Behaviour of sub-clad and through-clad cracks under consideration of the residual stress field

Aim of the present study is an assessment of the behaviour of cracks in the ferritic base metal of components supplied with an austenitic welded cladding under special consideration of the residual stress field caused by the welding and heat treatment processes. For this purpose, an experimental and numerical investigation has been performed. The experimental study consisted of two component tests at low temperature using large-scale specimens with sub-clad and surface cracks. Subsequently, the experiments were analyzed numerically where the residual stress field was determined in an advanced numerical simulation of the welding and heat treatment processes. Based on the results, a fracture mechanics assessment of the ferritic and austenitic material zones on crack initiation and arrest was performed. The experimental and numerical results reveal that fracture was initiated in the ferritic range whereas the austenitic cladding remained intact even in the case of a limited crack extension in the base metal underneath the cladding.