Modelling of the swelling induced by oxidation in SiC-based refractory castables

Abstract : Silicon carbide-based refractory castables (SiC-RC) have high mechanical and chemical resistances at high temperature. Nevertheless when subjected to both high temperature and aggressive oxidizing environment, due to phase transformation, a chemical strain appears that leads to additional stresses in industrial parts and may cause degradation. In this paper, macroscopic constitutive equations are proposed to model the complex relationship between stress, strain, temperature and oxidizing atmosphere in porous SiC-RC. To model the kinetics of the chemical swelling, oxygen content in the porosity of the heterogeneous material is estimated. It depends on both the oxidation reaction of SiC-based grains and the diffusion of oxygen through the connected porosity in the castable. The macroscopic chemical strain associated to the local SiO2 formation takes only place when the local small voids cannot absorb the reaction product anymore. Besides, the reduction of porosity is accompanied by a reduction in the gas permeability and consequently a reduction in the diffusion of oxygen. The multi-physical model is implemented in the finite element code Abaqus . It accounts for heat transfer,reactive oxygen transport and chemically induced strain. A validation test was carried out on a cylindrical sample subjected to high temperature with a thermal gradient in ambient air. Comparison between experimental results, microscopic observations and numerical results showed that the model provides a good description of the main physical phenomena.
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Tarek Merzouki, Eric Blond, Nicolas Schmitt, M. Bouchetou, Thierry Cutard, et al.. Modelling of the swelling induced by oxidation in SiC-based refractory castables. Mechanics of Materials, Elsevier, 2014, 68, pp.68 (2014) 253-266. 〈10.1016/j.mechmat.2013.09.001〉. 〈hal-00916918〉

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