Prediction of In-Service Stress States of Single Crystal Superalloys Based on Mathematical Analyses of γ/γ' Microstructural Morphologies

摘要

It has been well recognized that the morphology of γ/γ' microstructures of single crystal superalloys may be changed during their in-service period, associated with a reasonable manner following material science rules. This implied, it may be possible for us to use this phenomenon for failure analysis, through analysis of the morphological change in γ/γ' microstructure. In order to explore this possibility, the change of γ/γ' microstructure of a single crystal Ni-base superalloy, CMSX-4, was studied in this work, when the alloy was subjected to several modes of external lodgings. The experimental variables in the loading mode in this work were: level of stress in tension and compression, loading temperature, loading rate, monotonic/cyclic loadings and multi-axial level in stress states. The experimental results clearly demonstrated that the γ/γ' microstructures were changed, associated with a very sensitive manner depending on the above loading modes. A new image analysis method has developed to quantitatively analyze the morphological changes. These experimental results are summarized into a two-dimensional map so that it can be easily applied for failure analysis and other engineering applications.