CA2467846C

CA2467846C - Method of manufacturing a hollow blade for a turbine engine

Info

Publication number: CA2467846C
Application number: CA2467846A
Authority: CA
Inventors: Jean-Pierre Ferte; Jean-Michel Patrick Maurice Franchet; Daniel Gaston Lhomme; Alain Lorieux
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2003-05-27
Filing date: 2004-05-19
Publication date: 2011-07-19
Anticipated expiration: 2024-05-19
Also published as: CA2467846A1; JP2004353666A; EP1481755B1; RU2004116118A; ES2323461T3; FR2855440A1; FR2855440B1; EP1481755A1; UA83793C2; JP4130423B2; RU2338886C2; DE602004020422D1

Abstract

The invention relates to a method of manufacturing a hollow blade for turbine engine comprising a foot and a rotor blade, the method comprising a production stage of a blade preform (14) bearing a rotor blade part and a foot part, this production stage of the blade preform comprising the following operations: - the making of a unit (28) of at least two parts (30, 32) stacked and diffusion bonded together, in such a way that they solely form the rotor blade part of the preform; - the making of an additional element (34) intended to wholly form the foot part of the preform; and - the assembling of the additional element to the unit so as to obtain the blade preform.

Description

METHOD OF MANUFACTURING A HOLLOW BLADE FOR A TURBINE
ENGINE
TECHNICAL FIELD
The invention generally relates to the field of methods of manufacturing blades for turbine engine, such as hollow fan blades, or any other type of rotor or stator blades for turbine engine.
STATE OF THE PRIOR ART
Usually, a hollow fan blade for turbine engine comprises a relatively thick foot used to attach this blade into a rotor disk, this foot being radially extended towards the outside by a thin aerodynamic part, called rotor blade.
From the prior art, it is known a method of manufacturing such a hollow blade, principally based on the use of the diffusion bonding technique, associated with that of superplastic forming.
Indeed, in this method of the prior art, two or three component parts of the blade are firstly defined, then made separately before being stacked and assembled to each other via the diffusion bonding technique, with the purpose of obtaining a preform of the desired blade.
Subsequently, an airfoil profiling of the previously fabricated preform is carried out, then bulging via gas pressure and with superplastic forming of this preform, in order to achieve a blade substantially bearing its finished shape.
As was mentioned above, a production stage of the blade preform requires the making of two external parts,

2 and possibly a central part intended to be interposed between these two external parts, with the purpose of being used as a stringer later on.
The manufacturing of the external parts is typically carried out through the machining of supply elements that necessarily have relatively large initial dimensions, as each of the two machined external parts must have two radially facing sections of significantly different thickness, these sections respectively being used to define the foot part of the blade preform and the rotor blade part of this said preform.
Thus, the manufacturing of the external parts intended to constitute at least partially the blade preform, for example obtained via lamination, generates very high material costs and machining costs, and hence this method of manufacturing the hollow blade is not completely optimised.
To face up to this major inconvenience, it has been proposed to produce the blade preform by means of a single diffusion bonding stage implying a stacking of at least five parts, of which some extend radially along the entire length of the preform, and others only along the foot part of the latter.
However, this method, which is notably disclosed in the documents US-A-4 822 823 and EP-A-1 188 197, has the inconvenience that major difficulties in the implementing of the diffusion bonding technique appear when the unit to be welded has extremely variable thicknesses (foot/rotor blade), and a large number of stacked parts.

3 Furthermore, significant problems are also encountered in ensuring good leak tightness around the foot part of the stacked parts.
OBJECT OF THE INVENTION
The purpose of the invention is therefore to propose a method of manufacturing a hollow blade for turbine engine, resolving at least partially the aforementioned inconveniences associated with the method implemented in the prior art.
More precisely, the purpose of the invention is to present a method of manufacturing a hollow blade whose production stage of the blade preform engenders significantly reduced manufacturing costs compared to those encountered in the prior art.
To accomplish this, the object of the invention is a method of manufacturing hollow blades for turbine engine comprising a foot and a rotor blade, the method comprising a production stage of the blade preform bearing a rotor blade part and a foot part, the production stage of the preform being performed in such a way that it comprises a unit of at least two parts stacked and diffusion bonded together. According to the invention, the production stage of the blade preform comprises the following operations:
- the making of the unit of at least two parts stacked and diffusion bonded together, in such a way that it solely forms the rotor blade part of the preform;
- the making of an additional element intended to wholly form the foot part of the preform; and

4 - the assembling of the additional element onto the unit so as to obtain the blade preform.
Advantageously, in the method of manufacturing according to the invention, the unit of at least two parts stacked and diffusion bonded together is not intended to constitute the entire blade preform, but only the rotor blade part of the latter.
Consequently, the making of this diffusion bonded unit no longer integrates the rather costly production of two external parts each intended to have two sections of significantly different thickness and respectively be used to define the foot part of the rotor part of the blade preform. On the contrary, as this welded unit does not constitute the foot part of the preform, its two external parts can thus be wisely defined so that each of them has a relatively even thickness, thus naturally engendering a significant reduction in the material costs and machining costs.
Furthermore, another advantage of the invention resides in the non-integration of the foot part during the diffusion bonding stage, which makes it possible to avoid being confronted with the implementation difficulties of this welding technique encountered when the unit to be welded has extremely variable thicknesses (foot/rotor blade), and a large number of stacked parts. Indeed, the diffusion bonded unit being envisaged to solely constitute the rotor blade part of the preform, it can consequently be manufactured simply thanks to the stacking of only two or three parts, each having a substantially even thickness.

Furthermore, the non-integration of the foot part during the diffusion bonding stage makes it possible to considerably facilitate the leak tightness between the stacked parts intended to be welded, this leak

5 tightness being necessary for the implementing of the diffusion bonding technique. Indeed, the leak tightness at the foot part of the stacking is known to those skilled in the art as being very difficult to produce, so that not having to care for it constitutes a real advantage.
Moreover, the separate making of the additional element presents the possibility of carrying out all sorts of intermediary machining operations on this element, before it is assembled onto the diffusion bonded unit obtained at the same time.
Moreover, the additional element not being intended to enter into the constitution of the rotor blade part of the blade preform but solely to wholly form the foot part of the said preform, it is obvious that the manufacturing costs can also be minimised, notably due to their minor radial length.
The invention therefore envisages the making of the blade preform using a plurality of previously made parts prior to being assembled, notably via diffusion bonding for some of them, none of these parts extending along the entire radial length of the preform, which thus makes it possible to easily overcome the inconveniences directly linked to the extensive variation of thickness of the blade preform along its length.

6 Preferably, the operation of assembling each additional element to the unit is implemented using a technique taken from among the group constituted of linear friction welding and of friction stir welding, these techniques being preferred in that they are relatively easy to implement, reliable, inexpensive and barely destructive metallurgically speaking.
Preferably, the manufacturing stage of the blade preform is followed by the following stages:
- airfoil profiling of the preform; and - bulging via gas pressure and superplastic forming of the airfoil profiling preform.
It can be envisaged that the additional element intended to wholly form the foot part of the preform is made via extrusion, which constitutes a particularly beneficial advantage in terms of manufacturing costs.
Indeed, this inexpensive technique to be implemented, consists, from a material billet and through an appropriate die, in making a profile of the additional element bearing the desired geometry.
Other advantages and characteristics of the invention will appear in the detailed non-restrictive description below.
BRIEF DESCRIPTION OF THE DRAWINGS
This description will be made in relation to the annexed drawings among which;
- figure 1 represents a perspective view of a standard hollow blade far turbine engine;
- figure 2 represents a diagrammatic perspective view of a blade preform obtained during the

7 implementing of the manufacturing stage of the preform of the method of manufacturing according to the invention; and - figures 3a to 3d diagrammatically illustrate the embodiment stages of the method of manufacturing according to the invention.
DETAILED PRESENTATION OF THE PREFERRED EMBODIMENTS
In reference to figure 1, we can notice a standard hollow blade 1 for turbine engine (not represented), for example made of titanium or one of its alloys.
This hollow blade 1, of fan rotor blade type with large chord, comprises a foot 2 extended by a rotor blade 4 in a radial direction.
The rotor blade 4, intended to be placed in the circulation path of an airflow of the turbine engine, has two external surfaces 6 and 8, respectively called upper surface 6 and lower surface 8, connected by a leading edge 10 and a trailing edge 12.
Figure 2 represents a blade preform 16, such as is intended to be obtained during a manufacturing stage of the blade preform of the manufacturing method according to the invention.
This preform 14 comprises a foot part 16 of variable and large thickness, which is extended in a radial direction by a rotor blade part 18. As can be seen in figure 2, the foot part 16 has an internal radial section 20 of a high average thickness E, this section 20 being radially extended externally by an external radial section 22 of an average thickness a inferior to the average thickness E. For information

8 purposes it is noted that the internal radial section 20 is later intended to ensure the fixing of the blade in the rotor disk of the turbine engine, notably thanks to two projection parts 23a and 23b positioned on either side of a central part 23c slotted into the extension of the external radial section 22 of the foot part 16.
Furthermore, the rotor blade part 18 of the preform 14 has a radially internal end 24 of thickness e' substantially equal to the average thickness e, and a radially external end 26 of thickness a " inferior to the thickness e'. However, the rotor blade part 18 of the preform 14 has a substantially even thickness.
Furthermore, it is indicated that there is not clear demarcation between the radially internal end 24 of the rotor blade part 18 and the external radial section 22 of the foot part 16 of the preform 14, as these elements are substantially aligned. Nevertheless, a fictitious junction plan P diagrammatically represented in figure 2 shows the commonly accepted theoretical separation between the foot part 16 and the rotor blade part 18 of the preform 14.
In a preferred embodiment of the method of manufacturing according to the invention, a manufacturing stage of the blade preform 14 is carried out in the aforementioned manner, making reference to figures 3a to 3c.
First of all a unit 28 is made of at least two parts 30 and 32 stacked and diffusion bonded together, the only two parts 30 and 32 visible in figure 3a respectively constituting the upper and lower external

9 parts of the unit 28. In this regard, it is indicated that a third part (not represented) can also be inserted between the external parts 30 and 32, so as to constitute a stinger later on. Indeed, the unit 28, being intended to solely and wholly form the rotor blade part 18 of the preform 14, can therefore be classically made using two identical external parts with grooved internal surfaces, or even with three parts of which the two identical external parts have substantially smooth internal surfaces in contact with the third intermediary part.
In this preferred embodiment of the invention, the unit 28 solely forming the rotor blade part 18 of the preform 14 has a substantially even thickness, the same as the two identical external parts 30 and 32 constituting this unit 28. Thus, the technique to obtain the parts 30 and 32 via lamination is therefore particularly appropriate, and completely optimised in terms of material costs and machining costs, as the supply elements necessary for the manufacturing of the parts 30 and 32 can easily have dimensions similar to the final dimensions that these said parts 30 and 32 must have.
In the case when the unit 28 is solely constituted of two identical external parts 30 and 32, once these have been made as described above, they are then diffusion bonded together, in a similar manner to that encountered in the prior art in order to carry out the assembling of the different component parts of the preform. In this respect and in a continuous manner, it is noted that the diffusion bonding operation is preceded by a depositing operation of fuel rod coating according to a set pattern, the coatings being applied to the internal surfaces 30a and 32a in contact with the external parts 30 and 32.
5 At the same time as the manufacturing of the hollow unit 28 solely and wholly forming the rotor blade part 18 of the preform 14, a single additional element 34 is made, intended to solely and wholly form the foot part 16 of the said preform 14. Thus, it is

10 naturally specified that the unit 28 and the additional element 34 each have a respective geometry substantially identical to the geometry of the rotor blade part 18 and of the foot part 16 of the preform 14 represented in figure 2.
As is shown in figure 3b, the additional element 34 therefore comprises a part 36 of considerable thickness similar to the internal radial section 20 represented in figure 2, as well as a part 38 of inferior thickness similar to the external radial section 22 represented in the said figure 2. The element 34 can consequently be easily made via extrusion, this proven low cost technique consisting, from a material billet and through an appropriate die, in making a profile of the additional element 34 bearing the desired geometry. In this way, with such a technique, it is possible to manufacture the additional elements 34 one after the other, via single stripping.
Once the unit 28 and the additional element 34 have been simultaneously made, preferably in a titanium alloy, they are then assembled in such a way so as to

11 substantially obtain the geometry of the preform 14, as illustrated in figure 3c.
This assembling can thus be performed via welding, by putting an internal radial surface 40 of the unit 28 into contact with an external radial surface 42 of the additional element 34. These surfaces 40 and 42 are substantially flat and jointly define a flat contact zone 44, approximately placed in a location identical to that of the fictitious junction plane P represented in figure 2, in comparison to the foot part 16 and rotor blade part 18 of the preform 14.
By way of illustration, the assembling operation of the additional element 34 to the unit 28 is preferably done via linear friction welding, or by friction stir welding. These known welding techniques advantageously allow the welded zone to keep the metallurgical characteristics compatible with the diffusion bonding and superplastic forming techniques, and ensure mechanical properties in compliance with the specifications of the preform.
Of course, this welding operation is followed by a machining operation of geometric reconditioning of the welded zone.
Following the manufacturing stage of the blade preform 14 which has just been described, standard stages are then carried out first of all aiming at airfoil profiling the preform 14, so that it has a substantially twisted shape as illustrated in figure 3d.
Then, still in a continuous manner, bulging via gas pressure and superplastic forming stage makes it possible to obtain the blade 1 such as represented in

12 figure 1, this stage being generally followed by a final machining intended to strictly give the blade 1 the desired airfoil profile.
Of course, various modifications can be introduced by those skilled in the art into the method of manufacturing the hollow blade 1 which has just been described, solely by way of non-restrictive illustration.

Claims

1. Method of manufacturing a hollow blade (1) for turbine engine comprising a foot (2) and a rotor blade (4), said method comprising a production stage of the blade preform (14) bearing a rotor blade part (18) and a foot part (16), the production stage of the preform (14) being performed in such a way that it comprises a unit (28) of at least two parts (30, 32) stacked and diffusion bonded together, characterised in that the production stage of said blade preform (14) comprises the following operations:

- the making of said unit (28) of at least two parts (30, 32) stacked and diffusion bonded together, in such a way that they solely form said rotor blade part (18) of the preform (14);

- the making of an additional element (34) intended to wholly form said foot part (16) of the preform (14); and - the assembling of the additional element (34) to the unit (28) so as to obtain said blade preform (14).

2. Manufacturing method set forth in claim 1, characterised in that the assembling operation of the additional element (34) to said unit (28) is implemented using a technique taken from among the group constituted of linear friction welding and of friction stir welding.

3. Manufacturing method set forth in claim 1 or claim 2, characterised in that the manufacturing stage of the blade preform (14) is followed by the following stages:

- airfoil profiling of said preform (14); and - bulging via gas pressure and superplastic forming of said airfoil profiling preform (14).

4. Manufacturing method set forth in any one of claims 1 to 3, characterised in that the additional element (34) intended to wholly form said foot part (16) of the preform (14) is made via extrusion.