Quantitative analysis of diffusion processes associated with γ’-depletion in Ni-base superalloys
| Autor: | Matthias Senge, Adrian Rienäcker, John Steger, Angelika Brückner-Foit |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Arrhenius equation Materials science Diffusion Tantalum chemistry.chemical_element Thermodynamics 02 engineering and technology Rate equation 021001 nanoscience & nanotechnology 01 natural sciences Power law Superalloy symbols.namesake chemistry 0103 physical sciences symbols General Materials Science 0210 nano-technology Single crystal Chemical composition |
| Zdroj: | Materialia. 3:41-49 |
| ISSN: | 2589-1529 |
| DOI: | 10.1016/j.mtla.2018.08.037 |
| Popis: | High resolution quantitative EDX-analysis is used to gain new insights into the diffusive processes resulting in γ’-depletion after high temperature exposure of superalloys. The materials studied are two commercial single crystal alloys (PWA 1484 and PWA 1480) containing substantial amounts of tantalum Ta. It was found that chemical composition of the γ’-depleted zone reaches a stationary value after moderate exposure times, and that this composition resembles strongly the original composition of the matrix material. The transition between bulk material and γ’-depleted zone is defined by a diffusive region with concentrations given by a one-dimensional solution of Fick's law. The parameters of this functional relation were determined by solving the corresponding inverse problem. The width of the γ’-depleted zone can be uniquely defined from the EDX-database. It was shown that a combination of an Arrhenius term and a power law fits well to the dependence of the width of the γ’-depleted zone on time and temperature, and that the diffusion rates are very much reduced compared to the well-known parabolic rate law. This can be explained by the fact that both material loss by oxidation and continuous extension by diffusion contribute to the measured width of the γ’-depleted zone. |
| Databáze: | OpenAIRE |
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