Influence of oxygen content on the microstructure and mechanical properties of SPS SiC

In this paper, two different commercial silicon carbide powders were treated by HF etching, aging and heat treating to obtain various oxygen contents. Fully dense silicon carbide ceramics (> 99% th.density) were produced by spark plasma sintering technique at 1900 degrees C under an applied pressure of 50 MPa for 15 min holding time with boron carbide and carbon additions. Microstructure, polytype of SiC, density, Knoop hardness and fracture behaviors were examined to understand the effect of oxygen content on the properties of dense silicon carbide. The results show that oxygen content affects all of the measured mechanical and microstructural properties. High oxygen content is shown to be detrimental to the final density and hardness of SPS SiC.