Influence of the Gas Reaction Atmosphere on the Structure, Phase Composition, Functional Properties and Cytocompatibility of Porous Titanium–Nickel Alloys

This work studies the effect that argon and nitrogen atmospheres have on the structure, phase composition, cytocompatibility, and functional properties of porous NiTi alloys obtained by self-propagating high-temperature synthesis. Porous alloys obtained in the nitrogen atmosphere (NiTi-(N)) are characterized by brittle interstitial phases Ti4Ni2O(N) and the appearance of a finely dispersed TiNi3 phase in comparison with the alloy obtained in an argon atmosphere (NiTi-(Ar)). An increase in the volume fraction of the Ti4Ni2O(N) phase as well as an increase in the content of nitrogen in the surface layer of the NiTi-(N) alloy favorably affects the surface cytocompatibility with bone marrow mesenchymal stem cells. It was found that the mechanisms of martensitic transformations in porous NiTi alloys under load and without load are different. It has been established that the mechanical characteristics of NiTi-(N) alloys are noticeably lower than those of NiTi-(Ar) alloys. Thus, according to the data obtained, porous NiTi-(N) alloys can be considered more biocompatible under low physiological load. However, it is necessary to increase their reversible deformation and tensile strength in order to use porous NiTi-(N) alloys under high physiological load.