Fracture Behaviour of Mis-Matched Dissimilar Welds: Experimental Results

In nuclear plants, ferritic-austenitic welded joints are commonly used. To better understand their fracture performances, EDF and GKSS have carried out a joint R&D project. In order to study the only influence of the strength mismatch and not of the Heat Affected Zone (HAZ), diffusion bonding process has been used. The characterization plan included numbers of tensile and fracture mechanics tests, on homogenous and bi-material specimens. Some Single Edge Notched Bending specimens (SENB) with the crack at different positions (that is to say in the ferrific side, austenitic side and finally at the interface) were used for the fracture toughness evaluation of the bi-material configuration. They showed the effect of strength mismatch relaxing the crack tip stress state at the interface. The paper will discuss in detail further features of the ductile and brittle fracture observed on this bi-material system.