EFFECT OF POLISHING ON THE FRICTION BEHAVIORS AND CUTTING PERFORMANCE OF BORON-DOPED DIAMOND FILMS ON WC-CoINSERTS

Boron doped (B-doped) diamond films are deposited onto WC-Coinserts by HFCVD with the mixture of acetone, trimethyl borate (C3H9BO3) andH2. The as-depositedB-doped diamond films are characterized with scanning electron microscope (SEM), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, 3D surface topography based on white-light interferometry and Rockwell hardness tester. The effects of mechanical polishing on the friction behavior and cutting performance ofB-doped diamond are evaluated by ball-on-plate type reciprocating tribometer and turning of aluminum alloy 7075 materials, respectively. For comparison, the same tests are also conducted for the bare WC-Coinserts with smooth surface. Friction tests suggest that the unpolished and polishedB-doped diamond films possess relatively low fluctuation of friction coefficient than as-received bare WC-Cosamples. The average stable friction coefficient forB-doped diamond films decreases apparently after mechanical polishing. The values for WC-Cosample, unpolished and polishedB-doped diamond films are approximately 0.38, 0.25 and 0.11, respectively. The cutting results demonstrate that the low friction coefficient and high adhesive strength ofB-doped diamond films play an essential role in the cutting performance enhancement of the WC-Coinserts. However, the mechanical polishing process may lower the adhesive strength ofB-doped diamond films. Consequently, the polishedB-doped diamond coated inserts show premature wear in the machining of adhesive aluminum alloy materials.