This paper aims to establish the wear mechanisms of tungsten carbide (WC) tools coated with TiAlN and coated with diamond respectively when helical milling Ti-6Al-4V. During the helical milling experiments, cutting forces were measured using a dynamometer. In addition, a scanning electron microscope (SEM), a digital microscope and Energy-dispersive X-ray (EDX) were periodically used to measure the wear progression of tool surface and to analyze tool wear mechanisms. In the analysis of cutting force of two types of coating tools, cutting process of TiAlN-coated tool is more stable and cutting force of it is lower. TiAlN-coated tool showed a better cutting performance than diamond-coated tool. Tool wear mechanisms mainly include adhesive wear, oxidation wear, coating flaking and chipping and are combined effects of various wear forms. In view of flank wear analysis, diamond-coated tool has shorter life than TiAlN-coated tool, and it has undergone a relative severe wear.
