Convergent Manufacturing Utilizing Encapsulated Arc DED for AM of 316L Stainless Steel

Wire Arc (WA) Directed Energy Deposition (DED) additive manufacturing (AM) is emerging as a vital tool for producing and repairing components in expeditionary environments. Bringing this technology out of the lab and into the field presents two significant challenges: access to shielding gases required for process stability and development of build workflow and procedures to ensure high-quality parts.
Welding gases such as high purity Argon and mixes most often utilized for WA-DED are difficult to source, store, and reclaim under expeditionary conditions. This creates a strong need for processes that either minimize the amount of gas utilized for deposition. Developing a gas-less or high-efficiency shielded (HES) WA process is therefore a key step toward making this technology practical.
This project sponsored by the Office of Naval Research (ONR) focused on developing an HES DED-AM process for 316L stainless steel. Work included evaluating flux-cored arc consumables, designing and testing patented encapsulation hardware, and establishing qualified procedures. In addition, robotic convergent DED and spindle-based interpass techniques were created to support the preferred HES DED process. These elements were integrated into a custom platform that combined tool changers, offline programming, and digital workflows to move seamlessly from toolpath planning to processes.
Utilizing a custom designed HES encapsulated arc (EA) apparatus, the preferred gas shielded electrode was able to be reduced to 4 CFH while still meeting interstitial element requirements, maintaining compliant ferrite levels, and passing MIL-STD-2035A Class 1 non destructive evaluation criteria. The procedures were demonstrated on two propeller geometries at EWI.