Characterisation of electric arc spray formed Ni superalloy IN718

Nickel superalloy IN718 has been electric arc spray formed under a range of processing conditions as small diameter ring preforms. Top surface deposition temperature has been measured using an infrared thermal imaging video camera. The as-sprayed microstructure has been investigated by a combination of optical microscopy, image analysis and electron probe microanalysis, and characterised by the through thickness variation in porosity, grain morphology and microsegregation behaviour. Low top surface temperature preforms had an unfused splat microstructure with intersplat porosity. Intermediate temperature preforms had banded unfused and fused splat microstructures with some cross-splat columnar grains and low levels of porosity. High temperature preforms had banded unfused/fused splat and equiaxed grains. The extent of microsegregation depended upon the manufacturing temperature.