High temperature oxidation resistance of multicomponent Cr-Ti-Al-Si-N coatings

Nanosrystalline CrAlSiN and CrTiAlSiN coatings were deposited by using a cathodic-arc deposition system with lateral rotating arc cathodes. Titanium, chromium and Al89Si11 cathodes were used for the deposition of CrAlSiN and CrTiAlSiN coatings. For the high temperature oxidation test, the coated samples were annealed at 900 degrees C in air for 2 h. The oxidation characteristics of the deposited coatings were also studied by thermal-gravimetric analysis (TGA). In this study, chemical composition and bonding states of the deposited and annealed CrAlSiN and CrTiAlSiN coatings were evaluated by X-ray photoelectron spectroscopy (XPS). All the deposited Cr0.36Al0.57Si0.07N and Cr0.40Ti0.22Al0.36Si0.02N coatings showed B1-NaCl crystal structure and possessed nano-grain sizes of 8-12 nm. The oxide scale formed on the Cr0.40Ti0.22Al0.36Si0.02N coatings consisted of major TiO2 at the surface region, followed by a mixed layer of Al2O3 and Cr2O3 phases. TiO2 grew at an accelerated rate on to the aluminum and chromium oxide layers after oxidation at 900 degrees C. The oxidation rate of the Cr0.36Al0.57Si0.07N coated sample was much lower than that of Cr0.40Ti0.22Al0.36Si0.02N. A dense protective layer, mainly consisted of Al2O3 and Cr2O3, retarded the diffusion of oxygen into Cr0.36Al0.57Si0.07N. It indicated that Cr0.36Al0.57Si0.07N with higher Al, and Si contents possessed superior oxidation resistance lthan Cr0.40Ti0.22Al0.36Si0.02N. (C) 2009 Elsevier B.V. All rights reserved.