Within the NeT project [1], Task Group 8 examines a steel plate (French grade 18MND5 close to ASTM A508 Gr.3) containing a five pass “slot” weld made with Ni base alloy (Alloy 52) consumables. NeT TG8 has been organized to address welding repair issues. The TG8 round robin specimen is closely based upon the TG4 design [2], except for the plate thickness that is increased up to 30 mm for more thermal inertia, self-clamping conditions and to reduce distortions that may affect the accurate definition of residual measurement position. It thus presents all the advantages and challenges of the TG4 specimens, namely, the generation of a complex 3D residual stress distribution in a compact, portable specimen that is amenable to rapid measurement of residual stresses by diverse techniques, with a significant volume of weld metal that undergoes multiple high temperature thermo-mechanical load cycles. The use of a nickel-based alloy as filler metal adds considerable residual stress measurement challenges, while this configuration undergoes a complex mismatch behaviour with the base metal where phase transformations and tempering effects occur in the Heat Affected Zone (HAZ).

The residual stress measurement and simulation round robins for TG8 are ongoing. What is presented here is therefore the first phase results of the behaviour of the TG8 specimens. Finite element simulation results are compared with residual stresses determined experimentally thanks to different techniques. The agreement between stresses measured by the Contour Method and by neutron diffraction is generally very good, simulation exhibits complex behaviour that help to interpreted some of the measurements and the lessons learned will allow to conduct a second phase benchmark with possible improvement in residual stresses assessments and in-depth analyses for a better understanding of such a dissimilar weldment.

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