A method to compare the effects of the grain boundary misorientation and grain boundary plane orientation on thermal sensitisation

Thermal sensitisation of austenitic stainless steel may cause the premature failure of piping materials at an elevated temperature due to loss of corrosion resistance. Grain boundary properties are widely studied as the factors of thermal sensitisation. In this research, a new method is proposed to compare the relationship between thermal sensitisation of individual boundaries with two grain boundary properties: grain boundary misorientation and grain boundary plane orientation. A heat-treated UNS S30400 stainless steel sample was serial-sectioned by FIB (Focused Ion Beam), and two grain boundary properties can be obtained from the 3D reconstructed volume. EDS (Energy-Dispersive X-ray Spectroscopy) was performed on two foils extracted from the remaining material to quantify thermal sensitisation by measuring the chromium depletion of individual boundaries. • An experimental method was proposed to study the relationship between thermal sensitisation and two boundary properties of stainless steel. • FIB serial sectioning was used to reveal two grain boundary properties of thermally sensitised 304 stainless steel. • Thermal sensitisation was quantified by using EDS elemental profiling.