Combustion synthesis and consolidation B4C–TiB2 composites

V.A. Shcherbakov1, A.N. Gryadunov1, M.I. Alymov1, N.V. Sachkova1
1Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Academician Osipyan str., 8, 142432, Chernogolovka

Abstract

The paper presents experimental results of preparation the B4C-TiB2 composites by combining the self-propagating high-temperature synthesis (SHS) and pressing of hot product with use of an additional heat source (chemical oven). The adiabatic temperature and composition of equilibrium combustion product were calculated with use the program of thermodynamic calculations THERMO. It was shown during exothermic reaction are formed TiB2 as disperse phase and B4C as ceramic binder. Adiabatic combustion temperature and quantity of liquid phase are depended from content of ceramic binder. The influence of reaction mixture composition and mass of chemical oven on the magnitude of the residual porosity had been studied. Found that minimal residual porosity (3%) is achieved at 20-40 wt. % B4C content in end product and mass ratio of green sample and chemical oven 1:4. The influence of mixture composition on phase composition and microstructure of the ceramic composites has been studied. XRD analysis showed that during exothermic synthesis had been formed TiB2 and B4C. It was established B4C content has a significant influence on microstructure formation of SHS-composites. At the B4C content less than 20 wt. % ceramic composite was formed with homogeneous microstructure and TiB2 grain size of 10 microns. Increasing of the B4C contents up to 50 wt. % reduces the size of TiB2 particles down to 0.5 microns and results to formation of the ceramic composites with inhomogeneous microstructure. It is shown that the obtained ceramic composites possess high Vickers hardness (32.84–33.64 GPa).

Received: 07 July 2016   Revised: 24 August 2016   Accepted: 01 September 2016

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