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F. Klimashin, H. Euchner, P.H. Mayrhofer:
"Structure and mechanical properties of Mo-Cr-N hard coatings";
Talk: 42nd International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego (USA); 2015-04-20 - 2015-04-24.

High-performance, multifunctional protective coatings for machining applications have to combine for example high hardness, high thermal stability and excellent tribological properties. Especially ceramic-like coatings are well known for their outstanding properties combinations. Whereas many research activities are conducted on TiN, ZrN and CrN based coatings, only little is known for MoN based materials. Especially the cubic phase of molybdenum nitride (Mo2N) exhibits excellent mechanical properties but is extremely sensitive to the nitrogen content and the N2-partial pressure used during deposition. We therefore studied in detail the structural evolution of Mo-N coatings as a function of the nitrogen partial pressure used during deposition. Based on ab initio calculations and experimental studies within the binary Cr-N and Mo-N systems, ternary Mo-Cr-N thin films along the quasi-binary Mo2N-CrN tie-line were developed. Whereas all available literature reports deal with the Cr-rich side Mo/(Mo+Cr)<0.5 our studies concentrate on the Mo-rich side with Mo/(Mo+Cr)>0.5.
These coatings are studied in detail by scanning and transmission electron microscopy, X-ray diffraction and nanoindentation. The coating with an Mo/(Mo+Cr) ratio of ~0.85 exhibits the highest hardness of about 34 GPa as well as the highest resistance against plastic deformation with (H3/E*2) of ~0.2 GPa. The lattice parameters experimentally obtained for the individual high Mo-containing Mo-Cr-N coatings excellently fit ab initio calculations along the Mo2N-CrN tie line and thus verify their structural description.

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