Abstract
Though problems on a precise and concise evaluation method of strength behaviors of ceramics still remain open, extensive studies by many investigators have revealed the extremely low fracture toughness of engineering ceramics such as silicon nitride and silicon carbide. However, on the other hand, these engineering ceramics have several excellent properties; high compression strength, high strength at elevated temperatures and high wear resistance. Such opposite aspects in their mechanical properties must be taken into account when we intend to apply these creamics as a structural material. Furthermore, in order to establish the design concept for the application of engineering ceramics, the whole strength characteristics must be systematized by compiling the strength data covering mechano chemical reactions in aggressive environments and further the dynamic response to transientally varying load such as impact load.
The aim of the present study was to clarify the impact strength characteristics of representative engineering ceramics at high temperatures. For this purpose, the impact fracture strengths of silicon nitride and silicon carbide at high temperatures upto 1300°C were investigated by using an impact 3-point bending load device. The results indicate that the sintered silicon nitride has excellent high temperature impact strength, i.e., the degradation of fracture strength at high temperatures is less under impact load than under static load. The impact strengths of two types silicon carbides were also described.
