Ceramic-metal composites TiC-High-Entropy Alloy (HEA) CoCrFeNiMe (Me = Mn, Ti or Al) were first produced by combustion synthesis method. Self-sustained synthesis occurs due to heat release from exothermic reaction Ti + C = TiC; the binder content was varied between zero and 40-50 wt.%. The combustion velocity and temperature gradually decreased with increasing binder content. Resultant materials consist of TiC grains and two-phase (fcc and bcc) binder. Vickers microhardness (100 g) of compacted cermet materials with 30 wt.% of binder was in the range of 10-17 GPa and increased with increasing bcc to fcc ratio. Based on experimental results and thermodynamic calculations, the mechanism of microstructure formation in TiC-HEA cermets was suggested.

Bulk ceramic materials based on B 4 C-ZrB 2 systems have been produced by means of pressure-assisted Self-propagating High temperature Synthesis (SHS) using a mixture of elementary powders B, C and Zr. Reactant mixture compositions were chosen based on thermodynamic calculations to obtain synthesis regimes with the formation of a liquid phase, ensuring proper compaction. The liquid phase in the SHS products consisted from molten B 4 C. The influence of a "chemical oven" on densification of the SHS-products was studied. Significant reducing of ceramic residual porosity was obtained at mass ratio of the reaction mixture and the "chemical oven" 1 : 4. The minimum residual porosity of SHS composites obtained by a "chemical oven" is 1.7 %. X-ray analysis showed that SHS products were equilibrium and contain refractory compounds ZrB 2 and B 4 C, which formed a dispersed phase and a ceramic binder. The influence of the composition of the reaction mixture on the formation of the microstructure and phase composition of ceramic composites was studied. It is established that microstructure of SHS-composites depends on the B 4 C content. At the B 4 C content less than 10 % wt. the B 4 C-ZrB 2 ceramic composite has uniform microstructure with ZrB 2 grain sizes of 10 -20 µm. Increasing of the B4C contents up to 20 % wt. leads to decreasing of the ZrB 2 grain size up to 2 -5 µm. Vickers Hardness of the SHS composites are 21 -24.5 GPA.

The paper presents experimental results of preparation the B 4 C-TiB 2 composites by combining the self-propagating hightemperature 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 TiB 2 as disperse phase and B 4 C 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. % B 4 C 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 TiB 2 and B 4 C. It was established B 4 C content has a significant influence on microstructure formation of SHS-composites. At the B 4 C content less than 20 wt. % ceramic composite was formed with homogeneous microstructure and TiB 2 grain size of ~10 microns. Increasing of the B 4 C contents up to 50 wt. % reduces the size of TiB 2 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).

In the present paper dense ceramic composites TiB 2-B 4 C and ZrB2-B 4 C have been produced by means of pressure-assisted self-propagating high temperature synthesis (SHS). The method includes combustion synthesis of refractory compounds and its consolidation under high mechanical pressure. An equilibrium SHS product formed during the exothermic interaction in the mixture of Ti, Zr, B and C powders contains TiB 2 or ZrB 2 as a dispersed phase, and B 4 C as a ceramic binder. The influence of content of the ceramic binder (B 4 C) on the formation of the microstructure of SHS composites was studied. It is shown at the B 4 C content of 20 wt.% in the TiB 2-B 4 C composite and at 5 wt.% in the ZrB 2-B 4 C composite were formed dense TiB 2 and ZrB 2 particles. At content B 4 C 40 wt.% in the TiB 2-B 4 C-composite and 20 wt.% in the ZrB 2-B 4 C-composite the particles of the dispersed phase were formed in hollow shells form.. The size and thickness of the shells depend on the initial Ti and Zr particles size. It had been proposed formation mechanism of hollow shells, are including stages formation the TiB 2 and ZrB 2 layers on the metallic particles surface, melting of the internal unreacted part of the metallic particles, and spreading of the melt on the outer surface of the product layer. The experimental results showed the "chemical furnace" had provided thermal regime needed to efficient consolidation SHS composites to minimum residual porosity. Physical and mechanical characteristics of SHS composites were studied depending on content of ceramic binder. It is shown that the maximum microhardness of the TiB 2-B 4 C and ZrB 2-B 4 C composites are 39.1-44.8 GPa, and 20.4-24.5 GPa, accordingly. The flexural strength of the TiB 2-B 4 C-composites is 140-210 MPa.

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