High Temperature Coatings for Titanium Aluminides.

Abstract

The objective of this program was to select and evaluate environmentally protective coatings for alpha-2 and gamma titanium aluminide intermetallics. Many different coatings were selected including TiCrAl's, Alloy 718, APS YSZ, Cermet coatings (MCrAlY + Alumina), Modified Gamma TiAl compositions and MCr's. After a series of cyclic oxidation (760 and 900 deg C), burner rig (760 and 900 deg C) and hot salt stress corrosion cracking tests (400 to 565 deg C) , the cermet coatings were selected for further evaluation. Different cermet coatings containing NiCoCrAlY, CoCrAlY and NiCrAlY were evaluated in similar tests. The best overall performer was the NiCrAlY/Alumina system. An optimized system applied to gamma and alpha-2 was mechanically tested in creep, fatigue and thermomechanical fatigue. Pretreatments included cyclic oxidation, salt and a CVD-W diffusion barrier. The final coating recommended for both gamma and alpha-2 Ti-aluminides is composed of 40-50% by volume alumina with the remainder Ni-20Cr-10Al-0.3Ywt% and is 50 to 75 microns thick.

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Document Details

Document Type
Technical Report
Publication Date
Dec 13, 1995
Accession Number
ADA321321

Entities

People

  • J. C. Schaeffer
  • R. L. Mccarron

Organizations

  • General Electric

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Body Weight
  • Chemical Synthesis
  • Chemistry
  • Coatings
  • Crystal Structure
  • Materials
  • Measurement
  • Mechanical Working
  • Refractory Metals
  • Solid Solutions
  • Stress Corrosion
  • Stress Corrosion Cracking
  • Stress Tests
  • Tensile Properties
  • Tensile Strength
  • Tensile Testing
  • Test And Evaluation

Fields of Study

  • Materials science

Readers

  • Powder metallurgy of Titanium alloys.
  • Surface Engineering/Surface Coating Technology.