Chemical and morphological changes at Al{sub 2}O{sub 3}/NiAl interfaces and their relationship to scale adhesion

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Ni-(40,50)at%Al alloys with different C and S contents were oxidized at 1000-1150 C for various times in oxygen. Auger electron microscopy was used to study the interface chemistry after scale spallation in ultra high vacuum. The interfacial failure stresses were determined with a tensile pull tester and they were related to the interfacial pore density. Results show that sulfur did not segregate to the Al{sub 2}O{sub 3}/Ni50Al interface even after extended oxidation times. Small amounts, however, segregated to the Al{sub 2}O{sub 3}/Ni40Al interface. The difference in behavior may be related to the surface energy difference between Ni50Al and Ni40Al. On ... continued below

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11 pages

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Hou, Peggy Y. March 15, 2003.

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Ni-(40,50)at%Al alloys with different C and S contents were oxidized at 1000-1150 C for various times in oxygen. Auger electron microscopy was used to study the interface chemistry after scale spallation in ultra high vacuum. The interfacial failure stresses were determined with a tensile pull tester and they were related to the interfacial pore density. Results show that sulfur did not segregate to the Al{sub 2}O{sub 3}/Ni50Al interface even after extended oxidation times. Small amounts, however, segregated to the Al{sub 2}O{sub 3}/Ni40Al interface. The difference in behavior may be related to the surface energy difference between Ni50Al and Ni40Al. On the interfacial void faces of Ni50Al, C first segregated, then it was replaced by S after longer oxidation times; the amount of segregants varied with different crystallographic orientation of the void face. On Ni40Al, S segregated much earlier on the void faces due to a faster diffusion rate in the Ni-rich NiAl. The apparent S diffusivity in Ni50Al and Ni40Al at 1000 C was determined to be 10{sup -9} and 6 x 10{sup -9} cm{sup 2}/s respectively. Excess sulfur in Ni40Al greatly increased the interfacial pore density. Preliminary results on interfacial failure stress showed that it decreased with increasing pore density, regardless of whether S was present at the interface, indicating that the major detrimental effect of S on scale adhesion may be to enhance interfacial pore formation.

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11 pages

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OSTI as DE00823940

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  • ECS Spring meeting, Symposium High Temperature Corrosion and Materials Chemistry, IV, Paris (FR), 04/27/2003--05/02/2003

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  • Report No.: LBNL--52664
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 823940
  • Archival Resource Key: ark:/67531/metadc782815

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • March 15, 2003

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  • Dec. 3, 2015, 9:30 a.m.

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  • Sept. 21, 2017, 6:02 p.m.

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Hou, Peggy Y. Chemical and morphological changes at Al{sub 2}O{sub 3}/NiAl interfaces and their relationship to scale adhesion, article, March 15, 2003; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc782815/: accessed December 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.