Drilling of sintered Tungsten-Carbide (WC) with diamond coated tools

Cemented carbides obtained by powder metallurgy are one of the most hard-to-machine materials. Post-processes, like EDM (Electrical Discharge Machining) or grinding, are typically required to compensate the limited accuracy and finish quality of the components. Recently, a new emerging technology, consisting in CVD (Chemical Vapor Deposition) diamond coated tools, allows direct carbides machining improving the capacity of traditional methods. This paper investigates the direct drilling of high-aspect ratio holes (1.6 mm x 8 mm) in cemented Cobalt-Tungsten-Carbides (WC) with a hardness of 1550 HV. Cutting tests were executed on an ultra-high-precision machining center and process variables like cutting forces, tool wear and part quality were analyzed. Ductile machining was found to be the main cutting mechanism and tools were capable to produce highly accurate holes, with large enhanced productivity and tool-life span. However, highly variable tool life was showed among the tested tool units and a systematic tool wear mechanisms was found. This opens the possibility to implement tool monitoring algorithms furtherly enhancing the industrial applicability of this cutting solution.