Effect of solution parameters on microstructures and mechanical properties of K439B nickel-based superalloy

Abstract

The effect of different solution temperatures (1140, 1160 ℃ and 1180 ℃) and cooling conditions (AC, FC-900 ℃+AC, FC) on the microstructures and mechanical properties of K439B alloy were investigated using metallographic microscopy and field emission scanning electron microscopy (FE-SEM). The results show that the optical microstructures and morphology of γ' precipitates are similar and the width of grain boundary slightly increases after increasing the solution temperature. When cooled with AC, γ' precipitates are uniformly distributed and the average size is 50.7 nm; when cooled with FC-900 ℃+AC, the larger γ' precipitates of 250-510 nm are precipitated at the interdendritic area region and near the grain boundary, exhibiting a bimodal γ' microstructure; when cooled with FC, the volume fraction of larger γ' precipitates increases and the content of granular M23C6 carbides at grain boundary improves. The stress rupture life of K439B alloy at 815 ℃/379 MPa is enhanced after reducing the cooling rate, while different solution parameters have little effect on the room-temperature tensile property.

Keywords

• nickel-based superalloy
• k439b
• solution parameter
• microstructure
• mechanical property