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15XV International Symposium on Self-Propagating High-Temperature Synthesis
METALLOTHERMIC SHS OF ALLOYED COMPOSITES BASED ON Co
K. V. Zakharov*", D. E. Andreev", V. I. Yukhvid", N. V. Sachkova", and N. Yu. Khomenko"
aMerzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow, 142432 Russia *e-mail: [email protected]
DOI: 10.24411/9999-0014A-2019-10200
This work is aimed at the synthesis via gravity-assisted metallothermic SHS of cast alloyed composites based on cobalt: hard alloys (Co-Cr-Ti-C, etc.), refractory alloys (Co-Al-Mo, etc.). In addition to solving the fundamental problem associated with obtaining new cobalt-based composites with unique properties, the task of developing the foundations of high-tech, high-performance manufacturing technologies will be solved. The materials being developed can be used in metalworking (stamping), for solving problems of the aerospace complex (refractory materials). Earlier, the authors showed that the methods and approaches of metallothermic SHS can be effectively used to produce superalloys based on nickel and titanium, niobium silicides, as well as hard alloys and FGM based on titanium carbides and chromium. It was found that the autowave (frontal) chemical transformation of the initial mixture into final products occurs in the combustion wave. The target product of autowave synthesis is refractory material (RM), and a side product is the oxide phase (metal oxide of the reducing agent). High combustion temperature leads to gas formation and dispersion of the melt at atmospheric pressure [1, 2]. Increased pressure and centrifugal action allow to suppress the spread, therefore, SHS-metallurgy is carried out in reactors under gas pressure or, most often, in centrifugal installations. Optimization of the composition of the initial mixtures, the level of overload allowed to obtain composites (CM) with a high level of properties necessary for use in industry. At the initial stage of research, highly exothermic mixtures capable of burning were developed for the synthesis of the material and the production of composite materials based on Co-Cr-Mo -Nb-Ti-C with dispersion/dispersion hardening TiC/Ti + C, respectively; waves of combustion, experimental studies have been carried out in centrifugal installations, the influence of burning velocity and overload on the formation of chemical and phase composition, macro- and microstructure of cast products of combustion determined Helena optimal synthesis conditions. It was found that in the case of dispersed alloying with titanium carbide (TiC), the burning velocity, combustion temperature and, as a result, the formation of a cermet grade decrease. In turn, in the case of dispersion alloying, when Ti and C are introduced into the exothermic mixture, the combustion process in the form of titanium powder (PTOM) and soot undergoes the following changes: in the beginning, there is a significant variation in the reaction products due to the formation of metal suboxides and carbon black interaction with the resulting oxygen decomposition results of the starting oxides. In addition, the expansion of the limits of combustion and phase separation was revealed.
The research was supported by the Russian Foundation for Basic Research, no. 19-03-00088.
1. M.I. Alymov, V.I. Yukhvid, D.E. Andreev, V.N. Sanin, Chemical transformations of multicomponent thermite-type mixtures in combustion waves, Dokl. Phys. Chem., 2015, vol. 460, iss. 1, pp. 6-9.
2. D.E. Andreev, V.I. Yukhvid, D.M. Ikornikov, V.N. Sanin, T.I. Ignat'eva, Gravity-assisted metallothermic SHS of titanium aluminide with Al-Ca mixture as a reducing agent, Int. J. Self-Propag. High-Temp. Synth, 2018, vol. 27, iss. 2, pp. 89-91.
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