Assessment of machining performance using the wear map approach in micro-drilling

It is well established that nickel-based super alloys exhibit poor machinability. One of the challenges in micro-drilling of these alloys is to increase productivity while maintaining acceptable tool wear rates. In this regard, the wear map approach is a useful way to identify an operating window of cutting conditions. The progression of tool wear has been studied in relation to tool edge radius and undeformed chip thickness. A characteristic wear map of cutting conditions is constructed for the micro-drilling process. This helps identify the zones of lowest wear rate, commonly referred to as safe zones, as well as a scale effect in the micro-domain. The new wear rate map provides a quick and useful reference for selecting suitable cutting conditions with the aim of reducing manufacturing costs and/or increasing production rate for micro-drilling. A preliminary tool wear mechanism study suggests that abrasion, adhesion and micro-chipping are the active tool wear modes associated with wet micro-drilling of nickel-based super alloys.