Sinterability and mechanical properties of silicum carbide reinforced zirconia based ceramic composites

Yttria stabilized polycrystalline zirconia (YSZ) is an interesting material for many structural applications due to its excellent properties at high temperatures compared to metals, high strength as well as high toughness, low coefficient of thermal expansion. These properties make it a good candidate for use in many different types of structures. However, YSZ is not a very durable material against impacts and its mechanical properties need to be improved to expand its usage area. Therefore, in this study, the effects of SiC additives on the structural properties, hardness, fracture toughness and tribological properties of zirconia (8YSZ) stabilized with 8 mol% yttria were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Vickers hardness device and wear. investigated using the device. Samples were produced by alloying 8YSZ and 1-15% wt SiC powders by colloidal process. 8YSZ samples with 1-15% SiC additives by weight were sintered for 2 hours in the temperature range of 1200°C-1600°C. After sintering at 1450°C, the relative density of 8YSZ decreased from 98% to 63% with 15% by weight SiC additive. SEM microstructures of SiC doped 8YSZ samples after sintering showed that after 1% in 8YSZ matrix, SiC did not dissolve and precipitated around 8YSZ grains as a secondary phase. Due to the presence of secondary phases of SiC at the grain boundaries of 8YSZ, the average grain size of 8YSZ decreased from 4,34 µm to 1,95 µm with the addition of SiC. In addition, both the hardness and fracture toughness of the samples were measured with the Vickers hardness method. The addition of SiC to 8YSZ caused some decrease in hardness and increased fracture toughness from 1.65 MPa.m0.5 to 4.23 MPa.m0.5. In addition, wear tests of SiC added 8YSZ specimens were performed on 8YSZ disc against commercially available WC ceramic ball under dry sliding friction conditions, at room temperature, 3N load, 0,1 m/s sliding speed and 500 m sliding distance. The friction and wear test results showed that the friction coefficient and wear amount of 8YSZ decreased significantly with the addition of SiC. In conclusion, this study reveals that there are high improvements in mechanical properties and tribological properties of 8YSZ ceramics with SiC reinforcement.