Creep damage in welded joints of a Ni-base heat-resistant alloy Hastelloy XR

The relationship between creep rupture lives and cavitation damage is examined in a welded Ni-base alloy, Hastelloy XR, in an impure He gas at 1123–1273 K. The rupture lives of the welded joints are almost the same as those of the base metal at lower temperatures of 1123–1173 K, whereas the former lives become shorter than the latter ones at higher temperatures of 1223–1273 K. Microstructural observations reveal that the activity of cavitation in the weld metal is lower than that in the base metal at the lower temperatures, resulting in failure at base metal region, whereas the former becomes higher than the latter at the higher temperatures, resulting in failure at the weld metal region. The enhanced activity of cavitation and the resultant diminished rupture lives in the welded joints can be attributed to the enhanced recrystallization of the weld metal at the higher temperatures.