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F. Klimashin, M. Arndt, P. Polcik, H. Euchner, N. Koutná, D. Holec, P.H. Mayrhofer:
"Improvement of Thermal Stability and Oxidation Resistance of Molybdenum Nitride";
Talk: 44th International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego; 2017-04-24 - 2017-04-28; in: "ICMCTF 2017", (2017).

The ever-growing industry demands challenge researchers to develop ever-better performing materials. Evidently, the industry-university collaboration, implying funding for the research activities and monetization of the developed cutting-edge technologies, is mutually beneficial, and one of the most effective ways of engaging the knowledge exchange between industry and research institutions is a direct research collaboration of both.

The present research - conducted in cooperation with Oerlikon Balzers AG and Plansee Composite Materials GmbH - aimed at improving thermal stability and oxidation resistance of the cubic-structured molybdenum nitride γ-MoNx. The refractory metal Mo is successfully used as alloying element (for nitrides in particular) for the purpose of improving hardness1, toughness2,3, friction coefficient4, while the application of γ-MoNx - though high-temperature allotropy - is strongly limited to 300-500 °C unless an oxygen-free atmosphere is provided. Optimizing the composition of alloying elements (forming a dense oxide scale at elevated temperatures, e.g. Al and Cr) and vacancies (inherent in Mo-based nitrides), superhardness (over 40 GPa) combined with high resistance to plastic deformation (~0.4 GPa) and significantly improved thermal stability and oxidation resistance (both > 900 °C) could be achieved.

References:
1 Endrino, J. L. & Derflinger, V. The influence of alloying elements on the phase stability and mechanical properties of AlCrN coatings. Surface and Coatings Technology 200, 988-992 (2005).
2 Sangiovanni, D. G., Hultman, L. & Chirita, V. Supertoughening in B1 transition metal nitride alloys by increased valence electron concentration. Acta Materialia 59, 2121-2134 (2011).
3 Zhou, L., David, H. & Mayrhofer, P. H. Ab initio study of the alloying effect of transition metals on structure, stability and ductility of CrN. J. Phys. D: Appl. Phys. 46, 365301 (2013).
4 Glatz, S. et al. Influence of Mo on the structure and the tribomechanical properties of arc evaporated Ti-Al-N. Surface and Coatings Technology (2017).