EP3856698A1

EP3856698A1 - Method for producing a hollow part made from a ceramic matrix composite material

Info

Publication number: EP3856698A1
Application number: EP18792425.3A
Authority: EP
Inventors: Matthieu Arnaud GIMAT; Rémy DUPONT; Maxime François Roger CARLIN; Eric Philippe; Benjamin LACOMBE
Original assignee: Safran Ceramics SA
Current assignee: Safran Ceramics SA
Priority date: 2017-10-02
Filing date: 2018-09-25
Publication date: 2021-08-04
Also published as: BR112020006473A2; RU2020115056A; US11608299B2; CA3077612A1; CN111164061A; RU2770493C2; FR3071830B1; JP2020536042A; JP7197595B2; US20200270180A1; RU2020115056A3; WO2019068987A1; BR112020006473B1; FR3071830A1

Abstract

The invention relates to a method for producing a hollow part made of a ceramic matrix composite material, comprising the steps of: - shaping a hollow fibrous preform, wherein a core made of an oxidisable material is housed in or inserted into the preform (E1); - consolidating said preform (E3, E4); and - extracting the core by oxidising said core (E5).

Description

PROCESS FOR PRODUCING A HOLLOW PIECE OF CERAMIC MATRIX COMPOSITE MATERIAL

FIELD

The present invention relates to a method for producing a hollow part made of ceramic matrix or CMC composite material.

A field of application of the invention is the manufacture of structural parts used in hot parts of a turbomachine, for example parts of turbine, rear body or secondary nozzles of the turbomachine. More specifically, the invention can be used for producing dispensers or hollow turbine blades.

CONTEXT

[003] A turbine stage consists of a fixed blade or distributor belonging to a stator, followed by a mobile blade belonging to a rotor. The first distributor stages are generally hollow in order to convey air radially from the outside to the inside of the turbine, so as to feed the hub with air to ensure the pressurization and purging and its possible cooling . Part of this air may be intended for cooling the dispenser.

[004] Moreover, the blades may also be hollow in order to be traversed by cooling air. The use of hollow parts also reduces the mass of the turbomachine.

[005] A method for producing hollow parts in CMC is known from US 2014/0048978. This method comprises the steps of:

placing a silicon core in a hollow zone of a porous preform, heating the core and the preform so as to melt the core, the silicon of said core infiltrating the porous preform so as to consolidate it.

[006] Such a method has two main disadvantages.

[007] The first disadvantage is related to the fact that the core and the mold (or shaper) are made of different materials. Indeed, the core, made of silicon, has a thermal expansion different from the mold, made of carbon or metal, which can induce a variability of the finished part. Compensation is thus necessary to ensure the right fiber content and the good sizing of the part.

[008] The second disadvantage is related to having to correctly size the volume of the silicon core so that the whole of the porous preform is infiltrated by the silicon of the core. In general, if the silicon of the core is in excess, drainage means are provided to evacuate this excess out of the cavity. Similarly, if the amount of silicon in the core is not sufficient to infiltrate the entire porous preform, a crucible must be provided to bring into the cavity of the complementary silicon. This makes the infiltration step of the preform more complex. SUMMARY OF THE INVENTION

[009] The invention aims to overcome these disadvantages by providing a simple alternative, effective and inexpensive.

[010] For this purpose, the invention proposes a method for producing a hollow part made of ceramic matrix composite material comprising the steps of:

- Shaping a hollow fiber preform, a core of oxidizable material being housed or inserted into the preform;

consolidate said preform; and

extracting the nucleus by oxidation of said nucleus. In this way, the core can be easily removed, without risk of degradation of the preform. Indeed, the latter having been consolidated before removal of the core, said preform retains its size and shape after removal of the core.

[012] By oxidation is meant the chemical reaction of the nucleus with an oxidizing agent or oxidation agent transforming it into an oxide. Furthermore, the removal of the core by oxidation can easily be achieved within the current range of CMC parts manufacturing, without requiring significant adaptations of the manufacturing process.

[013] To facilitate its removal, the core can be pierced through or can be perforated.

The step of extracting the ring by oxidation may comprise the substeps consisting of:

- Heat the preform in which the core is inserted in an oven under oxidizing atmosphere;

mechanically removing the oxidized core, for example by scraping.

[015] Said heating can be carried out in the presence of a catalyst, such as for example potassium acetate.

[016] The presence of a catalyst makes it possible to reduce the duration of the heating step and to facilitate the removal of the core.

[017] Said heating can be carried out at a temperature between 400 ° C and 800 ° C.

[018] Said heating may comprise:

a first heating cycle lasting between 20h and 30h;

a second heating cycle lasting between 10h and 15h.

[019] In general, the first and second heating cycles may vary depending on the volume of the core and the section of the core which is in direct contact with the air.

[020] A mechanical removal operation of the core, for example a scraping operation, can be performed after each heating cycle. [021] The oxidizable core may be made of carbon, graphite or other material derived from carbon.

[022] Such materials are particularly resistant to the consolidation step.

[023] The hollow fiber preform can be made by draping or assembling fibrous textures around the core, or by weaving a preform having a hollow zone for insertion of the core.

[024] Said consolidation of the preform may comprise the substeps consisting of:

creating at least one interphase, for example boron nitride, on the fibers of the fibrous preform by chemical vapor infiltration;

creating at least one layer of ceramic matrix, for example silicon carbide, on the interphase by chemical vapor infiltration.

[025] It is also possible to consolidate the yarns for weaving the hollow fiber preform or the manufacture of fibrous textures, for example one-dimensional fabrics, assembled or draped around the core to produce the hollow fiber preform.

[026] Said consolidation of the son may comprise the substeps consisting of:

creating at least one interphase, for example boron nitride, on the son by chemical vapor infiltration;

[027] The hollow preform can then be shaped, a core of oxidizable material being housed or inserted into the preform. The hollow fiber preform can then be woven with these consolidated yarns or can then result from the assembly around an oxidizable core of one-dimensional fabrics made from these consolidated yarns. [028] The step of extraction of the nucleus by oxidation may be followed by a step of densification of the preform consisting at least in part of:

the introduction of a metal powder, for example a silicon powder, into the preform;

the infiltration of molten metal, for example molten silicon into the preform.

[029] The step of extracting the nucleus by oxidation may be followed by the steps of:

- machine the piece;

- cover the outer surface of the part with a coating forming a thermal or environmental barrier.

[030] The invention will be better understood and other details, features and advantages of the invention will become apparent on reading the following description given by way of non-limiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating the various successive steps of the method according to the invention;

- Figure 2 is a schematic view of the preform in which is inserted the core;

- Figure 3 is a schematic view of the preform after removal of the core by oxidation.

DETAILED DESCRIPTION

[031] Figure 1 shows schematically the various steps of a method of producing a hollow part made of ceramic matrix composite material (CMC) according to one embodiment of the invention.

[032] This method comprises a first step E1 in which a hollow fiber preform is shaped, a core of oxidizable material being housed or inserted into the preform. [033] The core is for example made of carbon, graphite or other material derived from carbon.

[034] The fibrous preform intended to form the fibrous reinforcement of the part according to the invention can be obtained by multilayer weaving between a plurality of layers of warp threads and a plurality of weft layers. The multilayer weave produced can be in particular an "interlock" weave weave, that is to say a weave weave in which each layer of weft yarn binds several layers of warp yarns with all the yarns of a weave. same column of weft having the same movement in the plane of the armor.

[035] Other types of multilayer weaving may of course be used.

[036] When the fiber preform is made by weaving, the weaving can be performed with warp son extending in the longitudinal direction of the preform, being noted that weaving with weft yarns in this direction is also possible. .

[037] In an exemplary embodiment, the son used may be silicon carbide (SiC) son provided under the name "Nicalon", "Hi-Nicalon" or "Hi-Nicalon-S" by the Japanese company Nippon Carbon or "Tyranno SA3" by the company UBE and having a titre (number of filaments) of 0.5K (500 filaments).

[038] For turbomachine blades intended for use at high temperature and especially in a corrosive environment (for example in a humid environment), it is advantageous to use, for weaving, son formed of ceramic fibers, in particular silicon carbide fibers. (SiC). For parts with shorter durations of use, carbon fibers can also be used.

Different multilayer weave modes are described in particular in document WO 2006/136755.

[040] Such a method makes it possible to produce a coherent preform comprising a hollow zone into which the core is inserted. [041] The fibrous reinforcement of the piece according to the invention can also be formed from a fibrous preform obtained by assembling two fibrous textures. In this case, the two fibrous textures may be bonded together, for example by sewing or needling, or simply juxtaposed. The two fibrous textures can in particular be each obtained from a layer or a stack of several layers of:

- one-dimensional fabric (UD),

- two-dimensional fabric (2D),

- braid,

- knit,

- felt,

unidirectional sheet of son or cables or multidirectional layers obtained by superimposition of several unidirectional sheets in different directions and by unidirectional webs connection between them, for example by sewing, by chemical bonding agent or by needling.

[042] In the case of a stack of several layers, they are interconnected for example by sewing, by implantation of son or rigid elements or by needling, or simply juxtaposed.

[043] As previously, such a method makes it possible to produce a coherent preform comprising a hollow zone into which the core is inserted.

[044] Finally, the fibrous reinforcement of the piece according to the invention can also be formed by draping unidirectional folds, fabrics or bands, around the core. In this case, the hollow zone in the preform is made directly by constructing the preform around the core.

The assembly comprising the preform and the core inserted in the hollow zone of the preform is then placed in a conformation tool (step E2) so as to maintain the preform in a shape close to that of the part to be manufactured. [046] Examples of formatting of fibrous preforms from a coherent fibrous structure can be found in particular in US patent application 201 1/0293828.

[047] A boron nitride (BN) interphase coating is then formed by chemical vapor infiltration or CVI ("Chemical Vapor Infiltration" - step E3), the preform remaining in the desired shape by means of the conformation tooling, said tool being placed in an oven. The tool may be made of graphite and may have holes for the passage of the gas phase. This gaseous phase can comprise boron trichloride BCb, ammonia NH3 and hydrogen gas H2.

[048] At the end of step E3, the preform and the core are still maintained in the conformation tooling in the furnace, a ceramic matrix layer is formed by CVI on the BN interphase for consolidation of the preform (Step E4), that is to say to bind the fibers of the preform sufficiently between them so that the preform can retain its shape without the assistance of the conformation tooling. This matrix layer is for example made of silicon carbide SiC.

[049] In steps E3 and E4, the preform and the core are subjected to a temperature of between 700 and 1100 ° C.

[050] The core 2 (visible in dashed lines in Figure 2) and the preform 1 are then removed from the conformation mold and are placed in an oven under an oxidizing atmosphere, that is to say in the presence of a catalyst , such as for example potassium acetate, to carry out the extraction of the nucleus by oxidation (E5). By oxidation is meant the reaction of a body with oxygen, giving an oxide.

[051] During this oxidation step E5, the core is thus removed by means of a chemical reaction transforming it into oxide. For this, the core and the preform undergo a first heating cycle in which the temperature in the oven is maintained between 400 ° C and 800 ° C, for example of the order of 600 ° C, for a period of between 20 and 30 hours, for example from the order of 25 hours. Part of the core is then removed by mechanical action, for example by scraping. At the end of the first cycle of heating and scraping, between 30 and 50% of the mass of the core can be removed.

[052] The core and the preform then undergo a second heating cycle in which the temperature in the oven is maintained between 400 ° C and 800 ° C, for example of the order of 600 ° C, for a period of between 10 and 15 hours, for example of the order of 12 hours. The remainder of the core is then removed by mechanical action, for example by scraping. At the end of the first heating and scraping cycle, almost the entire core has been removed and a preform 1 having a hollow zone 3 is obtained, said hollow zone 3 being illustrated in dashed lines in FIG.

[053] A ceramic matrix is then formed in the preform by impregnating said preform with a slip containing one or more carbon or ceramic powders, for example SiC, Si ₃ N ₄ , C, B and their mixtures, in aqueous suspension, or SC ("Slurry Casting" - step E6). This densification step is performed in a mold at room temperature. The preform is then removed from the mold and dried, and the formation of the ceramic matrix is continued in an oven by infiltration with molten silicon or a molten alloy containing predominantly silicon, or Ml ("Melt Infiltration" - step E7). The constituent (s) present within said molten silicon alloy may be chosen from B, Al, Mo, Ti, and mixtures thereof. This densification step is carried out at a temperature of, for example, between 1400 ° C. and 1450 ° C.

[054] A process of densification by Ml route is described in particular in US Patents 4,889,686, US 4,994,904 and US 5,015,540.

[055] The piece from step E7 is then removed from the oven and functional surfaces are optionally machined (step E8), for example by milling.

[056] A coating, forming an environmental and / or thermal barrier having a thermal protection and / or protection function against corrosion in an oxidizing and / or wet environment, is applied to the surface of the part (step E9). In particular, reference may be made to patent applications WO2010 / 063946, WO2010 / 072978, US2009 / 0169873 and US2010 / 003504.

Claims

1. A method for producing a hollow part made of a ceramic matrix composite material comprising the steps of:

- Shaping a hollow fibrous preform (1), a core (2) of oxidizable material being housed or inserted in the preform (E1);

consolidating said preform (E3, E4); and

extracting the core by oxidation of said core (E5).

The method of claim 1 wherein the step of extracting the core by oxidation (E5) comprises the substeps of:

heating the preform (1) in which the core (2) is inserted, in an oven under an oxidizing atmosphere;

mechanically removing the oxidized core, for example by scraping.

3. Method according to claim 2, wherein said heating is carried out in the presence of a catalyst, such as for example potassium acetate.

4. The method of claim 2 or 3, wherein said heating is performed at a temperature between 400 ° C and 800 ° C.

5. Method according to one of claims 2 to 4, wherein said heating comprises:

a first heating cycle lasting between 20h and 30h;

a second heating cycle lasting between 10h and 15h.

6. Method according to one of claims 1 to 5, wherein the core (2) oxidizable is made of carbon, graphite or other material derived from carbon.

7. Method according to one of claims 1 to 6, wherein the hollow fiber preform (1) is made by draping or assembly of fibrous textures around the core, or weaving a preform having a hollow zone for insertion of the core.

8. Method according to one of claims 1 to 7, wherein said consolidation of the preform (E3, E4) comprises the substeps consisting of:

creating at least one interphase, for example boron nitride, on the fibers of the fibrous preform (1) by chemical vapor infiltration;

9. Method according to one of claims 1 to 8, wherein the step of extraction of the core by oxidation (E5) is followed by a step of densification of the preform (E6, E7) consisting at least partly of :

the introduction of a metal powder, for example a silicon powder, into the preform (E6);

the infiltration of molten metal, for example molten silicon into the preform (E7).

The process according to one of claims 1 to 9, wherein the step of extracting the ring by oxidation is followed by the steps of:

- machining the part (E8);

- cover the outer surface of the part with a coating forming a thermal or environmental barrier (E9).