Wear patterns and mechanisms of cutting tools in high-speed face milling

High-speed machining has received important interest because it leads to an increase of productivity and a better workpiece surface quality. However, at high cutting speeds, the tool wear increases dramatically due to the high temperature at the tool–workpiece interface. Tool wear impairs the surface finish and hence the tool life is reduced. That is why an important objective of metal cutting research has been the assessment of tool wear patterns and mechanisms. In this paper, the wear performances of PCBN tool, ceramic tool, coated carbide tool and fine-grained carbide tool in high-speed face milling are presented when cutting cast iron, 45# tempered carbon steel and 45# hardened carbon steel. The tool wear patterns were examined through a toolmaker’s microscope. The research results show that the tool wear types differed in various matching of materials between the cutting tool and the workpiece. The dominant wear patterns observed were rake face wear, flank wear, chipping, fracture and breakage. The main wear mechanisms were mechanical friction, adhesion, diffusion and chemical wear promoted by cutting forces and high cutting temperature. Hence, the important considerations of high-speed cutting tool materials are high heat-resistance and wear-resistance, and chemical stability as well as resistance to the failure of coatings. The research results will be of great benefit in the design and the selection of tool materials and in the control of tool wear in high-speed machining processes.