Effect of boron and silicon doping on improving the cutting performance of CVD diamond coated cutting tools in machining CFRP

•B-doped diamond coated WC–Co drills are fabricated using trimethyl borate.•Si-doped diamond coated WC–Co drills are fabricated using tetraethyl orthosilicate.•Cutting performance of doped diamond coated drills is presented in drilling CFRP.

The boron-doped (B-doped) and silicon-doped (Si-doped) diamond films are deposited on Co-cemented tungsten carbide (WC–Co) drills by the hot filament chemical vapor deposition (HFCVD) method, adopting trimethyl borate (C3H9O3B) and tetraethyl orthosilicate (C8H20O4Si) as the dopant sources, respectively. The characterization of as-deposited diamond films are investigated by scanning electron microscopy (SEM) and Raman spectroscopy. The adhesive strength between the diamond films and the WC–Co substrates is assessed by Rockwell indention tests. The drilling tests for evaluating the performance of the diamond coated drills are conducted with carbon fiber reinforced plastics (CFRP) as the workpiece. For the sake of comparison, conventional diamond coated and bare WC–Co drills are also used in the drilling tests. The wear performance of the tools is compared and discussed in terms of the diamond coating microstructure. According to the results, the diamond coated drills exhibit a better wear resistant with respect to the uncoated one. Besides, the Si-doped diamond coated drill displays the best cutting performance for the smooth surface and favorable adhesive strength.