TG8: 5-Pass Slot Dissimilar Weld (Ni alloy) on Ferritic Steel

The Task Group 8 (TG8) round robin specimen is closely based upon the TG4 and TG6 designs, except the thickness that is increased up to 30 mm for more self-clamping conditions and to reduce distortions. It thus presents all the advantages and challenges of the TG4 and TG6 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 cyclic loads. The use of nickel-based alloys for 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.

Fig. 1. TG8 – 3-dim sketch of specimen and mid-length cross section

Fig. 2. TG8 – sketch of specimen cross section highlighting the envisaged weld bead sequence

Fig. 3. TG8 – detailed specimen design

Fig. 4. TG8 – plate with machined slots for test welding