Microstructure model and crack initiation for a SiC-reinforced Si3N4 ceramic with differently sized SiC particles

Abstract

In this study, a microstructure model was established combining the Voronoi tessellation method with Eshelby’s equivalent inclusion theory to study the failure mechanism of a Si3N4-bonded SiC refractory ceramic with differently sized SiC particles occurring under a great temperature gradient. The crack initiation and propagation under large thermal stress were calculated by employing the extended finite element method on the proposed microstructure model. The micro-cracks were found to originate in the matrix zone around the vertices of the big SiC inclusions and propagate through the matrix until encountering an adjacent SiC inclusion. The temporarily stopped micro-cracks will resume to propagate until eventually macroscopic failure occurs due to the repeated thermal shock. The thermal stress in the composite can be reduced by lowering the mismatch between the thermal expansion coefficients of the different phases in the composite, which results in a longer service life of the refractory ceramics.