| Abstract Scope |
Gas metal arc directed energy deposition (GMA-DED) is an additive manufacturing process that is becoming popular due to the high deposition rates and availability of equipment and feedstocks. Haynes 282 is gamma prime strengthened nickel based superalloy that was designed to be arc-weldable, so it is a prime candidate for GMA-DED to produce large components in power generation applications. When using GMA-DED to produce large complex components, thick sections necessitate the use of multiple weaved deposition passes where various defects can form depending on the width of the deposition pass and the hatch spacing. When the hatch spacing is too large relative to the width of the deposition pass, lack of fusion defects can form. When the hatch spacing is too small relative to the width of the deposition pass, the deposits can stack on top of each other leading to a progressive uneven change in layer height. In this work, the critical range of hatch spacings for a fixed deposition pass width needed to avoid lack of fusion and deposit stacking defects was evaluated using low heat input cold metal transfer (CMT), CMT Mix (a combination of CMT and high heat input pulse multi control (PMC)), and PMC. An analytical heat transfer model was used to predict deposit width based on the programmed weave width of the GMA-DED torch and processing parameters. The lower heat input CMT deposition mode is more susceptible to lack of fusion defect formation, but the higher heat input PMC process results in more dimensional distortion. CMT Mix provides for the best trade off in processing space. This work shows that process parameters can be designed up from width predictions of deposition passes, enabling the acceleration of the deployment of GMA-DED for manufacturing large structural components. |