Chemical deposition repair process for a part

Abstract

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

Description

Title of the invention: Method for repairing a part by chemical deposition. Scope of disclosure

[0001] The disclosure relates to a method for repairing a part by chemical deposition. The part is, in particular, a component of an aircraft turbomachine or turbojet engine, specifically a turbine element. State of the art

[0002] A turbine of a turbojet engine is located downstream of a combustion chamber. The turbine recovers some of the energy from the combustion of the exhaust gases to power a fan, a compressor, and the turbojet's accessories. The turbine comprises several stages, each stage having a fixed blade, called a distributor, and a moving blade, called a rotor.

[0003] Exiting the combustion chamber, the combustion gases expand in the distributor, which accelerates and deflects the flow. Under the effect of this flow, the rotor, which also has deflecting profiles, rotates, its function being to drive the fan and the compressor stages, particularly the low-pressure compressor.

[0004] On a first stage of the turbine distributor, at the level of its retention by a flange, wear by friction and corrosion by sulfur are observed.

[0005] 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.

[0006] One solution is to build up the metal part by brazing. A build-up metal is deposited onto the part, the melting point of which is lower than the melting point of the build-up metal. Such a solution is satisfactory in the short term. However, the time required to repair all the damaged parts of a turbomachine is considerable. Statement of Disclosure

[0007] The present disclosure aims to propose a robust, sustainable and low-cost solution.

[0008] To achieve this, in accordance with the disclosure, a chemical deposition operation of a repair layer is carried out by dipping at least a portion of the part to be repaired into an aqueous repair solution comprising 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.

[0009] Thus, an operator can treat several parts simultaneously by immersing them in the aqueous solution. With the same number of operators, this method allows for the repair of more parts than metal cladding by brazing.

[0010] Furthermore, chemical deposition allows for a more uniform deposition than electrolyte deposition. Consequently, less repair metal needs to be deposited to achieve the desired thickness.

[0011] Chemical deposition can be carried out by an autocatalytic reaction or be forced, for example by an electric current.

[0012] According to another feature in accordance with the disclosure, a machining pass is preferably carried out after the deposition of the repair layer to eliminate excess thickness.

[0013] Since the part is generally not worn and / or corroded uniformly, machining makes it possible to give the part the thickness it had before use.

[0014] According to an alternative feature in accordance with the disclosure, a machining pass is preferably carried out before the deposition of the repair layer to harmonize the surface on which the repair layer is deposited.

[0015] Thus, surface inequalities are eliminated before the repair layer is deposited.

[0016] According to another feature of the invention, the repair metal is preferably an alloy comprising a base metal and alloying elements, the base metal being in particular nickel and the alloying element in the highest proportion being in particular cobalt.

[0017] The repair process is particularly suitable for the chemical deposition of this type of repair metal.

[0018] According to another feature according to the invention, the repair filler metal can preferably be nickel, chromium, phosphorus and / or aluminum, considered individually or in combination.

[0019] Nickel, chromium, phosphorus and aluminum exhibit good corrosion resistance and redox reaction properties.

[0020] In particular, chromium has good corrosion resistance properties and aluminium has good oxidation resistance properties, phosphorus has good wear resistance properties.

[0021] Depending on the protection requirements of the part, it may be preferable to use one or the other.

[0022] According to another feature according to the invention, the repair reducing agent can preferably be silver, copper and / or gold, considered individually or in combination.

[0023] In various embodiments according to the disclosure, one and / or the other of the following provisions may also be used:

[0024] the part is a component of an aircraft turbomachine;

[0025] the part is a turbine element.

[0026] According to another feature in accordance with the disclosure, preferably, a corrosion or oxidation protection overcoat is deposited on the repair layer by immersing the portion to be repaired in a corrosion protection bath, composed of an aqueous corrosion protection solution comprising ions of a corrosion protection filler metal, chromium ions and a reducing agent.

[0027] The corrosion protection reducing agent 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.

[0028] Thus, not only does the part after repair regain the characteristics it had before use, so as to carry out a "second life", but in addition the part has better resistance to corrosion, so that the "second life" can be extended.

[0029] According to another feature in accordance with the disclosure, preferably, a wear protection overcoat is deposited on the repair layer by immersing the portion to be repaired in a wear protection bath, composed of an aqueous wear protection solution comprising ions of a wear protection filler metal, wear protection metal ions and a reducing agent.

[0030] Thus, as with the corrosion protection operation, the wear protection operation allows the part to be more resistant after repair than before use.

[0031] In various embodiments according to the disclosure, one and / or the other of the following provisions may also be used:

[0032] the filler metal for protection against corrosion or wear can preferably be nickel, chromium, phosphorus and / or aluminium, considered individually or in combination;

[0033] The reducing agent for protection against corrosion or wear may preferably be silver, copper and / or gold, considered individually or in combination. Brief description of the figures

[0034] Other features and advantages of this disclosure will become apparent in the following detailed description, with reference to the accompanying drawings in which:

[0035] [Fig-1] schematically represents a cross-sectional view of a turbomachine including a part comprising a portion to be repaired;

[0036] [Fig.2] represents a portion to be repaired of the part, on an enlarged scale, according to the arrow marked II in [Fig.1];

[0037] [Fig.3] represents, in cross-section along the line marked III of [Fig.2], the portion to be repaired;

[0038] [Fig.4] represents the portion to be repaired soaked in a repair bath, according to a first embodiment;

[0039] [Fig.5] represents the portion to be repaired that has come out of the repair bath, according to the first embodiment;

[0040] [Fig.6] represents the portion to be repaired after machining, dipped in a corrosion protection bath, according to the first embodiment;

[0041] [Fig.7] represents the portion to be repaired removed from the corrosion protection bath and immersed in a wear protection bath, according to the first embodiment;

[0042] [Fig.8] represents the portion to be repaired obtained after removal from the wear protection bath, according to the first embodiment;

[0043] [Fig.9] represents the portion to be repaired after machining, dipped in a repair bath, according to a second embodiment;

[0044] [Fig. 10] represents the portion to be repaired removed from the repair bath and immersed in a corrosion protection bath, according to the second embodiment;

[0045] [Fig. 11] represents the portion to be repaired, removed from the corrosion protection bath and immersed in a wear protection bath, according to the second embodiment; and

[0046] [Fig. 12] represents the portion to be repaired obtained after removal from the wear protection bath, according to the second embodiment. Detailed description of the disclosure

[0047] Fig. 1 schematically represents a cross-sectional view of a turbomachine 50. An airflow entering the turbomachine 50 passes through a blower 62, then separates into a primary flow 52 and a secondary flow 54. The primary flow 52 passes successively through a set of compressors, a combustion chamber 60, then a set of turbines.

[0048] 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.

[0049] The blower 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.

[0050] The combustion chamber 60 is supplied with fuel which is burned in the primary stream 52. The combustion gases form an outlet stream 56 downstream of the combustion chamber 60. The outlet stream 56 passes through the first turbine 82, the second turbine 84 and the third turbine 86.

[0051] More specifically, the third turbine 86 comprises several stages, each including a distributor and a rotor. The distributor of the first stage, considered with respect to the direction of flow of the outlet stream 56, forms a part 1 comprising a portion to be repaired 2.

[0052] Figures 2 and 3 respectively illustrate a portion to be repaired 2 of part 1, enlarged, according to the arrow marked II of [Fig.1] and seen in section according to the line marked III of [Fig.2], the portion to be repaired 2. More particularly, on [Fig.3], part 1 is schematically represented after use.

[0053] The portion to be repaired 2 includes a rough surface 4, which may include corrosion pustules 5.

[0054] 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 the corrosion pustules 5 on an external surface of the part 1.

[0055] 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 rid the portion to be repaired 2 of the corrosion pustules 5.

[0056] As illustrated in [Fig.4], the portion to be repaired 2 then has a cleaned surface 6. The part 1 is then immersed in a repair bath 15.

[0057] 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.

[0058] More specifically, the repair metal is identical to the material of part 1 comprising the portion to be repaired 2. The filler metal for the repair may result of different combinations corresponding to the need for the repair, such as volume restoration, corrosion protection, oxidation protection, wear protection... Finally, the reducing agent is a combining agent dependent on the repair filler metal used.

[0059] The portion to be repaired 2 may be made of a superalloy comprising nickel as the base metal and cobalt as the alloying element in the highest concentration. The repair metal present in the repair bath 15 is the same material as the portion to be repaired 2.

[0060] The repair metal is preferably nickel. Alternatively, chromium, phosphorus and / or aluminum may be used as the repair metal.

[0061] The reducing agent is preferably silver, copper and / or gold.

[0062] A repair layer 10 is then gradually deposited on the cleaned surface 6, in particular by an autocatalytic chemical process, as illustrated in [Fig.5].

[0063] The repair layer 10 has a repair surface 12. However, the repair surface 12 has asperities resulting from the unevenly distributed presence of corrosion pustules 5.

[0064] In order to restore the portion to be repaired 2 to its initial shape, machining is carried out on the repair layer 10. The repair layer 10 then presents a machined repair surface 14 which is uniform, preferably substantially flat in the embodiment illustrated in [Fig.6].

[0065] The dimensions of the repaired part 100 are then substantially in accordance with the nominal dimensions, that is to say the dimensions of the part 1 before use.

[0066] Moreover, it is operated in this way for all faces or surfaces of part 1 comprising portions to be repaired 2.

[0067] Optionally, as illustrated in [Fig.6], the portion to be repaired 2 of the repaired part 100 can then be immersed in a corrosion protection bath 25.

[0068] 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 corrosion protection reducing agent enabling a reaction to be carried out between the part to be repaired 2 and the ions of the corrosion protection bath 25.

[0069] The corrosion protection filler metal is preferably nickel. Alternatively, the protective filler metal is chromium and / or aluminum.

[0070] The corrosion-protective reducing agent is preferably silver, copper and / or gold.

[0071] As illustrated in [Fig.7], a substantially uniform corrosion protection overlayer 20, i.e. of substantially constant thickness, is thus gradually deposited on the machined repair surface 14 of the repair layer 10.

[0072] Furthermore, the corrosion protection overcoat 20 is likely to be deposited on all surfaces of the portion to be repaired 2 of the repaired part 100.

[0073] Optionally, as illustrated in [Fig.7], the portion to be repaired 2 of the repaired part 100 can then be immersed in a wear protection bath 35.

[0074] The wear protection bath 35 is composed of an aqueous wear protection solution comprising ions of the metal corresponding to the metal of the part to be repaired 2, wear protection metal ions and / or a wear protection reducing agent.

[0075] The wear-protecting metal is preferably phosphorus. Alternatively, the wear-protecting metal may be aluminum.

[0076] The wear protection filler metal is preferably nickel, chromium and / or aluminum.

[0077] The wear-protecting reducing agent is preferably silver, copper and / or gold.

[0078] As illustrated in [Fig.8], a substantially uniform wear protection layer 30, i.e. of substantially constant thickness, is thus gradually deposited on the repair layer 10 and the corrosion protection layer 20 of the repaired part 100.

[0079] Furthermore, it may be difficult to have only the portion of the part to be repaired 2 that is immersed in the repair bath 15, in the corrosion protection bath 25 and / or in the wear protection bath 35.

[0080] Thus, it can be envisaged that part 1 is fully immersed in the repair bath 15, the corrosion protection bath 25 and / or the wear protection bath 35.

[0081] Consequently, the deposition of the repair layer 10, the corrosion protection overlayer 20 and / or the wear protection overlayer 30 is therefore not limited to the portion to be repaired 2.

[0082] Consequently, since part 1 has been fully immersed in the repair bath 15, the corrosion protection bath 25 and / or the wear protection bath 30, part 1 is covered in whole or in part by the repair layer 10, the corrosion protection overlayer 20 and / or the wear protection overlayer 30.

[0083] Consequently, it may then be necessary to carry out at least one material removal operation, in particular by machining, not only at the level of the portion to repair 2, but also more generally in all areas of the repaired part 100 which must have dimensions conforming to nominal or defined values.

[0084] Furthermore, the material removal operation can be carried out before dipping part 1 into the repair bath 15, preferably after dipping part 1 into the wear protection bath 35, but it is also possible to do it between these two operations.

[0085] Figures 9 to 12 illustrate a second embodiment which differs from the first embodiment in that instead of immersing the portion to be repaired 2 in the repair bath 15 after simply cleaning the raw surface 4, the portion to be repaired 2 is previously machined, in order to present a machined repair surface 8 which is harmonized, that is to say free of asperities and corresponding to a general shape of the part 1 before use, in other words substantially flat in the illustrated embodiment.

[0086] Next, the portion to be repaired 2 is immersed in the repair bath 15, as illustrated in [Fig. 9]. The repair bath 15 according to the second embodiment has similar characteristics as described in relation to the first embodiment.

[0087] The repair layer 10 is then progressively deposited on the machined surface to be repaired 8, in particular by an autocatalytic chemical process, as illustrated in [Fig.10],

[0088] 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 are then substantially in accordance with the nominal dimensions, that is to say, the dimensions of the part 1 before use.

[0089] Optionally, as illustrated in [Fig.10], the portion to be repaired 2 of the repaired part 100 can then be immersed in the corrosion protection bath 25.

[0090] The corrosion protection bath 25 according to the second embodiment has similar characteristics as described in relation to the first embodiment.

[0091] As illustrated in [Fig.1 1], a substantially uniform corrosion protection overlayer 20, i.e. of substantially constant thickness, is thus gradually deposited on the repair surface 12 of the repair layer 10.

[0092] Optionally, as illustrated in [Fig.1 1], the portion to be repaired 2 of the repaired part 100 can then be immersed in the wear protection bath 35.

[0093] The wear protection bath 35 according to the second embodiment has similar characteristics as described in relation to the first embodiment.

[0094] As illustrated in [Fig. 12], a substantially uniform wear protection layer 30, i.e. of constant thickness, is thus gradually deposited on the repair layer 10 and the corrosion protection layer 20 of the repaired part 100.

[0095] Furthermore, the corrosion protection overcoat 20 is likely to be deposited on all surfaces of the portion to be repaired 2 of the repaired part 100.

[0096] 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 of the portion to be repaired 2 of the part 1.

[0097] 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.

[0098] Part 1 can optionally be removed before one of the deposits to be machined, before being re-immersed in the aqueous solution.

[0099] 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 according to the need and the properties sought, or a single bath containing all the ions of all the metals desired for the repair of the portion to be repaired 2 of the part 1.

[0100] Furthermore, the repair metal is not necessarily identical to the material of the portion to be repaired 2 of part 1. For example, another material could be deposited on a nickel alloy blade for the purpose of repairing it. However, to facilitate the application of the repair metal, it is preferable to have at least some of the material from the portion to be repaired 2 of part 1 present. Consequently, other metals can be added to the aqueous solution depending on the repair requirements.

Claims

Demands

1. A method for repairing a part (1), wherein 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 comprising: • ions of a repair metal, the portion to be repaired (2) being a superalloy comprising nickel as the base metal and cobalt as the alloying element in the highest content and the repair metal being the same material as the portion to be repaired (2), • and optionally: ions of a repair filler metal and / or a repair reducing agent.

2. A repair method according to claim 1, wherein a machining pass (14) is carried out after the deposition of the repair layer (10) to remove excess thickness.

3. Repair method according to claim 1 or 2, wherein a machining pass (8) is carried out before the deposition of the repair layer (10) to harmonize the surface on which the repair layer (10) is deposited.

4. A repair method according to any one of the preceding claims, wherein the repair filler metal is nickel, chromium, phosphorus and / or aluminum.

5. A repair method according to any one of the preceding claims, wherein the repair reducing agent is silver, copper and / or gold.

6. A repair method according to any one of the preceding claims, wherein the part (1) is a component of an aircraft turbomachine (50).

7. Repair method according to the preceding claim, wherein the part (1) is a turbine element (86).

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