Crystal orientation control of HFCVD diamond spherical film tools and tribological behavior on steel

(111)-oriented micron-crystalline diamond (111MCD), (110)-oriented micron-crystalline diamond (110MCD) and (110)-oriented nano-crystalline diamond (110NCD) spherical films were prepared on the surface of spherical WC -Co polishing tools by hot filament chemical vapor deposition technology. The microstructure, molecular structure, crystal orientation and surface roughness of spherical films were characterized by SEM, XRD, EBSD and White-light interferometer. The friction performance and material removal mechanisms were studied by friction experiments on steel. The results showed that both crystal orientation and grain size variation significantly influenced the tool properties. The roughness and friction coefficient of 111MCD, 110MCD, and 110NCD films decreased successively. During the friction process, the transformation of diamond to graphite reduced the friction coefficient but accelerated film delamination. 111MCD has the fastest material removal rate, but the graphitization rate and wear rate of the film are the highest, and there are a lot of abrasive chips in the friction interface. Diamond of (110) orientation can improve the wear resistance of the film and reduce the abrasive wear of the workpiece. Compared to 111MCD, 110NCD exhibited a 29.3 % reduction in friction coefficient, a 90 % improvement in wear resistance, a 49.4 % increase in surface smoothness of the processed workpiece, and the highest ID/IG value of 1.45 after film wear, demonstrating superior polishing performance and anti-graphitization properties. These results indicate that 110NCD tool is a highly efficient polishing tool with great potential.