FR3141701A1 - Process for repairing a part by chemical deposition - Google Patents

Abstract

The invention relates to a method for repairing a part (1) in which a chemical deposition operation of a repair layer (10) is carried out by dipping a portion to be repaired (2) of the part (1) in a an aqueous solution comprising ions of a repair filler metal, ions of a repair metal and a repair reducing agent. Figure for abstract: Figure 1

Description

Process for repairing a part by chemical deposition Area of disclosure

The disclosure concerns a process for repairing a part by chemical deposition. The part is, in particular, a component of an aircraft turbomachine or turbojet, in particular an element of a turbine.

State of the art

A turbine of a turbojet engine is placed downstream of a combustion chamber. The turbine recovers part of the energy from the combustion of flue gases for the operation of a fan, a compressor and turbojet accessories. The turbine comprises several stages, each stage comprising a fixed blade, called a distributor, and a movable blade, called a rotor.

Leaving the combustion chamber, the combustion gases will relax in the distributor which accelerates the flow and deflects it. Under the effect of such a flow, the rotor, also having deflector profiles, rotates, having the function of rotating the fan as well as the stages of the compressor, in particular the low pressure compressor.

We observe on a first stage of the turbine distributor, where it is held by a flange, wear by friction and corrosion by sulfur.

Wear and corrosion locally reduce the thickness of such a part. It is then necessary to repair the part to reduce the risk of breakage.

One solution is to reload the metal part by brazing. A hardfacing metal is deposited on the part whose melting temperature is lower than the melting temperature of the hardfacing metal. Such a solution is satisfactory in the short term. However, the time required to repair all damaged parts of a turbomachine is high.

Disclosure Statement

This disclosure aims to provide a robust, long-lasting and inexpensive solution.

To do this, in accordance with the disclosure, a chemical deposition operation of a repair layer is carried out by dipping at least one portion of the part to be repaired in an aqueous repair solution comprising ions of a filler metal. repair, ions of a repair metal and/or a repair reducing agent, in particular the repair metal being the same as a material of the portion to be repaired.

Thus, an operator can process several parts simultaneously by dipping them in the aqueous solution. With the same number of operators, the disclosure makes it possible to repair more parts than metal resurfacing by brazing.

Furthermore, chemical deposition allows a more uniform deposition than electrolyte deposition. Therefore, it is necessary to deposit less repair metal to achieve a desired thickness.

The chemical deposition can be carried out by an autocatalytic reaction or be forced, for example by an electric current.

According to another characteristic in accordance with the disclosure, a machining pass is preferably carried out after the deposition of the repair layer to eliminate excess thickness.

As the part is generally not worn and/or corroded uniformly, machining allows the part to be given the thickness it had before use.

According to an alternative characteristic in accordance with the disclosure, a machining pass is preferably carried out before deposition of the repair layer to harmonize the surface on which the repair layer is deposited.

In this way, surface unevenness is removed before applying the repair layer.

According to another characteristic according to the invention, the repair metal is preferably an alloy comprising a base metal and alloy elements, the base metal being in particular nickel and the alloy element being stronger proportion being in particular cobalt.

The repair process is particularly suited to the chemical deposition of this type of repair metal.

According to another characteristic in accordance with the invention, the repair filler metal can be, preferably, nickel, chromium, phosphorus and/or aluminum, considered individually or in combination.

Nickel, chromium, phosphorus and aluminum have good corrosion resistance and redox reaction properties.

In particular, chromium has good corrosion resistance properties and aluminum has good oxidation resistance properties, phosphorus has good wear resistance properties.

Depending on the protection needs of the room, it may be preferable to use one or the other.

According to another characteristic in accordance with the invention, the reducing repair agent can preferably be silver, copper and/or gold, considered individually or in combination.

In various embodiments according to the disclosure, it is possible to also use one and/or the other of the following provisions:

the part is a component of an aircraft turbomachine;

the part is a turbine element.

According to another characteristic in accordance with the disclosure, preferably, an operation is carried out to deposit an overcoat for protection against corrosion or oxidation on the repair layer by dipping the portion to be repaired in a bath for protection against corrosion. , composed of an aqueous corrosion protection solution comprising ions of a corrosion protection filler metal, chromium ions and a reducing agent.

The reducing agent for protection against corrosion allows a reaction between the ions of the repair filler metal, the ions of the repair metal and the portion to be repaired of the part immersed in the aqueous solution.

Thus, not only does the part after repair regain the characteristics it had before use, so as to achieve a "second life", but also the part has better resistance to corrosion, so that the "second life" can to be lying down.

According to another characteristic in accordance with the disclosure, preferably, an operation is carried out to deposit an overcoat of protection against wear on the repair layer by dipping the portion to be repaired in a bath of protection against wear, composed of an aqueous wear protection solution comprising wear protection filler metal ions, wear protection metal ions and a reducing agent.

Thus, as with the corrosion protection operation, the wear protection operation allows the part to be more resistant after repair than before use.

In various embodiments according to the disclosure, it is possible to also use one and/or the other of the following provisions:

the filler metal for protection against corrosion or against wear may preferably be nickel, chromium, phosphorus and/or aluminum, considered individually or in combination;

the reducing agent for protection against corrosion or against wear may preferably be silver, copper and/or gold, considered individually or in combination.

Brief description of the figures

Other characteristics and advantages of the present disclosure will appear in the following detailed description, referring to the appended drawings in which:

schematically represents a sectional view of a turbomachine comprising a part comprising a portion to be repaired;

represents a portion to be repaired of the part, on an enlarged scale, according to the arrow marked II of the ;

represents, in section along the line marked III of the , the portion to be repaired;

represents the portion to be repaired soaked in a repair bath, according to a first embodiment;

represents the portion to be repaired leaving the repair bath, according to the first embodiment;

represents the portion to be repaired after machining, soaked in a corrosion protection bath, according to the first embodiment;

represents the portion to be repaired taken out of the corrosion protection bath and dipped in a wear protection bath, according to the first embodiment;

represents the portion to be repaired obtained after exiting the wear protection bath, according to the first embodiment;

represents the portion to be repaired after machining, dipped in a repair bath, according to a second embodiment;

represents the portion to be repaired taken out of the repair bath and dipped in a corrosion protection bath, according to the second embodiment;

represents the portion to be repaired taken out of the corrosion protection bath and dipped in a wear protection bath, according to the second embodiment; And

represents the portion to be repaired obtained after exiting the wear protection bath, according to the second embodiment.

Detailed description of the disclosure

There schematically represents a sectional view of a turbomachine 50. A flow of air entering the turbomachine 50 passes through a fan 62, then separates into a primary flow 52 and a secondary flow 54. The primary flow 52 successively passes through a set of compressors, a combustion chamber 60, then a set of turbines.

In the illustrated embodiment, the compressor assembly comprises a low-pressure compressor 64 and a high-pressure compressor 66. Furthermore, the turbine assembly comprises a first turbine 82, a second turbine 84 and a third turbine 86 .

The fan 62 is connected to the third turbine 86 which drives it in rotation, via a first connecting shaft 72. The low-pressure compressor 64 is connected to the second turbine 84 which drives it in rotation, via a second connecting shaft 74. Finally, the high-pressure compressor 66 is connected to the first turbine 82 which drives it in rotation, via a third connecting shaft 76.

The combustion chamber 60 is supplied with fuel which is burned in the primary flow 52. The combustion gases form an outlet flow 56 downstream of the combustion chamber 60. The outlet flow 56 passes through the first turbine 82, the second turbine 84 and the third turbine 86.

More specifically, the third turbine 86 comprises several stages each comprising a distributor and a rotor. The first stage distributor, considered according to the direction of flow of the outlet flow 56, forms a part 1 comprising a portion to be repaired 2.

Figures 2 and 3 respectively illustrate a portion to be repaired 2 of part 1, on an enlarged scale, according to the arrow marked II of the and sectional view along the line marked III of the , the portion to be repaired 2. More particularly, on the , part 1 is schematically represented after use.

The portion to be repaired 2 comprises a raw surface 4, which may include corrosion pustules 5.

The corrosion pustules 5 are due to exposure of the portion to be repaired to the outlet flow 56 and to friction of the portion to be repaired 2 against a flange holding the part 1. The high temperature of the outlet flow 56 and the presence of sulfur in the combustion gases promote corrosion and therefore the appearance of corrosion pustules 5 on an exterior surface of the part 1.

According to a first method of repair, in order to repair the portion to be repaired 2 of the part 1, the raw surface 4 is first cleaned, deoxidized and/or descaled by mechanical and/or chemical action, in order to clear the portion to be repaired. repair 2 corrosion pustules 5.

As illustrated in , the portion to be repaired 2 then has a cleaned surface 6. The part 1 is then dipped in a repair bath 15.

The repair bath 15 is composed of an aqueous repair solution, which may contain ions of a repair filler metal, ions of a repair metal and/or a reducing agent.

More precisely, the repair metal is identical to the material of the part 1 comprising the portion to be repaired 2. The filler metal for the repair can result from different combinations corresponding to the need for the repair, such as a restoration of volume, protection against corrosion, protection against oxidation, protection against wear, etc. Finally, the reducing agent is a combination agent depending on the repair filler metal used.

The portion to be repaired 2 may consist of a superalloy comprising nickel as the base metal and cobalt as the alloying element with the highest content. The repair metal present in the repair bath 15 is the same material as the portion to be repaired 2.

The repair metal is preferably nickel. Alternatively, chromium, phosphorus and/or aluminum may be used as the repair metal.

The reducing agent is preferably silver, copper and/or gold.

A repair layer 10 is then gradually deposited on the cleaned surface 6, in particular by an autocatalytic chemical process, as illustrated in Fig. .

The repair layer 10 has a repair surface 12. However, the repair surface 12 has roughness resulting from the unevenly distributed presence of the corrosion pustules 5.

In order to restore the portion to be repaired 2 to an initial shape, machining is carried out on the repair layer 10. The repair layer 10 then has a machined repair surface 14 which is uniform, preferably substantially flat in the illustrated embodiment. to the .

The dimensions of the repaired part 100 then substantially conform to the nominal dimensions, that is to say the dimensions of the part 1 before use.

Furthermore, it is operated in this way for all the faces or surfaces of the part 1 containing portions to be repaired 2.

Optionally, as illustrated in , the portion to be repaired 2 of the repaired part 100 can then be dipped in a corrosion protection bath 25.

The corrosion protection bath 25 is composed of an aqueous corrosion protection solution comprising ions of the base metal of the part to be repaired 2, ions of a corrosion protection filler metal, such as chromium ions, and/or a reducing agent for protection against corrosion making it possible to carry out a reaction between the part to be repaired 2 and the ions of the bath for protection against corrosion 25.

The corrosion protection filler metal is preferably nickel. Alternatively, the protective filler metal is chrome and/or aluminum.

The reducing agent for corrosion protection is preferably silver, copper and/or gold.

As illustrated in , a substantially uniform corrosion protection overlayer 20 is thus gradually deposited, that is to say of a substantially constant thickness, on the machined repair surface 14 of the repair layer 10.

Furthermore, the corrosion protection overcoat 20 is likely to be deposited on all the surfaces of the portion to be repaired 2 of the repaired part 100.

Optionally, as illustrated in , the portion to be repaired 2 of the repaired part 100 can then be dipped in a wear protection bath 35.

The wear protection bath 35 is composed of an aqueous wear protection solution comprising metal ions corresponding to the metal of the part to be repaired 2, wear protection metal ions and/or a reducing agent to protect against wear.

The wear protection metal is preferably phosphorus. Alternatively, the wear protection metal may be aluminum.

The wear protection filler metal is preferably nickel, chromium and/or aluminum.

The reducing agent for protection against wear is preferably silver, copper and/or gold.

As illustrated in , a substantially uniform wear protection overlayer 30 is thus gradually deposited, that is to say of a substantially constant thickness, on the repair layer 10 and the corrosion protection overlayer 20 of the part. repaired 100.

Furthermore, it may be difficult to have only the portion of the part to be repaired 2 which is soaked in the repair bath 15, in the corrosion protection bath 25 and/or in the corrosion protection bath. wear 35.

Thus, it can be envisaged that part 1 is completely soaked in the repair bath 15, the corrosion protection bath 25 and/or the wear protection bath 35.

Consequently, the deposition of the repair layer 10, the corrosion protection overcoat 20 and/or the wear protection overcoat 30 is therefore not limited to the portion to be repaired 2.

Consequently, since part 1 has been entirely soaked in the repair bath 15, the corrosion protection bath 25 and/or the wear protection bath 30, part 1 is completely or partially covered by the repair layer 10, the corrosion protection overcoat 20 and/or the wear protection overcoat 30.

Consequently, it may then be necessary to carry out at least one material removal operation, in particular by machining, not only at the portion to be repaired 2, but also more generally in all areas of the repaired part 100 which must present dimensions conforming to nominal or defined values.

Furthermore, the material removal operation can be carried out before dipping the part 1 in the repair bath 15, preferably after dipping the part 1 in the wear protection bath 35, but it is also possible to do it between these two operations.

Figures 9 to 12 illustrate a second embodiment distinguishing itself from the first embodiment in that instead of dipping the portion to be repaired 2 in the repair bath 15 after having simply cleaned the raw surface 4, the portion to be repaired 2 is previously machined, in order to present a machined surface to be repaired 8 which is harmonized, that is to say devoid of roughness and corresponding to a general shape of the part 1 before use, in other words substantially flat in the mode of implementation illustrated.

Then, the portion to be repaired 2 is dipped in the repair bath 15, as illustrated in . The repair bath 15 according to the second embodiment has similar characteristics as described in relation to the first embodiment.

The repair layer 10 is then gradually deposited on the machined surface to be repaired 8, in particular by an autocatalytic chemical process, as illustrated in Fig. .

The repair surface 12 of the repair layer 10 of the repaired part 100 obtained is then substantially uniform. The dimensions of the repaired part 100 then substantially conform to the nominal dimensions, that is to say the dimensions of the part 1 before use.

Optionally, as illustrated in , the portion to be repaired 2 of the repaired part 100 can then be dipped in the corrosion protection bath 25.

The corrosion protection bath 25 according to the second embodiment has similar characteristics as described in relation to the first embodiment.

As illustrated in , a substantially uniform corrosion protection overlayer 20 is thus gradually deposited, that is to say of a substantially constant thickness, on the repair surface 12 of the repair layer 10.

Optionally, as illustrated in , the portion to be repaired 2 of the repaired part 100 can then be dipped in the wear protection bath 35.

The wear protection bath 35 according to the second embodiment has similar characteristics as described in relation to the first embodiment.

As illustrated in , a substantially uniform overcoat of protection against wear 30 is thus gradually deposited, that is to say of a constant thickness, on the repair layer 10 and the overcoat of protection against corrosion 20 of the repaired part 100.

Furthermore, the corrosion protection overcoat 20 is likely to be deposited on all the surfaces of the portion to be repaired 2 of the repaired part 100.

According to a particular embodiment, the repair process is carried out in a single aqueous solution, which may contain ions of the repair filler metal, ions of the repair metal, the reducing agent and/or all the ions of all the metals desired for the repair portion to be repaired 2 of part 1.

The deposits of the repair layer 10, the corrosion protection overcoat 20 and/or the wear protection overcoat 30 will be carried out successively depending on the elements in solution.

Part 1 can possibly be taken out before one of the deposits to be machined, before being immersed again in the aqueous solution.

Thus, it can be envisaged that the repair bath 15, the corrosion protection bath 25 and the wear protection bath 35 can constitute different dedicated baths, used successively depending on the need and the desired properties. , or a single bath containing all the ions of all the metals desired for the repair of the portion to be repaired 2 of part 1.

Furthermore, the repair metal is not necessarily identical to the material of the portion to be repaired 2 of part 1. It could thus, for example, be deposited another material on a nickel alloy blade for the purpose of fix. However, in order to facilitate installation of the repair metal, it is preferable to have at least a partial presence of the material of the portion to be repaired 2 of part 1. Subsequently, other metals can be added to the solution aqueous depending on the need for repair.

Claims (8)

Method for repairing a part (1), in which a chemical deposition operation of a repair layer (10) is carried out by dipping at least one portion to be repaired (2) of the part (1) in an aqueous solution including:

• ions of a repair filler metal,
• ions of a repair metal and/or
• a repair reducing agent,

in particular the repair metal being the same as a material of the portion to be repaired (2). Repair method according to claim 1, in which a machining pass (14) is carried out after deposition of the repair layer (10) to eliminate excess thickness. Repair method according to claim 1 or 2, in which a machining pass (8) is carried out before depositing the repair layer (10) to harmonize the surface on which the repair layer (10) is deposited. Repair method according to any one of the preceding claims, in which the repair metal is an alloy comprising a base metal and alloy elements, the base metal being in particular nickel and the alloy element being highest proportion being in particular cobalt. Repair method according to any one of the preceding claims, in which the repair filler metal is nickel, chromium, phosphorus. and/or aluminum. Repair method according to any one of the preceding claims, in which the repair reducing agent is silver, copper and/or gold. Repair method according to any one of the preceding claims, in which the part (1) is a component of an aircraft turbomachine (50). Repair method according to the preceding claim, in which the part (1) is a turbine element (86).