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Refinement of promising coating compositions for directionally cast eutectics. [Ni--19. 7Nb--6Cr--2. 5Al]

Technical Report ·
OSTI ID:7098896
; ;
The successful application of high creep strength, directionally solidified gamma/gamma'-delta (Ni--19.7Nb--6Cr--2.5Al) eutectic superalloy turbine blades requires the development of suitable coatings for airfoil, root and internal blade surfaces. In order to improve coatings for the gamma/gamma'-delta alloy, the current investigation had the goals of refining promising coating compositions for directionally solidified eutectics, evaluating the effects of coating/substrate interactions on the mechanical properties of the alloy, and evaluating diffusion aluminide coatings for internal surfaces. Burner rig cyclic oxidation, furnace cyclic hot corrosion, ductility, and thermal fatigue tests indicated that NiCrAlY+Pt(63 to 127 micron Ni--18Cr--12Al--0.3Y + 6 micron Pt) and NiCrAlY(63 to 127 micron Ni-18Cr-12Al-0.3Y) coatings are capable of protecting high temperature gas path surfaces of eutectic alloy airfoils. Burner rig (Mach 0.37) testing indicated that the useful coating life of the 127 micron thick coatings exceeded 1000 hours at 1366 K (2000 deg F). Isothermal fatigue and furnance hot corrosion tests indicated that 63 micron NiCrAlY, NiCrAlY + Pt and platinum modified diffusion aluminide (Pt + Al) coating systems are capable of protecting the relatively cooler surfaces of the blade root. Finally, a gas phase coating process was evaluated for diffusion aluminizing internal surfaces and cooling holes of air-cooled gamma/gamma'-delta turbine blades.
Research Organization:
Pratt and Whitney Aircraft, East Hartford, CT (USA)
OSTI ID:
7098896
Report Number(s):
N-77-11154; NASA-CR-135103; PWA-5441
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
COATINGS
ELEMENTS
EUTECTICS
METALS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
PLATINUM
PLATINUM METALS
PROTECTIVE COATINGS
TRANSITION ELEMENTS
TURBINE BLADES
VERY HIGH TEMPERATURE
YTTRIUM ALLOYS