High temperature behavior of Ni-base weld metal - Part II - Insight into the mechanism for ductility dip cracking

The ductility dip cracking susceptibility of two Ni-base filler metals, Filler Metal 52 (59%Ni-29%Cr-9%Fe-1%Mn-1%Al) and Filler Metal 82 (72%Ni-20%Cr-1%Fe-3%Mn-3%Nb) was evaluated using the strain-to-fracture test. The analysis of these results and detailed weld metal microstructural characterization (SEM and TEM) was presented in Part I. Part II of this work 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 composition, including both precipitate forming elements and impurity elements, on ductility-dip cracking is discussed. (C) 2004 Elsevier B.V. All rights reserved.