Wear Mechanisms of Coated Carbide Tools in High-Speed Dry Milling of Titanium Alloy

A series of experiments was conducted in high speed dry milling of Ti-6Al-4V alloy with CVD coated carbide indexable cutters. The main tool wear mechanisms were discussed by observing tool wear morphology utilizing scanning electron microscopy and detecting the element distribution of the worn tool surface using energy dipersive spectroscopy. The experimental results indicate that the tool failure mechanisms were synergistic interaction among abrasive wear, adhesive wear, oxidation wear, diffusion wear and thermal-mechanical fatigue wear. Just after the cutting tool was engaged into the workpiece, adhesion and scratches caused by friction were observed on tool flank face, and the adhesive layer was subjected to cyclic impacts in the intermittent cutting process which would lead to delamination of coating. During the process of tool degradation, coating delamination, adhesive wear and abrasive wear appeared in the process of tool failure. In addition, oxidation wear, diffusion wear and fatigue cracks were observed. With the increasing cutting speed, the newly produced chips can burn more easily and the degree of adhesion, oxidation and diffusion and thermal-mechanical fatigue wear increased.