During the last decade, there have been many studies on the new ceramics, especially engineering ceramics. Sintered silicon carbide is one of the main materials in engineering ceramics.
The optimum sintering behavior of SiC is obtained at 2050℃ in Ar atmosphere with additions of boron and carbon.
This study shows the effects of surface treatment and microstructure, especially the abnormal grain growth, on the strength of sintered silicon carbide.
Surface of sintered SiC is treated with 400, 800 and 1200 grit diamond wheel. Grain growth is introduced by increasing the sintering times at 2050℃. The β →α transformation occurs during the sintering of β-starting materials and is often accompanied by abnormal grain growth. The overall strength distributions are estimated using Weibull statistics.
The results show that the surface treatment and abnormal large grains have profound effects on the strength of sintered silicon carbide. The strength of sintered silicon carbide is limited by extrinsic surface flaws in normal sintered specimens. And the severity of grinding-induced flaws, relative to the grit size, decreases with grinding grit size. Hence, it is found that the finer the surface finishing and the grain size, the higher strength results. But the strength of abnormal sintering specimens is limited by the abnormally-grown large tabular grains.
The Weibull modulus increases with the decreasing grain size and the decreasing grinding grit size and the increasing of the degree of uniformity of grain shapes in silicon carbide.
