Influence of Creep Deformation on the Corrosion Behaviour of a CeO sub 2 Surface-Modified Alloy 800H in a Sulphidising--Oxidising--Carburising Environment

The corrosion behaviour of a CeO sub 2 surface-modified pre-oxidised wrought austenitic steel of the type Fe--20Cr--32Ni (Alloy 800H) was studied in a simulated coal gasification atmosphere at 700 deg C for exposure times up to 3000 h. The influence of creep deformation on the corrosion resistance of this material was assessed by comparison with its behaviour in the stress-free condition. The significant improvement in the corrosion resistance of Alloy 800H due to the CeO sub 2 treatment can be decreased by creep deformation. Both strain and strain rate govern the cracking behaviour of the pre-formed protective oxide layer, leading to enhanced internal and external attack. The preformed oxide layer tends to rupture at a lower strain with increasing strain rate. Graphs, Photomicrographs. 26 ref.--AA