Chemical pretreatments at surface of WC-6% Co for diamond coatings

The WC 6%Co(mass fraction) substrate surfaces were chemically pretreated with the two step etching method, using Murakami reagent for 3～ 7?min, and then an φ (HNO 3)∶ φ (HCl)=4∶1 solution for 1～ 15?min. Diamond films were deposited on the substrates by a hot filament chemical vapor deposition reactor. The results show that the Co content of the substrate surfaces can be reduced from 6% to 0.12% within the etching depth of 5～ 10?μm, the surface roughness of the substrates is increased up to R a= 1.0?μm, as well as the substrates hardness is decreased from HRA 89.5 to HRA 84.2 after the two step etching. A slight preference towards {111} orientation can be observed from the XRD patterns and SEM micrograph of diamond film on WC 6%Co sample. The morphology of small rice like ballas diamond was observed on the WC 6%Co substrates. A typical Raman spectrum with a sharp peak at 1?332?cm -1 for the diamond film indicates that the deposited films are good quality polycrystalline diamond. The indentation testing shows that the adhesion between diamond film and the substrate after HF CVD deposition is good.