Microstructure evolution of the Gleeble-simulated heat-affected zone of Ni-based superalloy

Paper in proceeding, 2019

The formation of liquation cracking in a simulated heat affected zone of René108 is reported.
The stress controlled thermo-mechanical experiments were carried out on a Gleeble®3800 testing system.
The base alloy was lost-wax cast and then solution treated and aged. Light and scanning electron
microscopy of this material revealed high volume fraction of γ' precipitates in the dendrite arms and residual
eutectic γ/γ' islands in the interdendritic areas. As a result of short-term exposure to high homologous
temperature, the volume fraction of γ' phase was significantly decreased due to the dissolution of
precipitates in the surrounding matrix. The thin non-equilibrium liquid film, formed locally along grain
boundaries, was a key-factor favoring initiation of cracks and their spreading during the Gleeble testing.
The liquid appeared as a result of constitutional liquation, mainly of the γ' precipitates.