Corrosion of Cr2AlC in Ar/1%SO2 Gas Between 900 and 1200 A degrees C

Abstract

Cr2AlC compounds were synthesized by a powder metallurgical route and corrosion tested at 900, 1000, 1100 and 1200 A degrees C for up to 150 h under an Ar/1% SO2 gas atmosphere. The compounds were resistant to corrosion because a thin alpha-Al2O3 barrier layer quickly formed on the surface which suppressed sulfidation. Virtually no sulfur was detected inside the scale except during the initial corrosion stage. The superior corrosion resistance of Cr2AlC originated from the high affinity of Al for oxygen to form the thermodynamically stable Al2O3. Unlike Al, Cr was not active because Cr was strongly bound to carbon as Cr2C layers in Cr2AlC. The small amount of Cr2O3 that had formed was dissolved in the Al2O3 layer. The corrosion of Cr2AlC resulted in the formation of an alpha-Al2O3 layer and an underlying Cr7C3 layer.