Effect of tin on high-temperature sulphidation of Fe–Cr alloys in H2/H2S atmospheres

The high temperature sulphidation behaviour of Fe–46Cr–xSn (x = 0; 0.2; 0.5; 1; 2) alloys has been studied at temperatures of 1073, 1173 and 1273 K in H2/H2S mixtures with different sulphur vapour partial pressures of 10−1, 10−3 and 10−5 Pa. Thermogravimetric studies in combination with scanning electron microscope (SEM), with energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) techniques, have displayed a significant influence of the sulphur partial pressure on the composition and growth rate of the sulphide scale. The results have shown that addition of tin increases the sulphidation rate of Fe–46Cr alloys but not considerably (except at temperatures of 1073 and 1173 K combined with sulphur partial pressure of 10−5 Pa). The metallic core of the studied samples was enriched in tin and iron, moreover tin was found in the internal layer close to the metallic core as metallic FexSny inclusions with tin concentrations of up to 12 at.%.