Patent ID: 12195406

DESCRIPTION OF THE EMBODIMENTS

The invention is now described by means of the figures which illustrate certain particular embodiments and which must not be interpreted as limiting.

FIG.1shows a final part105and several intermediate states101,102,103,104of the final part105during its preparation.

At least one face of the substrate10is covered by a tie layer11comprising silicon. The purpose of the tie layer11is to facilitate the subsequent attachment of the insulation layer12. For example, the tie layer11can be a layer comprising only silicon.

The substrate10is made of ceramic matrix composite material chosen from silicon carbide based substrates (SIC).

The tie layer11is then covered with an insulation layer12, on an opposite surface to the substrate. The purpose of the insulation layer12is to avoid any contact between the tie layer11and the thermocouple13.

More specifically, and as described above, the contact between the tie layer11and the thermocouple13is undesirable because silicon from the tie layer11can react with metal from the thermocouple13, which would harm the correct operation of the thermocouple13.

However, the insulation layer12has the lowest possible thickness. For example, the thickness of the insulation layer12can be less than or equal to 100 μm. More specifically, the smaller the thickness of the insulation layer12, the more the measurement by the thermocouple13is representative of the temperature effectively experienced by the substrate10.

As described above, the insulation layer12comprises either silica or a rare earth disilicate.

In an embodiment the insulation layer12consists of silica.

In an alternative embodiment, the insulation layer12comprises a rare earth disilicate chosen from ytterbium disilicate and/or yttrium disilicate.

In an embodiment, the insulation layer12can have the same composition as the barrier layer14. In such an embodiment, the continuity between the insulation layer12and the barrier layer14is excellent, and the production method is further simplified.

As shown inFIG.1, a thermocouple13is then formed on the insulation layer12. The methods for depositing such a thermocouple13will be described below, and in conjunction with the corresponding step from the second figure.

Of course, the thermocouple13is formed such that the measurement of the temperature can be accessed from outside the part.

For example, the thermocouple13may comprise connection means (not shown inFIG.1), for example wires, which can connect the thermocouple13to outside the part105. In an embodiment, the wires are formed at the same time as the thermocouple, and can be formed in the same manner.

In an embodiment, in order to obtain such a thermocouple, it is possible to form the thermocouple with wires on the insulation layer12and slightly beyond, then to deposit a mask on the end of the wires formed beyond the insulation layer12which will be covered by the barrier layer14, in order to deposit the barrier layer14only on the thermocouple13but not on the end of the wires, then to remove the cover and thus obtain access to the wires connected to the thermocouple13.

Of course, the metal or metal alloy composing the thermocouple13is chosen so that it can faithfully measure the temperatures of interest in the context of the normal use of the final part105.

For example, in the case of a turbomachine part, the temperatures measured at the substrate10, and thus of the thermocouple13, can be between 1000° C. and 1300° C. It is therefore preferable to choose a thermocouple composed of a copper-nickel-manganese alloy (CuNiMn), platinum (Pt) or a platinum-rhodium alloy (PtRh).

In an embodiment, the insulation layer12and the barrier layer14are electrically insulating. This embodiment is advantageous because it is not then necessary to pay particular attention to the insulation of the thermocouple13or of any wires enabling it to be connected to an instrumentation, because the thermocouple is sandwiched between two insulating layers. This results in a more reliable part because the risk of a contact between the bare wires is reduced.

Once the thermocouple13is formed on the insulation layer12, a barrier layer14is deposited on the surface of the insulation layer12. The thermocouple13is inserted between the insulation layer12and the barrier layer14.

As described above, the barrier layer14makes it possible to insulate the substrate10from the environment to which the part is exposed.

As indicated, the barrier layer14comprises a rare earth disilicate. The rare earth disilicate is preferably chosen from ytterbium disilicate and/or yttrium disilicate. More specifically, it is observed that these two rare earths, alone or in combination, make it possible to obtain the best compromise between cost and the desired performance for the barrier layer14.

The barrier layer14can, for example, have a thermally insulating or environmentally insulating function, in other words providing a seal against conventionally encountered environmental pollutants such as compounds comprising calcium, magnesium, aluminium or silicon, in particular oxides of these compounds (conventionally called CMAS).

In an embodiment, the barrier layer14can be covered with an additional barrier, not shown inFIG.1, able to fulfil an additional function to that already fulfilled by the barrier layer14.

In an embodiment, the thermocouple is in direct contact with the insulation layer12, and in direct contact with the barrier layer14.

The thickness of the barrier layer14is chosen to represent a compromise between the weight, cost and desired specifications for the final part105.

As described inFIG.1, in the final part105, the thermocouple13is located inserted between the insulation layer and the barrier layer. The thermocouple13inserted between the insulation layer and the barrier layer makes it possible to obtain a reliable measurement of the temperature effectively experienced in the final part105between the substrate10and the barrier layer14.

In an embodiment, the part comprises no layers other than the substrate10, the tie layer11, the insulation layer12and the barrier layer14. Of course, the part comprises a thermocouple13inserted between the insulation layer12and the barrier layer14.

FIG.2schematically shows the various steps E1to E7of a method for preparing a final part105, as described above, starting from a substrate10constituting an initial part101. The steps represented by the dashed boxes ofFIG.2are optional.

The preparation method shown comprises a first step E1of preparing a tie layer11at the surface of a substrate10.

For example, the tie layer11can be formed in a manner that is known per se, for example by thermal spraying, PVD or CVD on at least one surface of a substrate10.

This first step E1makes it possible to obtain an intermediate part102, wherein the substrate10is covered on at least one surface by the tie layer11.

The method then comprises a step E2of forming an insulation layer12. This step E2makes it possible to obtain the intermediate part103, wherein an insulation layer12has been formed at the surface of the tie layer11.

In the embodiments where the insulation layer comprises a rare earth disilicate, step E2of forming the insulation layer12can be carried out by thermal spraying, physical vapour deposition or chemical vapour deposition, or by liquid deposition then sintering of one or more powders.

The method can optionally further comprise a step E3of polishing the insulation layer12.

Such a polishing step can be carried out by mechanical polishing or chemical polishing.

This step makes it possible to achieve a better attachment of the thermocouple13and reduces the risk of electrical discontinuity in the thermocouple13.

The method then comprises a step E4of forming a thermocouple13on the insulation layer12, in order to form the intermediate part104.

For example, the thermocouple13can be formed directly on the insulation layer12by means of a conductive ink.

For example, the conductive ink can comprise a plurality of metallic particles dissolved in a solvent, as previously described.

For example, the formation can comprise depositing a conductive ink by ink jet, aerosol jet printing, screen printing or micro-extrusion.

Alternatively, the thermocouple can be deposited by air plasma spraying (APS), high velocity oxy-fuel (HVOF), solution plasma spraying, cold spraying, electron beam physical vapour deposition (EBPVD), chemical vapour deposition (CVD), pulsed laser, plasma or screen printing.

As described above, step E4of forming the thermocouple13can comprise the depositing of an ink, immediately followed by its sintering in order to form the thermocouple.

Alternatively, step E4of forming the thermocouple can comprise depositing of an ink, optionally followed by its drying.

If step E4of forming the thermocouple comprises a printing step which is not followed by a sintering step, then the heat treatment step E7can enable the sintering of the particles comprised in the ink in order to form the final thermocouple.

The method then comprises a step E6of depositing a barrier layer14comprising a rare earth disilicate on the insulation layer12and such that the thermocouple13is inserted between the insulation layer12and the barrier layer14.

The method presented inFIG.2then comprises a heat treatment step E7. This heat treatment step E7can stabilise the barrier layer14, and optionally the insulation layer12. Such a step E7also makes it possible, in certain embodiments, to finalise the sintering of the thermocouple13.

The expression “between . . . and . . . ” should be understood as including the limits.