Method for manufacturing component comprising metal substrate covered with protective layer

Abstract

One aspect of the invention relates to a method for manufacturing a component (1) comprising a metal substrate (Sub) at least partially covered with a trimmed protective layer (Rf), the method comprising the following steps: a first step (A) of preparing an initial surface to create a roughened surface without sandblasting, the first step comprising a sub-step of shot blasting the initial surface of the substrate to obtain a roughness of a rough surface having a total height Rt of the surface roughness profile of between 10 [mu] m and 15 [mu] m and a sub-step of cleaning the rough surface (Sub); a second step (B) of forming a rough coating (Rb) having a thickness of between 95 [mu] m and 120 [mu] m on the cleaned rough surface (S2) by spraying a powder mixture comprising submicron metal carbide particles according to the HVOF thermal spraying method; and a third trimming step (D) of forming a polished surface (S3) having a roughness of less than 0.2 [mu] m by polishing the surface (S2) of the rough coating formed from the powder mixture to form the trimmed protective layer (Rf) having a thickness of between 75 [mu] m and 100 [mu] m.

Description

Technical Field

[0001] The technical field of the invention is that of a method for manufacturing a component, such as an aerospace component, comprising a substrate at least partially coated with a protective layer protecting the substrate.

[0002] The invention relates to a method for producing a component comprising a metal substrate at least partially covered with a protective layer. Background Art

[0003] For example, methods are known for manufacturing components which involve applying a hard chrome coating to a metal substrate by means of a metal bath, the hard chrome coating serving both to protect the substrate and to impart a functional roughness thereto.

[0004] It is known that hard chrome coatings are produced in electrolytic cells in the presence of hexavalent chromium-based (Cr(VI)) chromic acid. Hexavalent chromium is harmful to humans and the environment and is classified as CMR (Carcinogenic, Mutagenic and Reprotoxic).

[0005] The aim is therefore to eliminate the use of hexavalent chromium, which is harmful to health and the environment.

[0006] A method is known, in particular from document EP2956564 B1 or document FR3002239 of the same patent family, for producing components (parts) with a coating by thermal spraying of the HVOF (High Velocity Oxygen Fuel) type on a substrate having a thickness between 30 μm and 50 μm. The method comprises a first step of preparing the surface of the substrate to be coated by sandblasting in order to increase its surface roughness Ra to about 0.6 μm to 1.6 μm. The method then comprises the step of forming a coating by HVOF-type spraying of a powder mixture comprising WC-type metal carbide particles and Co and Cr binders for the carbides onto the prepared substrate. The size of these carbide particles is strictly less than 1 μm, preferably about 450 nm+ / -50 nm, and the thickness of the finished coating thus formed is less than 50 μm. The method then comprises the step of finishing the surface by polishing the coating to ensure that its roughness Ra is less than 1.6 μm, thereby obtaining the desired dimensions and surface finish in the plane. These deposits provide corrosion resistance of about 500 hours in salt spray (salt spray test) and reduce the risk of detachment / peeling (cracking or delamination) of the coating from the substrate. However, this solution is insufficient, since improved corrosion resistance is required in the aerospace field compared to the prior art, while also providing resistance to spalling (stripping). In fact, corrosion tests in the aerospace field are currently 1000 hours in salt spray and it has been shown that corrosion resistance is not systematic, especially on cylindrical substrates.

[0007] Furthermore, the sandblasting step in this solution is costly and has an impact on the environment. The sandblasting step increases the roughness of the substrate and therefore increases the surface roughness profile Rt (Rt>20 μm). The total height Rt of the surface roughness profile corresponds to the sum of the height Zp of the largest profile peak and the depth Zv of the largest profile valley in a cross section with a length L measured relative to the mean line of the profile. In other words, the maximum distance between the highest peak and the lowest valley.

[0008] Furthermore, it is described in this document that it is previously known to deposit a coating having a thickness of more than 75 μm obtained with particles of a few micrometers and then to grind the coating (removing at least 50 μm for grinding).

[0009] There is a need to reduce the manufacturing costs of this method while maintaining corrosion resistance, particularly for the thin coating thicknesses (<100 μm) in the finished state of this manufacturing method.

[0010] The invention presented here therefore aims to improve this method for producing HVOF deposits. Summary of the invention

[0011] It has been noted within the industry (unpublished) that by impregnating the coating with an organic impregnant prior to polishing, the coating can have a trimmed thickness of less than 80 μm while meeting corrosion and spalling resistance standards by eliminating the sandblasting step.

[0012] It has also been noted within the industry (unpublished) that by applying the coating as in EP2956564 but with a trimmed thickness of 55 μm, there are still corrosion problems in a 1000 hour corrosion test.

[0013] However, this impregnation step is an additional step and thus has limitations in terms of cost and time as well as from the perspectives of health, safety, and environment.

[0014] The present invention provides a solution that improves the method described in EP2956564 B1, as it eliminates the surface sanding step before thermal spray coating and does not add an impregnation step, while having excellent corrosion resistance as it passes a 1000-hour corrosion test.

[0015] One aspect of the invention relates to a method for manufacturing a component comprising a metal substrate at least partially covered with a trimmed protective layer, the method comprising in sequence:

[0016] a first preparation step without surface modification by sandblasting, the first preparation step comprising: a sub-step of peening the initial surface to obtain a roughness of the initial surface with a total surface roughness profile height Rt between 10 μm and 15 μm; and a sub-step of cleaning the initial surface of the initial substrate,

[0017] - a second step: forming a raw coating with a thickness between 95 μm and 125 μm on the cleaned raw surface with a prepared roughness by spraying a powder mixture containing submicron metal carbide particles according to a high-pressure liquid HVOF type thermal spraying process,

[0018] - A third step: polishing and trimming the surface of the original coating made of the powder mixture to form the trimmed protective layer, thereby forming a polished surface with a roughness Ra of less than 0.2 μm, the thickness of the trimmed protective layer being between 75 μm and 100 μm.

[0019] Surprisingly, by depositing a conditioned protective layer of greater than 75 μm on the cleaned (prepared) raw surface of the substrate without increasing the impregnation, the roughness of the raw surface having a total surface roughness profile height Rt between 10 μm and 15 μm by only shot peening during preparation, the conditioned coating of greater than 75 μm adheres and does not flake off (this is different from the prior art in document FR3002239, which involves a sandblasting step on the substrate and a layer of less thickness). In other words, the present invention does not have a sandblasting step, but includes a shot peening step. Shot peening is a technique consisting of spraying metal shots onto the surface of an object for surface treatment, the purpose of which is to improve the appearance of the part. Shot peening further closes microscopic cracks (not visible to the naked eye) that, in use, can cause sealing failures due to internal pressure. This is an additional guarantee against corrosion. Shot peening, which is known for modifying the surface structure of an object or a part and therefore its appearance, makes it possible to obtain a higher surface roughness (Ra has a lower value) and a lower total height Rt of the surface roughness profile (here between 10 μm and 15 μm) than by a sandblasting step (Rt>20 μm), which is known for eliminating impurities in order to be compatible with the adhesion of powdered or liquid paints or lacquers. It is therefore surprising that the addition of the coating using only shot peening instead of sandblasting or without sandblasting produces a thicker coating (the finished layer is greater than 75 μm) that adheres and does not peel off. In addition, since the layer is thicker, the corrosion resistance is improved, allowing it to withstand a 1000-hour corrosion test.

[0020] The original surface of the substrate refers to a surface of the substrate whose roughness has not been changed, whether manufactured by molding or by machining (ie, the original surface has not been subjected to any treatment such as sandblasting).

[0021] A cleaned original surface refers to an initial surface that has been through a preparation step, ie, shot peening and cleaning of the initial surface.

[0022] Therefore, in the following description, the prepared surface refers to the cleaned original surface (prepared by shot peening according to PCS-2300 on the initial surface to obtain a Ra between 0.6 μm and 1.6 μm and cleaned).

[0023] A pristine coating consisting of a powder mixture means that the layer consists only of material 100% originating from the powder mixture and therefore does not include any additional material, such as organic impregnants.

[0024] Submicron metal carbide means that the size of each metal carbide particle is strictly less than 1 μm (submicron carbide).

[0025] The HVOF thermal process refers to a thermal process called high velocity oxygen fuel, which is a high velocity thermal process using liquid fuel (paraffin).

[0026] The invention makes it possible to obtain a substrate with an initial coating of optimized thickness without increasing the roughness of the substrate surface due to sandblasting, while improving the corrosion resistance. This therefore makes it possible to optimize the amount of powder mixture without requiring a roughness modification step or an impregnation step with an organic impregnant, while improving the level of corrosion resistance compared to the solutions of the prior art. In other words, this solution makes it possible to dispense with additional costly steps such as preparing the substrate by sandblasting directly on the initial surface or by a shot peening step on the initial surface or by sandblasting on the initial surface after impregnation.

[0027] The original thickness between 95 μm and 125 μm is due in particular to the manufacturing tolerances of the high-speed thermal spraying process using HVOF type liquid fuel (paraffin), but is also related to the shrinkage required during polishing to obtain a finished surface with a roughness Ra < 0.2 μm and to the manufacturing tolerances of the assembly of the components. Considering the concern, for environmental and cost reasons, to use as few submicron metal carbide particles as possible, while having good corrosion resistance, the Applicant has surprisingly and unexpectedly noticed that an increase in the finished thickness of the polished surface by 25 μm (corresponding to a coating thickness between 75 μm and 100 μm, with a roughness Ra of the polished surface less than 0.2 μm), by the method according to the invention (without sandblasting), compared to the solutions mentioned in patent FR3002239 and its prior art, allows passing the 1000 hours salt test, i.e. doubling the corrosion resistance compared to the solutions mentioned in patent FR3002239 and its prior art.

[0028] The thickness of the layer deposited by the spraying step according to the invention is equal to the size according to: the desired size plus the oversize removed by polishing. In fact, the step of polishing the finishing coating makes it possible to remove a thickness strictly less than 30 μm (in particular between 20 μm and 25 μm), while grinding removes at least 50 μm, taking into account the roughness and geometrical defects of the part. Thus, after the polishing step, by removing a maximum of 30 μm of the coating thickness, a thickness between 75 μm and 100 μm and a roughness of less than 0.2 μm can be obtained. Of course, the dimensions and manufacturing tolerances of the original substrate will be adjusted according to the manufacturing tolerances of the finished part (substrate tolerances + tolerances of the finished protective layer).

[0029] In conclusion, surprisingly, and contrary to what is indicated in document FR3002239, it is possible to have a coating thickness exceeding 75 μm while omitting the sandblasting step (sandblasting with a roughness with a total roughness profile height Rt of the roughness of the original surface greater than 20 μm). The problem of flaking of the deposited coating is also eliminated by the fact that the final roughness is less than 0.2 μm and the layer is formed of submicron metal carbide particles with a trimmed thickness between 75 μm and 100 μm. Moreover, the corrosion resistance is doubled by adding only 25 μm to 50 μm more coating than in document FR3002239.

[0030] Furthermore, in the prior art, it was necessary to prepare the initial or original surface of the substrate (after shot peening) by sandblasting in order to increase the surface roughness and thus the adhesion surface of the coating. Here, according to the invention, since the protective layer is dense, it has been noted that the level of mechanical adhesion of the protective layer to the cleaned original surface of the substrate to be coated is sufficient without increasing the risk of peeling. The invention thus enables such a substrate to be cleaned only on its original surface, which comprises a total height Rt of the surface roughness profile between 10 μm and 15 μm, and without having to modify its surface by sandblasting as in the prior art.

[0031] In addition to the characteristics just discussed in the preceding paragraphs, the method according to one aspect of the present invention may have one or more of the following additional features, which may be considered individually or in any technically possible combination:

[0032] According to one embodiment, the liquid fuel is paraffin.

[0033] According to only one embodiment, the HVOF type thermal spraying process is high pressure. This type of HVOF makes it possible to have higher particle velocities, which makes it possible to ensure good adhesion of small particles to the substrate.

[0034] According to one embodiment, the method for manufacturing a component comprises, prior to the preparation step, a preliminary step of manufacturing a substrate, which preliminary step comprises machining the substrate to form an initial surface.

[0035] According to another embodiment, the method for manufacturing a component comprises, prior to the preparation step, a preliminary step of manufacturing a substrate, which preliminary step comprises releasing the mold of the substrate to form an initial surface.

[0036] According to one embodiment, the method consists of a preliminary step of manufacturing a substrate and a consecutive first step, a second step and a third step.

[0037] Consisting of the above-mentioned preliminary step and three consecutive steps means that there are no further steps, ie no grinding or sanding steps or steps of adding materials to the layer, for example no impregnation with an organic impregnant.

[0038] According to one embodiment, the substrate cleaning sub-step makes it possible to obtain a pristine surface without dust or grease. The cleaning sub-step can be a degreasing step, which simplifies and reduces the cost and time of this method. The preparation step makes it possible to improve the adhesion of the submicron particles to form a pristine coating.

[0039] According to one example of the aforementioned embodiment, the cleaning sub-step is only a degreasing step to obtain a degreasing original surface, and the preparation step consists only of a shot blasting sub-step and a cleaning sub-step. The cleaning sub-step makes it possible to improve the adhesion of submicron particles to form a coating.

[0040] According to one embodiment, each metal carbide particle has a size strictly less than 1 μm (submicron carbide), and the average particle size of the majority of the metal carbide particles is about 400 nm to 800 nm. Particle sizes of this size enable the HVOF type spraying process to produce a dense coating while adhering to the prepared substrate surface with a roughness between 0.6 μm and 1.6 μm. In addition, corrosion resistance is made possible by the fact that the surface of the coating formed by particles of this size (the spray deposit of these particles has a roughness Ra of about 3 μm to 5 μm) is polished to a roughness as low as 0.2 μm. In addition, this allows reducing the spraying time required to produce the finished protective layer, thereby reducing the quality of the original coating thus formed.

[0041] Furthermore, the coating thickness provides a peel strength under stress (also called spalling resistance) much greater than that required in the field of the invention, and the fact that the thickness does not exceed 100 μm reduces the forces transmitted by the coating-substrate interface.

[0042] Another non-claimed aspect of the invention relates to a component comprising a metal substrate and a trimmed protective layer, the component being obtained according to the manufacturing method of the first aspect of the invention and having or not having the different features described in the preceding paragraphs.

[0043] Another unclaimed aspect of the invention relates to a component comprising a metal substrate and a conditioned protective layer consisting of a powder mixture comprising submicron metal carbide particles deposited according to an HVOF type spraying process, the conditioned protective layer being deposited onto an original surface of the substrate and comprising a polished surface having a roughness less than 0.2 μm, the original surface of the substrate having a roughness prepared by shot peening to obtain an original surface with a prepared roughness Ra between 0.6 μm and 1.6 μm.

[0044] Compared to a component (part) according to the method described in EP 2 956 564 B1, such a component has lower production costs and at the same time has better corrosion resistance.

[0045] According to one embodiment, the polished surface is intended to be subjected to abrasion and / or rotation. (Rotation means being subjected to the forces of the cylindrical part of the shaft (usually its end), pivoting in or on the part that holds it (yoke, bushing, flange, bearing)).

[0046] According to one example of this embodiment, the component is a hinge pin or a shaft in the aeronautical field.

[0047] According to one embodiment, the polished surface is intended to undergo a rotational (torsion) function (eg a shaft) as well as a dynamic seal (eg a slide rod).

[0048] According to one embodiment, the polished surface is intended to be subjected to a static and / or dynamic sealing area. For example, the component is a slide bar.

[0049] The present invention and its various applications will be better understood by reading the following description and examining the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] These drawings are provided to illustrate the invention and not to limit the invention.

[0051] [ Figure 1a ] is a schematic diagram showing a cross-section of a component including a substrate having a pristine surface.

[0052] [ Figure 1b ] is a schematic diagram showing a cross-section of a component including an original coating on a cleaned and prepared original surface of a substrate.

[0053] [ Figure 1c ] is a schematic diagram showing a cross-section of a component including a trimmed protective layer on a substrate.

[0054] [ Figure 2 ] shows a schematic diagram of the manufacturing method.

[0055] [ Figure 3 ] schematically shows samples including a surface polished according to the present invention and a protected surface polished according to the prior art, which were subjected to corrosion testing in a salt-containing atmosphere. DETAILED DESCRIPTION

[0056] These drawings are provided to illustrate the invention and not to limit the invention.

[0057] As mentioned above, the manufacturing method according to the invention is preferably used to produce a component 1, the enlarged cross section of which is schematically shown in FIG. Figure 1c middle.

[0058] In particular, the component 1 is used in the aeronautical field.

[0059] exist Figure 1c In the cross section shown in , the component 1 comprises a partially shown metal substrate Sub and a trimmed protective layer Rf, which comprises a polished surface S3.

[0060] Figure 2 A flow chart showing a method for manufacturing a component 1 is shown.

[0061] In the case where the component 1 is a rod, the component 1 is usually made by machining to have at least a portion of a cylindrical surface, and the component can be a hinge pin, a shaft or even a sliding rod of a landing gear. This cylindrical portion is hereinafter referred to as the substrate Sub. Therefore, the trimmed protective layer Rf is annular and is intended to play a role in the static and / or dynamic sealing area. For example, the trimmed protective layer Rf is intended to withstand the friction of the joint to allow the rod to slide relative to the strut of the landing gear, or is intended to withstand abrasion and / or rotation (for example, for a hinge pin or a shaft).

[0062] The trimmed protective layer Rf should provide protection against corrosion of the component, thereby providing a seal between the polished surface S3 of the trimmed protective layer Rf and another component (such as a strut landing gear) to limit the risk of hydraulic fluid leakage, wear resistance under pressure and spalling resistance, the spalling resistance is also called spalling test, in which tensile and compressive movements are alternately carried out with a load ratio of R=-1.

[0063] It should be noted that the base material Sub is a metal alloy of the steel or titanium type.

[0064] In the following example, the aim is to produce a trimmed component 1 having a cylinder with a diameter of 13 mm, with a total manufacturing tolerance (substrate+polishing trim) of + or -0.4 μm.

[0065] Here, the base material Sub is manufactured by, for example, machining by a lathe to obtain a diameter of 12.82 mm with a manufacturing tolerance.

[0066] like Figure 2 As shown, the method for manufacturing a component 1 comprises a step A: preparing an initial raw surface S1 of a substrate Sub to obtain a prepared initial raw surface S1n to be covered by a trimmed protective layer rf. Figure 1a represents a cross section of the substrate Sub including its original original surface S1, and Figure 1c as well as Figure 1b The prepared original surface S1n is referenced in Figure 1c and Figure 1b1 shows a component 1 including a prepared original surface S1n covered with an original coating Rb. In this example, the preparation step A here comprises a degreasing sub-step and a shot peening sub-step. Thus, the preparation step A changes the roughness of the initial surface by shot peening to change the initial surface into the original surface S1 of the substrate, and then cleans the original surface. Therefore, the cleaned original surface S1n has not been sandblasted or sanded.

[0067] The sub-step of shot peening the initial surface makes it possible to obtain a total height Rt of the surface roughness profile (in Figure 1a The raw surface of the blasting process is between 10 μm and 15 μm, which is different from sandblasting, which produces a roughness with a total height Rt of the surface roughness profile greater than 20 μm. Shot peening can also obtain a prepared roughness Ra of 0.6 μm and 1.6 μm.

[0068] Here, in this example, the cleaning sub-step is only to degrease the initial raw surface S1 of the substrate, thereby forming a cleaned raw surface S1n, which has the same roughness Ra as the roughness of the raw surface S1, for example, 1.6 μm. The roughness of the surface can be measured, for example, according to standards ISA3274-1997, ISO 4287-1997, ISO4288-1996, ISO 11562.

[0069] The method for producing the component 1 comprises, after the preparation step A, a step B of forming a raw coating Rb on a cleaned (prepared) raw surface S1n of a substrate Sub, which raw surface is here degreased, by HVOF-type spraying of a powder mixture containing submicron metal carbide particles. Figure 1b 1 shows a cross section of a component 1, which comprises a substrate Sub and an original coating Rb deposited on a cleaned surface S1n. The original coating Rb comprises Figure 1b The original coating surface S2 is visible in the figure.

[0070] In particular, in this example, the particles have a size strictly less than 1 μm, and the thickness Epmax of the original coating Rb formed thereby is between 95 μm and 120 μm, for example, in this example, the thickness is between 100 μm and 110 μm. The thickness of the original coating Rb can be changed according to the manufacturing tolerance of the coating, and therefore a finishing step (described later) can be performed by polishing C to remove the removed coating with a thickness of no more than 30 μm (here a maximum of 22 μm). The powder mixture contains metal carbide particles coated in a binder, where tungsten carbide WC is coated in cobalt Co and chromium Cr. Cobalt Co is used as a binder, and chromium Cr is used for oxidation protection.

[0071] In this example, the powder mixture is in the form of agglomerates / aggregates with a powder particle size of about 20 μm to 30 μm, and the deposition of the powder mixture by the HVOF process forms a stack of ceramic powder particles and a molten metal matrix. These ceramic powder particles are strictly smaller than 1 μm to form a maximum coating of less than 120 μm and greater than 95 μm. Agglomerates are usually produced by sintering to form bridges between carbides and binder materials. This sintering is usually carried out by a furnace to melt the binder without decarburizing the metal carbide particles.

[0072] Ideally, the metal carbide WC particles present in the powder mixture are calibrated to have a size strictly less than 1 μm, and preferably the average particle size is about 400 nm to 800 nm.

[0073] It should be noted that the invention can be implemented with other types of chemical compositions comprising at least one metal carbide and at least one binder. Examples of possible compositions include WCCo, which may be in the form of a mixture of 83% WC and 17% Co, or in the form of a mixture of 88% WC and 12% Co, or WCCoCr.

[0074] Since the original coating Rb and the powder agglomerates / agglomerates have a small particle size, the resulting roughness at the original coating surface S2 of the original coating Rb is about 3 μm just after spraying in this example.

[0075] The method for manufacturing the component 1 includes a third step immediately after the forming step B: polishing and trimming the original coating surface S2 to form a polished surface S3 with a roughness Ra less than 0.2 μm, until a component 1 having a desired diameter (e.g., 13 mm, i.e., a radius of 6.5 mm) is obtained. The trimmed protective layer Rf has a thickness between 75 μm and 100 μm. Here, in this example, due to the manufacturing tolerance of the substrate Sub and the tolerance of the polishing and trimming step, the thickness of the trimmed protective layer Rf is between 88 μm and 92 μm.

[0076] A third polishing trimming step is thus performed on the original coating surface S2 to remove a portion Rrp of the original coating Rb, thereby forming a trimmed protective layer Rf having a thickness between 88 μm and 92 μm.

[0077] The original coating surface Rb is porous, in this example comprising pores with diameters between 0.3 μm and 0.04 μm (depending on the type of powder), and 80% of the pores have diameters mainly between 0.25 μm and 0.1 μm. The median pore diameter is 0.2 μm per pore, with a porosity of 0.04 mL / g.

[0078] As mentioned above, the original coating Rb has a roughness Ra of the surface S2, where Ra=3 μm, which is of the same order of magnitude as the roughness Ra of the surface S1 (here 2 μm in this example). The third step C of polishing the original surface S2 ensures that the roughness Ra of the polished surface S3 of the trimmed protective layer Rf is less than 0.2 μm. Polishing can be performed, for example, with a diamond strip.

[0079] The step of polishing the original coating Rb reduces the thickness of this layer until the dimensions of the component are obtained, here a cylinder with a diameter of 13 mm with a manufacturing tolerance of + or -0.4 μm. Here, the polishing step reduces the thickness of the original coating Rb by removing a portion Rrp of the original coating with a thickness between 12 μm and 18 μm. In this example, the trimmed protective layer Rf therefore has a smaller thickness between 88 μm and 92 μm, with a roughness Ra of 0.2 μm, making it possible to obtain a component diameter of 13 mm (substrate: 12.82 mm) with a tolerance of + or -4 μm + (2 times the thickness of the coating from 88 μm to 92 μm (radius)) + or -0.4 μm.

[0080] The original surface S2 is polished by removing a thickness of a portion Rrp of the original coating Rb until a roughness Ra of less than 0.2 μm is obtained, forming a finished protective layer Rf, allowing the polished surface S3 to withstand static and / or dynamic sealing areas while being corrosion resistant.

[0081] It should be noted that conventionally, a coating grinding step is required to obtain a given layer geometry and layer surface finish. However, grinding of annular layers formed on a straight cylindrical portion requires providing a considerable layer thickness to ensure that a minimum layer thickness is maintained on the substrate after grinding.

[0082] By eliminating the step of grinding the annular layer, the method according to the invention makes it possible to obtain the desired layer thickness directly without having to grind the coating of the component, thus eliminating the risk of grinding defects (grinding cylindrical annular layers often leads to layer areas that are too thin, difficult to detect and can contribute to premature corrosion of the substrate due to uncertainties in positioning the component on the grinding machine). The invention eliminates the risk of having locally too thin layers that cannot be detected.

[0083] Figure 3 A test piece 2 is schematically shown, which comprises on the left a polished surface S3 of a trimmed protective layer rf formed similarly to component 1 according to the method of the invention and on the right a surface of a coating S4 with a maximum thickness of 50 μm and a roughness Ra of 1.6 μm.

[0084] Test piece 2 has been tested for corrosion resistance in a salt-containing atmosphere (salt spray) according to ASTM B117.

[0085] Test pieces 2' and 2" correspond to test piece 2 after 1000 hours in a salt-containing atmosphere.

[0086] It can thus be seen that the surface S3 of the component according to the invention, in which the minimum deposit thickness of the test piece 2 is 75 μm, shows no signs of pitting even after 1000 hours of exposure to salt spray (left part). On the other hand, the surface S4 with the thin coating (right part) is corroded: first pitting signs 9, then extensive corrosion development 90.

[0087] Furthermore, a wear resistance test was carried out on a component 1 obtained using the method of the invention, in the presence of lubricating oil, which component 1 has a cylindrical area with a diameter of 10 mm, which includes a surface S3 and on which a bronze ring (AMS4590) is mounted. The wear test consists of a first stage: 500 cycles of pressure of the ring on the surface S3 at 50 MPa, followed by a second stage: 500 cycles at 100 MPa, and a final stage: 4000 cycles at 200 MPa, and a frequency of 0.1 Hz. The friction coefficient and the wear rate (measuring the outer diameter of the shaft and the inner diameter of the ring) are recorded every 500 cycles, and the lubricating oil is renewed each time. The tests show that the component 1 obtained using the method of the invention comprises a level of wear resistance similar to that according to the method in EP2956564 B1.

[0088] The manufacturing method of the invention thus makes it possible to obtain a component that is cheaper than the method according to document EP 2 956 564 B1, while comprising a metal substrate Sub at least partially covered with a modified protective layer rf, thus having similar wear resistance and better corrosion resistance.

[0089] Furthermore, surprisingly, it is noted that, unlike in document EP2956564 B1, in which the substrate was subjected to a sandblasting or sanding step in the preparation step, starting from the fact that in the preparation step the substrate was only cleaned without modifying its roughness by sandblasting, in the present invention the protective layer makes it possible to maintain adhesion to the original surface with a total roughness profile height Rt between 10 μm and 15 μm. Moreover, due to the increased coating thickness, the modified substrate of the present invention is more corrosion resistant than the coating of document EP2956564 B1 (i.e., with a thickness of less than 50 μm and a roughness Ra of 1.6 μm).

[0090] Furthermore, spalling tests have been carried out on samples with a trimmed protective layer rf having a thickness of 100 μm in the trimmed state, i.e. without loss of adhesion between the deposit of the trimmed protective layer Rf and the substrate Sub of the test part, with alternating tensile and compressive movements at a load ratio of R = -1. The tests show that, for a thickness of 100 μm, the part comprising a metal substrate Sub at least partially covered with a trimmed protective layer Rf obtained by the manufacturing method according to the invention comprises spalling resistances at 1140 MPa, 1250 MPa and 1300 MPa.

[0091] Finally, fatigue tests were carried out on the part 1 obtained using the method of the invention, based on the same principle as the peeling test. These tests consisted of alternating tensile and compressive movements at a load ratio of R = 0.1. The results obtained show that the decay previously defined for this type of deposition / test is still respected in the aerospace sector.

[0092] Thanks to all these characteristics, the method of the invention makes it possible to obtain a trimmed component that is lighter, less expensive and has at least the same performance level, while keeping intact the characteristics necessary for a proper seal between component 1 and another component.

[0093] It should be noted that the carbide particles used may be metal carbides other than tungsten carbide, and the bonding material may be materials other than chromium and cobalt.

[0094] Unless stated otherwise, identical elements appearing in different drawings have unique reference numerals.

Claims

1. A method for manufacturing a component (1), comprising a metal substrate (Sub) at least partially covered with a trimmed protective layer (Rf), the method comprising in sequence: - a first preparation step (A) without surface modification by sandblasting, said first preparation step comprising: a sub-step of blasting the initial surface of said substrate to obtain a roughness of the initial surface with a total surface roughness profile height Rt between 10 μm and 15 μm; and a sub-step of cleaning said initial surface (Sub), - a second step (B): forming a raw coating (Rb) with a thickness between 95 μm and 125 μm on the cleaned raw surface (S2) with a prepared roughness by spraying a powder mixture containing submicron metal carbide particles according to a high-pressure liquid HVOF type thermal spraying process, - A third step (D): polishing and trimming the surface of the original coating composed of the powder mixture (S2) to form the trimmed protective layer (Rf), thereby forming a polished surface (S3) with a roughness Ra less than 0.2 μm, and the thickness of the trimmed protective layer (Rf) is between 75 μm and 100 μm.

2. The method according to claim 1, comprising a preliminary step of manufacturing the substrate (Sub) before the preparation step (A), the preliminary step comprising machining the substrate to form an initial surface (S1).

3. The method according to claim 1 or 2, wherein: The cleaning sub-step of the preparation step (A) is only a degreasing step to obtain a degreasing original surface (S2).

4. A method according to any one of the preceding claims, wherein: Most of the metal carbide particles have an average particle size of about 400 nm to 800 nm.

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