Field Evaluation of Gas Turbine Protective Coatings

[+] Author and Article Information
A. McMinn

Southwest Research Institute, San Antonio, TX 78284

R. Viswanathan, C. L. Knauf

Electric Power Research Institute, Palo Alto, CA 94303

J. Eng. Gas Turbines Power 110(1), 142-149 (Jan 01, 1988) (8 pages) doi:10.1115/1.3240077 History: Received January 14, 1986; Online October 15, 2009


The hot corrosion resistance of several protective coatings that had been applied to MAR-M-509 nozzle guide vanes and exposed in a utility gas turbine has been evaluated. The coatings included basic aluminide, rhodium-aluminide, platinum-rhodium-aluminide, and palladium-aluminide diffusion coatings, and cobalt-chromium-aluminum-yttrium (CoCrAlY) and ceramic overlay coatings. A combination of metallographic examination of vane cross sections and energy dispersive X-ray analysis (EDS) was employed in the evaluation. The results showed that none of the coatings was totally resistant to corrosive attack. The CoCrAlY and platinum-rhodium-aluminide coatings exhibited the greatest resistance to hot corrosion. The CoCrAlY coated vanes were, however, susceptible to thermal fatigue cracking. Except for the poor performance of the palladium-aluminide coating, the precious metal aluminides offered the best protection against corrosion. Hot isostatically pressing coatings was not found to be beneficial, and in one case appeared detrimental.

Copyright © 1988 by ASME
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