Abstract

This paper studied high temperature degradation behavior of gas turbine blades consisting of CoNiCrAlY coatings and Rene 80 substrates using a small punch (SP) testing technique at 295–1223 K and scanning Auger microprobe (SAM). In SP tests, coating cracks continuously propagated along the radial direction at 295 K and many cracks discretely were formed along more random directions at higher temperatures. The ductility of the coating at 295 K was reduced and the ductile-brittle transition temperature was increased during long time exposure of gas turbine blades to high temperature oxidation environments. SAM analyses on cross sections and fracture surfaces of the coatings indicated that oxidation and S segregation near the coating surface are profoundly induced in-service. The relationship between the mechanical properties and microstructural/chemical evolution near the coating surface is presented which serves as a data base for determining the remaining life of gas turbine blades.

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