Chlorine-Induced High Temperature Corrosion of Inconel 625 Alloy with the Addition of Yttrium at 800 °C

The chlorine-induced corrosion behavior of Inconel 625 alloys with the addition of 0- 1.0 wt.% Y has been investigated in N2 - 1.0 vol.% HCl-1.5 vol.% O2 -3.0 vol.% CO2 mixed gas at 800 ° C for 200 h. The scale grown on Inconel 625 alloy was composed of a thin continuous layer of Cr2O3 in contact with the alloy, partly covered by a discontinuous layer of SiO2 or even by isolated particles of SiO2. However, the scales grown on Inconel 625-0. 1 wt.% Y, Inconel 625-0. 3 wt.% Y and Inconel 625-0. 5 wt.% Y alloys were almost entirely composed of a continuous Cr2O3 layer. Therefore, the three alloys were of better corrosion resistance, with the total mass gain less than a fifth of that of Inconel 625 alloy. Inconel 625-0. 1 wt.% Y alloy showed the best corrosion resistance, with the smallest mass gain of 0.09533 mg/cm2 for 200 h. With further increases of Y content, Inconel 625-0.7 wt.% Y and Inconel 625-1.0 wt.% Y alloys did not obtain more satisfactory corrosion resistance. On the contrary, the protective performance of Cr2O3 layer declined and it could not effectively inhibit the outward evaporation of SiCl4. The addition of a small amount of rare earth element Y can promote the formation of a protective Cr2O3 layer and thus improve the corrosion resistance of Inconel 625 alloy, but the amount should be controlled within a very small concentration range.