Effect of solution treatment on microstructure and tensile properties of GH3230 superalloy

Abstract

The present work investigates the effect of solution treatment at 1140–1250 ℃ on the microstructure evolution and tensile properties of GH3230 superalloy. The results show that grain growth kinetics were synergistically controlled by the carbide pinning effect and solute drag effect. With the increase in temperature/time, the grains showed a parabolic coarsening trend, and the volume fraction of M₆C carbides decreased significantly leading to the weakening of the pinning effect. The quantitative analysis of the Gibbs interfacial excess values after 1200 ℃ solution treatment showed that the significant segregation of W (+15.34 atom/nm²) and Mo (+3.74 atom/nm²) elements at grain boundaries produces a strong solute drag effect. Accordingly, a kinetic model for the coupling of carbide pinning and W, Mo solute drag was developed, and the predicted grain sizes are in good agreement with the experimental values. The tensile properties results show that with the temperature increase from 1140 ℃ to 1250 ℃, the yield strength decreases from 370 MPa to 348 MPa, while the elongation remains stable (about 44 %). Quantitative analysis of the strengthening mechanism confirms that the increase in solution temperature enhances the solid solution strengthening, but weakens the grain boundary strengthening and carbide particle strengthening.