Composition driven phase evolution and mechanical properties of Mo-Cr-N hard coatings
2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 2, 025305Article in journal (Refereed) Published
Although many research activities concentrate on transition metal nitrides, due to their excellent properties, only little is known about Mo-N based materials. We investigate in detail the influence of Cr on the structural evolution and mechanical properties of Mo-N coatings prepared at different nitrogen partial pressures. The chemical composition as well as the structural development of coatings prepared with N-2-to-total pressure ratios (p(N2)/p(T)) 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 N-2-to-total pressure ratio to pN(2)/p(T) = 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 similar to 0.2, prepared with pN(2)/p(T) = 0.32, exhibits the highest hardness of similar to 34 GPa among all coatings studied. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Place, publisher, year, edition, pages
2015. Vol. 118, no 2, 025305
IdentifiersURN: urn:nbn:se:uu:diva-260294DOI: 10.1063/1.4926734ISI: 000357961000042OAI: oai:DiVA.org:uu-260294DiVA: diva2:847705