Oxidation behavior of arc evaporated Al-Cr-Si-N thin films

The impact of Al and Si on the oxidation behavior of Al-Cr-(Si)-N thin films synthesized by arc evaporation of powder metallurgically prepared AlxCr1-x targets with x = Al/(Al + Cr) of 0.5, 0.6, and 0.7 and (Al0.5Cr0.5)(1-z)Si-z targets with Si contents of z = 0.05, 0.1, and 0.2 in N-2 atmosphere was studied in detail by means of differential scanning calorimetry, thermogravimetric analysis (TGA), x-ray diffraction, and Raman spectroscopy. Dynamical measurements in synthetic air (up to 1440 degrees C) revealed the highest onset temperature of pronounced oxidation for nitride coatings prepared from the Al0.4Cr0.4Si0.2 target. Isothermal TGA at 1100, 1200, 1250, and 1300 degrees C highlight the pronounced improvement of the oxidation resistance of AlxCr1-xN coatings by the addition of Si. The results show that Si promotes the formation of a dense coating morphology as well as a dense oxide scale when exposed to air. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4748802]