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Title: Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C

Journal Article · · Surface and Coatings Technology
ORCiD logo [1];  [1];  [1];  [1];  [1]
  1. Forschungszentrum Julich (Germany)
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The microstructural changes of the aluminized alloy 625 during cyclic oxidation in air + 6% H2O at 900 °C and 1000 °C were analyzed using optical metallography (OM), scanning electron microscopy (SEM) with energy and wave length dispersive X-ray analysis (EDX/WDX) as well as electron backscatter diffraction (EBSD). An in-house developed thermodynamic-kinetic procedure was employed to predict the microstructural evolution of aluminized alloy 625 during high temperature exposure by considering simultaneously occurring surface oxidation and interdiffusion processes. Because of the lack of mobility data for the relevant alloying elements in the σ-phase, assumptions for the mobilities were made based on the value of the mobilities in α-Cr. Despite these assumptions, the calculated results were found to be in good agreement with experimental observations. The complete depletion of β-NiAl in the coating observed during exposure at 1000 °C was correctly predicted by the model. The model was also able to infer dissolution of the precipitate phases α-Cr and σ in the interdiffusion zone during exposures at 900 °C and 1000 °C. The model was yet unable to predict the formation of the μ-phase in the alloy after 1000 h of exposure at 1000 °C. The developed modelling method offers the potential to predict microstructural changes of aluminized nickel base alloys thus reducing cost and time consuming experimental efforts.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE; China Scholarship Council
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1558506
Journal Information:
Surface and Coatings Technology, Vol. 354, Issue C; ISSN 0257-8972
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 14 works
Citation information provided by
Web of Science

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Cited By (1)

Effect of surface modification on the hot corrosion resistance of Inconel 718 at 700 °C journal May 2019

Figures / Tables (21)

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Related Subjects

36 MATERIALS SCIENCE
Aluminide coating
Alloy 625
Microstructure
Interdiffusion
Simulation
Thermodynamic-kinetic data