Creep properties and life model of anisotropic Ni-based single crystal superalloys over a wide temperature range

Abstract

The current study is centered on the creep anisotropy of a nickel-based single crystal superalloy across a wide temperature range and with orientations of [001], [011], and [111]. Based on continuous damage mechanics, a new damage evolution law of anisotropic nickel-based single crystal materials is proposed. Based on the crystal slip theory, creep resistance is innovatively introduced and the modified creep constitutive model of nickel-based single crystal superalloy is presented. Meanwhile, in order to facilitate engineering application, an anisotropic creep life prediction model for single crystal superalloy was established based on continuous damage mechanics and crystal plasticity theory. By establishing the relationship between deformation gradient and shear strain rate on the sliding system, the combination of macroscopic creep deformation and microscopic crystal slip is realized. According to the working state of single crystal blade, a wide range of temperature creep tests at different load points were carried out. The creep parameters A (temperature dependent parameter), n (apparent stress index), Q (apparent activation energy) and τres(α) (creep resistance) are obtained by fitting on the basis of the slip theory of finite deformation crystals and test results. The creep behavior of anisotropic Ni-based single crystal superalloy is simulated by using a modified life prediction model considering creep resistance in finite element framework, and the numerical results are compared with the experimental results. The results show that the constitutive formula proposed in this paper can be used to simulate the mechanical properties of Ni-based single crystal superalloys at different orientations in the wide temperature range, and the constitutive formula also can accurately predict the creep life and creep deformation with different temperatures and directions. The life prediction error is in the range of 1.2 times.