Influence of pre-oxidation on the hot corrosion of Ti 3SiC 2 in the mixture of Na 2SO 4–NaCl melts

Abstract

Polycrystalline Ti 3SiC 2 suffered from serious hot corrosion attack in the mixture of 75wt.%Na 2SO 4 + 25wt.%NaCl melts at 850 °C. In order to improve the hot corrosion resistance of this material, pre-oxidation treatment was conducted at 1200 °C in air for 2 h. A duplex oxide scale with an outer layer of TiO 2 and an inner layer of a mixture of TiO 2 and SiO 2 was formed during the pre-oxidation. Because the outer oxide layer of the pre-oxidation treated specimens could inhibit hot corrosion process, they exhibited good hot corrosion resistance in the mixture of 75wt.%Na 2SO 4 + 25wt.%NaCl melts at 850 °C for 50 h. However, during the hot corrosion the outer layer of TiO 2 would degrade gradually. Once the outer layer damaged, the hot corrosion rate increased sharply, the corrosion behavior was similar to Ti 3SiC 2 corroded under the same conditions. The microstructure and phase compositions of the hot corrosion samples were investigated by SEM/EDS and XRD.