Strengthening Oxide–Oxide-Free Materials by Incorporation of Tic–Zrc Solid Solutions into their Structure during Spark Plasma Sintering of Initial Powder Mixtures under High Compression Loads

The effect of the formation of sintered TiC–ZrC solid solutions in mullite–WC–TiC–ZrC and mullite– c-BN–TiC–ZrC samples during spark plasma sintering of compositions at a compression load of 60 MPa in the range of 1200–1600°C on their phase composition, microstructure, relative density, open porosity, linear shrinkage, physicomechanical properties, and linear correlation of elastic modulus and fracture toughness is shown. The synthesized WC, c-BN powders, and solid solutions of TiC–ZrC prepared by spark plasma sintering at 1800°C are characterized by intensive crystallization of WC, c-BN and (Ti, Zr)C, respectively, with the formation of a uniform, densely sintered crystalline microstructure. Sintered samples containing 80/20 and 90/10 mol.% solid solutions of TiC and ZrC show intensive development of mullite and (Ti, Zr)C, a gradual increase in c-BN and (Zr, Ti)C, as well as a decrease in the intensity of the formation of the WC phase in the range of 1200 – 1600°C. The microstructure of more evenly and densely sintered samples containing c-BN and solid solutions of TiC–ZrC (in various proportions) is fine-grained with a small number of pores and most strengthened at the boundaries of the regions of oxide and oxide-free crystalline phases. As a result, such samples show higher values of the relative density, linear shrinkage and physicomechanical properties in the range of 1200 – 1600°C, high crack resistance at 1500°C and larger linear correlation of the elastic modulus and fracture toughness in the range of 1200 – 1600°C.