Wear on SiAlON ceramic tools in drilling of aerospace grade CFRP composites

Carbon fiber reinforced polymer (CFRP) composites are difficult to cut materials due to their anisotropic structure and extremely abrasive nature of the carbon fibers. The tool materials used for drilling of CFRP composites are limited; thus there is always a strong demand for new tool materials which can be utilized successfully for the high performance drilling process. In this study, wear behavior of different SiAlON ceramics, which are successfully used for machining of various materials such as gray cast iron, superalloys, etc., on the drilling of CFRP composites was investigated, compared and reported for the first time in the literature. Three different SiAlON-based drilling tools with the same geometry were manufactured and tested on the drilling of aerospace grade CFRP composites and their wear behaviors were compared to that of commercially available WC-Co tools. It was observed that the wear of the SiAlON tools occurs as micro-chipping of the cutting edge in the first few holes; then, severe abrasion takes place with further drilling. While SiAlON with high fracture toughness shows less micro-chipping, which occurs at the initial stage (1-5 holes) of the drilling process, SiAlON with high hardness has the highest abrasion resistance at the later stage. The increase in wear of the cutting edge of the SiAlONs and the WC-Co tools causes an increase in thrust force, and consequently, in peel-up delamination, which are desired to be as low as possible in order to achieve high performance from the drilling tools.