Mechanical Stability of Retained Austenite in Multi-Pass Cr-Ni Weld Metal in an Over-Matching Welded Joint

The mechanical stability of retained austenite in a Cr-Ni weld metal in a welded joint under a service load is related to the initial amount of retained austenite and the type of welded joint. The welded joint used is the over-matching type, i.e., the tensile strength of the weld metal is higher than that of the base metal. For this welded joint, when the initial amount is less than 7.5%, the retained austenite is stable enough to remain in the weld metal over the whole tension process. However, when the initial amount is 12-27%, the retained austenite is metastable, and a large amount of it has transformed into martensite at the applied stress level of 0.2% proof stress. At that stress level, 12% of the retained austenite is still present. As the applied strain further increases, the retained austenite continues to transform, but 7.5% of it is still available after the failure of the welded joint.