Deformation in the heat affected zone during spot welding of a nickel-based single crystal

Abstract

Constrained melting and solidification and associated thermal cycling during welding produces extensive microstructural changes. Such changes are observed during spot welding of single-crystal Ni-based superalloy TSM-75. Analysis of Laue diffraction patterns attained from the heat-affected-zone indicates the presence of a high density of dislocations. Dislocation rearrangement results in local rotations around the [100] direction, which is perpendicular to the temperature gradient. These dislocations exist over a large fraction of the heat-affected zone. The analyses also showed that the dislocation density was maximal near the fusion line and gradually decreases with an increase in the distance from the fusion line. The dislocation density increased with the cooling rate.