Features of the spark plasma sintering process of in situ TiC-Ni composites produced by high-energy ball milling

In this study, TiC-Ni composites were fabricated in situ by high-energy ball milling of Ti-C-Ni powder mixtures followed by spark plasma sintering (SPS) at 1000 and 1100 degrees C. Three compositions were chosen: 30 wt%(Ti-C)- Ni, 40 wt%(Ti-C)-Ni, and 50 wt%(Ti-C)-Ni. During milling, the TiC phase was synthesized and dense nano- structured powder agglomerates of TiC-Ni were formed. The compaction of the products of milling via SPS was accompanied by local melting of the material at the inter-particle contacts caused by high electric current densities. The TiC-Ni composites fabricated by SPS at a temperature of 1100 degrees C showed relative densities of 98-99 %. Partial melting helps reduce the porosity as pores are filled with the melt. When this melt re-solidifies, nickel-rich regions form in the structure. The phase composition of the materials subjected to SPS is represented by a nickel-based solid solution and non-stoichiometric titanium carbide TiC 0.65-0.8 . The size of TiC reinforcing particles in the sintered composites is less than 1 mu m. The Vickers hardness of the composites obtained by SPS at a temperature of 1100 degrees C from mixtures 30 wt%(Ti-C)-Ni, 40 wt%(Ti-C)-Ni and 50 wt%(Ti-C)-Ni was 740 f 10 HV1, 910 f 20 HV1 and 980 f 30 HV1, respectively.