WC-6%Co cutting tool inserts were coated with diamond films using a double bias-assisted hot-filament chemical vapor deposition method. Coating of the cutting tools with chemical vapor deposition diamond is taken as a three-step process in which the growth of diamond follows the pretreatment and nucleation of the substrate. The presented operating parameters allow to substantially suppress the presence of amorphous carbon and/or graphite phases in the diamond films deposited on WC/Co tools. The substrate temperature of similar to700 degreesC, and a low methane concentration result in a sharp diamond Raman peak centered at 1333-34 cm(-1) with FWHM of 6-7 cm(-1) as detected by micro-Raman spectroscopy. The diamond morphology is characterized by scanning electron microscopy, optical microscopy, and micro-Raman spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.