Performance evaluation of cathodic arc evaporated (CAE) TiAlCrN coated general purpose twist drills when dry machining grey cast iron

Recent advances in the commercial exploitation of physical vapour deposition (PVD) technology have focussed on improving the oxidation resistance of TiAlN coated cutting tools by making small additions of chromium to the coating. This paper presents results of a systematic study of the tool life of high speed steel (HSS) drills coated with high chromium content TiAlCrN. The coated drills were used to machine grey cast iron under dry conditions. Tool life data was obtained at different speeds and used to plot Taylor tool life regression lines to compare the uncoated and coated drills. The high chromium content in Ti1xyAlxCryN coatings showed excellent cutting tool performance with improvements of up to ten times that of uncoated tools. It was determined that TiN coatings were unsuitable for dry machining of grey cast iron. The results are discussed in terms of cutting forces, wear mechanisms and the competitive advantage of using advanced surface coatings.