A NEW ANALYTICAL METHOD OF γ/γ' MORPHOLOGY IN SINGLE CRYSTAL Ni-BASE SUPERALLOYS: FOR NEW ORIENTATION OF DAMAGE AND REMAINING LIFE ASSESSMENT

摘要

This paper focused on γ/γ' morphological changes in a single crystal Ni-base superalloy, CMSX-4, induced by monotonic plastic straining and cyclic fatigue loadings. It was shown by a series of experiments that an application of the monotonic straining at R.T. and the subsequent heat treatment at high temperature resulted in a directional coarsening of γ/γ' microstructure, depending on the sign, magnitude and history of strain. A critical strain was found to be needed to build up the microstructural changes. Not only monotonic but also cyclic loadings could induce similar changes in the γ/γ' microstructures. These changes have been summarized in tables. In order to quantify the γ/γ' morphologies, a new method, named by Cluster-Method, was proposed, where the degree of the coarsening and the directional coarsening can be displayed on an original 2-dimensional diagram. This method successfully evaluated various types of γ/γ' microstructures. Furthermore, this method may provide us new potentials for both the stress field detection and the remaining life analysis of superalloy components in service.