Characterization of build parameters and microstructure in low heat input WAAM of Ni-based superalloy Haynes 282

Ni-based superalloy Haynes® 282® is being targeted for various applications in advanced power generation systems for its superior fabricability, weldability, and excellent high temperature creep and corrosion performance. There are a wide variety of critical components in the gas turbine that range in size and complexity, where novel additive manufacturing (AM) techniques may improve cost and schedule saving with less material waste. Wire-arc direct energy deposition (WA-DED) offers near-net shaping of large components with high deposition rates; however, process-induced porosity may require additional thermal-mechanical treatment, such as Hot Isostatic Pressing (HIP), that can limit its integration and deployment.

This study aims to use a low heat-input, high deposition rate, controlled Gas Metal Arc Welding (GMAW) process, Cold Metal Transfer (CMT) by Fronius, to achieve fully dense fabrication and avoid the need for HIP. Single bead-on plate tracks of Haynes® 282® wire was used to identify an approximate range of suitable processing conditions. Eighteen multilayer blocks (~25x100x40 mm³) were deposited to explore a large set of build parameters variations within this range, focusing on travel speed and wire feed speed. A strong correlation has been observed between arc energy – controlled primarily by travel and wire feed speed – and bead height and angle, as quantified using surface profilometry of the single tracks, the latter a major factor in fusion between weld beads.

Visual inspection, internal microstructural examination, and computed tomography (CT) is underway to determine effects of built parameters on evolution of internal porosity and defects, as well as wall shape, dimensions and surface roughness, respectively. Advanced electron microscopy techniques allow for structural and compositional imaging of heterogeneity and changes in microstructural properties. Combination with datasets from mechanical screening tests, across various length scales, will provide complimentary insights into process-structure relationships of WA-DED builds.