PERFORMANCE OF MULTI-LAYERED CVD COATED CARBIDE TOOLS IN END MILLING HARDENED TOOL STEEL WITH 62 HRC

摘要

Nowadays with the development of mould and die machining technology, direct machining hardened steel into its final product is becoming more and more popular. In this way, tool life and cutting conditions are crucial since the harder the material, the shorter the tool life is. With those in mind, this study was carried out in order to investigate the performance of multi-layered CVD-coated (TiC/N, TiN, Al{sub}2O{sub}3) micrograin carbide tool in end milling of fully hardened tool steel AISI D2. Two inserts were fully mounted on a tool holder for each trial. Milling tests were performed under dry cutting condition in order to avoid thermal shock on the brittle carbide tool. In this research, various cutting speeds and feed rates were tested, while the axial and radial depth of cuts were set to be constant for all trials. Repetitions for each set of cutting condition were made three times and the average tool life was taken. The results showed that the flank wear starts with an initial stage and it is followed by gradual stage and finally abrupt stage of wear. Mechanical wear or abrasion is typically dominant during the initial cutting. Thermal wear is dominant at higher cutting speeds with the high cutting temperature, which can be observed through the changed of colours of the chips. Majority of the tool wear modes were due to flank face wear and excessive chipping on the tool edge.