National University of Science and Technology “MISiS”, Moscow, Russia:
V. V. Kurbatkina, Leading Researcher of Scientific and Education Center of Self-spreading High-temperature Synthesis, e-mail: vvkurb@mail.ru
E. I. Patsera, Researcher of Scientific and Education Center of Self-spreading High-temperature Synthesis
E. A. Levashov, Director of Scientific and Education Center of Self-spreading High-temperature Synthesis, Head of a Chair of Powder Metallurgy and Functional Coatings

We investigated the influence of NaCl additives on the parameters of combustion of Ni + Al mixture. NaCl reduces the heat generation, temperature and combustion velocity. Having the high content of NaCl (more than 20%), reaction mixture can not combust in self-supporting regime at Т₀ = Т_room. The phase composition of synthesis products depends on the content of NaCl in mixture: in addition to NiAl, the second phase of Ni₂Al₃ is formed during the concentration of more than 15%. Gaseous chlorides of sodium and aluminium play the active role in structural formation processes. The peaks of 466 and 569 сm^–1, corresponding to Al – Cl, are defined by IR-spectroscopy. Formation of NiAl begins in the heat penetration due to infiltration of volatile chlorides from combustion zone, turns into the active stage in combustion zone, and ends in combustion zone. NaCl is crystallized in combustion zone along the boundaries of NiAl grades, complicating the recrystallization, which contributes the formation of the fine-grain intermetallic structure. The products of synthesis, obtained from mixtures with NaCl, are more easily grinded into the narrowly-fraction powder with average particle size of 5 μm. The defined regularities show the new possibilities of obtaining of intermetallic powders with the given granullometric and phase compositions by variation of NaCl concentrations, control of combustion parameters and further grinding. The fraction powders of less than 10 μm are used in additive technologies of spraying and sintering and in production of compact billets by hot isostatic pressing and spark plasma sintering.
Our study was carried out with the financial support of the Federal Target Program “Investigations and developments by the priority ways of development of scientific and technological complex of Russia for 2014–2020”; unique identifier of the project: RFMEFI57817X0260; agreement No. 14.578.21.0260.

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