Creep of CMSX-4 superalloy single crystals: effects of rafting at high temperature

Non-Isothermal Creep Behavior of a Second Generation Ni-Based Single Crystal Superalloy: Experimental Characterization and Modeling

“…During isothermal creep at high temperature/low stress, it is generally accepted that the primary creep stage ends when the rafting process is completed and dislocations networks at the γ/γ' interfaces are well established [5,22,23,31]. However, in the case of non-isothermal conditions, a primary creep stage is systematically observed at the beginning of post-OEI creep whether the microstructure is built with γ' cubes (t pre = 0) or with γ' rafts with well-developed dislocations networks at the γ/γ' interfaces.…”

“…This produces non-isothermal creep conditions with the load only slightly increasing as the engine speed increases slightly, while the temperature varies due to the OEI simulation. In this context, long exposures of superalloys to extreme temperature are well documented in the literature [5,[13][14][15][16][17]: it provokes the dissolution of the γ' reinforcing phase and induces a severe loss in mechanical properties. In contrast, little is known about the mechanical behavior when the material is exposed to very high temperature transients, particularly when under load.…”

“…Actually, Ni-based single crystal superalloys exhibit superior creep resistance at temperature as high as 1100°C [2] due to their particular microstructure, consisting of 70% in volume of coherently precipitated γ' cubes (L1 2 lattice) separated by thin channels of face centered cubic (fcc) γ matrix [3]. Extensive literature is devoted to the study of their properties, especially on isothermal creep over a wide range of stress and temperature [4][5][6][7][8][9][10][11]. Two temperature/stress domains can be distinguished: (1) at low temperature (T < 950°C) and high stress, no significant evolution of the initial optimal microstructure occurs during the creep experiment, while (2) at higher temperature/lower stress, great modifications of the microstructure are observed during primary creep stage: rafting of the γ' phase perpendicular to the applied stress for negative γ/γ' misfit alloys and development of stable dislocation networks at the γ/γ' interfaces.…”

Shearing of γ′ precipitates by a〈112〉 dislocation ribbons in Ni-base superalloys: A phase field approach

“…Superalloys exhibit three distinct creep regimes [1]; rafting at high temperatures and low stresses where the microstructure evolves in response to the applied stress; tertiary creep at intermediate temperatures and stresses where dislocation activity is confined solely to the γ matrix; and primary creep at low temperatures and high stresses where dislocations propagate through both phases. Primary creep has been the chief focus of this work.…”

Creep and Stress Relaxation Anisotropy of a Single-Crystal Superalloy

“…[14] Several studies have shown that rafting plays a vital role during high temperature creep. [15,16] The orientation of the rafting is dependent on whether the alloy has a positive or negative lattice misfit between the c-and c¢-microconstituents. [17] For alloys with a negative misfit (like MD2 used for this study) compressive loading leads to rafts parallel to the loading direction, P-type.…”