Change of Grain Orientation and Effect of Grain Size on It in Creep Deformed Hastelloy X

Abstract

In this study, EBSP (electron backscatter diffraction pattern) method was applied to evaluate changes in crystal orientation during creep deformation. The tested material was a solid solution strengthened Ni base superalloy, Hastelloy X, and creep tests were conducted at 1123K under the stress of 49 MPa. It was confirmed that a distribution of crystal orientation changed with increasing a creep deformation. In the ruptured specimen, grains having the crystal orientation of ‹101› in the direction of the stress axis had decreased, while grains having the crystal orientation of ‹001› or ‹111› in the direction of the stress axis had increased. A new parameter that indicates the distribution of the crystal orientation was proposed. The change of crystal orientation distribution with creep damage and the effect of grain size on it were described clearly and quantitatively by this parameter. This parameter was thought to be an effective parameter for the evaluation of local damages on high temperature components such as turbine blades and pressure tubes.