Diffusion barrier layer

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent single phase metallic solid solution diffusion barrier layer including sufficient Ru to elevate the melting temperature of the layer above the melting temperature of the substrate and at least one element selected from the group consisting of Ni, Co, and Cr and combinations thereof;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl.

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent single phase intermetallic alloy diffusion barrier layer having an L12 lattice structure and having a composition, in atomic percent, of from about 12% to about 21% Al and at least one element selected from the group consisting of Ta, W and B so that the total amount of Al and elements from the group consisting of Ta and W and combinations thereof totals about 23-27%, optionally B from about 10-500 ppm, and the balance Ni and incidental impurities;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl.

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent single phase intermetallic alloy diffusion barrier layer of the form M3X where M is an element selected from the group consisting of Ni, Co and Pt and X is at least two elements selected from the group consisting of Ta, Nb, Cr and Al, at least one of the two X elements selected from the group consisting of Ta and Nb and having a composition, in atomic percent, of from about 22% to about 25% and at least one of the two X elements selected from the group consisting of Al and Cr and having a composition of from about 1% to about 5% so that the total amount of Ta+Nb+Al+Cr is from about 23-30%, and the balance M and incidental impurities;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl.

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent single phase intermetallic alloy diffusion barrier layer of the form M2AlX where M is an element selected from the group consisting of Ni and Co and optionally in atomic percent up to a maximum of 5% Cr, so that the total amount of Ni+Co+Cr is about 50% and X is at least one element selected from the group consisting of Ta, Hf and Nb, and incidental impurities;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl.

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent single phase intermetallic alloy diffusion barrier layer having a B2 lattice structure of the form RuX where X is an element selected from the group consisting of Al, Zr and Hf, and incidental impurities;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl.

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent, as-deposited, single phase, intermetallic alloy diffusion barrier layer having a capability of transforming, as a result of diffusion, into two phases, the layer further characterized by a refractory composition with a melting temperature at least as high as that of the substrate;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl, with reduced interdiffusion between the coating and the substrate through the intermetallic alloy.

An airfoil for use in a gas turbine engine, comprising:

• a nickel-based superalloy substrate;
• a tightly adherent as-deposited intermetallic alloy diffusion barrier layer, the layer further characterized by a refractory composition with a melting temperature at least as high as that of the substrate, the alloy being a Ni5(Al,Y) phase and having a composition, in atomic percent, of about 13% Al, about 17% Y and the balance Ni and incidental impurities;
• and
• a coating having a high concentration of Al wherein the concentration of Al in the coating is greater than the concentration of Al in the superalloy substrate, the coating selected from the group consisting of MCrAlY(X), PtAl and NiAl, with reduced interdiffusion between the coating and the substrate through the intermetallic alloy.