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A hollow airfoil is fabricated by providing a casting mold assembly including a casting mold, a casting core, and a standoff spacer that prevents the casting core from contacting the casting mold to define a casting space. A first nickel-base superalloy is cast into the casting space and solidified

A hollow airfoil is fabricated by providing a casting mold assembly including a casting mold, a casting core, and a standoff spacer that prevents the casting core from contacting the casting mold to define a casting space. A first nickel-base superalloy is cast into the casting space and solidified to form the hollow airfoil. The presence of a through-hole extending through a wall of the hollow airfoil is identified, and the through-hole is closed by welding using a second nickel-base superalloy, without using any freestanding closure element.

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What is claimed is: 1. A method for fabricating a hollow airfoil, comprising the steps of providing a casting mold assembly comprising a casting mold with an inner wall, a casting core that is received within the inner wall of the casting mold to leave a casting space between an outer wall of the c

What is claimed is: 1. A method for fabricating a hollow airfoil, comprising the steps of providing a casting mold assembly comprising a casting mold with an inner wall, a casting core that is received within the inner wall of the casting mold to leave a casting space between an outer wall of the casting core and the inner wall of the casting mold, wherein the casting space defines a portion of the hollow airfoil, and a standoff spacer that prevents the casting core from contacting the inner wall of the casting mold and thereby maintains the casting space; casting a nickel-base superalloy casting alloy into the casting space and solidifying the cast nickel-base superalloy casting alloy to form the hollow airfoil; separating the hollow airfoil from the casting mold assembly; identifying the presence of a through hole extending through a wall of the hollow airfoil that is present due to the standoff spacer; and, if there is a through hole present, welding the through hole by closing the through hole with a weld alloy different from the casting alloy and selected from the group consisting of (1) an alloy having a nominal composition, in weight percent, 0.01-0.03 percent carbon, 0.1 percent maximum manganese, 0.5-0.6 percent silicon, 0.01 percent maximum phosphorus, 0.004 percent maximum sulfur, 7.4-7.8 percent chromium, 2.9-3.3 percent cobalt, 0.10 percent maximum molybdenum, 3.7-4.0 percent tungsten, 5.3-5.6 percent tantalum, 0.02 percent maximum titanium, 7.6-8.0 percent aluminum, 1.5-1.8 percent rhenium, 0.005 percent maximum selenium, 0.3 percent maximum platinum, 0.01-0.02 percent boron, 0.03 percent maximum zirconium, 0.12-0.18 percent hafnium, 0.1 percent maximum niobium, 0.1 percent maximum vanadium, 0.1 percent maximum copper, 0.2 percent maximum iron, 0.0035 percent maximum magnesium, 0.01 percent maximum oxygen, 0.01 percent maximum nitrogen, balance nickel with other elements 0.5 percent maximum; (2) an alloy having a nominal composition in weight percent of about 7.5 percent cobalt, about 7.0 percent chromium, about 1.5 percent molybdenum, about 5 percent tungsten, about 3 percent rhenium, about 6.5 percent tantalum, about 6.2 percent aluminum, about 0.15 percent hafnium, about 0.05 percent carbon, about 0.004 percent boron, about 0.01 percent yttrium, balance nickel and minor elements; and (3) an alloy having a nominal composition in weight percent of about 12.0 percent cobalt, about 6.8 percent chromium, about 1.5 percent molybdenum, about 4.9 percent tungsten, about 2.8 percent rhenium, about 6.35 percent tantalum, about 6.15 percent aluminum, about 1.5 percent hafnium, about 0.12 percent carbon, about 0.015 percent boron, balance nickel and minor elements. 2. The method of claim 1, wherein the step of providing includes the step of providing the casting mold assembly for an aircraft gas turbine engine hollow airfoil. 3. The method of claim 1, wherein the step of providing includes the step of providing the casting mold assembly for an aircraft gas turbine engine turbine blade hollow airfoil. 4. The method of claim 1, wherein the step of providing the casting mold includes the step of providing the standoff spacer as a protrusion from and integral with the casting core. 5. The method of claim 1, wherein the step of providing the casting mold includes the step of providing the standoff spacer as a chaplet. 6. The method of claim 1, wherein the step of casting the nickel-base superalloy includes the step of casting a casting alloy selected from the group consisting of (1) an alloy having a nominal composition in weight percent of about 7.5 percent cobalt, about 7.0 percent chromium, about 1.5 percent molybdenum, about 5 percent tungsten, about 3 percent rhenium, about 6.5 percent tantalum, about 6.2 percent aluminum, about 0.15 percent hafnium, about 0.05 percent carbon, about 0.004 percent boron, about 0.01 percent yttrium, balance nickel and minor elements; (2) an alloy having a nominal composition in weight percent of about 12.0 percent cobalt, about 6.8 percent chromium, about 1.5 percent molybdenum, about 4.9 percent tungsten, about 2.8 percent rhenium, about 6.35 percent tantalum, about 6.15 percent aluminum, about 1.5 percent hafnium, about 0.12 percent carbon, about 0.015 percent boron, balance nickel and minor elements; and (3) an alloy having a nominal composition in weight percent of about 12.5 percent cobalt, about 4.2 percent chromium, about 1.4 percent molybdenum, about 5.75 percent tungsten, about 5.4 percent rhenium, about 7.2 percent tantalum, about 5.75 percent aluminum, about 0.15 percent hafnium, about 0.05 percent carbon, about 0.004 percent boron, about 0.01 percent yttrium, balance nickel and incidental impurities. 7. The method of claim 1, wherein the step of identifying includes the step of identifying the through hole having a maximum transverse dimension of not more than about 0.030 inch where the through hole intersects an external surface of the hollow airfoil. 8. The method of claim 1, wherein the step of welding includes the step of welding by microplasma welding, plasma welding, and gas tungsten arc or tungsten inert gas welding. 9. The method of claim 1, including an additional step, after the step of welding, of heat treating the hollow airfoil. 10. The method of claim 1, including an additional step, performed after the step of welding, of applying a coating overlying the casting alloy and overlying the weld alloy. 11. The method of claim 1, wherein the step of welding includes the step of welding the through hole by closing the through hole with a weld alloy, and without using any freestanding closure element. 12. A method for fabricating a hollow airfoil, comprising the steps of providing a casting mold assembly for an aircraft gas turbine hollow airfoil comprising a casting mold with an inner wall, a casting core that is received within the inner wall of the casting mold to leave a casting space between an outer wall of the casting core and the inner wall of the casting mold, wherein the casting space defines a portion of the hollow airfoil, and a standoff spacer that prevents the casting core from contacting the inner wall of the casting mold and thereby maintains the casting space; casting a nickel-base superalloy casting alloy into the casting space and solidifying the cast nickel-base superalloy to form the hollow airfoil; separating the hollow airfoil from the casting mold assembly; identifying the presence of a through hole extending through a wall of the hollow airfoil that is present due to the standoff spacer, wherein the through hole has a maximum transverse dimension of not more than about 0.030 inch where the through hole intersects an external surface of the hollow airfoil; and, if there is a through hole present, welding the through hole by closing the through hole with a weld alloy different from the casting alloy and selected from the group consisting of (1) an alloy having a nominal composition, in weight percent, 0.01-0.03 percent carbon, 0.1 percent maximum manganese, 0.5-0.6 percent silicon, 0.01 percent maximum phosphorus, 0.004 percent maximum sulfur, 7.4-7.8 percent chromium, 2.9-3.3 percent cobalt, 0.10 percent maximum molybdenum, 3.7-4.0 percent tungsten, 5.3-5.6 percent tantalum, 0.02 percent maximum titanium, 7.6-8.0 percent aluminum, 1.5-1.8 percent rhenium, 0.005 percent maximum selenium, 0.3 percent maximum platinum, 0.01-0.02 percent boron, 0.03 percent maximum zirconium, 0.12-0.18 percent hafnium, 0.1 percent maximum niobium, 0.1 percent maximum vanadium, 0.1 percent maximum copper, 0.2 percent maximum iron, 0.0035 percent maximum magnesium, 0.01 percent maximum oxygen, 0.01 percent maximum nitrogen, balance nickel with other elements 0.5 percent maximum; (2) an alloy having a nominal composition in weight percent of about 7.5 percent cobalt, about 7.0 percent chromium, about 1.5 percent molybdenum, about 5 percent tungsten, about 3 percent rhenium, about 6.5 percent tantalum, about 6.2 percent aluminum, about 0.15 percent hafnium, about 0.05 percent carbon, about 0.004 percent boron, about 0.01 percent yttrium, balance nickel and minor elements; and (3) an alloy having a nominal composition in weight percent of about 12.0 percent cobalt, about 6.8 percent chromium, about 1.5 percent molybdenum, about 4.9 percent tungsten, about 2.8 percent rhenium, about 6.35 percent tantalum, about 6.15 percent aluminum, about 1.5 percent hafnium, about 0.12 percent carbon, about 0.015 percent boron, balance nickel and minor elements. 13. The method of claim 12, wherein the step of providing the casting mold includes the step of providing the standoff spacer as a protrusion from and integral with the casting core. 14. The method of claim 12, wherein the step of providing the casting mold includes the step of providing the standoff spacer as a chaplet. 15. The method of claim 12, wherein the step of casting the nickel-base superalloy includes the step of casting a casting alloy selected from the group consisting of (1) an alloy having a nominal composition in weight percent of about 7.5 percent cobalt, about 7.0 percent chromium, about 1.5 percent molybdenum, about 5 percent tungsten, about 3 percent rhenium, about 6.5 percent tantalum, about 6.2 percent aluminum, about 0.15 percent hafnium, about 0.05 percent carbon, about 0.004 percent boron, about 0.01 percent yttrium, balance nickel and minor elements; (2) an alloy having a nominal composition in weight percent of about 12.0 percent cobalt, about 6.8 percent chromium, about 1.5 percent molybdenum, about 4.9 percent tungsten, about 2.8 percent rhenium, about 6.35 percent tantalum, about 6.15 percent aluminum, about 1.5 percent hafnium, about 0.12 percent carbon, about 0.015 percent boron, balance nickel and minor elements; and (3) an alloy having a nominal composition in weight percent of about 12.5 percent cobalt, about 4.2 percent chromium, about 1.4 percent molybdenum, about 5.75 percent tungsten, about 5.4 percent rhenium, about 7.2 percent tantalum, about 5.75 percent aluminum, about 0.15 percent hafnium, about 0.05 percent carbon, about 0.004 percent boron, about 0.01 percent yttrium, balance nickel and incidental impurities. 16. The method of claim 12, wherein the step of welding includes the step of welding by microplasma welding, plasma welding, and gas tungsten arc or tungsten inert gas welding. 17. The method of claim 12, including an additional step, performed after the step of welding, of applying a coating overlying the casting alloy and overlying the weld alloy. 18. The method of claim 12, wherein the step of welding includes the step of welding the through hole by closing the through hole with a weld alloy, and without using any freestanding closure element. 19. A method for fabricating a hollow airfoil, comprising the steps of providing a casting mold assembly comprising a casting mold with an inner wall, a casting core that is received within the inner wall of the casting mold to leave a casting space between an outer wall of the casting core and the inner wall of the casting mold, wherein the casting space defines a portion of the hollow airfoil, and a standoff spacer that prevents the casting core from contacting the inner wall of the casting mold and thereby maintains the casting space; casting a nickel-base superalloy casting alloy having a casting alloy solidus temperature into the casting space and solidifying the cast nickel-base superalloy to form the hollow airfoil; separating the hollow airfoil from the casting mold assembly; identifying the presence of a through hole extending through a wall of the hollow airfoil that is present due to the standoff spacer; and, if there is a through hole present, welding the through hole by closing the through hole with a weld alloy different from the casting alloy and having oxidation resistance and coating compatibility at least as good as that of the casting alloy, and having a weld alloy solidus temperature in the range of from 150�� F. below the casting alloy solidus temperature to 30�� F. above the casting alloy solidus temperature, without using any freestanding closure element. 20. The method of claim 19, including an additional step, performed after the step of welding, of applying a coating overlying the casting alloy and overlying the weld alloy.