High temperature bending creep behavior of a multi-cation doped alpha/beta-SiAlON composite

Abstract

SiAlON ceramics with high hardness and high toughness can be made through designing alpha/beta-SiAlON composites. An important advantage of alpha-SiAlON phase is that the amount of intergranular phase is reduced by the transient liquid phase being absorbed into the matrix of alpha-SiAlON phase during sintering. But, the thermal stability of the alpha-SiAlON phase is an important concern for alpha/beta-SiAlON composites especially at high temperatures. The use of different types of single or multiple cations during fabrication directly affects resultant microstructures and mechanical behavior of alpha/beta-SiAlON composites. In this study, the creep behavior of a multi-cation (Y, Sm and Ca) doped alpha/beta-SiAlON composite, in which aluminum-containing nitrogen melilite solid solution phase was designed as intergranular phase, was investigated by four-point bending creep tests under stresses from 50 to 150 MPa and at temperatures from 1300 degrees C to 1400 degrees C in air. The stress exponent was determined to be 1.6 +/- 0.13 at 1400 degrees C and the creep activation energy was calculated to be 692 +/- 37 kJ/mol(-1). Grain boundary sliding coupled with diffusion was identified as the rate-controlling creep mechanism for the alpha/beta-SiAlON composite