The Role of Replicated Service Atmosphere on Deformation and Fracture Behaviour of Carburised AISI Type 316H Steel

The UK Advanced Gas Cooled nuclear reactor fleet adopted CO2 gas as the heat transfer medium. Over the plant service life carbon diffuses into the stainless steel components as part of the overall oxidation process. This carbon enrichment promotes carbide precipitation and changes overall microstructure, thereby altering temperature deformation and fracture behaviour. Due to difficulties of replicating the high temperature/high pressure CO2 service environment, many tests are conducted under simulated CO2 conditions. We compare the role of a range of surrogate atmospheres on steel test specimens to one which failed in service to establish the influence of testing atmosphere on creep deformation and fracture characteristics.