Consumable development to tailor residual stress in parts fabricated using directed energy deposition processes

Distortion and residual stresses are major challenges that limit the ability to fabricate large scale structures using Additive Manufacturing (AM). Researchers worldwide are evaluating techniques to induce compressive residual stress in the parts via intermittent rolling. While reasonable success has been documented, the idea of lowering the martensite start temperature to induce compressive stresses has not been evaluated in the context of AM, despite demonstrated success by the welding community. This study validates the hypothesis that, by a proper selection of materials and process parameters, one may effectively reduce distortion and induce a compressive residual stress in AM parts. Using neutron diffraction to measure residual stresses in parts, we demonstrate that, in addition to selection of the correct materials, the inter pass temperature plays a major role in controlling the residual stress evolution. The observations relating to the residual stresses are rationalized based on a microstructural evolution in these samples. Based on this preliminary study, a strategy to fabricate large structures with minimal distortion and residual stress is outlined. [Display omitted] •Inspired by the design of welding consumables, we utilized a low temperature transformation filler material in additive manufacturing to reduce tensile strains and induce compressive strains in the part.•We observed that the overall compressive residual stress could be maximized by maintaining the entire build above the martensite start (Ms) temperature to ensure transformation in the entire build occurs simultaneously.•Maintaining the build below the Ms temperature resulted in improvements in toughness but an eradication of the compressive residual stresses•In order to achieve the benefits that LTT materials offer, it is necessary to ensure proper temperature control in the builds.