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Title: Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C

An accurate procedure for predicting oxidation-induced damage and lifetime limits is crucial for the reliable operation of high-temperature metallic components in practical applications. In order to develop a predictive oxidation lifetime model for Ni–Cr alloys, specimens of wrought NiCrW alloy 230 with different thicknesses were cyclically oxidized in air at 950–1050°C for up to 3000 h. After prolonged exposure, two types of carbides as well as a Cr-rich nitride (π-phase) precipitated in the γ-Ni matrix. In the case of oxidation-induced loss of Cr from the alloy resulted in the formation of subscale zones, which were free of the Cr-rich carbide and nitride but also of the Ni-W rich M 6C. The width of the M 6C-free zone was smaller than that free of the Cr-rich precipitates. Thermodynamic and diffusion calculations of the observed time- and temperature-dependent Cr depletion processes identified that back diffusion of C occurred which resulted in an increased volume fraction of M 23C 6 in the specimen core. Moreover, with increasing time and temperature, the amount of π-phase in the specimen core increased. The subscale depletion of the initially present Cr-nitrides and the formation of Cr-nitrides in the specimen center is believed to be related to amore » mechanism which is qualitatively similar to that described for the Cr carbide enrichment. However, with increasing time and decreasing specimen thickness, N uptake from the atmosphere becomes apparent. As a result, the precipitates present in the specimen center eventually consisted almost exclusively of nitrides.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1]
  1. Julich Research Centre (Germany)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; 03EK3032
Type:
Accepted Manuscript
Journal Name:
Journal of The Minerals, Metals & Materials Society
Additional Journal Information:
Journal Volume: 67; Journal Issue: 11; Journal ID: ISSN 1047-4838
Publisher:
Springer
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; NiCr alloys; oxidation; lifetime model; thermodynamics; kinetics
OSTI Identifier:
1265880

Jalowicka, A., Duan, R., Huczkowski, P., Chyrkin, A., Grüner, D., Pint, B. A., Unocic, K. A., and Quadakkers, W. J.. Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C. United States: N. p., Web. doi:10.1007/s11837-015-1645-8.
Jalowicka, A., Duan, R., Huczkowski, P., Chyrkin, A., Grüner, D., Pint, B. A., Unocic, K. A., & Quadakkers, W. J.. Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C. United States. doi:10.1007/s11837-015-1645-8.
Jalowicka, A., Duan, R., Huczkowski, P., Chyrkin, A., Grüner, D., Pint, B. A., Unocic, K. A., and Quadakkers, W. J.. 2015. "Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C". United States. doi:10.1007/s11837-015-1645-8. https://www.osti.gov/servlets/purl/1265880.
@article{osti_1265880,
title = {Effect of Specimen Thickness on Microstructural Changes During Oxidation of the NiCrW Alloy 230 at 950–1050°C},
author = {Jalowicka, A. and Duan, R. and Huczkowski, P. and Chyrkin, A. and Grüner, D. and Pint, B. A. and Unocic, K. A. and Quadakkers, W. J.},
abstractNote = {An accurate procedure for predicting oxidation-induced damage and lifetime limits is crucial for the reliable operation of high-temperature metallic components in practical applications. In order to develop a predictive oxidation lifetime model for Ni–Cr alloys, specimens of wrought NiCrW alloy 230 with different thicknesses were cyclically oxidized in air at 950–1050°C for up to 3000 h. After prolonged exposure, two types of carbides as well as a Cr-rich nitride (π-phase) precipitated in the γ-Ni matrix. In the case of oxidation-induced loss of Cr from the alloy resulted in the formation of subscale zones, which were free of the Cr-rich carbide and nitride but also of the Ni-W rich M6C. The width of the M6C-free zone was smaller than that free of the Cr-rich precipitates. Thermodynamic and diffusion calculations of the observed time- and temperature-dependent Cr depletion processes identified that back diffusion of C occurred which resulted in an increased volume fraction of M23C6 in the specimen core. Moreover, with increasing time and temperature, the amount of π-phase in the specimen core increased. The subscale depletion of the initially present Cr-nitrides and the formation of Cr-nitrides in the specimen center is believed to be related to a mechanism which is qualitatively similar to that described for the Cr carbide enrichment. However, with increasing time and decreasing specimen thickness, N uptake from the atmosphere becomes apparent. As a result, the precipitates present in the specimen center eventually consisted almost exclusively of nitrides.},
doi = {10.1007/s11837-015-1645-8},
journal = {Journal of The Minerals, Metals & Materials Society},
number = 11,
volume = 67,
place = {United States},
year = {2015},
month = {9}
}