GRK2802: Production of MgO/TiC Composites From MgO-CRecyclates Using Spark Plasma Sintering

Abstract

Using the spark plasma sintering technique, compact MgO/TiC composites were produced from the MgO-C recyclates, which were crushed, sieved, and mixed with titanium powder. The sintering temperatures were 900°C, 1200°C, and 1500°C. The sintering times were 10–30 min. Analysis of the sintered composites using X-ray diffraction unveiled their phase composition and the progress of the TiC1-x formation. Scanning electron microscopy that was complemented by X-ray spectroscopy and electron backscatter diffraction revealed local distribution of individual phases. As TiC1-x is a product of the carbon diffusion into titanium, the sintering temperature and the sintering time play a crucial role in the phase and microstructure formation. Further important factors are the spatial distribution of MgO, graphite, and Ti in the starting powder mixture, because they influence the local availability of graphite as carbon source, and the size of the original Ti grains, which decides about the final concentration gradient of carbon in TiC and about the stoichiometry of this phase, in particular at lower sintering temperatures and/or at shorter sintering times. The presence of impurities stemming from the original MgO-C recyclates is discussed in context of the sintering temperature and sintering time.