EFFECT OF METHANE CONCENTRATION ON PHYSICAL PROPERTIES OF DIAMOND-COATED CEMENTED CARBIDE TOOL INSERTS OBTAINED BY HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

Diamond-coated tools can greatly improve the productivity of machining highly abrasive materials such as high silicon-aluminium alloys used in the automotive industry. Cemented-carbide diamond-coated tool inser ts have not become an off-the-shelf product owing to several difficult ies including insufficient adhesion of diamond to the substrate and qu estionable reproducibility in their machining performance in the manuf acturing. In order to overcome these difficulties, a better understand ing of the effects of the chemical vapour deposition (CVD) conditions such as methane concentration, reactor pressure and substrate temperat ure is important. In this work, cemented tungsten carbide tool inserts with 6 wt% Co (WC-Co) were coated with diamond films deposited at fiv e different methane concentrations (1-9 vol %). Here we present prelim inary results of the effect of methane concentration variation on the following physical properties of the diamond coating: surface morpholo gy; crystal structure; chemical quality; surface roughness; residual s tress. The results indicate that the best physical properties of diamo nd-coated tool inserts using hot-filament CVD are achieved with diamon d coatings deposited at methane concentrations ranging from 1 to 3%.