Low-temperature densification of TiCN by spark plasma sintering with Si aids
OJALVO C. 1, MINEIRO R. 2, FERNANDES C. 3, M. R. SENOS A. 2, ORTIZ Á. 1
1 Department of Mechanical, Energy and Materials Engineering, University of Extremadura, 06006, Badajoz, Spain; 2 Department of Materials and Ceramic Engineering, CICECO – Aveiro Materials Institute, University of Aveiro, Campus Santiago, 3810-193, Aveiro, Portugal; 3 Palbit S.A., P.O. Box 4, 3854-908 Branca, Albergaria-a-Velha, Portugal
The feasibility of densifying TiCN by spark plasma sintering (SPS) with Si aids at only 1400°C was investigated. Importantly, it is demonstrated that TiCN is fully densifiable at such a smooth SPS temperature even with only 5 vol.% Si aids, and that the resulting ceramics are superhard and have fine-grained microstructures. It is shown that this is possible because Si acts as a reactive sintering additive that promotes densification by transient liquid phase sintering, leading to the in situ formation of SiC, TiSi2 and N-rich TiC1-xNx second phases dispersed in the TiCN matrix. The formation of these second phases is consistent with the theoretically calculated pseudo-binary TiCN–Si phase diagram. Interestingly, it is also found that hardness of these TiCN-based multiphase ceramics is little affected, while toughness increases, with the increase of the proportion of Si aids up to 25 vol.%. Finally, implications of interest for the ceramic and hard-material communities are discussed.