Influence of hydrogen from cathodic protection on the fracture susceptibility of 25%Cr duplex stainless steel – Constant load SENT testing and FE-modelling using hydrogen influenced cohesive zone elements

Laboratory experiments and cohesive zone simulation of Hydrogen Induced Stress Cracking in SENT tests specimens of 25%Cr duplex stainless steel have been performed. A polynomial formulation of the traction separation law and hydrogen dependent critical stress was applied. Best agreement with the experiments was found for an initial critical stress of 2200 MPa and a critical separation of 0.005 mm. Proposed threshold stress intensity factor and lower bound net section stress is 20 MPa√m and 480 MPa. High crack growth rates and typical hydrogen influenced fracture topography suggest large influence of the stress and strain in the fracture process zone on the hydrogen diffusion rate.