Nickel-base superalloy and article with high temperature strength and improved stability
AssigneeGeneral Electric Company
InventorsWilliam S. Walston, Earl W. Ross, Kevin S. O'Hara, Tresa M. Pollock
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Abstract
A nickel base superalloy capable of being made into a single crystal article is provided with high temperature strength and improved stability by limiting the Presence of an undesirable SRZ constituent. Significant to the control of formation of such undesirable constituents is the control of the amount of Re in the alloy in combination with elements such as Al, Cr, Ta, Mo, Co and W. A solution heat treatment is provided for additional control.
Claims11
A nickel base superalloy of improved high temperature stability, characterized by a unique combination of Re content in the presence of Al, Cr, Ta and Mo in defined ranges to provide desired mechanical properties for high temperature use while avoiding the detrimental formation of a Secondary Reaction Zone (SRZ) in the microstructure of the alloy after exposure to the combination of temperatures of at least about 2000.degree. F. and operational load, consisting essentially of, in weight percent, the combination of about 5.1-5.6% Re, about 5 to less than 6.25% Al, greater than 4.25 to about 6% Cr, about 7 to less than 9.25% Ta, and about 0.5-2% Mo, along with about 10-15% Co, about 5-6.5% W, about 0.1-0.5% Hf, about 0.02-0.07% C, about 0.003-0.01% B, about 0-0.03% Y, about 0-6% Ru, about 0-1% Cb, balance Ni and incidental impurities.
A single crystal article having improved high temperature strength and stability and including a surface coated with a metal selected from the group consisting of Al, Pt and their mixtures and alloys, and characterized further by no more than about 2 Percent SRZ Phase linearly beneath and adjacent the coating after exposure to at least about 1800.degree. F. for about 400 hours.
A method for heat treating a nickel base superalloy of improved high temperature stability, characterized by a unique combination of Re content in the presence of Al, Cr. Ta and Mo in the defined ranges to provide desired mechanical properties for high temperature use while avoiding the detrimental formation of a Secondary Reaction Zone (SRZ) in the microstructure of the alloy after exposure to the combination of temperatures of at least about 2000.degree. F. and operational load, the alloy consisting essentially of in weight percent, the combination of about 5.1-5.6% Re, about 5 to less than 6.25% Al, greater than 4.25 to about 6% Cr, about 7 to less than 9.25% Ta, and about 0.5-2% Mo, along with about 10-15% Co, about 5-6.5% W, about 0.1-0.5% Hf about 0.02-0.07% C, about 0.003-0.01% B, about 0-0.03% Y, about 0-6% Ru, about 0-1% Cb, balance Ni and incidental impurities, comprising the step of solution treating the alloy by heating in the range of about 2390.degree. F. to below incipient melting of the alloy and holding at the temperature for a time sufficient to result in a Segregation Parameter (S.P.) of no more than about 15 by minimizing the compositional gradient of Re between dendritic and interdendritic areas.
Dependencies are inferred from the claim text.