The Synthesized Processing Study Of Diamond Films Deposition On The WC-Co Tools Substrate By DC Arc Discharge Plasma CVD

The investigation has been carried out to study the effectiveness of various processing parameters such as the gas source, reaction pressure and substrate temperature on the diamond films deposited on the 6wt.%Co-cemented tungsten carbide substrate by DC arc discharge plasma chemical vapor deposition (CVD). The surface morphologies, crystal characterizes and adherence strength of diamond film coating deposited were investigated by means of Scanning Electron Microscope (SEM) and Rockwell hardness tester respectively.After the study has got a optimal processing parameters, an investigation has been carried out to study the effectiveness of various parameters such as the current type and etching time of two-step pretreatments method of electrochemistry which use first electrochemical erosion for 5-20min, and afterwards an aqua regia (HNO3+3HCL) solution for 240s on the structure and performance of WC-6%wt-Co tools polished substrates. The surface morphology, composition, roughness and strengthen of the substrates pretreated and diamond films deposited were investigated by means of Scanning Electron Microscope (SEM), Energy dispersive X-ray diffraction analysis (EDXA), perthometer (perthometer M3P) and Rockwell hardness tester respectively, as well as Co content of aqua regia solution were characterized by Atom Absorption Spectrometry (AAS). By analyzing the results, conclusion were drawn as following:(1)With increasing methane concentration, the diamond film morphologies shift from {111} facets→{100}facets→{111}＋{100} facets toward microcrystalline aggregates(cauliflower types). Whiles the surface roughness and holes of diamond films deposited was linerar decreased. (2)The morphologies of diamond crystal deposited by DC arc discharge plasma CVD is perdomiantly cubic-octahedron, then is octahedron and less is cubic. With increasing methane concentration, the crystals size is change from microcrystalline to naocrystalline.(3)With increasing argon gas flow, concentration of atom hydrogen and carbon-hydrogen particles was increased, and the varing rule of diamond film morphologies is smailiar to the methane' s.(4)The parameters of physics such as reaction pressures and substrates cooling water flow have evident effect on the nucleation and growth of diamond film, the best physics parameters of diamond on cemented carbide by DC arc discharge plasma chemical vapor deposition is showed as reaction pressure 30Kpa, substrate cooling water flow 80ml/s.(5)The "hard film" of substrates polished surface can be effectively removed by the electrochemical pretreatments of direct current (DC) and alternating current (AC). However, the erosion efficiency of AC electrochemical pretreatments with substrates polished is very low, and nucleation density of the diamond films is very poor on the substrates. In contrast, the DC electrochemical erosion gives good results. Etching with two-step pretreatment method of DC electrochemistry not only reduces Co content substantially but also increases the surface roughness of the substrate. The Co content of aqua regia solution is increase up to 9.37(μg/ml*cm*cm), the surface roughness Ra of substrate is increased from 0.12(untreated) to 0.56μm, Rz from 0.79 to 4.22μm. The indentation testing shows that the adhesion between diamond coatings and the substrate pretreated by DC electrochemical etching is good.(6) Based on above study, we conculde the best processing parameters of diamond films deposition on cemented carbide by DC arc discharge plasma chemical vapor deposition shown as following: CH₄/H₂ is 0.9%, argon flow is 600ml/min; reaction pressure is 30Kpa, substrate cooling water flow is 80ml/s. The best pretreatment parameters of two-step pretreatments method of electrochemistry on the WC-6%wt-Co tools polished substrates is which use first DC 1.0A electrochemical erosion for 5min, and afterwards an aqua regia(HNO3＋3HCL) solution for 240s.