METHOD OF FABRICATING A TURBOMACHINE ROTOR DISK

Abstract

Fabricating an IBR, in particular a two-part IBR. A metal container is defined, made up of a plurality of parts that define between them at least one annular cavity, an insert made of composite material is positioned in the or each cavity, the assembly is subjected to hot isostatic compacting, and a rotor disk is machined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood and other advantages thereof appear more clearly in the light of the following description of a method in accordance with the principle of the invention, given purely by way of example and made with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows a flat coil used in making a reinforcing insert;

FIG. 2 is a section on II-II of FIG. 1, and on a larger scale;

FIG. 3 shows a first annular metal part provided with two grooves in which reinforcing inserts are placed;

FIG. 4 shows two annular side plates being put into place to form covers;

FIG. 5 shows the covers being closed by vacuum welding;

FIG. 6 shows the hot isostatic compacting operation;

FIG. 7 shows the resulting blank;

FIG. 8 shows the machining operations on said blank; and

FIG. 9 shows a two-insert two-part IBR obtained after said machining.

MORE DETAILED DESCRIPTION

One of the steps of the method consists in separately fabricating a plurality of flat coils 12. Each coil 12 has one turn per row, radially. It is constituted by a silicon-carbide wire 14 coated in titanium 16. This example is not limiting. It is possible to envisage other types of fiber and other types of coating alloy. Strips of adhesive 18 extending radially serve to stabilize the coil. Nevertheless, the adhesive is removed subsequently. Such flat coils are for being stacked one on another within a metal container 20 shown in FIGS. 3 to 5, in particular. The metal container comprises in particular two coaxial annular blocks 21 and 22 superimposed about an axis x, and two annular side plates 23a, 23b. Said annular blocks and the two side plates define between them at least one annular cavity. In the example shown more particularly, the two coaxial annular blocks 21 and 22 are made in a single annular part 26 (made of titanium) that includes an intermediate portion 25 interconnecting the two coaxial annular blocks 21 and 22. The intermediate portion 25 is axially narrower than are the two annular blocks 21 and 22, thereby defining two grooves 24a and 24b that are spaced apart axially from each other. The grooves 24a and 24b are designed to be closed by the two side plates 23a, 23b, respectively so as to define the two closed annular cavities 28a and 28b that are likewise spaced apart axially.

It should be observed that the intermediate portion 25 need not exist, which would make it possible to define a metal container constituted by two independent coaxial annular blocks 21, 22 that are assembled together by two annular side plates 23a, 23b. That would define a single annular cavity of greater axial extent.

The or each cavity 28a, 28b is designed to be filled with a stack of flat coils 12 made in the manner described above. The inside diameter of such a flat coil corresponds to the outside diameter of the inner annular block 22, while its outside diameter corresponds to the inside diameter of the outer annular block 21. In other words, the radial extent of a flat coil corresponds to that of the cavity, and also to the radial extent of the intermediate portion 25 interconnecting the two coaxial annular blocks 21, 22.

The two grooves 24a, 24b open respectively into the two axial faces of the central annular part 26. Slightly sloping annular portions connect the edges of the grooves to the respective plane faces of the central annular part. The two side plates are also made of titanium, but they are of smaller thickness. Nevertheless, they include annular portions of profile substantially complementary to the portions of the central annular part. Each side plate also has a rib 29 of small thickness that is positioned and dimensioned so as to engage into the opening of the corresponding groove 24a, 24b.

The stack of flat coils 12 constitutes an insert 30 that fills each cavity. Naturally, such an insert could be made by forming a coil out of at least one silicon-carbide wire coated in titanium, said coil being dimensioned to occupy substantially all of the space in such a cavity.

With an insert that is made up of a stack of flat coils, the adhesive is eliminated by means of solvent once the flat coils fill the grooves.

In the step shown in FIG. 5, the two side plates 23a, 23b are put into place on either side of the central annular part 26 and the three metal parts are assembled together by making circular peripheral welds between each side plate edge and the corresponding edge of the central annular part. Assembly is performed by welding in a vacuum using an electron beam. Once this step has been completed, a metal container 20 has been defined that is made of titanium and that includes two cavities 28a, 28b about a common axis and offset axially, each cavity being filled with an annular reinforcing insert 30. The following operation, shown in FIG. 6, is hot isostatic compacting. For titanium, the metal container containing the insert is raised to 940° C. under a pressure of 90 megapascals (mPa). During this operation, the titanium of the two side plates, and the titanium coating of the wires, creeps into the cavities 28a, 28b so as to fill in all the empty spaces between the turns. The resulting one-piece blank 20A as shown in FIG. 7 reveals that the side plates become deformed over the two cavities. However the silicon-carbide turns are completely embedded in the metallic mass that has become uniform.

FIG. 8 shows conventional machining operations, known in themselves, that do not need to be described in detail. The purpose of the machining is to define a two-part IBR, i.e. comprising two rings 32a, 32b reinforced by silicon-carbide coils and offset axially (i.e. with material being removed between the two reinforced parts). The blades 34 are likewise integral with the two-part ring. The result is shown in FIG. 9.

As mentioned above, the same process can be used for obtaining two rotor disks, each including one annular reinforcing insert. To obtain two separate disks, it suffices to cut the blank into two equal portions, radially, and to then machine each portion separately in order to define the central disk (containing the insert) and the blades integrally attached to the disk. In order to obtain a drum (an assembly of a plurality of disks) with such IBRs, it suffices to machine them and the ferrule uniting them in the block obtained by the hot isostatic compacting.

Naturally, the invention is not limited to forming an integrally bladed rotor as shown. It can be applied to fabricating a rotor disk (without blades) by machining slots in the periphery thereof for the purpose of receiving independent blades.

The invention also relates to a turbomachine rotor including at least one disk obtained by implementing the method described above, as well as to a turbomachine fitted with such a rotor.

Claims

1. A method of fabricating a turbomachine rotor disk provided with at least one annular reinforcing insert of composite material, the method consisting: in defining a metal container comprising two coaxial annular blocks, respectively an outer annular block and an inner annular block, together with two annular side plates, said blocs and said side plates defining between them at least one annular cavity;in positioning a said insert in the or each cavity;in subjecting the resulting assembly to an operation of hot isostatic compacting, in order to form a one-piece blank; andin machining at least a said rotor disk in said blank.

2. A method according to claim 1, wherein the two annular blocks are defined in a single annular block that includes an intermediate portion that is narrower in the axial direction, interconnecting said inner and outer annular blocks so as to form two grooves that are axially spaced apart from each other, said grooves being closed by respective ones of said side plates to define two annular cavities situated on either side of said intermediate portion, each cavity receiving a said insert.

3. A method according to claim 1, wherein a said insert is made by forming a coil of at least one wire of silicon carbide or the like coated in metal, said coil being dimensioned to occupy substantially all of the space in a said cavity.

4. A method according to claim 1, wherein a said insert is made by forming a plurality of flat coils of a wire of silicon carbide or the like coated in metal, each flat coil being shaped to occupy the full radial extent of said cavity, and wherein such flat coils are stacked in the or each cavity until the cavity is full.

5. A method according to claim 3, wherein said metal coating said silicon-carbide wire is titanium.

6. A method according to claim 1, wherein the machining operation comprises forming a rotor disk including two axially spaced-apart inserts.

7. A method according to claim 1, wherein the machining operation comprises forming two distinct rotor disks, each including a said insert.

8. A method according to claim 1, wherein the machining operation comprises forming two linked-together rotor disks, each including a said insert.

9. A method according to claim 1, wherein the machining operation comprises forming blades integrally with the or each disk.

10. A turbomachine rotor, including a disk obtained by implementing the method according to claim 1.

11. A one-piece bladed ring, being obtained by implementing the method according to claim 9.

12. A turbomachine, including a rotor according to claim 10.