Laser Spot Welding of Cold-Rolled Boron-Free Ni3Al Foils

Abstract

We have recently developed thin foils of boron-free Ni3Al by cold rolling the single crystals. The welding behavior of the foils was examined in this study using the hybrid laser-laser spot welding method. Autogenous full-penetration welds were made on the foils with two different thicknesses of 30 and 100 μm. Solidification cracking occurred in both foils. The cracks were fine, shallow, and confined near the shrinkage hole in the 30-μm-thick foils. In contrast, they extensively propagated through the heat-affected zone (HAZ) to the base metal in the 100-μm-thick foils, but the crack propagation was effectively confined near the shrinkage hole by preheating with a secondary laser. No HAZ cracking occurred in both foils. As a result, both foils were successfully welded except for the formation of fine solidification cracks. We estimated the fracture stress in the fusion zone and HAZ from the grain boundary character distribution and discussed the effect of the foil thickness and preheating on the propagation of the solidification cracks.