Changes in Hot Corrosion Due to Composition Modifications in CoCrAlY Coatings

摘要

Burner rig and engine test which describe differences in the hot corrosion resistance of sputter deposited CoCrAlY coatings with varied compositions and coating designs are presented. The objective of this study is to determine the potential of modifying CoCrAlY coatings to provide significantly longer lifetimes for gas turbine engine components operating on alternative fuels or in marine environments. Modified coatings that contain a high chromium surface composition, a gradient in chromium and aluminum composition, and a platinum underlayer or graded platinum addition have been examined. Twenty-nine different samples have been burner rig tested for 500 h at 677 exp 0 C (1250 exp 0 F) in an aggressive, marine-type hot corrosion environment and then ranked according to their performance. Also, four chromium rich coatings have been tested for 20 h in a Rolls Royce Olympus C turbine engine operated at 1067 exp 0 C on residual fuels. Results from these tests indicate that a high chromium surface composition and composition gradients through the coating thickness can improve the hot corrosion resistance of coatings in aggressive, low temperature environments.