Influence of amorphous ceramic interlayers on tribological properties of CVD diamond films

摘要

This work deals with the influence of amorphous ceramic interlayers on the tribological behaviors of CVD diamond films on WC-Co substrates. Two types of amorphous ceramic films (a-SiO_2 and a-SiC) are synthesized as interlayers by pyrolysis of precursors in a hot filament chemical vapor deposition (HFCVD) apparatus. Tetraethoxysilane (C_8H_(20)O_4Si) and dimethyldiethoxysilane (C_6H_(16)O_2Si) are used as source materials respectively. Subsequently CVD diamond top layers are deposited on the amorphous ceramic interlayers. For the sake of comparison, the conventional diamond film with no interlayer is also fabricated. The grain sizes and crystal orientations among as-deposited specimens show little difference, while the diamond top layers on amorphous ceramic interlayers exhibit lower surface roughness than the conventional diamond film with no interlayer. Ball-on-disc experiments are chosen to check the tribological properties of as-fabricated diamond top layers on amorphous ceramic interlayers, which show that the bi-layer (amorphous ceramic + diamond) films obviously present lower friction coefficient than the conventional diamond film with no interlayer. The amorphous ceramic interlayers can act as amorphous binder to fill up the space between the diamond grains and the brittle WC particles, reduce the surface roughness and remarkably improve the tribological behaviors of diamond films. In this study, the a-SiC interlayered diamond film exhibits both the lowest friction coefficient and the lowest surface roughness.