High temperature environmental attack and mechanical degradation of coatings in gas turbine blades

AbstractThis paper describes examination of in-service coating degradation in land based gasturbine blades by means of a small punch testing (SP) method and scanning Auger microprobe(SAM). SP tests on coated specimens with unpolished surfaces indicated large variations ofthe mechanical properties because of the surface roughness and curvature in gas turbine blades, SP tests on polished specimens better characterized the mechanical degradation of bladecoatings. The coated specimens greatly softened and the room temperature ductility of thecoatings and substrates tended to decrease with increasing operation time. The ductile-brittletransition temperature of the coatings shifted to higher temperatures during the bladeoperation. From SAM analyses on fracture surfaces of unused and used blades, it has beenshown that oxidation and sulfidation near the coating surface, which control the fractureproperties, result from high temperature environmental attack.

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UDIMET L-605

Alloy Digest ◽

10.31399/asm.ad.co0109 ◽

2004 ◽

Vol 53 (12) ◽

Keyword(s):

Corrosion Resistance ◽

High Temperature ◽

Physical Properties ◽

Tensile Properties ◽

Gas Turbine ◽

Oxidation Resistance ◽

Turbine Blades ◽

Heat Treating ◽

Gas Turbine Blades ◽

Temperature Performance

Abstract Udimet L-605 is a high-temperature aerospace alloy with excellent strength and oxidation resistance. It is used in applications such as gas turbine blades and combustion area parts. This datasheet provides information on composition, physical properties, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, and joining. Filing Code: CO-109. Producer or source: Special Metals Corporation.

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High Temperature Degradation of Coating and Substrate in Gas Turbine Blade

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award ◽

10.1115/95-gt-358 ◽

1995 ◽

Cited By ~ 1

Author(s):

Y. Sugita ◽

M. Ito ◽

N. Isobe ◽

S. Sakurai ◽

C. R. Gold ◽

...

Keyword(s):

High Temperature ◽

Gas Turbine ◽

Cross Sections ◽

Turbine Blades ◽

Temperature Oxidation ◽

Gas Turbine Blades ◽

Coating Surface ◽

Ductile Brittle Transition Temperature ◽

Scanning Auger Microprobe ◽

Long Time

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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