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H. Riedl, E. Aschauer, C.M. Koller, P. Polcik, M. Arndt, P.H. Mayrhofer:
"Ti-Al-N/Mo-Si-B multilayers: An architectural design for high temperature oxidation resistant hard coatings";
Talk: Plansee Seminar 2017, Reutte; 2017-05-29 - 2017-06-02; in: "19th Plansee Seminar 2017", Plansee Seminar 2017 Proceedings, (2017), Paper ID RM 14, 14 pages.

State of the art mechanical engineering is in need of high temperature and oxidation resistant materials. Major aspects in the design of highly oxidation resistant coatings are the formation of a continuous, non-volatile oxide scale, the adherence of this scale as well as retarded transport mechanisms within the scale. Considering these criteria combined with the requirements for excellent mechanical properties, we present an innovative design concept of extremely oxidation resistant multilayered Ti1-xAlxN/Mo-Si-B coatings. Through the variation of the bilayer period (from 7 to 237 nm for our Ti1-xAlxN/Mo-Si-B multilayers), hardness, growth morphology, thermal stability and oxidation resistance are adjusted. Detailed high resolution transmission electron microscopy, as well as X-ray diffraction investigations of as deposited and annealed coatings highlight, that coatings with a bilayer period of 37 nm (composed of 6 nm thin Mo-Si-B and 31 nm thick Ti1-xAlxN layers) are superior to the other variations. Only if the individual Ti1-xAlxN layers are thinner than 21 nm the hardness of our Ti1-xAlxN/Mo-Si-B multilayers is below that of Ti1-xAlxN coatings without a multilayer architecture. Isothermal thermo-gravimetric analysis in synthetic air for 420 min at 700, 800, and 900 °C, yield extremely oxidation resistant behavior of the 37-nm-bilayer multilayer with growth rates (parabolic growth rate constant, kp*) of 8.2·10-5, 8.6·10-4, and 3.2·10-3 (mg/mg)²·s-1, respectively. Above 1000 °C, the significant formation of volatile Mo-based oxides, lead to a rapid degradation of these coatings. Based on our results we can conclude that the combination of very thin high-temperature stable Mo-Si-B with Ti1-xAlxN layers results in multilayers with excellent oxidation resistance and outstanding mechanical properties for certain bilayer periods.