METHOD FOR MANUFACTURING AN ENVIRONMENTAL BARRIER

Abstract

A method for manufacturing an environmental barrier comprising the steps of coating a rare earth silicate powder with a precursor of a densification agent in order to form a rare earth silicate powder coated with the precursor of the densification agent, thermally spraying the coated powder onto a substrate in order to obtain an at least partially amorphous environmental barrier on the substrate and thermally treating the environmental barrier in order to crystallize and densify the environmental barrier.

Claims

1. A method for manufacturing an environmental barrier, the method comprising the following steps: coating a rare earth silicate powder with a precursor of a densification agent in order to form a rare earth silicate powder coated with the precursor of the densification agent; thermally spraying the coated powder onto a substrate in order to obtain an at least partially amorphous environmental barrier on the substrate; and thermally treating the environmental barrier in order to crystallize and densify the environmental barrier.

2. The manufacturing method according to claim 1, wherein the coating is carried out by wet process.

3. The manufacturing method according to claim 2, wherein the rare earth silicate powder is immersed in a solution comprising a solvent and the precursor of the densification agent, the solvent is evaporated to form an agglomerated coated powder, and the agglomerated coated powder is deagglomerated to form the coated powder.

4. The manufacturing method according to claim 2, wherein the rare earth silicate powder is fluidized in a solution comprising a solvent and the precursor of the densification agent.

5. The manufacturing method according to claim 1, wherein the coating is carried out by gas process.

6. The manufacturing method according to claim 1, wherein the precursor of the densification agent is an organometallic precursor.

7. The manufacturing method according to claim 1, wherein the coated powder has a core-shell structure.

8. The manufacturing method according to claim 1, wherein the substrate is a ceramic matrix composite material substrate.

9. The manufacturing method according to claim 1, wherein the environmental barrier comprises a bonding layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other characteristics and advantages of the object of this presentation will emerge from the following description of embodiments, given by way of non-limiting examples, with reference to the appended figures.

[0036] FIG. 1 is a schematic sectional view of a substrate and an environmental barrier according to one embodiment.

[0037] FIG. 2 is a schematic sectional view of a substrate and an environmental barrier according to a detailed embodiment.

[0038] FIG. 3 is a schematic sectional view of a coated powder according to one embodiment.

[0039] FIG. 4 is a schematic sectional view of a coated powder according to another embodiment.

[0040] FIG. 5 is a flowchart representing the steps of a method for manufacturing an environmental barrier.

[0041] In all the figures, the elements in common are identified by identical reference numerals.

DETAILED DESCRIPTION

[0042] FIG. 1 is a schematic representation of a substrate 12 covered with an environmental barrier 10.

[0043] By way of non-limiting example, the substrate 12 may be a ceramic matrix composite material substrate.

[0044] By way of non-limiting example and as shown schematically in FIG. 2, the environmental barrier 10 may comprise a silicon bonding layer 14 and an yttrium disilicate layer 16.

[0045] At the interface between the bonding layer 14 and the yttrium disilicate layer 16 there is a silica layer 18. The silica layer 18 is a layer of silicon oxide formed by oxidation of the silicon bonding layer 14.

[0046] The yttrium disilicate layer 16 comprises a densification agent.

[0047] By way of non-limiting examples, the densification agent may be a sintering agent and/or a healing agent.

[0048] By way of non-limiting examples, the sintering agent may be magnesium oxide, iron oxide.

[0049] By way of non-limiting example, the healing agent is mullite, silica or an aluminophosphate.

[0050] By way of non-limiting example, the yttrium disilicate layer 16 may comprise between 0.1 and 5% by mass of sintering agent, for example 0.4% by mass of sintering agent.

[0051] The environmental barrier 10 may be obtained by the manufacturing method 100 of FIG. 4.

[0052] The method 100 for manufacturing the environmental barrier 10 comprises a step of coating 102 a rare earth silicate powder 22 with a precursor of a densification agent 24 to form a rare earth silicate powder 20 coated with the precursor of the densification agent.

[0053] The coated powder 20 may have a core-shell structure, as shown in FIG. 3, the coated powder 20 comprising a core of rare earth silicate powder 22 coated by an outer layer (or shell) formed by the precursor of the densification agent 24.

[0054] Alternatively, the coated powder 20 may have particles formed by the precursor of the densification agent 24 present on the surface of the rare earth silicate powder 22, as shown in FIG. 4.

[0055] These two types of structures may be obtained by the wet process or by the gas process.

Example of Coating

[0056] Rare earth disilicate powder, magnesium acetate and distilled water.

[0057] In 1 L (liter) of distilled water, dissolve 5% by mass of magnesium acetate (typically between 0.1 and 10% by mass).

[0058] Pour 1 kg of rare earth disilicate powder into the aqueous solution of magnesium acetate.

[0059] Mix with a magnetic bar.

[0060] Drying at 90° C. in an oven.

[0061] On the blocks of agglomerated powder, perform a heat treatment at 400° C. for 1 hour in air so that the blocks become brittle.

[0062] The coated powder 20 is available.

[0063] The coated powder 20 is sprayed by a thermal spraying method 104 onto the substrate 12 in order to obtain an environmental barrier 10 that is at least partially amorphous onto the substrate 12.

[0064] In the example of the organometallic precursor of the densification agent described above, the organometallic precursor of the densification agent, that is to say magnesium acetate, will dehydrate and oxidize during thermal spraying to form the densification agent around the rare earth disilicate powder, in a desired and controlled concentration. A partially amorphous environmental barrier 10 may be obtained with flattened grains (also called “splats”) of rare earth disilicate and the densification agent evenly distributed around the flattened grains of rare earth disilicate.

[0065] The environmental barrier 10 then undergoes a heat treatment step 106 in order to crystallize and densify the environmental barrier.

[0066] As a non-limiting example, the crystallization and densification heat treatment 106 may comprise a temperature rise at 100° C./h (degrees Celsius per hour) up to 1300° C., a plateau of 50 hours at 1300° C. and a temperature drop at 100° C./h and down to room temperature, that is to say around 20° C.

[0067] As a non-limiting example, the crystallization and densification heat treatment 106 may comprise a temperature rise at 300° C./h (degrees Celsius per hour) up to 1350° C., a plateau of 5 hours at 1350° C. and a temperature drop at 100° C./h and down to room temperature, that is to say around 20° C.

[0068] Although this presentation has been described with reference to a specific embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments discussed may be combined in additional embodiments. Accordingly, the description and the drawings should be considered in an illustrative rather than restrictive sense.