Method for producing a friction layer in a bore of a metal guide member, and guide member comprising such a friction layer

Abstract

The invention relates to a method for producing a friction layer (3) having a thickness greater than 0.5 mm on an inner surface of a bore of a metal guide member (1) intended to receive a counterpart shaft (2) in sliding friction contact with the friction layer (3). According to the invention, the method comprises at least the steps of: - directly depositing material on the inner surface of the bore in order to form the friction layer (3), the material being deposited so as to create a continuous or discontinuous recessed pattern (4) in at least part of the thickness of the friction layer, the recessed pattern (4) acting as a lubricant reservoir; - grinding the surface of the friction layer (3).

Description

Description Title of the invention: Method for creating a friction layer in a bore of a metallic guide element, and guide element comprising such a friction layer technical field

[0001] The present invention relates to the field of guiding elements, comprising, in general, a bore with a cylindrical internal surface coated with a friction layer of a thickness greater than 0.5 mm.

[0002] In particular, the bore is intended to receive an opposing shaft in contact by sliding friction with said friction layer, and the friction layer has a recessed pattern, for example cavities, grooves, etc., acting as lubricant reservoirs.

[0003] An advantageous application of the invention lies in the field of mechanical systems operating in oscillation, translation and / or rotation under heavy loads and subjected to shocks in abrasive environments, such as the guide bearings of an axis, forming the articulation of a public works or mining machine, agricultural vehicle, industrial machine, etc. Previous art

[0004] The aforementioned guide elements, mounted on machines, are subjected to significant mechanical stresses.

[0005] Typically, such a guiding element is described, for example, in document W02006087498.

[0006] This type of guide element includes a friction layer with cavities that act as lubricant reservoirs, and preferably coated with a self-lubricating material, particularly useful for joints and bearings in harsh, abrasive and possibly corrosive environments, such as public works or mining, steelmaking, agricultural or industrial machinery and transport vehicles.

[0007] The prior art document CN111304649 describes a method for preparing a wear-resistant layer for cast iron bearings to increase their service life.

[0008] This document describes in particular the creation of a nickel alloy transition layer by the technique known under the English expression "laser cladding" on an internal cylindrical surface of the bore of the guide element, then the creation of a wear-resistant tin-based friction layer.

[0009] Also known is document CN109267064 which describes a similar process, enabling the production of wear-resistant coatings on iron-based alloy bearings, using a combination of low-pressure cold spraying techniques and "laser cladding" to obtain high-quality, high-adhesion coatings.

[0010] The document US20150055909, which describes a technique for reconditioning a guide element in order to reduce replacement costs and increase its performance and durability, using the "laser cladding" technique to generate a new wear layer on the internal surface after deterioration of the previous one.

[0011] In all these examples, whether for repair operations of worn friction layers or for a first deposit, after the friction layer has been made, it is machined to create internal hollow patterns intended to act as lubricant reservoirs, which lengthens the manufacturing time and the inherent costs.

[0012] Furthermore, current technologies for creating recessed patterns remain limited in terms of the complexity of shapes and patterns, especially for small diameters, less than 80 mm for example.

[0013] In any case, there remains the disadvantage of having to dismantle the guide element installed on a machine to reload a layer, but especially to create the recessed patterns, which act as lubricant reservoirs, particularly by machining. Description of the invention

[0014] One of the aims of the present invention is therefore to overcome the disadvantages of the prior art by proposing a method for producing a friction layer for the wear resistance of a guiding element, which is provided with a hollow pattern intended to act as a lubricant reservoir, the production costs of which are reduced, both for the manufacture and for the reconditioning of said guiding element.

[0015] Another objective of the invention is to enable a considerable improvement in the possibilities of lubricant distribution by creating complex patterns or patterns adapted to the application under consideration, thereby reducing friction and wear.

[0016] To this end, the invention relates to a method of producing a friction layer with a thickness greater than 0.5 mm on an internal surface, preferably cylindrical or of any other shape, of at least a part of a bore of a metallic guide element intended to receive an opposing shaft in contact by sliding friction with said friction layer.

[0017] According to the invention, the method is remarkable in that it comprises at least the following steps: - direct deposition of material on the internal surface of the bore part to form the friction layer, the material being deposited in such a way as to generate a continuous or discontinuous groove pattern in at least part of the thickness of the friction layer, the groove pattern acting as a lubricant reservoir; - possibly rectification of the surface of the friction layer.

[0018] In this way, the invention makes it possible to create the hollow patterns that act as lubricant reservoirs, directly during the friction layer production stage, which reduces the costs and duration of the manufacturing process.

[0019] The invention applies equally to a one-part guide element and to a two-part guide element, i.e., a guide element composed of two half-shells. The material can be deposited on each of the parts, which are then assembled together to form the guide element as such.

[0020] Furthermore, the invention also offers the ability to create complex recessed patterns, according to various designs, impossible to achieve with conventional technologies, to create cavities serving as reservoirs of lubricants specifically adapted to particular and varied operating conditions.

[0021] The invention also allows the use of low-quality steel as a support, and functionalizing only the internal friction surface over a few millimeters.

[0022] The invention also makes it possible to revalue end-of-life rings, limiting the duration and cost of the process, but also to plan for complex lubricant distribution networks.

[0023] Direct deposition modeling (DED) is a process where materials are melted during deposition using a concentrated thermal energy source. This energy source can be a laser beam, an electron beam, or a plasma arc. The materials used are in wire or powder form and are primarily metals such as titanium and its alloys, Inconel, tantalum, tungsten, niobium, stainless steel, aluminum, nickel, cobalt, tin, and copper.

[0024] The DED technique involves applying successive layers of material to the internal bore of the guide element. The material is applied, for example, by a nozzle mounted on a multi-axis arm (usually 4 or 5 axes) and is directly melted during deposition. This procedure is repeated several times until the layers solidify and the friction layer is created or repaired.

[0025] In one particular embodiment, direct material deposition can be achieved by cold spraying a powder accelerated in a supersonic gas jet. This technique is well known by the English term "cold spray".

[0026] The "cold spray" technique preserves the original properties of the filler material, such as microstructure and chemical composition, because there is no melting or significant thermal reactions, and the resulting friction layer has low porosity and high density, thus improving resistance to corrosion and wear.

[0027] The advantage of the "cold spray" technique is also that it can be used with a wide variety of materials, including metals, alloys, composites, and some polymers.

[0028] Alternatively, direct material deposition can be carried out hot, i.e. by thermal projection so as to fuse the material with the internal surface of the bore.

[0029] Using specific techniques, direct material deposition can be achieved by HVOF (High Velocity Oxygen Fuel) or HVAF (High Velocity Air Fuel) thermal spraying. In these processes, a mixture of fuel gas and oxygen or air is burned in a combustion chamber, producing high-velocity gases. A metallic or ceramic powder is then injected into this gas stream, where it melts and is accelerated toward the part to be coated. The particles strike the surface at high speed, cool, and bond to form the friction layer.

[0030] The resulting friction layer exhibits high density and excellent adhesion to the bore's internal surface. The HVOF or HVAF technique also produces coatings with very low porosity, thus improving their resistance to corrosion and oxidation. The HVOF technique also allows for the application of a wide range of materials, including metal alloys, ceramics, and composites.

[0031] According to another technique, direct material deposition is performed under concentrated energy, for example with a laser or an electron beam, by depositing a molten bead, for example of powder or wire, onto the internal surface of the bore. This technique is well known by the English term "laser cladding" when the energy used comes from a laser.

[0032] This laser cladding technique can also be used with a wide range of materials, including metals, alloys, certain types of composites, and ceramics, and its control allows for material deposition along more complex paths. The advantage of laser cladding also lies in its ability to produce a friction layer with a porosity of less than 1%, and because it does not create oxidation, there is no need for a vacuum or controlled atmosphere. Furthermore, this technique This facilitates the metallurgical adhesion of the friction layer to the bore. The laser also allows for more precise material deposition, with less heating of the material, at least to a shallower depth than other techniques.

[0033] Advantageously, powders, such as ceramic or metallic powders used in these different processes, can be functionalized to give particular properties to the friction layer.

[0034] According to a particular embodiment, the recessed pattern goes through the entire thickness of the friction layer, that is to say, it opens onto the internal surface of the bore, which allows for deeper lubricant reserves, and possibly for different properties to be obtained between the side walls and the bottom of the recessed pattern.

[0035] In this latter configuration, the groove pattern is preferably coordinated with a groove pattern already present in the bore of the guide element, i.e. that the grooves of the friction layer are opposite the grooves of the bore, in order to further increase the depth of the lubricant reserves.

[0036] Advantageously, the friction layer comprises a surface layer and at least one sublayer of a material different from that of the surface layer, in order to provide layers that can have different functions. The sublayer(s) can, for example, be one or more transition layers, improving the adhesion of the surface layer.

[0037] Under these conditions, the recessed pattern can be made either solely in all or part of the thickness of the surface layer, or also in all or part of the lower layers.

[0038] For example, the recessed pattern is generated in at least part of the thickness of the sub-layer and in the entire thickness of the surface layer.

[0039] According to a particular embodiment, the process may include, prior to the step of depositing material on the internal surface of the bore, a grinding step, which either exposes the bore or retains part of a friction layer or an underlayer already present.

[0040] This allows, for example, the reconditioning of end-of-life guide components by depositing a new friction layer with the characteristics of the invention, i.e., with cavities directly formed during the manufacturing of said layer. This resurfacing step with a friction layer, directly incorporating the lubricant reservoirs, can be carried out directly on the machine, i.e., without removing the guide component from its operating position.

[0041] The invention also relates to the aforementioned guide element comprising a friction layer having a recessed pattern acting as a lubricant reservoir, remarkable in that the recessed pattern of the friction layer is not machined and is formed by friction layer areas of variable thickness, i.e. lesser thickness, or even zero thickness.

[0042] Preferably, the friction layer has a porosity of less than 1%, which improves its resistance to corrosion and wear.

[0043] For the same purpose, the bore of the guide element, excluding the friction layer, has a hardness greater than or equal to 500 Hv1 at least over a depth of between 5 and 50 pm, and preferably, the friction layer has a hardness greater than that of the internal surface of the bore of the guide element, which allows the use of a more economical material for the body of the bore and confers wear and corrosion resistance properties through the friction layer.

[0044] Thus, the invention provides a high-performance guide element for applications under heavy loads and shocks in abrasive environments, offering an excellent balance between galling resistance, abrasion resistance, and accommodation. The proposed solution is more competitive, with an improved performance-to-price ratio.

[0045] The invention also relates to a mechanical system comprising a guiding member according to one of the preceding claims, and an axis disposed in the bore of this guiding member. Brief description of the drawings

[0046] [Fig.1] is a longitudinal cross-sectional view of an embodiment of a guiding element according to the invention.

[0047] [Fig. 2] is a longitudinal cross-sectional view of a mechanical system comprising the guide member of Figure 1, and a shaft disposed in the bore of this guide member. Detailed description of the invention

[0048] With reference to Figures 1 to 2, the invention relates to a guiding element (1) comprising, for example, a metallic ring (1a), for example made of a ferrous material, having a bore for receiving an opposing shaft (2) in sliding friction contact to form, for example, the guide bearing of a joint in a construction machine. In practice, the diameter of the bore is between 60 mm and 150 mm, without this being a limitation.

[0049] In particular, the internal surface, preferably cylindrical, of the bore is coated with at least one surface layer called a friction layer (3) intended to resist wear and wear slowly in operation.

[0050] To limit wear and increase the service life of the guiding element (1), the friction layer (3) has a recessed pattern (4), for example cavities, grooves, etc., which acts as a lubricant reservoir.

[0051] The ring (1a) is made from a metallic material, such as low-alloy steel or structural steel, preferably with a yield strength Re between 200 and 600 MPa. Generally, this ring (1a) undergoes a surface hardening treatment by diffusion (nitriding, nitrocarburizing, carbonitriding, case hardening, chromizing) or by structural transformation (high-frequency surface hardening). This treatment is followed by a finishing treatment, such as surface oxidation or phosphating, and the application of a coating to the friction layer (3) suitable for reducing galling and the coefficient of friction, such as a polymer containing graphite, molybdenum disulfide, or PTFE. The treatment(s) can be carried out either before or after the application of the friction layer.

[0052] The shaft (2) can also receive a similar treatment to improve its resistance to seizing and reduce the coefficient of friction.

[0053] The invention consists of loading or reloading the ring (1a) with the friction layer (3) by 3D printing technologies, such as Directed Energy Deposition, such as "laser cladding", by directly printing the internal topography of the ring (1a), i.e. the recessed patterns (4) acting as lubricant reservoirs.

[0054] In this way it is possible to create complex patterns that can adapt to all types of applications, constraints, and loads, in order to distribute the lubricant locally and optimally in areas where the stresses are maximum, depending on the application considered.

[0055] Direct material deposition (DED) additive manufacturing is used to create a friction layer (3) with a thickness greater than 0.5 mm, preferably between 2 and 5 mm, on an internal surface of the ring bore (1a). The materials used include metals such as titanium, Inconel, tantalum, tungsten, niobium, stainless steel, aluminum, nickel, cobalt, tin, and copper.

[0056] Direct material deposition can also be achieved by cold spraying of powder, known as "cold spray", allowing the original properties of the material to be retained without significant melting.

[0057] According to another technique, direct material deposition can be achieved by thermal spraying HVOF, HVAF, plasma torch, etc., producing dense coatings with excellent adhesion and low porosity.

[0058] The complex and varied recessed patterns (4) can be coordinated with patterns already present in a layer of the bore to increase the depth of the lubricant reservoirs. The lubricant reservoirs are generally between 0.3 and 4 mm deep and between 0.5 and 8 mm wide.

[0059] The friction layer (3) can be multilayered, each layer being deposited by the additive manufacturing technique, with a sub-layer (3a), forming for example a transition promoting the adhesion of a surface layer (3b).

[0060] The bore coated with the friction layer (3) then undergoes a surface grinding step of the friction layer (3) to give the appropriate smooth surface condition.

[0061] The invention also makes it possible to recondition worn guide elements. In this configuration, the process includes, prior to the step of depositing material on the internal surface of the bore, a grinding step, which either exposes the bore or retains part of a friction layer or sub-layer (3a) already present.

[0062] The friction layer obtained according to the invention preferably has a porosity of less than 1%, improving its resistance to corrosion and wear. It also preferably has a hardness greater than or equal to 500 Hv1 over a depth of between 5 and 50 µm.

[0063] The guide element (1), designed in this way and with optimized lubricant distribution, offers high performance in terms of resistance to seizing, abrasion, and corrosion, while remaining cost-competitive. It is particularly suited to applications under heavy loads and shocks in abrasive environments, with an excellent performance-to-price ratio.

[0064] Finally, the invention includes a mechanical system combining the guide member (1) described above and an axis (2) disposed in the bore of this guide member (1), offering an efficient and durable solution for various industrial applications.

Claims

Demands 1. Method for producing a friction layer (3) with a thickness greater than 0.5 mm on an internal surface of a bore of a metallic guide element (1) intended to receive an opposing shaft (2) in sliding friction contact with said friction layer (3), characterized in that it comprises at least the following steps: - direct deposition of material on the internal surface of the bore to form the friction layer (3), the material being deposited in such a way as to generate a hollow pattern (4), continuous or discontinuous, in at least part of the thickness of the friction layer, the hollow pattern (4) acting as a lubricant reservoir. - rectification of the surface of the friction layer (3).

2. A method according to claim 1, characterized in that the direct deposition of material is carried out by cold projection of a powder accelerated in a supersonic gas jet.

3. Method according to claim 1, characterized in that the direct deposition of material is carried out by HVOF or HVAF thermal projection.

4. Method according to claim 1, characterized in that the direct deposition of material is carried out under concentrated energy consisting of depositing a molten bead so as to create a layer on the surface of the bore.

5. A method according to any one of the preceding claims, characterized in that the recessed pattern (4) goes through the entire thickness of the friction layer (3).

6. Method according to claim 5, characterized in that the recessed pattern (4) is coordinated with a recessed pattern (4) already present in the bore of the guiding member (1).

7. A method according to any one of the preceding claims, characterized in that the friction layer (3) comprises a surface layer (3b), and in less an underlayer (3a) of a material different from that of the surface layer (3b).

8. Method according to claim 7, characterized in that it consists of generating the recessed pattern (4) in at least part of the thickness of the sub-layer (3a) and in the entire thickness of the surface layer (3b).

9. A method according to any one of the preceding claims, characterized in that it comprises, prior to the step of depositing material on the internal surface of the bore, a grinding step, which either exposes the bore or retains part of a friction layer or an underlayer (3a) already present.

10. Metallic guide element (1) comprising a bore with an internal surface coated with a friction layer (3) of a thickness greater than 0.5 mm, intended to receive an opposing shaft (2) in contact by sliding friction with said friction layer (3), the friction layer (3) having a continuous or discontinuous recessed pattern (4) acting as a lubricant reservoir characterized in that the recessed pattern (4) of the friction layer (3) is formed by areas of friction layer (3) of variable thickness deposited on the internal surface of the bore.

11. Guiding element (1) according to claim 10, characterized in that the friction layer (3) has a porosity of less than 1%.

12. Guide element (1) according to any one of claims 10 to 11, characterized in that the bore, excluding friction layer (3) has a hardness greater than or equal to 500 Hv1, at least over a depth between 5 and 50 pm.

13. Guide element (1) according to any one of claims 10 to 12, characterized in that the friction layer (3) has a hardness greater than that of the internal surface of the bore of the guide element (1).

14. Mechanical system, comprising a guide member (1) according to any one of claims 10 to 13, and a shaft (2) disposed in a bore of this guide member (1).

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