Tool Life Time Extension with Nano-crystalline Diamond Coatings for Drilling Carbon-fibre Reinforced Plastics (CFRP)

Abstract

Carbon fibre reinforced plastics (CFRP) are delicate to machine as the material is highly abrasive and tends to show multiple workpiece damages like delamination, fibre pull out, uncut fibres and burnt matrix material. In result machining CFRP requires on the one hand tools which can withstand the massive wear, on the other hand geometrical highly adaptable tools to produce flawless workpieces. Diamond coated solid carbide tools can provide an excellent wear resistance in combination with a highly adaptable tool geometry. Nano-crystalline diamond coatings provide a good layer adhesion and can be applied to machining tools.This study focuses on required drilling tool characteristics for a large tool life time of diamond coated carbide tools. The workpiece material used is the M21/35%/370H5/AS4C-6K from Hexcel© which finds its main application in the aircraft industry. The machining tests are being conducted using a Mori Seiki NMV5000DCG at different feed rates and cutting velocities. Two different nano-crystalline diamond coatings are being evaluated regarding wear resistance depending on the drill geometry and tool diameter. The workpiece quality is measured using a microscope. It is shown that the tool geometry influences the wear resistance intensively. A change in wear resistance depending on the tool geometry is not unique for different diamond coatings. Finally, it is shown that cutting velocity and feed have only a small influence on tool life time.