Ductility-dip cracking and solidification cracking were observed during the cladding and buttering of a low alloy steel pipe with Ni-Cr filler wire.  Both experiment and integrated numerical models were developed to understand the mechanical and metallurgical reasons for the cracks and to suggest procedural changes for mitigating cracking.
A mockup of the pipe was designed and built to calibrate the numerical models.  The mockup includes two weld build-ups on the OD surface of the pipe: cladding and buttering.  The cladding is built up in an L-shaped groove at the end of the pipe in seventeen layers.  Each layer of cladding contains two passes: one adjacent to the base metal (inner bead) and one removed from it (outer bead).  The experiment shows that the cracking is mainly in the outer bead region.  Temperature measurements show that the outer bead has a higher temperature than the inner bead.  The configuration and results are similar for the buttering region as well.
Integrated thermo-mechanical and metallurgical models were developed to predict strains, temperature distributions, and precipitation as a function of location and time during welding.  The models were calibrated with temperature, displacement, and microstructure experimental data.  The thermo-mechanical model shows a higher temperature in the outer bead versus the inner bead.  The outer bead has higher tensile thermo-mechanical strains than the inner bead in the hoop direction.  The metallurgical mode shows that the microstructure at the end of the weld solidification was gamma dendrites with interdendritic niobium carbides.  Therefore, a reduction of heat-input for the outer beads was studied to improve the microstructural and thermo-mechanical conditions.  Numerical results show that the thermo-mechanical strains were reduced after reduction of the heat input.
In summary, both experiment and modeling results suggest that reducing the heat input in the outer bead is a valid method toward reducing the cracking tendency.