Diamond as a wear-resistant coating for cutting tools, part 2

Since the discovery of diamond film synthesis by chemical vapour deposition (CVD), many technologically important applications have been developed. In the machining industry, Co-cemented tungsten carbide (WC-Co) tool inserts can benefit from CVD diamond technology insofar as their wear life is concerned. However, premature failure of diamond-coated WC-Co tools caused by thermal and mechanical stresses still remains a challenging difficulty. In this paper, the authors discuss the state-of-the-art of CVD diamond films adhesion, since the most important failure mechanisms of diamond-coated hard metal tools are usually related to film delamination during machining. The main issues related to the development of CVD diamond-coated wear re sistant parts are addressed. The literature analysis shows that substrate surface pretreatments play an important role in determining sufficiently large interface toughness values. Therefore, a survey of advancements in techniques to enhance adhesion of CVD diamond coatings is presented. In addition, the combined effect of substrate pretreatment and microstructure on the cutting performance of CVD diamond-coated WC-Co inserts is discussed on the basis of metal matrix composites (MMCs) machining results.