| Abstract Scope |
Dissimilar metal laser welding of stainless steel to titanium alloys remains one of the most challenging combinations. The two alloy classes cannot be directly joined without the formation of brittle intermetallic phases in the fusion zone which compromises the integrity of the joint. In this work, we have addressed this issue by applying interlayers to form a barrier between stainless and titanium base materials. The interlayers were implemented by different techniques including vanadium sheet inserts, laser beam directed energy deposition, and cold dynamic gas spraying (“cold spray”). Vanadium was chosen for compatibility to titanium and in an attempt to minimize intermetallic formation with stainless steel. For the subsequent laser welding, different laser welding processes, including continuous wave vs. pulsed seam vs. beam oscillation (i.e., “wobble”) were used to evaluate the effect on microstructure and mechanical properties. The laser welds and as-deposited interlayers were characterized with light optical and scanning electron microscopy, as well as X-ray fluorescence spectrometry, to understand the resultant microstructures and chemical compositions of the fusion zones. Especially with regards to the wobble welds, the amplitude and frequency of oscillation were correlated with chemical homogeneity in the fusion zone. For vanadium sheet insert interlayer welds, most welding conditions produced defect free welds. Mechanical behavior of the vanadium sheet insert laser welds was evaluated with microhardness mapping and tensile testing. The joints exhibited moderate strength and ductility, aligned well with the strength of the vanadium interlayer. The results are significant in that the overall joint performance can be tailored depending on the desired properties based on interlayer alloy selection. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & 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. |