MEANS2: Knowledge Oriented Materials Engineering of Layered Thermal Barrier Systems (NOMELT)

Abstract

The hot-section turbine components of aircraft engines can depend on a thermally-grown, thin alpha-alumina layer for corrosion and oxidation protection. This thermal processing can leave a continuous layer of gamma-Ni (Al) adjacent to the oxide. Since the oxide must remain adherent upon thermal cycling, it is essential to quantify the factors affect adhesion at the gamma-Ni (Al) /alpha-alumina interface. We have previously shown that this adhesion is sensitive to the stoichiometry or atomic termination of the interface and that this stoichiometry depends on the Al activity in the Ni (Al). It was required then to determine the temperature and Al concentration dependence of the Al activity in Ni(Al). This was done via first principles, density functional theory. Results indicate that the Al activity can vary by 14 orders of magnitude over a temperature range 400 K < T < l700 K. We find the interface stoichiometry to be Al-rich, but located near the stoichiometric phase on the phase diagram. Software we developed for activity computations is available on request.

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Document Details

Document Type
Technical Report
Publication Date
Jun 04, 2007
Accession Number
ADA473891

Entities

People

  • John R. Smith

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Adhesion
  • Air Force
  • Aircraft Engines
  • Contracts
  • Density Functional Theory
  • Diagrams
  • Engineering
  • Engines
  • High Temperature
  • Materials
  • Materials Engineering
  • Oxides
  • Phase
  • Phase Diagrams
  • Stoichiometry
  • Turbine Components

Fields of Study

  • Materials science

Readers

  • Powder metallurgy of Titanium alloys.
  • Surface Engineering/Surface Coating Technology.
  • Thin Film Deposition Science.