MEASUREMENT OF THE VOLUME EXPANSION OF SIC REFRACTORIES INDUCED BY MOLTEN SALT CORROSION

摘要

Corrosion tests of oxide-bonded SiC-based refractory cylinders by molten salts (mainly CaSO_4, K_2SO_4) were performed at high temperature to better understand the corrosion mechanisms operating in these materials. Salt pellets were placed on the upper surface of small refractory cylinders. After melting, the corrosive product soaked into the pores of the refractory cylinders and partially corroded the SiC phase. SEM-EDS analyses showed that CaSiO_3 was the main new phase formed, growing from SiC aggregates into the pores. The shapes of the initial and corroded cylinders were measured at room temperature using a 3D coordinate measuring machine equipped with a laser-plane sensor. These measurements allowed for the monitoring of the evolution of the residual radial deformation versus the depth from the surface in contact with the salt pellets and consequently the characterisation of the local volume expansion induced by the phase change. Coupling SEM-EDS analyses with 3D digitising revealed the link between the corrosion product and the volume expansion.