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Influence of different technological conditions on the synthesis processes of TiN-TiB2 ceramic composite by spark plasma sintering method |
Oleksander S. Petukhov , Igor V. Khobta , Andrey V. Ragulya |
Institute for Problems of Materials Science, 3, Krzhizhanovsky, Kyiv 03142, Ukraine |
Abstract |
The powder mixtures TiH2+BN, TiH2+BN+TiN, TiH2+BN+В with ratios of components, corresponded to ТiB2 content 20-80 wt.% in the final samples, were used as the raw materials. TiN – TiB2 ceramic composite (practically clean) with relative density 64-99 % were synthesized. The composite with TiB2 content 36-60 wt.% and properties: hardness HV=19,7-25,4 GPa (the load was P=100 g), fracture toughness K1C=5,4-5,8 MPа*m1/2 (Р=20 kg) were obtained. High heating rate (42-50 °С/sec) and, consequently, simultaneous passage of dehydrogenation, synthesis and starting stage of densification leads to increasing of the properties of obtained samples with enhancement of TiB2 content. Increase of TiB2 content to 80 wt.% results in extreme heat generation, heating-up and failure of the graphite die as a result of intensification of reaction of self-propagating high-temperature synthesis between Тi and В under high heating rate and sufficient partial pressure of hydrogen. Low heating rate (2-4 °С/sec) leads to formation of the structural skeleton on initial stage of the sintering and, therefore, to final structure inhomogeneity in consequence of scin-effect. It results in increasing of obtained samples properties does not occur though considerable densification. Passing of reaction between Ti and B which has higher velocity leads to primary initial formation of TiB2 crystal lattice. Higher hardness of TiB2 (34 GPа) in comparison with TiN (25 GPа) by approximately equal melting points (3123-3220 К) results in hardness increase of formed skeleton in consequence of increasing of TiB2 content and, consequently, to decrease of density and mechanical properties of final samples. |
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Presentation: Oral at E-MRS Fall Meeting 2008, Symposium I, by Andrey V. RagulyaSee On-line Journal of E-MRS Fall Meeting 2008 Submitted: 2008-05-17 15:55 Revised: 2009-06-07 00:48 |