A case study of environmental assisted cracking in a low alloy steel under simulated environment of pressurized water reactor

The electromechanical behavior of a pressure vessel grade steel A516 has been investigated using potentiodynamic polarization curves and slow strain rate test (SSRT) in simulated environment of pressurized water reactor. The anodic polarization behavior shows that the steel remains active in the solution till localized attack (pitting) starts. The cracks initiated at the surface propagate in a trans-granular mode. These cracks are initiated at the inclusion (MnS) sites and at the interfaces between local anode (ferrite) and local cathode (pearlite). It seems that the ultimate fracture occurs when the propagating surface cracks join the subsurface hydrogen induced cracks. The addition of oxygen in the testing chamber to supersaturation levels shifts the corrosion potential to anodic side and significantly lowers the strength and ductility. Compared to the room temperature properties, the UTS and tensile elongation in various simulated conditions are reduced by 10–25% and 25–75%, respectively.

► We study environmental assisted cracking (EAC) in simulated PWR environment.
► The corrosion rate in simulated coolant is low but increases with B conc.
► A516 steel shows EAC in simulated coolant particularly at high oxygen levels.
► Fracture occurs when the surface cracks join the subsurface cracks.
► Corrosion of MnS inclusions and ferrite provide crack nucleation sites.