Corrosion Behaviour of Porous Chromium Carbide/Oxide Based Ceramics in Supercritical Water

Abstract

Porous chromium carbide with a high density of open pores was fabricated by a reactive sintering method. Chromium oxide ceramics were obtained by re-oxidizing the porous chromium carbides formed. Some samples were added with yttria at 5 wt. %, prior to reactive sintering to form porous structures. Corrosion tests in SCW were performed at temperatures ranging from 375°C to 625°C with a fixed pressure at around 25~30 MPa. The results show that chromium carbide is stable in SCW environments at temperatures up to 425°C, above which disintegration of carbides through oxidation occurs. Porous chromium oxide samples show better corrosion resistance than porous chromium carbide, but disintegrate in SCW at around 625°C. Among all the samples tested, chromium oxide ceramics with added yttria exhibited much better corrosion resistance compared with the pure chromium carbide/oxides.  No evidence of weight change or disintegration of porous chromium oxides with 5 wt % added yttria was observed after exposure at 625°C in SCW for 600 hours.