One of the advantages of inertia welding over fusion welding is the capability of joining difficult to weld dissimilar alloys. This has potential application for joining turbine engine discs of different alloys. Before inertia welds can be put into commercial use, the residual stresses have to be known to facilitate component lifing. Residual stresses in one dissimilar nickel-based superalloy weld (RR1000/Inconel 718) have been measured in depth by neutron diffraction before and after post weld heat treatment (PWHT). The PWHT applied for this sample is optimised to anneal Inconel 718. It was found that the residual stresses in the weld and heat affected zone generated by the welding process are large, especially close to the inner diameter of the welded ring. The maximum generated residual stresses on each side of the weld are dependent on the strength of the alloy in the vicinity of the weld line. The maximum as-welded hoop stresses are about 1000MPa in RR1000 and 700MPa in Inconel 718. After PWHT, the hoop stresses are still significant, particularly in RR1000. The axial stresses reflect a bending moment, which is almost completely removed after PWHT.
展开▼
