Grain growth of Ni-based superalloy IN718 coating fabricated by pulsed laser deposition

The pulsed laser deposited Ni-based superalloy coating was fabricated with successive 12 layers using single tracks. The microstructure of the deposited coating was observed by scanning electron microscopy (SEM). The grain growth and the grain boundary misorientation were investigated by electron back scatter diffraction (EBSD), the precipitation phase was determined by transmission electron microscope (TEM). The results showed that the dendrites were the most common microstructure in the coating, and the dendritic growth orientation was paralleled to the direction of the laser deposition. The dendrite got coarser and its space was increased with increasing laser deposited layers. Most grains grew along the preferential grain orientation (001) and formed anisotropy with grain boundaries misorientation angle about 2 degrees in the pulsed laser deposited coating. The grain size along the texture orientation was 3-10 times larger than that in the transverse orientation. The cross section microhardness of the coating ranged between 240-280 HV, and decreased along the depositional direction due to the reasons of the variation of eutectic morphology, grain size distribution, grain misorientation and a small amounts of strengthening phase precipitation. (C) 2016 Elsevier Ltd. All rights reserved.