Microstructural analysis of failure progression for coated carbide tools during high-speed milling of Ti-6Al-4V

Abstract

In this study, the microstructural failure progression of coated carbide tools was analyzed during milling Ti-6Al-4V under dry conditions. The microstructure and compositional characterization of worn tool inserts were examined using SEM and EDS analysis. It was found that the coated carbide cutting tools undergo several stages during interrupted cutting Ti-6Al-4V alloy: coating delamination, cobalt diffusion, attrition wear, cracking and flaking. Firstly, coating delamination firstly occurred around the cutting edge and then extended to the rake face and flank face as cutting process proceeds. The diffusion of the binder phase cobalt (Co) was observed after coating delamination and cutting speed significantly promoted the process of cobalt diffusion. Then, attrition wear occurred around the cutting edge as the WC particles were pulled out and removed from the tool substrate. In addition, Microcracks initiated and propagated from the voids introduced by cobalt diffusion due to cyclic thermomechanical loadings. Brittle fractures were found to be the main failure modes of coated carbide tools at high cutting speeds.