초록 ▼

The invention provides a method of fabricating a turbine stator casing, the method comprising the operations consisting in: between the walls of portions of a mold, forming a cavity of shape corresponding to the shape of the shroud of said casing, securing soluble cores to at least one of said mold

The invention provides a method of fabricating a turbine stator casing, the method comprising the operations consisting in: between the walls of portions of a mold, forming a cavity of shape corresponding to the shape of the shroud of said casing, securing soluble cores to at least one of said mold portions, said cores being held at a distance from the wall of said mold portion and representing empty spaces that are to be formed inside said shroud; putting soluble inserts into place between the cores to represent flow paths between said empty spaces; filling said cavity with a metal alloy powder; sintering said powder by hot isostatic pressing; eliminating the cores and the inserts by dissolving them; and extracting the shroud as molded in this way. The invention is applicable to fabricating a turbine stator casing for an airplane turbojet.

대표청구항 ▼

What is claimed is: 1. A method of fabricating a turbine stator casing, said casing comprising a double-skinned shroud with inner and outer skins and empty spaces between the inner and outer skins, the method comprising: between walls of portions of a mold comprising at least two portions, forming

What is claimed is: 1. A method of fabricating a turbine stator casing, said casing comprising a double-skinned shroud with inner and outer skins and empty spaces between the inner and outer skins, the method comprising: between walls of portions of a mold comprising at least two portions, forming a cavity of shape corresponding to that of said shroud; securing cores made of soluble material to at least one of said mold portions with tubular pegs, said cores being held spaced apart from the wall of said mold portion by said pegs and representing said empty spaces that are to be provided inside said shroud, each peg having a first end and a second end, said first end being mounted in a first housing formed in one of said cores and said second end being mounted in a second housing formed in the mold portion, and wherein each peg defines a through hole opening out through its first and second ends, filling said cavity with a metal alloy powder such that said pegs are in contact with said powder; sintering said powder by hot isostatic pressing such that said powder densifies to form said shroud during said sintering and such that said pegs are welded to said outer skin of said shroud during said sintering; eliminating said cores by dissolving said cores with a solvent that does not dissolve said pegs such that said first end of each peg is located in said empty spaces between the inner and outer skins of the shroud; and extracting the shroud from said mold with the second end of each peg protruding from said outer skin of said shroud such that said through hole of each peg provides a cooling air passage from outside said shroud, through said outer skin of the shroud and into paid empty spaces between the inner and outer skins of the shroud. 2. A method according to claim 1, further comprising: placing inserts between the cores to represent flow paths between said empty spaces; and eliminating the inserts after the sintering operation. 3. A method according to claim 2, wherein said inserts are made of a soluble material, and wherein the inserts are eliminated by being dissolved. 4. A method according to claim 1, wherein said second end of at least one of said pegs is suitable for co-operating with an end of a cooling air feed pipe. 5. A method according to claim 1, wherein the pegs are secured to the shroud by diffusion welding during sintering of the powder, the material of the pegs and of the shroud being compatible for diffusion-welding purposes. 6. A method according to claim 1, said casing further comprising fastener hooks for supporting at least one turbine nozzle, wherein the shroud is molded in such a manner as to provide projections on an inside face of the shroud facing towards the inside of the casing, and wherein said projections are machined so as to give them a shape of said hooks. 7. A method according to claim 1, wherein the casing further comprises fastener hooks for supporting at least one turbine nozzle, wherein the hooks are fabricated prior to molding the shroud, and wherein the hooks are subsequently fastened to an inside face of the shroud facing towards the inside of the casing. 8. A method according to claim 7, wherein the hooks are fastened to the shroud by diffusion welding while the powder is being sintered, materials of the hooks and of the shroud being compatible for diffusion-welding purposes. 9. A method according to claim 1, wherein the mold portions are made of a soluble material, and wherein said mold portions are eliminated by dissolving them. 10. A method according to claim 1, wherein said soluble material is selected to be mild steel, and wherein nitric acid is used as a solvent to eliminate said cores. 11. A method according to claim 4, wherein said second end of at least one of said pegs is threaded for co-operating by screw-engagement with the end of a cooling air feed pipe. 12. A method according to claim 1, wherein some of the pegs present an inside or an outside thread configured to secure tools to said pegs for putting said pegs into position. 13. A method according to claim 1, wherein said eliminating of said cores is performed by dissolving said core with a solvent that passes through said first and second ends of each tubular core. 14. A method according to claim 2, wherein said eliminating of said cores is performed by dissolving said core with a solvent that passes through said first and second ends of each tubular core. 15. A method according to claim 14, wherein said eliminating of said inserts is performed by dissolving said inserts with said solvent so as to interconnect said empty spaces, and wherein said dissolving of said inserts with said solvent is performed with said dissolving of said cores with said solvent. 16. A method according to claim 15, wherein said tubular pegs are connected to a cool air feed pipe, wherein dissolving said cores is performed so as to form a plurality of air inlets connected to said cool air pipe and distributed along said shroud, and wherein said dissolving of said cores and said dissolving of said inserts are performed by passing said solvent through a solvent path that corresponds to a cooling air path including said air inlets, said cooling air path forming a path for air from said air feed pipe to cool said shroud during operation of a turbine comprising said shroud.