Residual Stress Measurements by X-Ray Diffraction in the Ferritic-Austenitic Interface Weldment

Abstract

A mathematical model of calculating residual stresses at the weld interface of ferritic-austenitic steels has been developed. The Kurdjumov-Sachs orientation relationship (110)bcc[111]// (11 l)fcc[011] was determined at the interface of the transition joint. The resultant bcc-fcc lattice misfit gives rise to significant residual stresses. The performed X-ray analysis establishes macro- and microstress profiles extending up to 22 mm and 55 µm, respectively. The profiles indicate the development of compressive and tensile stresses on either side of the weld interface. With respect to this, tensile stresses in increasing sequence were computed from the parent metal toward the interface and compressive stresses were determined from the interface inward toward the weld bead in decreasing sequence. A remarkable stress discrepancy between the two profiles was observed, with the macrostresses falling in the range of +185 to −245 MPa and the microstress level ranging between +340 and −420 MPa. While the developed interfacial residual stresses are due to the difference in the bcc-fcc lattice parameters, the discrepancy observed in the determined stress level has its origin in the varying percentage of the two phases involved within a narrow mixing zone at the weld interface.