Abstract:Amorphous SiO₂ (a-SiO₂) films were synthesized on WC-Co substrates with H₂ and tetraethoxysilane (TEOS) via pyrolysis of molecular precursor. X-ray diffraction (XRD) pattern shows that silicon-cobalt compounds form at the interface between a-SiO₂ films and WC-Co substrates. Moreover, it is observed by transmission electron microscope (TEM) that the a-SiO₂ films are composed of hollow mirco-spheroid a-SiO₂ particles. Subsequently，the a-SiO₂ films are used as intermediate films and chemical vapor deposition (CVD) diamond films are deposited on them. Indentation tests were performed to evaluate the adhesion of bi-layer (a-SiO₂ + diamond) films on cemented carbide substrates. And the cutting performance of bi-layer (a-SiO₂ + diamond) coated inserts was evaluated by machining the glass fiber reinforced plastic (GFRP). The results show that a-SiO₂ interlayers can greatly improve the adhesive strength of diamond films on cemented carbide inserts; furthermore, thickness of the a-SiO₂ interlayers plays a significant role in their effectiveness on adhesion enhancement of diamond films.

Key words: hot filament chemical vapor deposition (HFCVD); diamond film; WC-Co substrate; interlayer; adhesion