| Summary: | Centrifugal spray deposition (CSD) is being investigated for the production of ring-shaped preforms using Ni superalloys for aerospace applications. Experiments with different metal flow rate and different substrate movements have been performed to investigate the effects on the macro and microstructure of the resulting ring-shaped preforms. Modelling of heat flow during deposition was also performed to better understand the heat transfer and solidification behaviour of preforms. The mass flow rate and substrate reciprocation strongly influenced the micro- and macrostructure of the preforms. 'Hot' deposition conditions produced coarse microstructures, with interdendritic Laves phase and solidification shrinkage; 'cold' deposition conditions produced a banded equiaxed grained microstructure containing layering, prior droplet boundaries, and inter-splat porosity; and intermediate deposition conditions produced a good surface finish, equiaxed grain morphology, and reduced porosity. Heat flow modelling linked these microstructural observations to both short time scale re-heating/re-melting phenomena, and longer time scale behaviour related to the local solidification time and distribution of solid fractions. The as-sprayed preforms required a modification to standard heat treatment procedures, and produced a microstructure comprising fine-scale carbides, carbonitrides, and equiaxed grains.
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