New Insight into the Mechanism of Ductility-Dip Cracking in Ni-base Weld Metals

The ductility dip cracking resistance of Ni-base Filler Metal 52 (AWS A5.14, ERNiCrFe-7; ISO SNi6052, 59 % Ni, 29 % Cr, 9 % Fe, 1 % Mn, 1 % Al) and Filler Metal 82 (AWS A5.14, ERNiCr-3; ISO SNi6082, 72 % Ni, 20 % Cr, 1 % Fe, 3 % Mn, 3 % Nb) has been extensively evaluated using the recently developed strain-to-fracture test in conjunction with microstructural characterization using electron microscopy. This paper provides new insight into the creep-like, grain boundary sliding mechanism that leads to elevated temperature intergranular cracking in these weld deposits. The effect of precipitation on grain boundary tortuosity and sliding, and its influence on ductility-dip cracking resistance is discussed in the context of current theories of high temperature creep. Finally, the effect of impurity and interstitial elements on ductility-dip cracking is discussed.