| In the paper, by means of the treatment of the hot isostatic pressing (HIP) and heat treatment at the different temperatures, the creep properties measuring and microstructure observation, an investigation has been made into the influence of heat treatment regimes on the microstructure and creep properties of FGH95 nickel-based superalloy, and discussing the deformation and fracture mechanisms of the alloy during creep. And by means of XRD diffraction analysis and electrolytic extraction, the composing of the phases and granularity distribution ofγ' phase in FGH95 nickel base superalloy are investigated.Results show that the quantities and size of the primary coarser y'phase in the PPB regions of FGH95 superalloy diminishs gradually as the HIP temperature raises. After treated by HIP at different temperatures, the alloy is solution treated at 1155℃, and cooled in the molten salt at lower temperature and aging treated, there are only a few coarser y' phase precipitated in the alloy, thereinto, the particle-like carbide phase are precipitated along the boundaries to improve the cohesive strength between the grains, which is the main reason of the alloy possessing a better creep resistance and longer creep lifetimes because the particle-like carbides may restrain the boundaries slipping due to the pinning effect of them. In the ranges of the applied temperatures and stresses, the activation energies and stress exponents of the "1120℃HIP/1155℃solution" and "1180℃HIP/1140 "C solution" heat treated alloys during steady state creep are calculated to be Q1= 534.7kJ/mol and Q2=592.6 kJ/mol. As the aging times of the alloy at 450℃and 550℃prolong, the parameters ofγ',γphases in the alloy increase slightly, and the misfits of theγ', y phases decreaase slightly, which decreases slightly the creep lifetimes of the alloy. The deformation feature of the alloy during creep is that the twinning and dislocation bypassing over by Orowan mechanim and shearing into theγ' phase, thereinto, the<110> super-dislocation which shears into theγ' phase may be decomposed to form the configuration of (1/3)<112> super-Shockley partial dislocation and stacking fault, which can hinder the cross-slipping of dislocations to improve the creep resistance. During creep of the alloy, the traces of the single orientations slipping appear on the surface of the sample, and the slipping traces with different orientations are activated within the different grains, thereinto, the directions of slipping traces may be changed by the boundaries which may hinder the slipping of dislocations, which is thought to be one of the main reasons of the alloy possessing a better creep resistance. The deformation dislocations during creep are piled up in the regions near the boundary, which may bring.out the stress concentration to promote the initiation and propagation of the micro-cracks along the boundaries, this is thought to be the fracture mechanism of the alloy in the latter stage of creep. And the fracture features of the alloy during creep are the occurrence of the intergranular and transgranular fracture, thereinto, the nonsmooth surface appeared in the fracture is attributed to the finer carbides precipitated along the boundaries to restrain the slipping of them.
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