Effect of Anisotropy on Creep Strain and Porosity Evolution in Single Crystal Superalloys

A new model for description of creep in porous single crystal superalloys is presented. Key in the formulation is the use of a 3-D inelastic threshold function that accounts for both tension–compression asymmetry and anisotropy. Analysis of the response according to the new model is conducted for uniaxial, equibiaxial, and multiaxial creep loadings for various crystal orientations. Specifically, under multiaxial loadings, the predicted response is investigated for various loadings with principal directions along the \ (100 ;\; 110, \; 111\) directions, having the same mean stress and stress triaxiality, but different ratios between the stress eigenvalues, corresponding to Lode parameter ranging from − 1 < \ (\) < 1. It is revealed a pronounced sensitivity of the creep strain to the applied loading, showing a combined effect of anisotropy and tension–compression asymmetry. Namely, if the principal stresses are applied along the \ (100\) directions or along the 110, \ (1 10\), 001 directions, there is a strong influence of the Lode parameter, the minimum creep strain being obtained for loadings with \ (\) = − 1, and maximum creep strain for loadings with \ (\) = 1. In contrast, when the principal stresses are applied along the 111, \ (1 21 \), \ (1 01\) directions, the influence of the Lode parameter and loading path on the creep strain is markedly reduced.