Assessment of flaws in cladded components under consideration of residual stress field

Cladded pressure vessels and pipes made from ferritic steels with an austenitic cladding are widely used in power generation and chemical plant technology. Difficulties in the integrity assessment arise due to the complex residual stress field resulting from the welding and heat treatment processes as well as due to the thermo-mechanical mismatch of the two bonded materials and their different failure modes. In the present study, experimental and numerical investigations of sub-clad and surface flaws in ferritic cladded plates are reported. The plates with a sub-clad crack and a surface crack, respectively, were tested under combined mechanical and thermal loading conditions until failure. In order to describe the deformation and failure behavior numerically, at first the residual stress field due to the cladding process was determined by simulation of the welding and heat treatment processes. Subsequently, the results were transferred to finite element models for the two cracked specimens and the tests under thermal and mechanical loading conditions were simulated