Effects of solution temperatures on enduring fracture mechanism of FGH95 nickel-base superalloy

By means of the enduring properties measurement and microstructure observation, the influence of the microstructure on the enduring properties and fracture mechanism for FGH95 nickel-base superalloy was investigated. The results show that after solution treated at 1150°C, the thicker γ' phase is distributed discontinuously in the wider boundary regions in which exists the poor-zone of the finer γ' phase. When the solution temperature rises to 1160°C, the thicker γ' phase in the alloy is fully dissolved, and the fine γ' phase with high volume fraction is dispersively distributed within the grains, and thereinto the particles of (Nb, Ti)C carbide phase are discontinuously precipitated along the boundaries. After solution treated at 1165°C, the grain sizes are obviously grown up, and the films of the carbide is continuously precipitated along the boundary. The particle carbides which are discontinuously precipitated along the boundary can effectively pin the grain boundaries and restrain boundaries sliding, resulting in the alloy possessing better enduring properties under the applied stress of 1034 MPa at 650°C. In the later stage of creep, the deformed characteristic of the alloy is single and double orientation slipping, and the slipping trace on the sample surface increases to bring out the stress concentration as the creep goes on, which results in the initiating and propagating of the micro-cracks along the boundaries up to rupture. Copyright © 2012, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.