An Investigation of Tool Chip Contact Phenomena in High-Speed Turning Using Coated Tools

This paper focuses on the investigation of contact length and chip morphology in high-speed turning. In this study the performance of five different coatings: TiN, TiCN, TiAlN and CrTiAlN PVD coatings, and an advanced Dymon-IC hydrogenated amorphous carbonbased coating (a-C:H) deposited by plasma-enhanced chemical vapour deposition (PECVD) is investigated in high-speed machining (HSM) of AISI/SAE - 4140 high-strength alloy steel at cutting speeds ranging between 210 and 925 m/min. Modelling of chip contact length is revisited and the results of extensive machining tests supported by use of a high-speed camera are reported. The effects of coatings on the chip compression ratio, back flow angle, tool-chip contact length, frictional force, and tool wear are explored. The paper contributes towards a fundamental understanding of heat generation and partition in metal cutting using coated tools.