Accession Number : ADA321321

Title :   High Temperature Coatings for Titanium Aluminides.

Descriptive Note : Final rept. 22 Jan 91-13 Dec 94,

Corporate Author : GENERAL ELECTRIC CO CINCINNATI OH AIRCRAFT ENGINE TECHNICAL DIV

Personal Author(s) : Schaeffer, J. C. ; McCarron, R. L.

PDF Url : ADA321321

Report Date : 13 DEC 1995

Pagination or Media Count : 439

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.

Descriptors :   *TITANIUM ALUMINIDE, *PROTECTIVE COATINGS, THERMOMECHANICS, HIGH TEMPERATURE, ALUMINUM COATINGS, TENSILE PROPERTIES, CHEMICAL VAPOR DEPOSITION, METAL MATRIX COMPOSITES, PHASE STUDIES, CRACK PROPAGATION, OXIDATION, ALUMINUM OXIDES, THERMAL FATIGUE, STRESS CORROSION, THERMAL CYCLING TESTS, NICKEL INTERMETALLICS, ALUMINUM INTERMETALLICS, THERMAL STRESSES, FATIGUE TESTS(MECHANICS), TITANIUM ALLOYS, METALLOGRAPHY, CREEP TESTS, CERMETS, DIFFUSION COATING.

Subject Categories : Coatings, Colorants and Finishes
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE