Cutting Performances of Nanocrystalline Diamond Coated Milling Tools in Machining Graphite

In this study, diamond films are deposited by using hot filament chemical vapor deposition (HFCVD), Nanocrystalline diamond (NCD) coated cemented tungsten carbide (WC-Co) milling tools are characterized, compared with microcrystalline diamond (MCD) and composite diamond coated ones, in terms of morphology with field emission scanning electron microscope (FESEM). Moreover, the diamond coated tools are evaluated in machining graphite materials. The results show that the NCD and composite diamond coated tools have smoother surfaces than the MCD coated tools because of the smaller grain size. In milling tests, diamond coated tools allow to be give a higher wear resistance and longer tool life, when compared to bare WC-Co milling tools. Coating delamination is noted as the major tool failure mode for MCD and composite diamond coated cutting tools, but the NCD exhibit a better adherent strength to the substrate, and consequently improve the tool life by a factor of 6 than that of uncoated milling tools.