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F. Klimashin, H. Euchner, P.H. Mayrhofer:
"Composition driven phase evolution and mechanical properties of sputtered Mo-Al-N hard coatings";
Poster: 42nd International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego (USA); 2015-04-20 - 2015-04-24.

Cubic molybdenum nitride coatings exhibit high hardness and thermal stability and thus have a high potential to be used as wear-protection for various high-demanding applications. However, the formation of volatile molybdenum oxides requires an improvement of their oxidation resistance. Here, alloying of MoNx thin films with aluminium is an ideal tool, since Al forms stable dense oxides preventing both, further oxygen inward and molybdenum outward diffusion.
Although face centred cubic fcc-Mo2N (nitrogen deficient NaCl structure) and hexagonal close packed hcp-AlN (wurtzite ZnS structure) are thermodynamically not miscible, using non-equilibrium physical vapour deposition (PVD) techniques allows to synthesise their metastable solid solutions. We show, that by PVD single-phase fcc-Mo-Al-N coatings can be developed for Al-contents [x=Al/(Mo+Al)] up to 0.34, where also the hardness reached its maximum with 37.4 GPa. Furthermore, these coatings exhibit also a relatively high resistance against plastic deformation with H3/E*2 = 0.24 GPa. According to X-ray diffraction analysis and ab initio calculations these single-phase fcc-Mo-Al-N coatings crystallize along the quasi-binary Mo2N-AlN tie-line.

Mo-Al-N; hard coatings; reactive sputtering; nitrogen partial pressure; vacancies.