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

Abstract

The microstructural changes of the aluminized alloy 625 during cyclic oxidation in air + 6% H 2O 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 themore » potential to predict microstructural changes of aluminized nickel base alloys thus reducing cost and time consuming experimental efforts.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1]
  1. Forschungszentrum Julich (Germany)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE; China Scholarship Council
OSTI Identifier:
1558506
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Surface and Coatings Technology
Additional Journal Information:
Journal Volume: 354; Journal Issue: C; Journal ID: ISSN 0257-8972
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Aluminide coating; Alloy 625; Microstructure; Interdiffusion; Simulation; Thermodynamic-kinetic data

Citation Formats

Leng, Wencai, Pillai, Rishi R., Huczkowski, P., Naumenko, D., and Quadakkers, Willem Joseph. Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C. United States: N. p., 2018. Web. doi:10.1016/j.surfcoat.2018.09.043.
Leng, Wencai, Pillai, Rishi R., Huczkowski, P., Naumenko, D., & Quadakkers, Willem Joseph. Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C. United States. doi:10.1016/j.surfcoat.2018.09.043.
Leng, Wencai, Pillai, Rishi R., Huczkowski, P., Naumenko, D., and Quadakkers, Willem Joseph. Tue . "Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C". United States. doi:10.1016/j.surfcoat.2018.09.043. https://www.osti.gov/servlets/purl/1558506.
@article{osti_1558506,
title = {Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C},
author = {Leng, Wencai and Pillai, Rishi R. and Huczkowski, P. and Naumenko, D. and Quadakkers, Willem Joseph},
abstractNote = {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.},
doi = {10.1016/j.surfcoat.2018.09.043},
journal = {Surface and Coatings Technology},
number = C,
volume = 354,
place = {United States},
year = {2018},
month = {9}
}

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