Fabrication and application of nanocrystalline diamond films

Abstract

Nanocrystalline diamond films are deposited on Co-cemented carbide substrates using bias-enhanced hot fila- ment chemical vapor deposition(HFCVD) technique by appro- priately controlling deposition parameters and Ar addition.The evidence of nanocrystallinity,smoothness and purity is ob- tained by characterizing the sample with scanning electron microscopy(SEM),X-ray diffraction(XRD),Raman spectros- copy,atomic force microscopy (AFM),high-resolution trans- mission electron microscopy (HR-TEM) and selected-area electron diffraction (SAED).The results show that nanocrystal- line diamond films consist of nanocrystalline diamond grains with sizes range from 20 to 80 nm and contain a large amount of grain boundaries.Surface roughness is measured at R_a＜50 nm. Smooth diamond films are liable to polishing.A new process was used to deposit composite diamond coatings by a two-step chemical vapor deposition procedure including first the deposi- tion of the rough polycrystalline diamond and then the smooth fine-grained nanocrystalline diamond coating.The dia- mond-coated drawing dies with these composite coatings dis- play excellent performances in the practical application.