The intergranular oxidation behavior of low-angle grain boundary of alloy 600 in simulated pressurized water reactor primary water

The preferential intergranular oxidation (PIO) behavior of low-angle grain boundaries (LAGBs) with misorientation angle θ ranging from 5.7 to 14.0° on alloy 600 were investigated after exposure to simulated pressurized water reactor primary water. Interestingly, all LAGBs are susceptible to PIO. When θ <8.8°, diffusion-induced grain boundary migration (DIGM) does not occur as Cr is immobile and the PIO depth varies slightly among those LAGBs. As θ increases above 8.8°, Cr starts to diffuse outwards and DIGM occurs. The depths of PIO and DIGM are positively correlated in this case. Also, the PIO depth is not related to the change of θ, but instead poses an inverse relationship with the atom packing density of GB planes.