The invention relates to the general field of fixed ring assemblies of a gas turbine. It relates more particularly to the manufacture or repair of such assemblies or fixed casing ring of a turbine engine high pressure turbine.

In gas turbine engines here concerned, the pressurized air and fuel are burned in a combustion chamber to add thermal energy to the circulating gas.

The effluent from the chamber comprises high temperature gases which flow downstream along an annular flow path through the engine turbine section.

At the entrance of the turbine after the combustion chamber, the gases are directed to a series of blades which extend radially outwardly from the motor rotor, the radial direction being defined relative to the general axis motor rotation.

An annular shroud that is supported by the turbine case surrounds the radially outer ends of these blades to contain the gas in the duct created.

The free radial space between tips or blade tips and the shroud is minimized to prevent leakage of gas around said vertices.

Fixed rings, as above, provide a friction surface for the blade tips.

One then seeks that the blade tips rub the surface in strips or sealing plates which typically overlap, radially inner with respect to them, the bodies of said rings, thus reducing the amount of air that can bypass turbine blades.

Minimize the amount of bypass air increases engine efficiency.

A secondary function of the ring is to thermally protect the external environment vis-à-vis the hot gas stream.

Thus, the ring must be designed to be at once resistant to corrosive and oxidation effects of the hot gases and mechanical erosion by friction. The wear of the coating is therefore problematic.

When the original manufacture of the new part, the tongues or platelets, so that the cover body rings are typically deposited coating on these bodies by a technique called HVOF (High Velocity Oxy Fuel / method "oxyfuel" high speed).

The HVOF is, as known, a surface treatment technique dry. In this thermal spray system, a carrier gas is used to accelerate and transport to the fine particles substrate (typically 5 to 500 microns) which can be in liquid, pasty, solid view. This carrier gas may also be a source enthalpy for heating the particles to the melting point. An electrical arc can also be used to melt the material. The particles thus projected onto the substrate according crash speed, physical condition, temperature etc. The accumulation of particles on the substrate allows for the coating.

The HVOF has the disadvantages of being uncommon and difficult to implement. Especially the equipment settings to achieve are difficult. And the ring body of the surface condition must be oxide free for good bonding with the coating. In addition, a sandblasted state (rough) is required for a good bond and good adhesion of the deposit HVOF.

But it is clear from the foregoing that at some point needs to replace either the entire piece (ring and coating), is the only coating to restore engine performance. This is also true even if the ring in question is not that of a HP turbine.

In a parts repair process, in this case a well made ring that we will seek to repair rather than replace two

then problems will arise: first, it is an uncommon approach; further, it is necessary that there is no trace of the old HVOF deposition, which would require machining long base material (ring body). This is a serious constraint. The HVOF is not suitable for repair of ring.

An alternative solution is to find, especially as the typical material of a ring body is a superalloy, expensive and delicate material to be machined.

Also, to thus realize a sealing piece, new or repaired, comprising a body coated superalloy article (typically on one side) of a new coating to be placed in contact with a blade tip of a gas turbine, is, he proposed to conduct the following steps:

- a) is manufactured by molding said new coating of an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) boron (B),

- b) and is brazed together and said body superalloy new coating, so as to obtain said sealing piece.

In this context is also referred to the specific embodiment of a turbine ring comprising a body covered with a coating, the method of embodiment being in accordance with the foregoing, with possibly all or part of additional features that follow, said superalloy body and said new coating once brazed together according to step b) constituting respectively those of said ring which defines a sealing piece.

A general advantage of this solution is that the solder permits a surface state with a little oxide or without finely sanded surface condition; traces of CoNiCrAIY are acceptable, thereby machining least the body of the material for soldering. Therefore, the ring can be repaired more times this technique if we had tried to cover the new coating superalloy body by using a new deposit HVOF.

Another advantage is that the solder coating is diffused most important layer, which improves the strength of the coating on the superalloy body. With HVOF deposits, sometimes there are flaking of the coating phenomena, if the surface condition is not perfectly sanded.

In addition, HVOF projection requires a very long time; and there is a deposit of detachment risk

Brazing is favorably a brazing. Memory for brazing is a joining process of assembling articles using a filler metal in liquid state, having a melting temperature lower than that of the items to be joined, and wetting the material base which does not participate by fusion to form the joint. Brazing produces chemically and structurally heterogeneous links. Soldering is strong if made with filler metals whose melting point is higher than 450 ° C.

And as a reminder, for any purpose, the ISO 4063 relates to soldering.

As surely noted, the technique of the above solution can be used to achieve a new sealing room.

As part of a repair, the first repair will be favorably conducted with the following steps:

- c) before step b) on a previously used sealing member made with a new body of a superalloy coated with a deteriorated coating, an alloy of Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) -a therefore priori without boron - we withdraw said deteriorated coating,

- d) then lead step b), brazing together the body (3) and said new superalloy coating (1) containing boron, instead of the deteriorated coating removed.

During the realization of the new part, so there will be previously coated with the coating body is HVOF deposition either already by brazing. Of the latter, to produce a new part, it

be soldered directly on the body in new superalloy, in full replacement of HVOF. The HVOF will no longer be used at all.

In a subsequent repair (second, third ...), one will take place preferably as follows:

- c) before step b), a sealing part already used (including the new fabrication technique is not necessarily identifiable) having a body of a superalloy coated with a deteriorated coating, an alloy of cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) boron, it will withdraw said deteriorated coating,

- d) then lead step b), by brazing together the superalloy body and said new coating containing boron, instead of the deteriorated coating removed.

Is also concerned the case where realize a new sealing part thus comprising a superalloy body covered with a new coating can be placed in contact with a blade tip of a gas turbine.

In this case, the implemented method include steps where:

- a) manufacture by molding said new coating of an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) boron,

- b) and by a HVOF deposition, overlap with said new coating the superalloy body, so as to obtain said sealing piece.

Convincing results are especially obtained when the body material superalloy was ΑΜ1. Another superalloy can also be used: RENE N5.

The body superalloy and said new coating containing the boron thus being solderable together, it is also advisable to take maximum advantage of the presence of boron, to achieve preferably said brazing at a temperature lower than the solutionizing temperature complete phase Y 'of the base material of the body type Ni3AI in the preferred example, and / or preferably at a temperature between 1000 ° C and 1300 ° C, this phase Y' largely giving the characteristics mechanical superalloy.

And always for the sake of optimizing the quality of brazing, it is recommended that the alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) coating has the composition by weight (wt%) below:

Ni Cr Al Y Other (s) (max) Co

29.0 - 35.0 18.0 - 24.0 5.0 - 1.0 0.1 1 - 0.8 0.5-1.0 supplements 100

The "Other max: 0.5-1 .0 wt%" refers to impurities.

With the same aim, it is advisable that the amount by weight (wt%) of boron in the alloy type coating Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) is between 1 .7% and 2.5%, and preferably between 1 .9% and 2.2%.

This will be in particular suitable with a body AM1, as will be (although we retain another superalloy body) if one performs said brazing new coating containing boron at a temperature between 1000 ° C and 1250 ° C and preferably between 1150 ° C and 1210 ° C.

A coating of the difficulty of manufacture of an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) will also be resolved by making the by metal injection molding (MIM) of a sintered coating thermally densified board (CCT ).

Indeed, tests have shown (see below) a new coating deposited by brazing a TDC wafer has similar characteristics to a coating deposited by HVOF a perspective abradability, hardness and porosity.

A further description will now follow, with reference in particular to Figure 1 which shows a longitudinal (axial) section of a portion of the turbine engine.

Even if another environment can see the invention apply we will, in what follows, treat the application of the invention to an HP turbine, since the sealing stresses and temperature are high there.

Figure 1 are shown very schematically, from upstream to downstream in the flow direction of gas flow in a gas turbine, according to the longitudinal axis 1a of the turbine engine, a combustion chamber 1, a turbine nozzle 2 disposed at the outlet of the combustion chamber, a high-pressure (HP) turbine 3, a flow straightener 4 and a first stage of a low pressure turbine (LPT) 5.

The HP turbine 3 includes a turbine wheel 6 rotatably around the axis 1a and carrying blades 7 and a set of impeller ring. The blades 7 are in a single crystal Ni base superalloy; in Example privileged in AM1.

The set of impeller ring includes a turbine ring 10 which is therefore a sealing piece.

Typically, the ring of such a stationary ring assembly is sectorized, that is to say it consists of a plurality of segments joined end to end, circumferentially about the axis 1a.

The stationary ring assembly defines locally one wall (radially outer one) of the duct 16 the flow of hot gases from the combustion chamber 1 of the turbomachine and passing through the turbine.

To withstand the imposed temperature the turbine ring 10 comprises a body 1 1 covered, facing the blades 7, a cover 1 3 brazed. At least the coating 13 is sectored. The body 1 1 is in a single crystal Ni base superalloy; in Example privileged in AM1.

According to the operating conditions, and particularly when the turbomachine operates, the blades 7 come into contact with the coating 13 at their free ends 7a.

Typically via a spacer device, the turbine ring 10 is fixed to the casing 8 of the turbine which is radially outwardly relative to the blades.

As shown in Figure 1, the ring 10 may for this be supported by a metal support structure 15. The support structure 15 may for example comprise a first annular support, upstream 20 and a second annular support, downstream, 30, which clamp axially the ring 10 between them, and a metal ring 40 as clamped between the brackets 20,30 and which surrounds the ring. A branch 50 connects and fixes the supports 20,30 to the turbine casing 8.

The body 10 provided with the one turbine ring 1 covered with the coating 13 may be soldered after manufacturing, thus being a new part.

The coating 13 can also be soldered a replacement part, although this surface is new, in the sense that he will then be replaced on the body 1 1, an old deteriorated coating.

Two assumptions in this case:

- either it was an old coating of the same composition as the new coating brazed 13,

- either it was an old coating of different composition.

Indeed, an advantage of the brazed coating 13 is that it may have been brazed in replacement of a coating identical (in composition) previously brazed to the body 1 1, or of a different composition original coating.

In the latter case, the coating 13 has a priori brazed taken the place of a deteriorated coating made of an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY), free of boron, covered with a body 1 1 superalloy , typically a body AM1, during the original manufacture of the turbine ring 10.

Indeed, it is typical to date to realize a new ring 10 by covering its body 1 1 such CoNiCrAIY type cladding via a deposit HVOF (High Velocity Oxy Fuel / method "oxyfuel" high

speed); but with the already exposed drawbacks can be summarized in that once damaged, the HVOF is not a technique suitable for a repair on the ring 10. In particular, there was a bad by sandblasting surface preparation, there is a risk of detachment of the HVOF coating.

Under these conditions, the proposed alternative to then refurbish the lining of the body 1 1 is, as has already understood:

- a) manufacture by molding the coating 13 in a new type alloy Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) boron,

- b1) to rid the body of the remains of the damaged coating,

- b2) to come together and brazing the body 1 1 and this new superalloy coating, which will allow to find a sealing piece 10 adapted.

To put to good ratings, a machining of the new coating is made.

Typically, to remove the remains of the damaged coating, the corresponding face is machined of the body 1 1, so as to remove the CoNiCrAIY material still present.

In this regard, it is recalled that ring may in particular be repaired more easily and more times by brazing, in particular a MIM wafer containing boron by HVOF. From the second repair, solder traces on TDC will also do more posing problems associated with HVOF.

Indeed, manufacturing a coating 13 new from a sintered coating board densified thermally (TDC: Thermal Densified Coating) manufactured by MIM (Metal Injection Molding / metal injection molding) is an interesting practical solution in terms of finished part quality and ease, reliability and manufacturing safety.

In parallel with the preparation of the surface to be brazed of the body 1 1, so it will advantageously method for the manufacture of a series of TDC platelets of the correct chemical composition of the coating and dimensions to be observed. In this regard, platelets will be preferably slightly larger than the body of the ring with (substantially) the same as the rounded inner surface to be brazed of the body 1 1. For memory, the MIM is an injection molding of metallic powders. Metal (typically the alloy) is mixed with a binder, and then injected into a mold; the piece is then "stripped of binder" (chemical decomposition of the binder) in a furnace under controlled atmosphere, and then sintered in a vacuum oven. Sintering is at high temperature, eg 1250-1350 ° C for several hours, so as to obtain cohesion of the metal particles together, bringing the densification of the material and the strength of parts. This technique has the advantage of allowing you to create complex shapes with a good surface finish and fine tolerances. It is possible to create extremely homogeneous alloys, which have a very good corrosion resistance, among other qualities.

As new coating 13, one of these TDC MIM platelets is then placed on the machined face of the body 1 1.

The assembly is then brazed in the oven (ie, a second under a partial vacuum, typically less than 10 "2 Pa) before the coating 13 is machined to proper odds.

For brazing works, the coating materials 13 and the body 1 1 have of course been chosen to be solderable together.

In particular with an alloy type Cobalt-Nickel-chromium-aluminum-yttrium (CoNiCrAIY) having the above composition in weight and therefore boron between 0.5 and 5% by weight (% wt), a single crystal body or AM1 René N5 (Ni-based superalloys) appropriate, for example.

Favorably, it will carry out the brazing at a temperature below the temperature of complete solutioning of the gamma prime phase (here NÏ3AI type) of the body material, and / or preferably at a temperature between 1000 ° C and 1300 ° C.

This complete solutioning temperature, that is to say, austenitizing, which allows to dissolve the various soluble components in the solid solution and thus keep the material properties, so is the temperature below wherein the solder is lead to the expected results: the quality of soldering, resistance over time.

Favorably, the alloy coating nine 13 compatible with the base material of the body 1 1 will have a melting point below the melting point of the base material.

And it is even possible to choose, for safety and ease of implementation, the brazing temperature is below the melting temperature of the body material; for reminder about 1 385 ° C in the case of René N5 or AM1, for example.

In fact, with a body AM1, and more so if, as the considerations of the inventors and the results below are invited, the amount by weight (wt%) of boron in the alloy of the type of coating cobalt nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) is between 1 .7% and 2.5%, and preferably between 1 .9% and 2.2%, is favorably carry out the brazing of new coating 13 containing boron at a temperature between 1000 ° C and 1250 ° C, and preferably between 1150 ° C and 1210 ° C.

As has been overcome a main difficulty with the fact that the CoNiCrAIY is brazed at a temperature of 1230 ° C minimum. But various superalloys, including ΑΜ1, can not be subjected to a high temperature.

Include boron under the conditions mentioned will be possible to lower the brazing temperature. And a proportion of boron between 1 .7 and 2.5 wt%, with a preference for 1 .9 to 2.2 wt%, has been significantly favorable to good wettability of CoNiCrAIY on the piece and an area

distributed according to the subsequent use to make the part, the percentage of said boron being fixed with respect to the (range of) temperature (s) of said solder; see following results with 1 .5% boron (lack of wettability of the wafer on the substrate AM1) and 2.5% boron (the wafer CoNiCrAIY collapses and no retention of the preform to a suitable subsequent machining).

It actually turned out that the use of CoNiCrAIY alloy with the addition of boron provided (therefore between 0.5 and 5 wt%, with therefore a preference for 1 .7 to 2.2 wt%) actually corresponds to a cobalt braze alloy type base with a percentage of boron which is in phase with a solder-type nickel base, or cobalt; see composition RBD RBD 191 and 61 below (in wt%).

RBD 191 :

Elements Co Ni Cr W If BCP

Mini Base 17.2 4.5 27 1 2 0.8 0.3

Maxi 30 18,6 5,6 1 ,5 0,95 0,40 0,04

RBD 61 :

Elements Co Cr Al Si BC I ZR P

Mini Base 16.5 10.4 3.3 2.85 2.45 1 0.68

Maxi 19 12,2 4,2 3,15 2,8 1 ,30 0,8 0,06 0,05 0,01

In addition, feasibility tests with Silicon replacing boron have not provided consistent results at the broadcast area (porosity phenomena); hence the choice confirmed Boron, in the mentioned conditions.

The thickness of the new coating 13 will be favorably between 2.5 and 8.5mm, preferably 3 to 5 mm.

platelet brazing tests (coating 13) TDC manufactured by MIM, in CoNiCrAIY on rings AM1 were conducted.

In the case of use of solder supplied in the form of powder, it is suggested to use a binder. The mixture powder + binder should be smooth and uniform, and should not contain excess binder. The binder must maintain the solder on the assemblies up to the brazing temperature.

TDC used for the repair of these parts were an alloy mixture CoNiCrAIY (Amdry 995 Powder) and boron. Three tests were conducted at different boron contents (1, 5% to 2.5% wt).

For memory, a TDC is a wafer with a preform corresponding to the receiving part, of dimensions greater than what is desired.

The preparation of TDC platelets has been performed by MIM process, following the steps below, with furnace brazing under high partial vacuum:

- manufacture of 3 parts (mixture of CoNiCrAIY + B);

- three series shaping TDC at different contents by weight of B (1, 5%, 2% and 2.5%);

- chemical binder removal;

- thermal debinding under H2 with bearing 1 h at 1000 ° C for presintering TDC;

- Standard 15 min brazing to 1210 ° C + 2 h at 1060 ° C of TDC on support piece in AM1.

At the output of thermal debinding treatment and pre-sintering, the TDC placed on the exterior of the furnace had a surface oxidation.

The results showed that 2% (mass) of B in the CoNiCrAIY lowers the brazing temperature to 1210 ° C. This temperature is almost the acceptable upper limit for ΑΜ1. This is due to the standard temperature of other parts repair cycles; we can thus combine several types of rooms in the same batch. In addition 2% boron (optimum) provides good wettability; neither too much nor too little, which improves the strength of the coating and the diffused layer. The maximum permissible temperature for the brazing AM1 will be 1230 ° C

A 1, 5%, is not obtained a sufficient decrease in T ° C brazing. The wettability is limited.

And 2.5% high wettability and a deterioration of the shape of the wafer were observed; This is not fatal.

It can be estimated with reference to the above, but also the experience and knowledge of the inventors, as boron proportion interval [1 .7 to 2.5 wt%] with a preference for [1 .9 to 2.2 wt%].

The coatings deposited by TDC wafer brazing with similar characteristics to a coating deposited by HVOF a perspective abradability, hardness and porosity.

The tests showed that the new coating deposited by TDC wafer brazing had similar characteristics to the coating deposited by HVOF a perspective abradability, hardness and porosity.

A benefit was found that once brazed coating 13 creates a diffused most important layer that HVOF deposit, which improves the strength of the coating on the support part (AM1 in testing) impeccable at this deposit.

CLAIMS

1. Method for producing a sealing piece (10) comprising a body (1 1) superalloy coated with a new coating (13) being placed in contact with a blade tip (7) of a gas turbine, characterized in that it comprises steps wherein:

- a) molding said new coating is made of an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) boron,

- b) and is brazed together and said body superalloy new coating (1) so as to obtain said sealing piece.

2. The method of claim 1, wherein the sealing piece (10) after step b) is a fixed part obtained with the following steps: - c) prior to this step b), on a piece of sealing already performed new used with a body (1 1) of a superalloy coated with a deteriorated coating, an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) is removed said deteriorated coating,

- d) then leads to step b), brazing together the body (1 1) and said new superalloy coating (13) containing boron, instead of the deteriorated coating removed.

3. The method of claim 1, wherein the sealing piece (10) after step b) is a fixed part obtained with the following steps:

- c) before the step b) on a previously used sealing piece having a body (1 1) of a superalloy coated with a deteriorated coating, an alloy of Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) of boron was removed deteriorated said coating,

- d) then leads to step b), brazing together the body (1 1) and said new superalloy coating (13) containing boron, instead of the deteriorated coating removed.

4. Method for producing a sealing piece (10) new comprising a body (1 1) superalloy coated with a new coating (13) being placed in contact with a blade tip (7) of turbine gas, characterized in that it comprises steps wherein:

- a) is manufactured by molding said new coating type alloy

Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) further containing between 0.5 and 5% by weight (wt%) boron,

- b) and by a HVOF deposition is covered with said new covering (1) the body superalloy so as to obtain said sealing piece. 5. Method according to one of the preceding claims, wherein the body material (1 1) is a superalloy single crystal superalloy based on nickel, e.g. ΑΜ1.

6. A method according to one of claims 1 to 3, or 5, wherein in step b) brazing the body (1 1) superalloy and the new coating (13) containing boron, said brazing is carried out a temperature lower than the complete solution heat temperature of the phase Y 'of the body material, and / or preferably at a temperature between 1000 ° C and 1300 ° C.

7. Method according to one of the preceding claims wherein the alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) has the following composition by weight:

Ni Cr Al Y Other (s) (max) Co

29.0 - 35.0 18.0 - 24.0 5.0 - 1.0 0.1 1 - 0.8 0.5-1.0 supplements 100

8. Method according to one of the preceding claims, wherein the amount by weight (wt%) of boron in the alloy type coating Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) is between 1% and .7 2.5%, and preferably between 1 .9% and 2.2%.

9. A method according to claim 5 alone or in combination with one of Claims 6 to 8, wherein said brazing is carried out of the nine coating (13) containing boron at a temperature between 1000 ° C and 1250 ° C, and preferably between 1150 ° C and 1210 ° C.

10. A method according to any preceding claim wherein the fabrication of said coating (13) in an alloy type Cobalt-Nickel-Chromium-Aluminum-Yttrium (CoNiCrAIY) is produced by metal injection molding (MIM) of a wafer sintered thermally densified coating (TDC).

January 1. A method according to claim 2 alone or in combination with one of Claims 5 to 10, wherein before step c), during the realization of the new part was covered with the coating (13) the body (1 1) by HVOF deposition.

12. A method according to any preceding claim wherein the sealing part is a turbine ring comprising a body coated with a coating wherein said body (1 1) and said new superalloy coating (13) are those respectively of said ring which defines a sealing piece (10).