Abstract: Diamond films were deposited on the cemented carbide WC-15%Co substrates by a hot-filament chemical vapor deposition reactor. The substrate surfaces were chemically pretreated by the following two-step etching method: first using Murakami reagent for 1-3min, and second an HNO3:HCl=1:1 solution for 10-40min. It is indicated that the Co content of the substrate surfaces could be reduced from 15% to 0.81-6.04% within the etching depth of 5-10μm, the surface roughness of the substrates was increased up to Ra=1.0μm, and the substrates hardness was decreased from 89.0 HRA to 83.0HRA after the two-step etching. It is observed that the morphologies of the diamond films on the WC-15%Co substrates emerge in various shapes. The indentation testing shows that the good adhesion between diamond film and the substrate after HF CVD deposition could be obtained.

Key words: chemical pretreatment, cemented carbide, diamond coating