The microstructure and properties of IN718 rings produced by centrifugal spray deposition

Centrifugal spray deposition (CSD) is explored as an alternative route for manufacturing ring-shaped pre-forms for casings in gas turbines. CSD offers metallurgical and economic benefits compared with conventional routes. Research centred on optimising CSD processing to produce nickel alloy rings suitable for thermo-mechanical processing. Alterations to the mass flow-rate and substrate motion produced microstructures characteristic of hot and cold deposits. Hot deposits contained coarse inter-dendritic microstructures and solidification shrinkage. Cold deposits had a banded equiaxed grained microstructure comprising layering, prior droplet boundaries, and inter-splat porosity. Intermediate mass flow-rates created microstructures common to both deposition conditions. Increasing reciprocation speed led to more layering and inter-splat porosity. Slowing reciprocation produced a near optimised microstructure of equiaxed grains, some layering adjacent to the substrate and minimal porosity (≤1.0%). Following thermo-mechanical treatments, tensile properties consistent with commercial specifications were achieved. Improvements in mechanical performance are expected through future process optimisation.