Dan Tung and Jeff Rodelas
Sandia National Laboratories
The fabrication weldability of AM parts, i.e., the propensity to forming cracks as a direct result of the welding process, has been evaluated by a variety of weldability tests focused toward investigating hot cracking susceptibility; hot cracking is designated as cracking occurring at temperatures where liquid is present. AM 304L manufactured by a laser powder bed process and commercially-available wrought 304L were compared in this study. Hot Ductility testing, Longitudinal Varestraint testing, Sigmajig testing, and microstructural characterization after multiple repeated welding cycles are evaluation techniques utilized for comparison of the aforementioned materials. These testing techniques targeted Gas Tungsten Arc welding and Laser Welding.
No discernable difference in hot cracking susceptibility was found between AM 304L and wrought 304L for the alloy compositions studied. Moreover, the 304L weld microstructures examined were a function of the welding process and the composition irrespective of starting microstructure. The weld microstructure-process-composition relationships determined for conventional 304L were also found applicable to AM 304L; therefore, it is reasonable to conclude that the same alloy composition controls for conventional 304L (e.g., (Cr/Ni)eq, impurity concentration, etc.) used to mitigate solidification cracking risk can also be applied to the starting AM powder composition. With prudent starting powder composition control, hot cracking during typical welding processes can likely be avoided.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.