Intragranular precipitation variations in laser deposited Waspaloy due to compositional inhomogeneities

Laser direct metal Deposition (DMD) has attracted considerable attention in recent years and has been developed for use in the aerospace industry with various high temperature materials. In nickel-base superalloys, due to the processing conditions found in DMD, little precipitation of γ' is seen in the as-deposited condition. In order to recover the mechanical properties local aging is required, which could be undertaken using a defocused laser beam if γ′ precipitation is sufficiently rapid. Detailed characterisation of the γ′ precipitation and coarsening response during aging of DMD Waspaloy has been undertaken. Novel in-situ studies were carried out using small angle synchrotron x-ray scattering (SAXS) for studying precipitation and coarsening of γ′ at various temperatures. For some aging temperatures, two populations of γ′ precipitates coarsening at different rates were found. Detailed ultra high resolution SEM and energy dispersive x-ray spectroscopy (EDS) revealed that the two γ′ populations can be attributed to chemical segregation in the material.