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E. Aschauer, M. Bartosik, S. Kolozsvári, H. Bolvardi, H. Riedl, P.H. Mayrhofer:
"Stress evolution in high-temperature oxidation resistant Mo1-x-ySixBy/Ti1-xAlxN multilayer coatings";
Talk: Stress 2016, Chicago; 2016-10-02 - 2016-10-05; in: "Stress Evolution in Thin Films and Coatings: from Fundamental Understanding to Control", (2016), 24.

High temperature and oxidative environments lead to severe stress-changes and formation in various kind of materials. At elevated temperatures, the kinetics of diffusion processes are enhanced which in turn leads to increased attacks through oxygen containing atmospheres. In general, a material breakdown through oxidation depicts a complex mixture of different mechanisms, especially in coating materials. Nevertheless, the formation of an oxide scale on top is a key-factor during oxidation. A major failure mechanism is the delamination of these protective oxide scales through the formation of new phases and hence induced stresses.
To gain a deeper understanding on the evolution of stress and strain during oxidation processes, we present within this study an innovative approach for multilayered
Mo1-x-ySixBy/Ti1-xAlxN coatings. Within the coating architecture, Ti1-xAlxN provides its well-known superior thermomechanical properties and Mo1-x-ySixBy its outstanding oxidation resistance - as one of the new high-temperature structure materials.
The residual stresses of single and multilayered Mo1-x-ySixBy/Ti1-xAlxN coatings are evaluated by nano-beam X-ray diffraction after various thermal treatments up to 1600 °C. To investigate the effects of phase formations, which are only driven by enhanced temperatures, the stress states are also analyzed on vacuum annealed coatings. In addition, the multilayer arrangement is validated for the effects of the individual layer thickness (bilayer variation from 20 to 800 nm) as well as number of interfaces on the residual stresses. These results are correlated with the distinct coating characteristics such as hardness, structure and morphology, thermal stability and the obtained oxidation resistance.

oxidation; Mo1-x-ySixBy/Ti1-xAlxN; nano-beam X-ray diffraction; multilayer arrangement

Project Head Paul Heinz Mayrhofer:
Christian Doppler Labors für anwendungsorientierte Schichtentwicklung