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

Abstract

Boron doped ( B -doped) diamond films are deposited onto WC- Co inserts by HFCVD with the mixture of acetone, trimethyl borate ( C 3 H 9 BO 3) and H 2. The as-deposited B -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 of B -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- Co inserts with smooth surface. Friction tests suggest that the unpolished and polished B -doped diamond films possess relatively low fluctuation of friction coefficient than as-received bare WC- Co samples. The average stable friction coefficient for B -doped diamond films decreases apparently after mechanical polishing. The values for WC- Co sample, unpolished and polished B -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 of B -doped diamond films play an essential role in the cutting performance enhancement of the WC- Co inserts. However, the mechanical polishing process may lower the adhesive strength of B -doped diamond films. Consequently, the polished B -doped diamond coated inserts show premature wear in the machining of adhesive aluminum alloy materials.