Effect of misorientation angle and chromium concentration on grain boundary sensitisation in an austenitic stainless steel

Grain boundaries (GB) in an austenitic stainless steel were analysed using electron microscopy techniques and the results show that there exists a threshold misorientation angle below which GBs are likely to be immune to sensitisation. No direct correlation was found between the extent of corrosion attack and the associated misorientation angles of random high angle GBs (HAGBs). GB attacks were observed when the chromium concentration at GB was below 14.3 wt% and substantial attack occurred when the chromium concentration was <13.0 wt%. At individual random HAGBs, the magnitude of chromium depletion has been found to be the key factor affecting sensitisation, but not the misorientation angle.