Method for repairing parts with a hole and a damaged surface surrounding the hole

Abstract

Method for repairing parts having a hole and whose surface bordering the hole is deteriorated. The method comprises the following successive steps: excavation of the part (1) to be repaired by machining to remove a thickness of deteriorated material (5) and form a recess (6) whose bottom (8) opens into the hole (2); introduction into the hole (2) of a plugging element (9) so that its external face (10) is flush with the bottom of the recess (6) and at least partially plugs the hole (2); deposition of a repair material (7) in the recess (6) and on the external face (10) of the plugging element (9) with an excess thickness of repair material (7) extending beyond the nominal dimensions of the surface (3) and the hole (2); Removal of the sealing element (9) and machining of the part (1) to be repaired so that the surface (3) and the hole (2) are restored to their nominal dimensions. Figure to be published with the abbreviation: Figure 8

Description

Title of the invention: Method for repairing parts with a hole and whose surface bordering the hole is damaged. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the repair of mechanical parts having a hole and whose surface bordering the hole is deteriorated.

[0002] The present invention relates to a method for repairing such parts, as well as a sealing element which is used during the implementation of this method. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Currently, to repair wheels damaged at the bolt holes, the applicant uses a process based on resurfacing the damaged areas.

[0004] This process, illustrated in [Fig. 3], [Fig. 4], and [Fig. 5], is based on an additive repair using a dynamic gas spray technique at ambient temperature (more commonly known as cold spray), in which a powder, most often metallic, is sprayed at very high speed onto a surface to form a coating. This technique is described in greater detail in patent application EP3120968 and will be referred to hereafter as the dynamic cold spray technique.

[0005] This repair method can be applied to any part 1 having at least one hole 2 of nominal diameter N and whose surface 3 bordering the through end 4 of said hole 2 has a thickness of deteriorated material 5. Thickness of deteriorated material means a change in the surface condition (for example roughness), a reduction in thickness by friction or wear, a chemical alteration of the surface (for example formation of corrosion products), etc.

[0006] A thickness of material is first removed from the damaged area, for example by machining (see [Fig.3]). This step generates a recess 6 around the hole, which extends into it to a certain depth in the form of a counterbore, usually chamfered.

[0007] A repair material 7 in powder form is then deposited into the recess 6 by a cold gas dynamic spraying technique (see [Fig. 4]). During this repair process, the repair material 7 consolidates upon impact and at least partially replaces the material removed in the previous step. An excess of repair material 7 is deposited, particularly because an additional surface finishing operation (e.g., machining) is required due to the high surface roughness.

[0008] Part 1 is then machined by removing the excess repair material 7, for example by finishing machining, in order to restore part 1 to its original dimensions Nominal linear dimensions (see [Fig. 5]). Nominal linear dimensions refer to the geometric properties and dimensions that part 1 must have when new or restored.

[0009] However, during the application of the repair material 7, the applicant observed a chamfering phenomenon at the edges of the deposited repair material 7. This chamfering is related to the distribution of the repair material 7 particles in the projected flow.

[0010] However, this chamfering phenomenon of the deposit can be particularly critical at the edges of the counterbore cut into hole 1. Indeed, after machining the part 1 to be repaired, the depositor observed that this chamfering phenomenon resulted in a lack of repair material 7 at the edge of hole 2. This lack of repair material 7 is shown in [Fig. 5] where the nominal linear dimensions of the repaired part 1 are represented by dashed lines. It can be seen that at the surface 3 bordering the through end 4 of hole 2, the diameter D of the latter does not conform to its nominal value N.

[0011] The current cold gas dynamic projection repair process therefore generates material gaps L in the repaired parts and therefore does not allow a part 1 to be perfectly repaired so that the hole 2 and the surface 3 bordering the through end 4 of said hole 2 regain their nominal linear dimensions.

[0012] Other repair material deposition techniques are also likely to generate such gaps due to a lack of material in the parts to be repaired. Summary of the invention

[0013] The invention offers a solution to the problem mentioned above, by compensating for the chamfering phenomenon observed when repair material is deposited at the edges. This solution relies on the use of a plugging element in the hole, which temporarily reduces the diameter of the hole at the bottom of the counterbore, thus allowing a greater excess of repair material to be deposited. This excess material can then be machined to restore the hole to its nominal diameter along its entire length.

[0014] One aspect of the invention relates to a method for repairing a part having a hole and a surface bordering an open end of said hole, said surface having a thickness of deteriorated material, the method allowing the nominal dimensions of the surface and the hole to be restored before deterioration, and comprising the following successive steps: • Excavation of the part to be repaired using a material removal technique that removes the thickness of deteriorated material and widens the opening end of the hole to a depth P, this excavation of material forming a hollow whose bottom opens into the hole; • introduction into the hole of a sealing element having an external face directed towards the open end of the hole, said sealing element being positioned so that its external face is flush with the bottom of the recess and at least partially seals the hole; • depositing a repair material in the recess and on the external face of the plug so as to replace the entire thickness of the excavated deteriorated material and to form an excess of repair material extending beyond the nominal dimensions of the surface and the hole; and • Removal of the sealing element and machining of the part to be repaired by a material removal technique so as to remove the excess thickness of repair material so that the surface and the hole regain their nominal dimensions.

[0015] Thanks to the invention, and in particular thanks to the use of the sealing element, it is possible to deposit a greater thickness of repair material at the open end of the hole and thus avoid a lack of repair material at the edge of the hole after machining. Therefore, the method according to the invention advantageously allows the hole and the surface bordering its opening to regain their nominal dimensions.

[0016] In addition to the characteristics mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: • The excavation stage of the part to be repaired is carried out by machining. • During the step of introducing a sealing element, the sealing element is housed in a tight fit in the hole. • The step of introducing a sealing element includes a step of heating and thermal expansion of the part to be repaired, or a step of cooling and thermal contraction of the sealing element. • The repair material application stage is carried out using a projection technique. • The repair material deposition step is carried out by a dynamic cold gas projection technique of the repair material in the form of a solid powder. • During the repair material application stage, the repair material is the same as that from which the part to be repaired is made. • The machining stage of the part to be repaired is carried out by machining.

[0017] According to one aspect of the invention, the external face of the sealing element is flat, which makes it possible in particular to deposit sufficient repair material at the open end of the hole.

[0018] According to another aspect of the invention, the sealing element is made of a material belonging to the same family of material as the part to be repaired, and more preferably in the same material as the part to be repaired, which makes it possible in particular to machine the sealing element while machining the hole with the same cutting tool, and also makes it possible not to contaminate the repaired part with an input of elements from other materials.

[0019] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0020] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0021] [Fig. 1] is a cross-sectional view of a part having a hole, the hole and the surface bordering the outward end of the hole having nominal linear dimensions.

[0022] [Fig.2] is a cross-sectional view of a part similar to that of [Fig.1] where the surface bordering the open end of the hole has a thickness of deteriorated material.

[0023] [Fig.3], [Fig.4] and [Fig.5] are cross-sectional views illustrating the repair of the part of [Fig.2] according to a prior art process.

[0024] [Fig.6], [Fig.7], [Fig.8] and [Fig.9] are cross-sectional views illustrating the repair of the part of [Fig.2] according to a method of the invention. DETAILED DESCRIPTION

[0025] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0026] The repair method according to the invention is intended to repair a part 1 having at least one hole 2 and where a surface 3 bordering an open end 4 of said hole 2 has a thickness of deteriorated material 5. This repair aims to restore the nominal dimensions of the surface 3 and the hole 2 before deterioration, without generating material gaps in the repaired parts.

[0027] The part 1 to be repaired can be an aircraft wheel, a flange or any mechanical part, preferably made of metal, and having at least one hole 2.

[0028] Hole 2 can be a blind hole or a through hole.

[0029] The method according to the invention comprises a first step in which the part 1 to be repaired is excavated (see [Fig. 6]). The purpose of this step is to remove at least the entire thickness of the damaged material 5 in order to prepare the part 1 before 7. Reload it with repair material. The excavation step is carried out using a material removal technique, preferably machining. This material removal can be performed by any known technique suitable for the nature of the material of the part.

[0030] During the removal of the deteriorated material 5, the open end 4 of the hole 2 is generally excavated, in the form of a counterbore, usually chamfered, to a depth P, which locally enlarges the hole 2 at the level of the excavated portion. Indeed, this excavation of material usually generates a recess 6 whose bottom 8 opens into the hole 2.

[0031] The method according to the invention includes a second step in which a sealing element 9 is introduced into the hole 2 (see [Fig. 7]). This step is intended to create an additional deposition surface 3' where repair material 7 can be deposited with sufficient thickness to avoid creating material gaps in the repaired parts after machining, particularly at the edge of the through end 4, as is the case with prior art techniques (see [Fig. 5]). Thus, the plugging element 9 has an external face 10 directed towards the through end 4 of the hole 2, this external face 10 forming an additional deposition surface 3' for repair material 7, and it is positioned so that its external face 10 is flush with the bottom 8 of the recess 6 (i.e. its external face 10 is at a depth P inside the hole 2) and plugs at least partially the hole 2.

[0032] The sealing element 9 preferably has a substantially central through orifice 11 opening into its external face 10.

[0033] The external face 10 of the sealing element 9 is preferably flat. It preferably has a roughness Ra less than or equal to 1.6 pm in order to meet general surface finish tolerances similar to those applied to the surface 3 of the part 1 to be repaired and on the internal lateral face(s) 12 of the hole 2.

[0034] According to one embodiment of the invention, the sealing element 9 can be in the form of a straight cylindrical pin whose cross-section has a shape substantially identical to that of the hole 2 in which it is housed.

[0035] Other forms can be envisaged, as long as the sealing element 9 is able to remain in place in the hole 2 during the step of depositing a repair material 7, and in particular able not to be displaced by the pressure exerted by the projection of repair material 7. Thus, the sealing element 9 is represented schematically in the form of a cylindrical pin on [Fig.7] and [Fig.8], by way of example only and these figures should not be interpreted restrictively.

[0036] According to another embodiment of the invention, the sealing element 9 can be in the form of a simple plate or sheet, associated with retaining means allowing it to be held in position in the hole 2 where it is housed.

[0037] The sealing element 9 is preferably made of a material belonging to the same material family as the part 1 to be repaired; that is, it is predominantly made from the same material as the part 1 to be repaired. For example, if the part 1 to be repaired is made of aluminum, then the sealing element 9 is preferably predominantly made of aluminum. More preferably, the sealing element 9 is made of the same material as the part 1 to be repaired. If the sealing element 9 were made of a harder material than that of the part 1 to be repaired, this could cause material rebound during the deposition phase of the repair material 7. Non-adherent particles of repair material 7 could then contaminate subsequent layers and impair the homogeneity of the deposit.

[0038] The shape and diameter of the external face 10 of the sealing element 9 are preferably substantially the same as the shape and nominal diameter N of the hole 2 so as not to create a gap between the sealing element 9 and the lateral walls of the hole 2 in which it is housed.

[0039] In the case where the sealing element 9 is in the form of a straight cylindrical pin, it preferably has a diameter substantially identical to and very slightly smaller than the nominal diameter N of the hole 2 in order to be housed in tight fit in the latter, for example with a clamping between 1‰ and 9‰ of the nominal dimension of the pin, which allows the pin to be held during the projection of repair material 7, while allowing its removal.

[0040] According to one embodiment of the invention, the introduction of the sealing element 9 is achieved by thermal difference between said sealing element 9 and the part 1 to be repaired, in particular by a step of heating and thermal expansion of the part 1 to be repaired, or by a step of cooling and thermal contraction of the sealing element 9. For reasons of simplicity and risk of alteration of the part 1 to be repaired in the event of heating it, it is preferred to cool the sealing element 9, for example by immersing it in liquid nitrogen, which allows, for example, it to be cooled to a temperature between -160 °C and -170 °C for the time of its introduction into the hole 2, while the part 1 to be repaired remains at ambient temperature.

[0041] According to one embodiment of the invention, the introduction of the sealing element 9 into the hole 2 can be carried out using a centering tool, for example having the shape of the hole 2, which allows the sealing element 9 to be positioned in the hole 2 at a desired depth.

[0042] The method according to the invention includes a third step in which repair material 7 is deposited in the recess 6 and on the outer face 10 of the sealing element 9 (see [Fig. 8]). This step aims to replace the entire thickness of the excavated damaged material 5 with repair material 7 and to form an excess of repair material 7 extending beyond the nominal dimensions of the hole 2 and the surface 3 bordering it. In order to avoid any material gaps after machining, repair material 7 is generally also deposited beyond the recess 6 formed by the excavated portion of damaged material 5, in particular on an additional deposition surface 3' to be repaired that did not have any thickness of damaged material 5 on the part 1 to be repaired.

[0043] By "forming an excess thickness of repair material 7 extending beyond the nominal dimensions of the surface 3 and the hole 2", it is understood that not only does the deposited repair material 7 replace the thickness of deteriorated material 5 that was removed during the first step, but that an additional volume of repair material 7 is further deposited over the entire surface 3 of the recess 6 that was generated during the excavation of the deteriorated material 5. Thus, an excess thickness e of repair material 7 is formed on the surface 3 bordering the through end 4 of the hole 2 and an excess thickness E of repair material 7 is formed in the hole 2, on the external face 10 of the plugging element 9, at least at the level of the internal lateral face(s) 12 of the hole 2.

[0044] During this third step, the portion of the hole 2 located on the external face 10 of the sealing element 9 is at least partially filled by repair material 7. In the recess 6 where the repair material 7 is deposited, the diameter d of the hole 2 thus at least partially filled is less than the nominal diameter N of the hole 2.

[0045] This extra thickness makes it possible to avoid any material deficiency after machining of the part 1 to be repaired and to ensure that the nominal dimensions of the hole 2 and the surface 3 which borders it are recovered before deterioration.

[0046] The step of depositing the repair material 7 is preferably carried out by spraying said repair material 7, but other deposition techniques may be considered. Indeed, the two main families of coating deposition processes that can be used are: • Wet deposition (e.g. electrochemical baths, conversions). • Dry deposition methods (e.g. PVD, CVD, welding, thermal spraying, cold spray).

[0047] The repair material 7 is preferably a material belonging to the same material family as the part 1 to be repaired. More preferably, the material The repair compound 7 is the same as that from which the part 1 to be repaired is formed. It is preferably deposited in powder form.

[0048] According to one embodiment of the invention, the deposition is preferably carried out by a dynamic cold gas projection technique of the repair material 7 in the form of a solid powder.

[0049] The method according to the invention includes a fourth step in which the sealing element 9 is removed and the part 1 to be repaired is machined (see [Fig. 9]). This step aims to remove the sealing element 9 and the excess repair material 7 so that the surface 3 and the hole 2 regain their nominal dimensions.

[0050] This machining step is preferably carried out by a material removal technique, for example by grinding.

[0051] During this step, the removal of the sealing element 9 can be carried out simultaneously with the machining of the part 1 to be repaired, the said sealing element 9 then being removed, for example, by the same cutting tool used to machine the part 1 to be repaired. Other means of removal can be considered for the removal of the sealing element 9, for example, dissolution, melting, breaking, fragmentation, dismantling, etc.

[0052] Although described through a number of examples, variants and embodiments, the repair method and the sealing element according to the invention include various variants, modifications and improvements which will be obvious to a person skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

1.

2.

3. Demands A method for repairing a part (1) having a hole (2) and a surface (3) bordering an open end (4) of said hole (2), said surface (3) having a thickness of deteriorated material (5), the method enabling the nominal dimensions of the surface (3) and the hole (2) to be restored before deterioration, and being characterized in that it comprises the following successive steps: - excavation of the part (1) to be repaired by a material removal technique which removes the thickness of deteriorated material (5) and widens the open end (4) of the hole (2) to a depth (P), this material excavation forming a recess (6) whose bottom (8) opens into the hole (2); - introduction into the hole (2) of a plugging element (9) having an external face (10) directed towards the open end (4) of the hole (2), said plugging element (9) being positioned so that its external face (10) is flush with the bottom of the recess (6), is at a depth P inside the hole (2) and plugs at least partially the hole (2) to form an additional deposition surface (3') for repair material (7); - depositing a repair material (7) in the recess (6) and on the outer face (10) of the sealing element (9) so as to replace the entire thickness of the excavated deteriorated material (5) and to form an excess thickness of repair material (7) extending beyond the nominal dimensions of the surface (3) and the hole (2); and - removal of the sealing element (9) and machining of the part (1) to be repaired by a material removal technique so as to remove the excess thickness of repair material (7) so that the surface (3) and the hole (2) regain their nominal dimensions. A repair method according to claim 1, characterized in that the step of excavating the part (1) to be repaired is carried out by machining. A repair method according to claim 1 or 2, characterized in that during the step of introducing a sealing element (9), the sealing element (9) is housed in tight fit in the hole (2).

4. Repair method according to the preceding claim, characterized in that the step of introducing a sealing element (9) includes a step of heating and thermal expansion of the part (1) to be repaired, or a step of cooling and thermal contraction of the sealing element (9).

5. Repair method according to any one of the preceding claims, characterized in that the step of depositing repair material (7) is carried out by a cold gas dynamic projection technique of the repair material (7) in the form of a solid powder.

6. Repair method according to any one of the preceding claims, characterized in that during the step of depositing repair material (7), the repair material (7) is the same as that from which the part (1) to be repaired is formed.

7. Repair method according to any one of the preceding claims, characterized in that the machining step of the part (1) to be repaired is carried out by grinding.

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