Influence of pre-oxidation on the hot corrosion of Ti_3SiC_2 in the mixture of Na_2SO_4-NaCl melts

摘要

Polycrystalline Ti_3SiC_2 suffered from serious hot corrosion attack in the mixture of 75wt.%Na_2SO_4 + 25wt.%NaCl melts at 850℃. In order to improve the hot corrosion resistance of this material, pre-oxidation treatment was conducted at 1200℃ 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℃ 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.