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Title: High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy

Abstract

An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion inmore » Cr, leading to accelerated internal oxidation.« less

Authors:
 [1]
  1. King Fahd Univ. of Petroleum and Minerals, Shahran (Saudi Arabia)
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
245144
Resource Type:
Journal Article
Journal Name:
Oxidation of Metals
Additional Journal Information:
Journal Volume: 45; Journal Issue: 3-4; Other Information: PBD: Apr 1996
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; NICKEL ALLOYS; OXIDATION; CHROMIUM ALLOYS; TUNGSTEN ALLOYS; MANGANESE ALLOYS; SILICON ALLOYS; LANTHANUM ALLOYS; REACTION KINETICS; TEMPERATURE RANGE 1000-4000 K; HOT WORKING

Citation Formats

Tawancy, H.M. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy. United States: N. p., 1996. Web. doi:10.1007/BF01046988.
Tawancy, H.M. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy. United States. doi:10.1007/BF01046988.
Tawancy, H.M. Mon . "High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy". United States. doi:10.1007/BF01046988.
@article{osti_245144,
title = {High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy},
author = {Tawancy, H.M.},
abstractNote = {An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion in Cr, leading to accelerated internal oxidation.},
doi = {10.1007/BF01046988},
journal = {Oxidation of Metals},
number = 3-4,
volume = 45,
place = {United States},
year = {1996},
month = {4}
}