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

• Dendrite gets coarser and its space increases with increasing deposited traces.
• Most grains grow in 〈001〉 with disorientation about 2° and form an anisotropy.
• Large size grains in the deposited coating are beneficial to mechanical properties.
• Coating hardness is effected by grain size, grain misorientation, Laves and γ″ phase.

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 backscatter 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° 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.