Abstract
In this study, flank wear of physical vapor deposition (PVD) coated cutting tools during continuous turning of alloy 718 were investigated. The similar damages were observed on the rake face and the flank face. Incidentally, wear rate of the coating on the flank face was higher than the one of the rake face. The aim of this study is to clarify the wear mechanism of the coating on the flank face. A typical Ni based superalloy (alloy 718) was machined by using TiN coated and uncoated cutting tools. After the cutting test, the damages on the flank face of the cutting tool were observed through scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). Enrichment of (Nb,Ti)C was observed on the interface between the coating and adhered material. The (Nb,Ti)C layer was made from strengthening phase in alloy 718. Therefore, the (Nb,Ti)C layer adhered on the flank face might cause the strong abrasive wear on the flank face. Thus, the wear modes of the coating on the flank face were composed of abrasive wear, in addition to adhesive wear and fatigue wear. Corrosive wear by oxidation and diffusion between the work and the coating material was not confirmed. It is indicated that the required coating properties for alloy 718 machining were higher softening-resistance and hardness of the coating than (Nb,Ti)C.
