprehensive evaluation of the film properties is conducted. The results indicate that owing to constraints related to growth rate and diamond film purity, it may not serve as an effective approach for enhancing the performance of conventional coated tools. Nonetheless, the inherent capability of this technique in inhibiting cobalt diffusion is strategically harnessed to pioneer the development of a derivative technique referred to as the "low-temperature to high-temperature HFCVD (LT-HT-HFCVD)". This innovative method leverages a low-temperature deposited diamond layer as an intermediate layer to impede cobalt diffusion while serving as a densely nucleated layer for subsequent diamond growth. Subsequently, the conventional technique is employed to facilitate an effective growth rate and maintain high growth purity. The diamond -coated tools generated by this technique are subject to a comprehensive comparative analysis against those generated by low-temperature HFCVD (LT-HFCVD) and conventional HFCVD (CT-HFCVD) techniques. The results reveal that tools fabricated using the LT-HT-HFCVD combine the advantages inherent to both the LTHFCVD and CT-HFCVD techniques, thereby manifesting superior toughness, enhanced film-substrate adhesive strength, and outstanding cutting performance.