Spark Plasma Sintering of Al2O3–SiC Ceramics. Study of the Microstructure and Properties

The features of spark plasma sintering of submicron Al2O3 powders with different contents (0, 0.5, 1.5, 5 vol %) of β-SiC nanoparticles have been studied. The microstructure and hardness of Al2O3 + 5 vol % SiC ceramics obtained by sintering Al2O3 powders with β-SiC particles of various types (nanoparticles, submicron particles, fibers) have been studied. Sintering was carried out at heating rates (Vh) from 10 to 700°C/min. The sintering process of Al2O3 + SiC ceramics with low heating rates (Vh = 10–50°C/min) has a complex three-stage character, with a flat area in the temperature range of 1200–1300°C. At high heating rates (Vh > 250°C/min), the usual three-stage character of sintering is observed. The analysis of temperature dependences of compaction was carried out using the Young–Cutler model; it was found that the kinetics of powder sintering is limited by the intensity of grain boundary diffusion. It is shown that the dependence of the hardness of Al2O3 + SiC ceramics on Vh has a nonmonotonic character, with a maximum. In the case of pure alumina, an increase in Vh leads to a monotonic decrease in hardness.