Removal of casting porosity in superalloy IN738 using hydrostatic pressure sintering

Effect of Hot Isostatic Pressing on the Microstructure of K417G Cast Turbine Discs

“…The diameter distributes in the range from 0 to 100 µm in the as-cast specimen, while it is in the range from 0 to 50 µm after the HIP treatment. The reference [9] indicates that the driving force of healing the porosities is the excessive vacancy concentration caused by surface tension on the porosity surface [10], that is, the vacancies ceaselessly diffuse away from the porosity surface and eventually result in the reduced size or even complete disappearance of the porosity. The healing or disappearance of porosities contributes to the improvement of the mechanical properties, such as creep resistance [11], and high-cycle fatigue strength [10].…”

“…The reference [9] indicates that the driving force of healing the porosities is the excessive vacancy concentration caused by surface tension on the porosity surface [10], that is, the vacancies ceaselessly diffuse away from the porosity surface and eventually result in the reduced size or even complete disappearance of the porosity. The healing or disappearance of porosities contributes to the improvement of the mechanical properties, such as creep resistance [11], and high-cycle fatigue strength [10]. The carbides in the as-cast specimen are blocky-shaped or long strip-like, which are unevenly distributed at the grain boundaries.…”

The Influence of Materials Processing on the High Temperature Low Cycle Fatigue Properties of the Cast Alloy IN-738LC

“…In both cases, the improvement in the properties was ascribed to the elimination of casting porosity. The practical application of HIPping, hOwever, does require an upper limit to be imposed upon the casting pore size because the largest pOres, which are also those that most affect fatigue behaviour, sinter most slowly (4) the load amplitude at half-life was taken to be the cyclic stress response to that imposed strain amplitude and the complete separation of the specimen was taken to be the fatigue life.…”