Microstructure, mechanical properties, and milling performance of arc-PVD AlTiN-Cu and AlTiN/AlTiN-Cu coatings

AlTiN, AlTiN-Cu and AlTiN/AlTiN-Cu coatings were prepared on WC-6%Co substrates by cathode arc evaporation deposition technology. Two kinds of nitrogen pressures were used to deposit both AlTiN-Cu and AlTiN/AlTiN-Cu coatings. Surface and cross-sectional morphologies of films were observed by scanning electron microscopy (SEM). Crystal structure of films was analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Hardness and adhesion of films were measured by nano-indentation and nano-scratch tester. Cutting tests were performed under milling conditions during wet machining of TC4 alloy. The results show that with addition of Cu, more droplets occur on AlTiN coating surface, but the grain size of it is refined, and the hardness decreases but the toughness is improved. Under higher N2 pressure, the defects on the surface of AlTiN-Cu and AlTiN/AlTiN-Cu coatings diminish, and the hardness of them is enhanced, while the adhesion is reduced. Compared to AlTiN coated cemented carbide tool, the lifetimes of AlTiN-Cu and AlTiN/AlTiN-Cu coated tools under the same N2 pressure are improved by 11% and 24%, respectively.