Three sets of Co-cemented tungsten carbide (94 wt. percent WC-6wt. percent Co) blades with different average grain size (0.5, 1.5 and 3 um) were used as substrates. After usual acid etching and scratching with diamond powders, H2 gas etching decarburization by microwave plasma and cleaning in an ultrasonic bath of acetone solution, substrates with different WC grain size were placed in the electron aided hot filament chemical vapor deposition (EACVD) reactor to fabricate diamond thin films. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, indention tests and surface scanning profilometer showed that substrate grain size plays an important role in determining the performance of diamond films deposited on the tungsten carbide substrates such as film adhesive strength, film surface roughness and diamond film quality. The related conclusions were beneficial to the optimization of CVD diamond process and also to the metallurgical process of tungsten carbide.
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