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ArticleName High-temperature ceramic MoSi2 – MoB – HfB2 obtained by the combination of self-propagating high-temperature synthesis and hot pressing
DOI 10.17580/tsm.2018.09.09
ArticleAuthor Vorotilo S., Pogozhev Yu. S., Potanin A. Yu.

National University of Science and Technology “MISiS”, Moscow, Russia

S. Vorotilo, Post-Graduate Student at the Department of Powder Metallurgy and Functional Coatings, e-mail:
Yu. S. Pogozhev, Senior Researcher of the Scientific and Education Center SHS, e-mail:
A. Yu. Potanin, Researcher of the Scientific and Education Center SHS, e-mail:


In this work, macrokinetic features of the combustion of mixture Mo – Hf – Si – B, mechanisms of phase and structure formation in the combustion front as well as structure and properties of combustion products were investigated. It was demonstrated that self-heating is initiated when the reaction mixtures are pre-heated above 150 oС. At Т0 = 25 oС the combustion temperature Тc = 2050 oС, while the combustion velocity Uc = 22 mm/s. However, when Т0 is increased to 230 oС, partial oxidation of the components (molybdenum and boron) occurs, leading to the self-heating of the reaction mixture and subsequent decrease of combustion temperature to 1770 oС and combustion velocity to 14.5 mm/s. Further increase of Т0 leads to the linear increase of Тc0) and Uc0). Using the time-resolved XRD method, mechanisms of the structural and phase transformations in the combustion front of Mo – Hf – Si – B mixture were studied. Primarily, in the pre-heating zone, the formation of HfB2 takes place via gas-transport reaction. Subsequently, in the combustion zone, the silicon melts and spreads over the surface of particles of Mo, Hf, and B, with the dissolution of B in the Si melt. MoSi2 grains are formed on the boundary between the melt and Mo via the reaction diffusion of Si into Mo, while the borides of Mo and Hf are formed as a result of diffusion of Mo and Hf into the melt. In the aftercombustion zone, the equilibrium structure is formed, comprised of MoSi2 grains with the size up to 15 μm, surrounded by the interlayers of MoB with the size of 2–4 μm and needle-like grains of HfB2 with the size of 0,5–1 μm. Hot pressing of the SHS powder produced the hierarchically organized ceramic composite MoSi2 – MoB – HfB2 with a high hardness HV10 of 17.6 GPa and porosity less than 1%.

This research was funded under the Federal Target Programme “Research and development initiatives in the priority areas of Russian science and technology for 2014–2020”, Grant Agreement No. 14.578.21.0227 (Project ID: RFMEFI57817X0227).

keywords Сeramic, combustion kinetics, hafnium diboride, molybdenum disilicide, molybdenum boride, composite powders, hardness

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