A comparative study on cutting performance of TiN-coated tungsten carbide cutting tool with a cobalt interlayer

Abstract

To improve the adhesion strength between TiN coatings and WC-Co substrate, interlayer of Co was pre-deposited onto WC-Co substrates prior to the TiN coating process. The thickness and post-annealing effects of Co interlayer on the adhesion property were investigated through scratch tests in this work. The highest critical load of approximately 84 N was obtained for the TiN coating with Co-interlayer sputter-time of 10 min and the critical load increased up to 97 N after post-annealing at 600 °C for 2 h. It was found that the adhesion of TiN coatings was strongly influenced by the thickness of Co interlayer. TiN without Co interlayer and TiN with three kinds of Co interlayer coatings were applied to end-mill tools made of WC-Co material with a hybrid coating technique. Cutting tests for die steel AISI D2 cold-worked die steel (60 HRC) and their reliability tests were studied. The tool life of TiN-coated tool with Co interlayer having the critical thickness of 0.027 μm was improved for over 36% as compared to only TiN-coated tools. The experimentation was repeatedly performed in order to verify the goodness of fit for tool wear distribution. The flank wear of TiN-coated tool with Co interlayer at given time condition is suitable for normal distribution and log-normal distribution by chi-squared test.