Microstructure and enduring fracture features of FGH95 Ni‐base superalloy

Abstract By means of the enduring properties measurement and microstructure observation, an investigation has been made into the influence of the microstructure on the enduring properties of FGH95 superalloy. The results show that, after solution treated at 1150 °C, the coarser γ′ phase is distributed within the wider boundary regions in which exists the poor‐zone of the fine γ′ phase. After solution temperature raised to 1160 °C, the coarser γ′ phase in the alloy is fully dissolved, and fine γ′ phase with high volume fraction is dispersedly distributed within the grains, and the (Nb, Ti)C carbides are precipitated along the boundaries. After solution treated at 1165 °C, the grain sizes obviously grow up, and the films of the carbide are continuously precipitated along the boundaries. The deformed mechanisms of the alloy (solution treated at 1160 °C) during enduring properties measuring are that some dislocations are both over the γ′ phase by Orowan mechanism and shearing into the γ′ phase. The particle‐like carbides which are precipitated along the boundaries can effectively hinder the dislocation motion, which results in the alloy possessing a better enduring properties under the applies stress of 1034 MPa at 650 °C. In the later stage of enduring properties measuring, the single orientation slipping of dislocations is activated in the alloy, some of the dislocations are piled up in the regions near the boundaries as creep goes on, this may bring out the stress concentration to promote the initiation and propagation of micro‐cracks, which is thought to be the fracture mechanism of the alloy during enduring properties measuring.