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AssigneeUnited Technologies Corporation
InventorsRobert J. Henricks, John J. Marcin, Jacqueline B. Wahl
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A coated nickel base superalloy single crystal turbine airfoil blade (1), which is subject to gas turbine engine operation, can crack during refurbishment by a stress corrosion mechanism when exposed to certain corrosive media. The rapid thermal cycling that occurs during typical gas turbine engine operation results in high, non-uniform stresses across the airfoil, producing large localized residual strains in the article at ambient temperatures. Exposure to a corrosive environment, such as during coating removal or agressive cleaning, can produce chordwise cracks in a large number of the airfoils exposed. Such cracking is avoided by subjecting the articles to a preliminary stress relieving heat treatment which reduces the residual strains to a level below which cracking will not occur, prior to exposure to the corrosive media.
A method for preventing the cracking, upon exposure to a corrosive media, of a single crystal nickel base superalloy article which has accumulated residual strains, said method characterized by prior to said exposure subjecting said article to a stress relieving heat treatment, such that the residual strains are reduced to a level below which cracking will not occur.
A method for preventing the cracking, upon exposure to a corrosive media, of a single crystal nickel base superalloy airfoil article which has accumulated residual strains through cyclic use in a gas turbine engine, said method characterized by prior to said exposure subjecting said article to a stress relieving heat treatment, such that the residual strains are reduced to a level below which cracking will not occur.
Dependencies are inferred from the claim text.