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19XV International Symposium on Self-Propagating High-Temperature Synthesis
SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS OF METAL MATRIX COMPOSITE POWDERS FROM MECHANOACTIVATED POWDER MIXTURES
G. A. Pribytkov*", A. V. Baranovskii"A, M. G. Krinitsyn^, V. V. Korzhova", and E. N. Korosteleva"'A
aInstitute of Strength Physics and Materials Science, SB, RAS, Tomsk, 634055 Russia bNational Research Tomsk Polytechnic University, Tomsk, 634050 Russia *e-mail: gapribyt@mail.ru
DOI: 10.24411/9999-0014A-2019-10132
Mechanical activation (MA) of reaction mixtures on the basis of metal powders is usually used to promote combustion reaction. When there is a metal excess in metal - nonmetal powder mixtures SHS products represent metal matrix composites (MMC). MMC structure corresponds disperse particles of hard compounds (carbide, boride, silicide) imbedded into metal matrix (binder). Disperse compound particles serve as strengthening phase in the composite. Less is size of the particles more is the strengthening effect. The most often titanium carbide is used as a strengthening phase in the SHS metal matrix composites. Due to high negative enthalpy of TiC it is possible to get high volume fraction of the metal matrix in the SHS composite. It is known, that the more is concentration of inert metal matrix powder in reactive mixture the more is a dispersion of TiC particles in SHS composite. A size of TiC particles varies from 10 to 1 |im [1-4] depending of the metal binder concentration in the reaction mixtures. Representative structures of the composites synthesized from powder mixtures with high content of metal binder powder are shown in Fig 1.
SHS TiC + Me binder powders are used for cladding and spraying of wear resistant coatings [4, 5]. The powders can be easy produced by crashing of porous SHS cakes and screening out granules of required size. To get more fine carbide phase in SHS metal matrix composite a processing of reaction powder mixtures of titanium, carbon and metal matrix in high energy planetary mills is used. As a result, concentration limits of wave mode SHS extend and the combustion temperature goes down. However, damping effect of metal matrix powder resists MA of titanium and carbon powders. That is why we failed to get considerable effect of MA on metal binder concentration for Ti +C + cast iron and Ti + C + high speed steel (HSS) powder mixtures. The same damping effect of the metal binder prevents disintegration of TiC particles in the granules. A single positive impact of a processing SHS metal matrix powder in high energy planetary mills is formation rounded shape of the MMC granules (Fig. 2a). The rounded shape of the granules is needed to promote a steady powder delivery to plasma spray or to cladding pool.
Another way to get TiC + Me matrix composite powders with submicron carbide inclusions is intensive processing powder mixture of fine carbide and metal matrix. If metal matrix powder is ductile enough composite granules are formed by impregnation of carbide particle into metal matrix powder. We produced TiC + 50 vol % Ti binder composite powder via three steps route: SHS of TiC + 25 vol % Ti binder powder from titanium and black carbon powder mixtures ^ intensive processing of SHS powder in planetary mill (MA) to get submicron size powder (Fig. 2b) ^ blending of Ti powder with MA treated SHS composite powder and at last MA retreatment of TiC + Ti powder mixture. The TiC + 50 vol % Ti binder composite powders (Fig. 2c) were used for cladding and sputtering of wear resistance coatings and in additive technologies.
iSHS 2019
Moscow, Russia
Fig. 1. Microstructure of SHS MMC synthesized from Ti, C, and Me binder powder mixtures. Powder binder content (vol %): (a) 50% cast iron; (b) 40% high speed steel; (c) 50% nichrom; (d) 25 % Ti; (e) 50% Al.
(a) (b) (c)
Fig. 2. Effect of planetary mill processing on morphology of SHS metal matrix composites. (a) TiC + 50 vol % HSS; (b) TiC + 25 vol % Ti; (b) TiC + 50 vol % Ti.
The research was performed within the frame of the Fundamental Research Program of the State Academies of Sciences for 2013-2020, line of research III.23.
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