Method of repairing parts having a hole and whose surface bordering the hole is damaged

Abstract

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

Description

Title of the invention: Method for repairing parts having 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 the surface bordering the hole of which is damaged.

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

[0003] Currently, to repair wheels damaged at the bolt holes, the applicant uses a method 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 cold spray technique, in which a powder, most often metallic, is projected at very high speed onto a surface to form a coating. This technique is more fully described in patent application EP3120968 and will be referred to hereinafter as a cold gas dynamic 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 emerging end 4 of said hole 2 comprises a thickness of deteriorated material 5. By thickness of deteriorated material is meant a modification of 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 previously removed in 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 the form of powder is then deposited in the recess 6 by a cold gas dynamic projection technique (see [Fig. 4]). During this reloading, the repair material 7 consolidates upon impact and replaces at least partially the material that was removed during the previous step. The repair material 7 is deposited in excess, in particular because it is necessary to carry out an additional surface finishing operation (for example by machining), because the roughness is high.

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

[0009] However, when depositing the repair material 7, the applicant observed a chamfering phenomenon of the deposit of repair material 7 at the edges. This chamfering is linked to the distribution of the particles of the repair material 7 in the projected flow.

[0010] Now this phenomenon of chamfering of the deposit can be particularly critical at the edges of the counterbore dug in the hole 1. Indeed, after machining the part 1 to be repaired, the applicant noted that this chamfering phenomenon generated an absence of repair material 7 at the edge of the hole 2. This absence of repair material 7 is highlighted in [Fig. 5] where the nominal linear dimensions of the repaired part 1 are shown in dotted lines. It can be seen that at the surface 3 bordering the open end 4 of the hole 2, the diameter D of the latter is not in accordance with its nominal value N.

[0011] The current repair process by dynamic cold gas projection generates therefore gaps L of material 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 techniques for depositing repair material 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 provides a solution to the problem mentioned above, by making it possible to compensate for the chamfering phenomenon observed for the deposition of repair material at the edges. This solution is based on the use of a sealing element in the hole which makes it possible to temporarily reduce the diameter of the hole in the bottom of the counterbore and therefore to deposit a greater excess of repair material there, which can then be machined to restore the hole to its nominal diameter over 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 comprising a thickness of damaged material, the method making it possible to recover the nominal dimensions of the surface and of the hole before damage, and comprising the following successive steps: • excavation of the part to be repaired using a material removal technique which removes the thickness of damaged material and widens the opening end of the hole to a depth P, this excavation of material forming a recess 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 sealing element so as to replace the entire thickness of deteriorated material excavated and to form an excess thickness 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 using a material removal technique so as to remove the excess repair material so that the surface and the hole return to 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 opening end of the hole and therefore to avoid an absence of repair material at the edge of the hole after machining. Thus, 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 which have just been mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the step of excavating 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 comprises 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 deposition step is carried out using a projection technique. • the repair material deposition step is carried out by a cold gas dynamic projection technique of the repair material in the form of a solid powder. • during the repair material deposition step, the repair material is the same as that from which the part to be repaired is formed. • the machining step 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 in particular makes it possible to deposit sufficient repair material at the open end of the hole.

[0018] According to another aspect of the invention, the sealing element is manufactured from a material belonging to the same family of materials as the part to be repaired, and more preferably from the same material as the part to be repaired, which in particular makes it possible to machine the sealing element while machining the hole with the same cutting tool, and also makes it possible not to pollute the repaired part with an addition 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 information purposes only and in no way limit the invention.

[0021] [Fig. 1] is a sectional view of a part provided with a hole, the hole and the surface bordering the opening end thereof having nominal linear dimensions.

[0022] [Fig.2] is a sectional view of a part similar to that of [Fig.l] 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 sectional views illustrating the repair of the part of [Fig.2] according to a method of the prior art.

[0024] [Fig.6], [Fig.7], [Fig.8] and [Fig.9] are 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 in different figures has a single 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 comprises a thickness of damaged material 5. This repair aims to restore the nominal dimensions of the surface 3 and of the hole 2 before damage, without generating gaps in the material 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 during 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 damaged material 5 in order to prepare the part 1 before reloading it with repair material 7. The excavation step is carried out by a material removal technique, preferably by machining. This material removal can be carried out by any known technique adapted to the nature of the material of the part 1.

[0030] When removing the damaged material 5, the opening end 4 of the hole 2 is generally excavated, in the form of a counterbore, usually chamfered, to a depth P, which locally widens the hole 2 at the level of the excavated part. 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 comprises a second step during which a sealing element 9 is introduced into the hole 2 (see [Fig.7]). The purpose of this step is to create an additional deposition surface 3' where repair material 7 can be deposited with sufficient thickness so as to avoid creating gaps in the material in the repaired parts after machining, in particular at the edge of the emerging end 4, as is the case with prior techniques (see [Fig.5]). Thus, the sealing element 9 has an external face 10 directed towards the emerging 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 at least partially seals the hole 2.

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

[0033] The external face 10 of the closure 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 condition tolerances similar to those applied to the surface 3 of the part 1 to be repaired and to the internal lateral face(s) 12 of the hole 2.

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

[0035] Other shapes 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 moved by the pressure exerted by the projection of repair material 7. Thus, the sealing element 9 is shown schematically in the form of a cylindrical pin in [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 closure element 9 may be in the form of a simple plate or sheet, associated with means of support allowing it to be held in position in hole 2 where it is housed.

[0037] The sealing element 9 is preferably manufactured from a material belonging to the same family of materials as the part 1 to be repaired, that is to say that it is mainly manufactured from the same material as that of 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 mainly manufactured from aluminum. More preferably, the sealing element 9 is manufactured from the same material as the part 1 to be repaired. In the case where the sealing element 9 is manufactured from a harder material than that of the part 1 to be repaired, this could cause material rebounds during the phase of deposition of the repair material 7. Non-adherent particles of repair material 7 are then likely to contaminate the following layers and deteriorate the homogeneity of the deposit.

[0038] The shape and diameter of the external face 10 of the closure element 9 are preferably substantially the same as the shape and diameter nominal diameter N of the hole 2 so as not to create an empty space between the closure element 9 and the side walls of the hole 2 inside which it is housed.

[0039] In the case where the closure element 9 is in the form of a straight cylindrical pin, it preferably has a diameter that is substantially identical to and very slightly smaller than the nominal diameter N of the hole 2 in order to be housed in a tight fit therein, for example with a tightening of 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 closure element 9 is done by thermal difference between said closure 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 closure element 9. For reasons of simplicity and risk of alteration of the part 1 to be repaired in the event of heating thereof, it is preferred to cool the closure element 9, for example by immersing it in liquid nitrogen, which allows for example to cool it 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 room temperature.

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

[0042] The method according to the invention comprises a third step during which repair material 7 is deposited in the recess 6 and on the external face 10 of the sealing element 9 (see [Fig.8]). The purpose of this step is to replace the entire the thickness of deteriorated material 5 excavated by repair material 7 and to form an excess thickness of repair material 7 extending beyond the nominal dimensions of the hole 2 and the surface 3 bordering it. In order to avoid any gap in material after machining, repair material 7 is generally also deposited beyond the recess 6 formed by the portion of deteriorated material 5 which has been excavated, in particular on a portion of additional deposition surface 3' to be repaired which did not have any thickness of deteriorated 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 meant that not only does the deposited repair material 7 replace the thickness of deteriorated material 5 which was removed during the first step, but that an additional volume of repair material 7 is also deposited over the entire surface 3 of the recess 6 which 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 open 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 closure 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 with 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 sealed is less than the nominal diameter N of the hole 2.

[0045] This excess thickness makes it possible to avoid any gap in the material after machining 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 found 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 can be envisaged. Indeed, the two main families of coating deposition processes that can be used are: • Wet deposition (e.g. electrochemical baths, conversions). • Dry deposition (e.g. PVD, CVD, welding, thermal spraying, cold spray).

[0047] The repair material 7 is preferably a material belonging to the same family of materials as the part 1 to be repaired. More preferably, the repair material 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 cold gas dynamic projection technique of the repair material 7 in the form of a solid powder.

[0049] The method according to the invention comprises a fourth step during which the closure element 9 is removed and the part 1 to be repaired is machined (see [Fig.9]). The purpose of this step is to remove the closure element 9 and the excess thickness of repair material 7 so that the surface 3 and the hole 2 regain their nominal dimensions.

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

[0051] During this step, the removal of the closure element 9 can be carried out at the same time as the machining of the part 1 to be repaired, said closure element 9 then being for example removed by the same cutting tool as that used to machine the part 1 to be repaired. Other means of removal can be envisaged for the removal of the closure element 9, for example dissolution, fusion, rupture, fragmentation, disassembly, etc.

[0052] Although described through a certain 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 those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

Claims

1. 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) comprising a thickness of damaged material (5), the method making it possible to recover the nominal dimensions of the surface (3) and of the hole (2) 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 damaged material (5) and widens the open end (4) of the hole (2) to a depth (P), this excavation of material forming a recess (6) whose bottom (8) opens into the hole (2);- introduction into the hole (2) of a sealing element (9) having an external face (10) directed towards the emerging end (4) of the hole (2), said sealing element (9) being positioned so that its external face (10) is flush with the bottom of the recess (6) and at least partially seals the hole (2); - depositing a repair material (7) in the recess (6) and on the external face (10) of the sealing element (9) so as to replace the entire thickness of deteriorated material (5) excavated and to form an excess thickness of repair material (7) extending beyond the nominal dimensions of the surface (3) and of 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.;

2. Repair method according to claim 1, characterized in that the step of excavating the part (1) to be repaired is carried out by machining.

3. 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 a 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) comprises 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 step of machining the part (1) to be repaired is carried out by grinding.

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