FR3101629A1 - Manufacturing process of a part in CMC - Google Patents

Abstract

Method of manufacturing a part in CMC The invention relates to a method of manufacturing a part in CMC with a consolidation phase comprising silicon carbide and having a high Young's modulus. Figure for the abstract: Fig. 2.

Description

Manufacturing process of a CMC part

The invention relates to ceramic matrix composite (CMC) parts and methods for making such parts.

A field of application of the invention resides in the production of parts which are intended to be exposed to high service temperatures, specifically in the fields of aviation and space, and in particular of parts for parts hot air turbine engines, it being understood that the invention can be applied to other fields, for example to the field of industrial gas turbines.

CMC materials have good thermostructural properties, that is to say good mechanical properties which make them suitable for the constitution of structural parts, together with the ability to retain these properties at high temperatures. CMC materials comprise a fibrous reinforcement made of cables of ceramic or carbonaceous materials present in a ceramic matrix. The use of CMC materials instead of metallic materials for parts that are exposed to high service temperatures is desirable, especially since these materials have a density that is considerably lower than the density of the metallic materials they replace .

It is known in particular to manufacture a CMC part by means of a technique in which plies of fibers coated with an interphase are impregnated with a mixture of resin and then superimposed in the desired orientation so as to obtain a preform of the part to be get. After the formation of the preform, the resin is pyrolyzed and then a densification of the preform is carried out by infiltration with molten silicon or a molten silicon alloy to form a ceramic matrix. The inventors have observed that the product thus obtained may not be entirely satisfactory because layers of matrix between each ply may lead to weakness in creep at temperature, due to the presence of free silicon. In this type of product, the embedded matrix phases, characterized by low creep resistance, in the form of free silicon in the matrix obtained by melt infiltration, can lead to an overload of the fibers exceeding their creep resistance. and therefore to a reduction in the breaking time.

It is therefore desirable to provide CMC parts having better mechanical properties, and in particular better resistance to creep, at high temperatures.

The present invention provides a method for manufacturing a CMC part, the method comprising at least:
- coating a plurality of cables with an interphase by transporting the cables through a processing chamber into which a gaseous phase is injected, the cables being tensioned during their transport and the interphase being formed by vapor deposition from the injected gas phase;
- the formation of a fibrous preform by three-dimensional weaving using the cables coated with the interphase; And
- forming a consolidated fibrous preform by treating the fibrous preform by chemical vapor infiltration to form a consolidation phase on the interphase, the consolidation phase comprising silicon carbide and having a Young's modulus greater than or equal to at 350 GPa.

Unless otherwise stated, the Young's modulus of the consolidation phase is measured at 20°C.

The combination of the reinforcement obtained by three-dimensional weaving and the silicon carbide consolidation phase obtained by chemical vapor infiltration (CVI) with a high modulus leads to an interconnected and rigid 3D network without free silicon, which gives the material a resistance to high creep at high temperature. The inventors have also observed that the formation of the interphase by vapor phase deposition on a cable transported under tension produces an individual coating around each fiber of the cable, as well as a good intra-cable filling, due to an effect advantage of the spacing of the fibers in the cable. The filling of the cable is therefore more homogeneous in comparison with the formation of the interphase by CVI on the fibers of an already woven preform in which the gas permeability of the cables is limited. In the invention, the formed interphase notably offers better fiber-to-fiber load transfer and also avoids the risk of glassy bonding ("glass linkage") and rupture of adjacent fiber bundles during oxidative exposure. . The solution proposed by the present invention therefore provides a CMC part having better mechanical properties at high temperatures.

In one embodiment, the consolidation phase has a Young's modulus greater than or equal to 375 GPa, for example greater than or equal to 400 GPa.

This feature further improves the creep resistance of the CMC part.

In one embodiment, the residual volume porosity of the consolidated fiber preform is in the range of 25% to 45%, for example in the range of 30% to 35%.

The inventors have observed that this characteristic advantageously optimizes the resistance to creep at high temperatures.

In one embodiment, the method further comprises densifying the consolidated fibrous preform by forming a silicon carbide matrix phase on the consolidation phase by infiltration with a molten composition comprising silicon, carbon particles and / or ceramic being present in the porosity of the consolidated preform before infiltration.

This feature advantageously leads to a ceramic matrix having low porosity, thereby reducing stress concentrations under mechanical load and improving the resistance of the matrix to cracking.

In one embodiment, the interphase is formed of at least one layer of the following materials: boron nitride, boron nitride doped with silicon, pyrolytic carbon or carbon doped with boron. In one example, the interphase can be covered with a protective layer of at least one of the following materials: silicon nitride or silicon carbide.

In one embodiment, the cables include silicon carbide fibers having an oxygen content that is less than or equal to 1 atomic percent.

The present invention also provides a CMC part comprising at least:
- a 3D woven fibrous reinforcement comprising a plurality of tows, the tows having a plurality of fibers which are individually coated with an interphase; And
- a consolidation phase densifying the fibrous reinforcement and located on the interphase, the consolidation phase comprising silicon carbide and having a Young's modulus greater than or equal to 350 GPa, the consolidation phase not containing free silicon.

This CMC part can be obtained by implementing the method described above.

In one embodiment, the consolidation phase has a Young's modulus greater than or equal to 375 GPa, for example greater than or equal to 400 GPa.

As noted above, this feature further improves the creep resistance of the CMC part.

In one embodiment, the volume fraction of the consolidation phase is in the range of 5% to 30%, for example in the range of 10% to 30%.

This characteristic advantageously optimizes the resistance to creep at high temperatures.

In one embodiment, the part also comprises a silicon carbide matrix phase located on the consolidation phase, said silicon carbide matrix phase having a residual volume porosity less than or equal to 8%.

As indicated above, this feature advantageously reduces stress concentrations under mechanical load and improves the resistance of the matrix to cracking.

In one embodiment, the interphase is formed of at least one layer of the following materials: boron nitride, silicon-doped boron nitride, pyrolytic carbon, and boron-doped carbon.

In one embodiment, the cables include silicon carbide fibers having an oxygen content that is less than or equal to 1 atomic percent.

By way of example, the part may be a turbine engine part. By way of example, the part can be a turbine ring or a sector of a turbine ring, a moving blade, a stationary blade, a combustion chamber wall, or a distributor.

Other features and advantages of the invention will become apparent from the following description, which is presented in a non-limiting manner and with reference to the accompanying drawings, in which:

Figure 1 is a flowchart of an example of a method according to the invention; And

Figure 2 generally illustrates a device for forming the interphase on cables as they are transported through a processing chamber which may be used in the invention.

The method begins by coating the cables with an interphase by means of implementing vapor deposition (step S10 in Fig. 1).

The cables can comprise ceramic fibers, for example nitride or carbide fibers, for example silicon carbide fibers. In another variant, the cables can comprise carbon fibers. In one example, the cables include silicon carbide fibers having an oxygen content that is less than or equal to 1 atomic percent. Examples of such cables are marketed under the name “Hi-Nicalon-S” by the company NGS, under the name “Tyranno SA3” by the supplier UBE, or under the name “Sylramic i-BN” by the supplier COI Ceramics. A cable comprises a plurality of fibers, for example at least one hundred fibers, typically 500 fibers.

The interphase serves to slow down the breakage of cable fibers by cracks that initially start in the matrix. By way of example, the defragilization interphase can comprise a material with a lamellar structure which, for a crack reaching the interphase, is capable of dissipating the cracking energy by localized separation at the atomic scale so that the crack is deviated in the interphase. The interphase is a coating that can comprise a single layer or several layers. The interphase may contain one or more layers of: boron nitride BN, silicon-doped boron nitride BN(Si) (having a mass content of silicon in the range from 5% to 40%, the remainder being nitride boron), pyrolytic carbon PyC or boron-doped carbon (having an atomic content of boron in the range of 5% to 20%, the balance being carbon) or boron carbide. The thickness of the interphase can be greater than or equal to 10 nanometers (nm), and for example can be located in the range from 10 nm to 1000 nm. In a known way, it may be preferable to carry out a surface treatment on the fibers of the cables before the formation of the interphase in order to eliminate the size and a surface layer of oxide such as silica SiO ₂ present on the fibers.

Methods and devices for coating the cables with an interphase formed by vapor deposition while these cables are transported under tension through a treatment chamber are known. Regarding this aspect, it is for example possible to refer to document FR 3 044 022.

A brief description of an example of a suitable device 1 for forming the interphase on the cables 2 is presented below with reference to Figure 2.

The device 1 comprises a treatment chamber 4 in which a plurality of cables 2 intended to be coated are transported by being driven by a conveying system 6, here comprising first 6a and second 6b sets of pulleys. Each set 6a or 6b includes one or more pulleys. During coating, the cables 2 are transported by the conveying system 6 from the entry end 5a to the exit end 5b. The conveying system 6 is configured to convey the cables 2 through the processing chamber 4 along a conveying axis Y. In the example shown, the conveying axis Y is parallel to the longitudinal axis X of the device 1. Cables 2 are tensioned between pulleys 6a and 6b and are tensioned between input and output ends 5a and 5b. Due to the tension applied, the fibers of the cables 2 move apart, which leads to a more homogeneous filling of the cables 2 and to an individual coating of the fibers. The cables 2 can be transported continuously through the processing chamber 4 during coating with the interphase. In this case, the cables 2 do not stop as they are transported through the treatment chamber 4.

The cables 2 which must be coated with the interphase may not be bonded together (in particular the cables 2 are not woven, knitted, or braided together). The cords 2 may not have been subjected to a textile operation and may not form a fibrous structure during coating with the interphase.

The interphase is obtained by injecting a gaseous phase 10 into the treatment chamber through an inlet 7 to form the interphase on the cables 2. The interphase can be formed by chemical vapor deposition (CVD ). The interphase can be formed in contact with the fibers of the cables. The unreacted gas phase, together with reaction by-products, are pumped out via an outlet port 8 (arrow 11). The device 1 also comprises a heating system configured to heat the processing chamber 4 in order to carry out vapor phase deposition. The heating system can heat the treatment chamber 4 by inductive or radiant heating. When a PyC interphase is to be formed, the gaseous phase 10 can comprise one or more gaseous hydrocarbons, for example chosen from methane, ethane, propane and butane. In a variant, the gaseous phase 10 can contain a gaseous precursor of a ceramic material, such as a combination of boron trichloride BCl ₃ and ammonia NH ₃ . In order to produce a given interphase, the selection of the precursor or precursors to be used together with the pressure and temperature conditions to be imposed in the treatment chamber 4 are part of the general knowledge of those skilled in the art.

A multilayer interphase can be made by placing a plurality of such units in series, each comprising a device for injecting a gaseous phase and a device for removing the residual gaseous phase.

Once the cables 2 have been coated with the interphase, the method continues by carrying out a three-dimensional weaving of the coated cables to form a fibrous preform of the part to be obtained (step S20 in FIG. 1).

The fibrous preform is used to form the fibrous reinforcement of the part to be obtained. The fibrous preform is obtained by three-dimensional weaving between a plurality of layers of warp cords and a plurality of layers of weft cords. The fibrous preform can be made in one piece by three-dimensional weaving. Three-dimensional weaving can be achieved with an "interlock" weave, i.e. a weave in which each layer of weft cords binds a plurality of layers of warp cords, with all the cords of a single column of frame having the same movement in the plane of the weave. The roles of the warps and wefts can be reversed, and this reversal should also be considered to be covered by the claims. The use of other types of 3D weaving is of course not within the scope of the invention. Various suitable weaving techniques are described in WO 2006/136755.

In a known manner, it may be preferable to treat the coated cables before weaving with a sizing composition comprising a linear polysiloxane, to avoid any risk of damage to the interphase during weaving. An example of such a sizing composition is disclosed in document US 2017/073854. Another solution to avoid any risk of damaging the interphase consists in forming the preform using a loom having elements which come into contact with the cables which are made of molybdenum. This type of loom is disclosed in document FR 3045679.

After the formation of the 3D woven preform, a consolidation phase comprising silicon carbide is formed by CVI in the pores of the fiber preform and on the interphase (step S30 in Fig. 1). The consolidation phase can be formed in contact with the interphase. The consolidation phase obtained by CVI does not contain free silicon and has a high Young's modulus, greater than or equal to 350 GPa. The Young's modulus of the consolidation phase can for example be located in the range from 350 GPa to 450 GPa, for example in the range from 350 GPa to 420 GPa. As mentioned above, this consolidation phase gives the part the desired creep resistance at elevated temperatures. The consolidation phase includes silicon carbide, optionally doped with a self-healing material such as boron B or boron carbide B ₄ C.

The thickness of the consolidation phase can be greater than or equal to 500 nm, for example located in the range from 1 micrometer (µm) to 30 µm. The thickness of the consolidation phase is sufficient to consolidate the fibrous preform, i.e. to bind the cords of the blank together sufficiently to allow the preform to be manipulated while retaining its shape without the assistance of a holding tool.

After the formation of the consolidation phase and before the start of the optional additional densification (step S40 in FIG. 1), the residual volume porosity of the consolidated fibrous preform can be less than or equal to 45%, for example can be located in the range from 30% to 35%. The volume fraction of the consolidation phase in the consolidated fibrous preform (or in the CMC part) can be greater than or equal to 5%. In one example, this consolidation phase volume fraction is in the range of 10% to 30%.

After the formation of the consolidation phase, an additional densification step can be performed to complete the densification of the preform (step S40). The ceramic matrix phase formed during the additional densification step S40 is formed on the consolidation phase and may be in contact with the consolidation phase.

In one embodiment, this additional densification step corresponds to densification by slurry-cast infiltration followed by melt infiltration. In this case, a ceramic and/or carbon powder can be introduced into the pores of the consolidated fibrous preform. To do this, the consolidated preform can be impregnated with a slip containing the powder in suspension in a liquid medium, for example water. The powder can be retained in the preform by filtration, optionally with the assistance of suction or pressure. It is preferable to use a powder consisting of particles having an average size (D50) less than or equal to 5 μm, or even less than or equal to 2 μm. Prior to infiltration with the molten composition, the powder is present in the pores of the consolidated fibrous preform. The powder can include silicon carbide particles. Instead of or in addition to particles of silicon carbide, particles of another material, for example such as carbon, boron carbide, silicon boride, silicon nitride, may be present in the pores of the fibrous preform.

Next, the consolidated fibrous preform comprising the particles is infiltrated with a molten composition comprising silicon. This composition can correspond to molten silicon alone or to a silicon alloy in the molten state which also contains one or more other elements such as titanium, molybdenum, boron, iron or niobium. The proportion by weight of silicon in the molten composition may be greater than or equal to 50%, for example greater than or equal to 75%, for example greater than or equal to 90%.

The use of other types of techniques for the additional densification step S40 obviously does not go beyond the scope of the invention. For example, the additional densification step can be carried out in a manner known by CVI or by a technique of polymer infiltration and pyrolysis ("Polymer Infiltration and Pyrolysis"; "PIP"). In one example, the CVI technique used to form the consolidation phase can be continued to completely densify the fiber preform. In this case, the entire ceramic matrix of the CMC part can be obtained by CVI.

The expression "located in the range from … to …" should be understood to include the terminals.

Claims (12)

Method for manufacturing a CMC part, the method comprising at least:
- the coating of a plurality of cables (2) with an interphase by transporting the cables through a treatment chamber (4) into which a gaseous phase (10) is injected, the cables being put under tension during their transport and the the interphase being formed by vapor phase deposition from the injected gas phase;
- the formation of a fibrous preform by three-dimensional weaving using the cables coated with the interphase; And
- forming a consolidated fibrous preform by treating the fibrous preform by chemical vapor infiltration to form a consolidation phase on the interphase, the consolidation phase comprising silicon carbide and having a Young's modulus greater than or equal to at 350 GPa. Process according to Claim 1, in which the consolidation phase has a Young's modulus greater than or equal to 375 GPa. A method according to claim 1 or claim 2, wherein the residual volume porosity of the consolidated fibrous preform is in the range from 25% to 45%. A method according to any of claims 1 to 3, wherein the method further comprises densifying the consolidated fibrous preform by forming a silicon carbide matrix phase over the consolidation phase by infiltration with a molten composition comprising silicon, and in which carbon and/or ceramic particles are present in the pores of the consolidated preform before infiltration. A method according to any of claims 1 to 4, wherein the interphase is formed of at least one layer of the following materials: boron nitride, silicon-doped boron nitride, pyrolytic carbon or boron-doped carbon. A method according to any of claims 1 to 5, wherein the cables (2) comprise silicon carbide fibers having an oxygen content which is less than or equal to 1 atomic percent. CMC part comprising at least:
- a 3D woven fibrous reinforcement comprising a plurality of cords (2), the cords having a plurality of fibers which are individually coated with an interphase; And
- a consolidation phase densifying the fibrous reinforcement and located on the interphase, the consolidation phase comprising silicon carbide and having a Young's modulus greater than or equal to 350 GPa, the consolidation phase not containing free silicon. CMC part according to Claim 7, in which the consolidation phase has a Young's modulus greater than or equal to 375 GPa. CMC part according to claim 7 or 8, wherein the volume fraction of the consolidation phase is in the range from 5% to 30%. CMC part according to any one of claims 7 to 9, which part further comprises a silicon carbide matrix phase located on the consolidation phase, said silicon carbide matrix phase having a residual volume porosity less than or equal to at 8 %. CMC part according to any one of claims 7 to 10, in which the interphase is formed of at least one layer of the following materials: boron nitride, boron nitride doped with silicon, pyrolytic carbon, and carbon doped with boron . CMC part according to any one of Claims 7 to 11, in which the cables (2) comprise fibers of silicon carbide having an oxygen content which is less than or equal to 1% in atomic percentage.