AlxTi1−xN hard coatings synthesized by reactive sputtering using mosaic target

In this paper, the effects of N2 partial pressure on the microstructure and mechanical properties of reactively sputtered AlxTi1−xN coatings were studied. A series of AlxTi1−xN coatings were deposited by using a Ti–Al mosaic target, which was sputtered in a mixture gas of Ar and N2. The deposition rate, composition and microstructure of the coatings were characterized with energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray diffraction and transmission electron microscopy, and a nanoindentor was used to measure the mechanical properties of the coatings. The results reveal that N2 partial pressure has important effects on the microstructure and mechanical properties of AlxTi1−xN coatings. At suitable N2 partial pressure, AlxTi1−xN coating with stoichiometric ratio can be easily obtained and the coating presents a NaCl structure with a strong (1 1 1) preferred orientation. It reaches the highest hardness and elastic modulus of 36.9 and 476 GPa, respectively. AlxTi1−xN coatings prepared at lower N2 partial pressure show low N and Al content as well as low hardness. On the other hand, at overhigh N2 partial pressure, the deposition rate decreases and the coatings show a microstructure of nanocrystalline or amorphous and low hardness.