Wear Development and Cutting Forces on Cbn Cutting Tool in Hard Part Turning of Different Hardened Steels

摘要

The aim of this research work is to investigate the wear mechanisms of PCBN cutting tool in turning of different hardened steels, SS2244 (DIN 42CrMo4), SS2511(DIN 16MnCr5) and SS2260 (DIN X100CrMoV51), with focus on the interaction between the CBN/binder and the workpiece materials. The workpiece materials have been characterized according to the chemical composition, microstructure, residual stress and residual austenite for each hardening method (e.g. induction hardening, case hardening and through hardening). The results show that the interaction between the tool and each workpiece material is reflected in different morphology of the tool wear surfaces. Groves and ridges are found to be formed on the tool wear surfaces due to the metallic binder of the CBN tool. The role of the chip in forming of the groves and ridges is considered. EDS analysis and different phase diagrams are used to explain the mechanism behind the fast development of the crater wear. The crater depth and the volume of the CBN diffused during the cutting process are calculated by using the white light interferometer. The results show the dominant wear mechanism is a mixed of abrasive and diffusion wear irrespective of the hardening methods and there is no linear relationship between the crater area and crater depth. The evolution of cutting forces clearly indicates that the radial force (Fr) becomes dominant for all three hardened steels.