Characterisation Of Liquation Products In A Nickel Base Superalloy
Keywords:
Superalloy, nickel, Electron microscopy, Heat-affected zonesAbstract
In this communication, detailed micro structural examination has been made on the dissolution behavior of the γ' strengthening precipitates in the heat affected zone (HAZ) during a solid state welding process of a powder metallurgy (PM) nickel based superalloy. The HAZ microstructures of this nickel based superalloy were simulated using Gleeble thermomechanical simulation system. The microstructural examination of the simulated HAZs shows that the large sized γ' precipitates (~0.8–3µm) survived their solvus temperature during the welding simulation to temperatures where they are thermodynamically favourable to react with the surrounding γ matrix, resulting in localized melting of the precipitates below the alloy’s solidus and concomitant formation of eutectic liquid film by a eutectic type reaction. Microanalysis and electron diffraction were used to study the liquation products. The results are used to derive the origin of the liquation during the solid state welding of the alloy.
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