Microstructure And Creep Behaviors Of GH4169G Superalloy

In the paper, by means of heat treatment at different conditions, creep properties measurement and microstructure observation, the influence of heat treatment regimes on the creep properties of the GH4169G alloy is investigated. In the further, the creep activation energy and stress exponent of the alloy are calculated according to the data of the creep curves, and the deformation and fracture mechanisms of the alloy during creep are discussed.Results show that, the grain size of ITF-GH4169G alloy is about 15~20μm, and the microstructure of the alloy consists of theγ,γ′,γ″,δphases and carbides. The precipitated phase in the alloy treated by different regimes displays the various configuration. The particle-likeδphase is precipitated along the boundaries after direct aged (DA), and the needle-likeδphase is precipitated along the boundaries after standard heat treatment (STD). Thereinto, the elements Cr and Fe is thought to be the main reason of theδphase transformed into the needle-like configuration. Compared to other treatment technologies, GH4169G alloy treated by direct aged displays the better creep resistance. And the creep lifetime of the alloy at 660℃\650MPa is measured to be 295, in the ranges of the applied temperatures and stresses, the activation energy of DA-GH4169G alloy during steady state creep is calculated to be 532.7kJ/mol. The deformation mechanisms of GH4169G alloy during creep is the dislocations slipping and twinning, and the twinning plane activated in the alloy during creep is determined as {111} plane. And it is thought that the traces phosphorus and boron may promote the particle-like carbides precipitated along the boundaries to restrain the boundaries slipping, which is thought to be the main reason of alloy displaying the better creep resistance.During creep of the alloy, the slipping traces with single oriented feature appear in the surface of the sample. As the creep goes on, the direction of the slipping traces is changed or the slipping step is kept in the original trace when the activated another slipping trace or twinning shears through the trace. During the later stage of creep, the cracks are easily initiated along the boundaries vertical to the stress axis, as the creep goes on, the cracks are propagated along the boundaries up to occurring creep fracture. Compared to GH4169 alloy, the creep fracture of GH4169G alloy displays the non-smooth surface, thereinto, the adding trace phosphorus and boron may improve the adhesive strength of the boundaries and restrain the boundaries slipping to enhance the creep resistance of the alloy, which is the main reason of the creep fracture displaying the non-smooth surface.