Toward single crystal nickel fabrication using WAAM - A first report

The present study is focused on investigating the feasibility of additive manufacturing of single crystal nickel components using MIG processed wire arc additive manufacturing (WAAM) technique. The feasibility was validated by depositing the material first on 99.999 % pure polycrystalline nickel substrate and then onto a 99.995 % pure single crystal nickel specimen oriented in <111> direction. Optical microscopy and EBSD results prove the possibility for regions of single crystal to be deposited. The process yielded distinct regions of single crystal. Columnar and equiaxed grains occurred in a region with the highest local thermal gradient and slowest solidification rate. EBSD analysis confirmed that the single crystal region revealed in optical microscopy was in one orientation and the etchant was effective in highlighting individual grain boundaries.