Preliminary results on the effects of reduced gravity on laser welding of stainless steel and other materials are reported. Laser welding experiments using a low power (10-18 watts) Nd-YAG laser have been performed on the NASA KC-135, which flies parabolic manuevers to simulate reduced gravity conditions. Previous experiments with 0.005 - 0.010 inch thick stainless steel samples displayed a pronounced change in convective flow and surface tension with gravity. Reduced gravity processing resulted in smaller weld beads, deeper penetration and increased surface ripple in comparison with 1 g processing.
In order to understand the phenomenological aspects of the laser melting process and convective flow in reduced gravity, the study has been extended to include laser processing of thicker samples by using the same laser system with an organic model, succinonitrile. The succinonitrile is transparent to the laser energy, but it can be doped with graphite particles to achieve an absorbing condition. The weld volume of the organic model is much larger than that obtained with stainless steel; however similar results are obtained.