Spark plasma sintering and microstructural characterization of additive-free polycrystalline β-sic

Additive-free beta-SiC powders were sintered by means of Spark Plasma Sintering System. Experiments were performed in the temperature range from 1650 degrees C to 2200 degrees C, 3 to 10 min holding time and pressure from 50 until 150 MPa. In order to favour sinterization, the starting powder was mechanically activated: defect concentration was increased by centrifugal ball milling. Applied temperature, holding time and/or pressure were varied to analyze their effect on the densification and grain growth kinetics. The full sinterization of the material was obtained for temperatures as high as 1900 degrees C and over. The relative density of the obtained material was high, up to 97.0 +/- 0.6 % the theoretical density for 2200 degrees C sintering temperature. An intense grain growth took place while sintering. The final microstructure exhibited a grain size distribution range from 1.0 to 2.5 mu m, depending on the sintering conditions. Such grain growth strongly depends on the sintering time, not so much on the sintering temperature.