Microstructure and mechanical properties of 4YTZP-SiC composites obtained through colloidal processing and Spark Plasma Sintering

Abstract

Bulk composites of silicon carbide reinforced zirconia were obtained through colloidal processing and spark plasma sintering, and their microstructural and mechanical properties were investigated. Mixtures of powders of 4mol% yttria-doped zirconia and silicon carbide, with percentages of 15 and 20wt% of silicon carbide, were prepared by colloidal processing and freeze-drying to guarantee the homogeneity of powders, and sintered by SPS at temperatures ranging from 1300 to 1400°C to obtain dense composites. The spark plasma sintering technique makes it possible to control sintering energy and speed, and impedes the oxidation of silicon carbide to ensure larger reproducibility. The microstructure of the composites reveals that some defects arise during sintering due to the differences of coefficient of thermal expansion between zirconia and silicon carbide. Mechanical properties were studied, such as Vickers hardness, Young's modulus, and bending strength. Compared with 4YTZP monolithic material, composites have better fracture strength values (∼588MPa and 492MPa, for 15wt% and 20wt% of silicon carbide, respectively) when sintered at 1400°C. It is also demonstrated that silicon carbide particles act as an absorption centre for propagating cracks.