Method of fabricating a turbomachine rotor disk

The invention relates to fabricating a turbomachine rotor disk including, in its structure, at least one annular reinforcing insert of composite material, e.g. a ring of metal-coated ceramic wire, e.g. of titanium-coated silicon carbide. The invention relates more particularly to a method of fabricating such a disk, which can either be adapted to receive blades, or else can be directly bladed integrally, i.e. it can form a one-piece bladed ring known as an integrally-bladed rotor (IBR).

U.S. patent publication 2005/0166386 describes a method of fabricating an annular metal matrix reinforced by an annular insert of composite material. In that method, an annular groove is formed in a first annular metal part, a second annular metal part is formed that is suitable for constituting a cover for said groove, composite fiber turns are introduced into the groove, the cover is put into place, and the assembly is subjected to hot isostatic compression.

During that operation, the metal of the cover creeps into the cavity until all of the empty spaces between the turns have been filled.

It is known that such a hot isostatic compression operation is lengthy and expensive.

With the above-described prior method, it is not possible to make a metal matrix including an annular insert of considerable axial length.

In addition, with the prior method, making a drum of IBRs (a part that results from assembling a plurality of disks) assumes that welding is to be performed after each IBR has been individually fabricated. Such an operation carries risks, particularly since each IBR is expensive to make.

The invention enables this problem to be solved.

More particularly, the invention relates to 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; and in machining at least a said rotor disk in said blank.

In the above definition of the method in accordance with the invention, it is possible to integrate at least one insert of relatively great length, the two cover-forming side plates deforming towards each other during the hot isostatic compacting operation.

Most advantageously, the invention also makes it possible in a single hot isostatic compacting operation to make a disk that includes two axially spaced-apart inserts. The advantage of such a disk or IBR having two inserts has been demonstrated for certain applications, in particular for a fan disk.

To this end, the invention also provides a method in accordance with the above definition, 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.

In the two-insert variant, it should be observed that the blank resulting from hot isostatic compacting can also be used for making two disks, each including a single insert. It suffices to cut said blank in two after the hot isostatic compacting operation, and then to proceed with subsequent machining steps on each of the two portions. This serves to halve the time and the expense relating to hot isostatic compacting.

It is also possible to make two bladed disks that are linked together, each including a respective insert.

It is possible optionally to integrate a plurality of said inserts, and in particular more than two inserts, by spacing them apart in a said annular cavity by means of flat metal rings that are suitable, after compacting, for constituting intermediate metal partitions between the inserts, serving to separate said inserts axially.

Starting from the blank, it is possible to make (by machining) a slotted disk that is suitable for receiving blades. It is also possible to machine an IBR in said blank.

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;

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

FIG. 10 shows another embodiment of the first annular metal part and the two annular side plates.

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 23 a , 23 b . 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 24 a and 24 b that are spaced apart axially from each other. The grooves 24 a and 24 b are designed to be closed by the two side plates 23 a , 23 b , respectively so as to define the two closed annular cavities 28 a and 28 b 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 23 a , 23 b , as shown in FIG. 10 . That would define a single annular cavity of greater axial extent.

The or each cavity 28 a , 28 b 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 24 a , 24 b 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 24 a , 24 b.

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 23 a , 23 b 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 28 a , 28 b 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 28 a , 28 b so as to fill in all the empty spaces between the turns. The resulting one-piece blank 20 A 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 32 a , 32 b 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.