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P.H. Mayrhofer, F. Klimashin, N. Koutná, H. Euchner, D. Holec:
"Vacancies as the Key to Excellent Properties Within Mo-Cr-N";
Talk: 43rd International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego (USA); 2016-04-25 - 2016-04-29; in: "ICMCTF 2016", (2016), 25.

Although many research activities concentrate on transition metal nitrides, due to their excellent properties, only little is known on the pronounced effect of vacancies on their structure evolution and mechanical properties. We investigate in detail - by ab initio and experimental studies - the influence of vacancies on the structural evolution and mechanical properties of Mo-N based coatings. The chemical composition as well as the structural development of coatings prepared with N2-to-total pressure ratios (pN2/pT) of 0.32 and 0.44, can best be described by the quasi-binary Mo2N-CrN tie line. Mo2N and CrN are face centered cubic (fcc), only that for Mo2N half of the N-sublattice is vacant. Consequently, with increasing Cr content also the N-sublattice becomes less vacant and the chemical composition of fcc single-phase ternaries can be described as Mo1-xCrxN0.5(1+x). These coatings exhibit an excellent agreement between experimentally and ab initio obtained lattice parameters of fcc Mo1-xCrxN0.5(1+x). When increasing the N2-to-total pressure ratio to pN2/pT = 0.69, the N-sublattice is already fully occupied for Cr-additions of x ≥ 0.4, as suggested by elastic recoil detection analysis and lattice parameter variations. The latter follows the ab initio obtained lattice parameters along the quasi-binary MoN-CrN tie line for x ≥ 0.5. The single-phase fcc coating with Cr/(Mo+Cr) of x ~0.2, prepared with pN2/pT = 0.32, exhibits the highest hardness of ~34 GPa among all coatings studied.