Contact layer on the surface of a metal component and hinge with such contact layer

Abstract

The present invention relates to a contact layer (8) formed by a deposition method on the inner surface (7B) of a first metal element (7) through a centrifugal step. The present invention also relates to a hinge component (1), which comprises a first metal element (7) having a surface (7B) on which the first contact layer (8) is provided, and a second metal element (3) having a second surface (3B), wherein the first element (7) and the second element (3) move relative to each other through the first surface (7B) and the second surface (3B).

Description

Technical Field

[0001] The invention relates to a contact layer applied to the surface of a metal component which moves relative to another metal component.

[0002] The invention relates to a contact layer or a combination of contact layers applied to a hinge of the ball joint type. The invention is particularly useful for applications in the aeronautical field, where it is necessary to use alloys such as titanium alloys, nickel alloys or certain types of steel because of their mechanical temperature, fatigue, weight reduction characteristics and their limited lifespan. Background Art

[0003] In the aerospace industry, it is known practice to use metal ball joints to fix two components (such as a link and a structural part) in translation relative to each other, while allowing relative rotational movement of these components.

[0004] For example, such a spherical joint described in EP 1 431 597 generally comprises a metal inner ring and a metal outer ring. The inner surface of the inner ring is suitable for mounting on the shaft, while its outer surface is substantially spherical and can cooperate with the corresponding inner surface of the outer ring. The inner ring and the outer ring thus have three relative degrees of freedom in rotation while being subject to each other in translation. The inner ring can be composed of two connected elements, each of which has a C-shaped cross section.

[0005] In order to obtain a lightweight metal ball joint, it is advantageous to form the inner and outer rings from metal or low-density metal alloys, in particular titanium and titanium alloys. In order to ensure satisfactory mechanical strength, it may also be necessary to produce the rings from nickel alloys or certain steel grades. However, the friction characteristics of the above-mentioned metals and metal alloys do not prevent the joint from wearing under dynamic loads with the relative movement between the inner and outer rings or between the inner ring and the shaft.

[0006] To alleviate this problem, it is known to use coatings to protect the contact surfaces of the ball joint, as described in FR 2 907 468 and EP 2 048 389. A thin coating of high hardness can be applied to the first contact surface by vapor phase deposition (VPD). A thick coating of copper alloy, which exhibits lower hardness and sacrificial wear properties compared to the VPD layer described above, can be applied to the second contact surface.

[0007] However, the coatings obtained by thermal spraying have a small thickness, 150 to 250 μm after final machining, reduced adhesion, implying a risk of fouling, and limited cohesion, resulting in a significant wear rate, limiting the life and load capacity of the hinge.

[0008] Furthermore, it is usually not possible to apply coatings by thermal spraying on internal surfaces with small diameters without affecting the coating quality. Due to this limitation, the external ball joint rings are usually coated by the VPD method, while the spherical surface of the internal ring is usually coated by thermal spraying. From a mechanical point of view, this configuration is not optimal. In fact, coatings that exhibit sacrificial wear behavior should be applied to surfaces with a small movement length, so that the contact consistency can be maintained despite the wear.

[0009] Finally, the limitations of the thermal spray method also dictate the use of a bronze alloy tubular bearing, which is inserted between the inner ring and the shaft to prevent wear between these two surfaces. Summary of the invention

[0010] The present invention aims to remedy the above-mentioned disadvantages.

[0011] More specifically, the present invention aims to provide a contact layer applied to the surface of a metal element that moves relatively against another metal element, for example for applications in hinge systems such as ball joints, providing stable performance and improved life for increased load capacity.

[0012] The invention relates to a contact layer applied to the inner surface of a first metal element intended for relative movement with respect to the surface of a second metal element, said contact layer being formed by a method comprising the following consecutive steps:

[0013] (a) introducing and fixing the metal element into a cylindrical mold so that the inner surface of the layer to be received is away from the inside of the mold;

[0014] (b) introducing the material to form the layer into the mould;

[0015] (c) rotating the mold at a gradually increasing speed, the impregnation of the surface being carried out under the action of centrifugal force;

[0016] (d) hardening the layer and cooling the element;

[0017] (e) Removing the component from the mold.

[0018] According to the invention, the contact layer is deposited on the inner surface of the element by centrifugal casting. This method has no effect on the base metal material of the ring, either on the surface or on the inner layer.

[0019] Another advantage of the method is the ability to apply a layer of defined thickness, which can be particularly thick compared to layers applied by other known methods. Thus, a portion, such as a groove, can be machined directly on the contact layer, the walls of which remain covered by the contact layer. It is no longer necessary to first carry out machining and then apply the contact layer, the thickness of which is difficult to control in the machined portion by known methods.

[0020] The method according to the invention also allows for better chemical adhesion between a correctly deposited contact layer and the base metal material of the ring surface, thereby reducing the risk of delamination of the contact layer.

[0021] The contact layer deposited by centrifugation has better cohesion by enhancing the grain metallurgical continuity, thereby improving the wear resistance of the layer. The composition of the material forming the contact layer can also be graded with standardized rings depending on the desired application.

[0022] Finally, the inner surface of the metal element is covered with a contact layer, the material of which is specifically chosen for relative movement against the surface of another metal element, which may also be covered with a contact layer, similar or different or dissimilar.

[0023] According to other advantageous but non-mandatory characteristics of the invention, this contact layer is a copper alloy with a copper content of 50 to 90% by weight and may also include the following features, considered alone or in any technically acceptable combination:

[0024] - said layer also comprises other elements including aluminium in an amount of 5-15% by weight, nickel in an amount of 2-8% by weight, iron in an amount of 1-7% by weight.

[0025] - the contact layer is a copper alloy having a copper content of 70 to 90% by weight and comprising other elements including nickel in a content of 10 to 20% by weight and tin in a content of 5 to 12% by weight.

[0026] The surface hardness of the contact layer is 50 to 400 HB, advantageously 150 to 300 HB.

[0027] The contact layer has a thickness of 20 to 2000 μm, advantageously 100 to 300 μm.

[0028] According to other advantageous but non-mandatory characteristics of the invention, this contact layer is a tin alloy with a tin content of 75 to 95% by weight and may also include the following features, considered alone or in any technically acceptable combination:

[0029] - The contact layer also comprises other elements, such as antimony in an amount of 5 to 15% by weight, copper in an amount of 2 to 10% by weight.

[0030] - The surface hardness of the contact layer is 20 to 40 HB.

[0031] - The contact layer has a thickness of 50 to 300 μm.

[0032] According to other advantageous but non-mandatory features of the invention, the contact layer comprises a bottom first layer formed of a copper alloy according to any of the preceding embodiments, and a top second layer applied to the first layer and formed of a tin alloy according to any of the preceding embodiments, and may also comprise the following features, considered alone or in any technically acceptable combination:

[0033] - The bottom first layer has a thickness of 100 to 300 μm.

[0034] - the thickness of the top second layer is from 2 to 20 μm.

[0035] The invention also relates to an articulated component comprising a first metal element having an inner surface provided with a first contact layer according to one of the preceding embodiments and a second metal element having a second surface, the inner surface being provided with a first contact layer according to one of the preceding embodiments, the first and second elements being able to move relative to each other via the first and second surfaces.

[0036] According to other advantageous but non-mandatory features of the present invention, the hinged portion may also include the following features alone or in any acceptable combination:

[0037] - said first and second elements are formed from a titanium alloy.

[0038] - said first and second elements are formed from a nickel alloy.

[0039] - said first and second elements are formed from steel.

[0040] - The second surface of the second element is free of an additional coating.

[0041] The second surface of the second element is provided with a second contact layer having a harderness greater than the first contact layer of the first surface of the first element.

[0042] The dry sliding friction coefficient of the second layer is less than 0.5, advantageously less than 0.2.

[0043] The lubricating sliding friction coefficient of the second layer is less than 0.2, advantageously less than 0.12.

[0044] According to other advantageous but non-mandatory features of the invention, the second contact layer is deposited on the second surface of the second element by a thermal spraying method, in particular by plasma spraying, high velocity oxygen fuel or HVOF, or cold spraying, and may also include the following features alone or in any acceptable combination:

[0045] - The second contact layer comprises tungsten carbide in an amount of 50 to 90% by weight.

[0046] - The second contact layer also contains cobalt in an amount ranging from 5 to 25% by weight.

[0047] The second contact layer comprises other elements, such as chromium in an amount of 0 to 10% by weight, and / or nickel in an amount of 0 to 30% by weight.

[0048] The surface hardness of the second contact layer is 500 to 2000 HB, advantageously 800 to 1500 HB.

[0049] The thickness of the second contact layer is from 10 to 2000 μm, advantageously from 50 to 200 μm.

[0050] According to other advantageous but non-mandatory features of the invention, the second contact layer is deposited by a gas phase condensation method or "physical vapor deposition" or PVD, and may also include the following features alone or in any acceptable combination:

[0051] The second contact layer consists of a carbon coating of the diamond type, “diamond-like carbon” or DLC.

[0052] The second contact layer of the -DLC also includes an additional metal.

[0053] - The metal may be tungsten, titanium, silicon or nickel.

[0054] - The concentration of said metal is 3-20% by weight.

[0055] The surface hardness of the second contact layer of DLC is 800 to 5000 HB, advantageously 1200 to 2500 HB.

[0056] The thickness of the second contact layer of DLC is from 1 to 20 μm and advantageously from 2 to 5 μm.

[0057] - Alternatively, the second contact layer comprises chromium nitride.

[0058] The surface hardness of the second contact layer of chromium nitride is 100 to 2800 HB, advantageously 1500 to 2300 HB.

[0059] The thickness of the second contact layer of chromium nitride is 1 to 50 μm, advantageously 5 to 25 μm.

[0060] - Optionally, said second contact layer comprises a bottom first layer comprising metal and a top second layer applied to said first layer and consisting of DLC.

[0061] - The bottom first layer comprises chromium nitride.

[0062] The bottom first layer consists of a metallic connection layer comprising chromium, titanium or silicon and having a thickness of 0.02 to 5 μm, advantageously 0.1 to 1 μm.

[0063] According to another advantageous but non-mandatory aspect of the present invention, the articulated portion according to any of the preceding embodiments consists of a spherical joint and may include the following features alone or in any technically acceptable combination:

[0064] - The first element consists of an outer ring, the inner surface of which is provided with a first contact layer according to any of the preceding embodiments.

[0065] The second element consists of an inner ring, the outer surface of which is provided with a second contact layer according to any of the preceding embodiments.

[0066] - The inner and outer surfaces are spherical.

[0067] - The inner ring is provided with a central hole.

[0068] - The central hole is provided with a contact layer according to any of the preceding embodiments.

[0069] -The center hole is equipped with a bearing.

[0070] -The bearings are made of bronze.

[0071] - The bearing is provided with an inner cylindrical surface provided with a contact layer according to any of the preceding embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The invention will be better understood on reading the following description given purely by way of non-limiting example.

[0073] The description is given with reference to the accompanying drawings, in which:

[0074] Figure 1 is a cross-section of a ball joint mounted on a shaft according to an embodiment of the present invention; and

[0075] Figure 2 yes Figure 1 A magnified schematic diagram of detail III. DETAILED DESCRIPTION

[0076] Figure 1 An articulated component of the ball joint type is shown, generally designated 1.

[0077] The ball joint 1 comprises an inner ring 3 and an outer ring 7. These rings are made of a titanium alloy, for example type TA6V. Alternatively, these rings are made of a nickel alloy or steel.

[0078] The outer ring 7 comprises a substantially cylindrical outer surface 7A. The outer ring 7 also comprises a spherical inner surface 7B, more specifically in the form of a part of a sphere, which is connected to the outer surface 7A by a side wall 7C.

[0079] The inner ring 3 comprises a substantially cylindrical inner surface 3A designed to be arranged against the outer circumference of a corresponding cylindrical shaft 9. The inner ring 3 also comprises an outer surface 3B having a spherical profile, more specifically in the form of a part of a sphere, which corresponds to the inner surface 7B of the outer ring 7. The inner ring 3 and the outer ring 7 thus have three degrees of rotational freedom relative to each other. The inner surface 3A and the outer surface 3B of the inner ring 3 are connected to each other by a side wall 3C. Figure 1 , the side walls 3C of the inner ring 3 protrude on either side of the side walls 7C of the outer ring 7 in axial section, wherein the cylindrical surface 7A is coaxial with the shaft 9. According to an embodiment not shown, the inner ring 3 may also have a cylindrical sleeve fitted between its inner surface 3A and the outer periphery of the shaft 9. This sleeve may be made of bronze, for example.

[0080] The spherical joint 1 further comprises a first contact layer 8 and a second contact layer 4, which are deposited on the spherical surfaces 7B and 3B of the outer ring 7 and the inner ring 3, respectively. The first contact layer 8 deposited on the surface 7B forms part of the outer ring 7 and forms the contact surface of the outer ring 7 for mating with the inner ring 3 in the mating zone Z. Similarly, the second contact layer 4 deposited on the surface 3B forms part of the inner ring 3 and forms the contact surface of the inner ring 3 for mating with the outer ring 7 in the mating zone Z.

[0081] The contact layers 4 and 8 each have specific properties suitable for increasing the friction coefficient at the interface between the inner ring 3 and the outer ring 7. More specifically, the hardness of the second contact layer 4 added to the outer surface 3B of the inner ring 3 is greater than the hardness of the first contact layer 8 on the inner surface 7B of the outer ring 7.

[0082] It is particularly advantageous if the second contact layer 4 added to the outer surface 3B of the inner ring 3 has a coefficient of friction in dry sliding of less than 0.5, preferably less than 0.2, and a coefficient of friction in lubricated sliding of less than 0.2, preferably less than 0.12.

[0083] According to a first embodiment not shown, the second contact layer 4 on the outer surface 3B of the inner ring 3 is deposited on the second surface of the second element by a thermal spraying method, in particular by plasma spraying, high velocity oxygen fuel (or HVOF) or cold spraying.

[0084] The second contact layer 4 comprises tungsten carbide in an amount of 50 to 90% by weight. The second contact layer may also comprise cobalt in an amount of 5 to 25% by weight, and possibly other elements, such as chromium in an amount of 0 to 10% by weight, and / or nickel in an amount of 0 to 30% by weight.

[0085] According to this first embodiment, the second contact layer 4 has a surface hardness of 500 to 2000 HB, preferably 800 to 1500 HB, and a thickness of 10 to 2000 μm, preferably 50 to 200 μm.

[0086] According to a second embodiment, the second contact layer 4 is deposited by a gas phase condensation method or “physical vapor deposition” PVD.

[0087] According to a first variant of the second embodiment not shown, the second contact layer 4 consists of a carbon coating of the diamond type or "diamond-like carbon" DLC. The second contact layer 4 of DLC may further comprise additional metals, such as tungsten, titanium, silicon or nickel, in a concentration of 3 to 20% by weight.

[0088] According to this variant, the second contact layer 4 of DLC has a surface hardness of 800 to 5000 HB, preferably 1200 to 2500 HB, and a thickness of 1 to 20 μm, preferably 2 to 5 μm.

[0089] According to a second variant of this second embodiment, not shown, the second contact layer 4 comprises chromium nitride. The second contact layer 4 has a surface hardness of 100 to 2800 HB, preferably 1500 to 2300 HB, and a thickness of between 1 and 50 μm, preferably 5 to 25 μm.

[0090] according to Figure 2 In the third variant of this second embodiment shown, the second contact layer 4 comprises a bottom first layer 6 comprising a metal and a top second layer 41 applied to the first layer 6 and consisting of DLC. For example, the bottom first layer 6 may comprise chromium nitride, or the bottom first layer 6 consists of a metal connection layer comprising chromium, titanium or silicone, with a thickness between 0.02 and 5 μm, advantageously between 0.1 and 1 μm.

[0091] According to a third embodiment not shown, the outer surface 3B of the inner ring 3 is not provided with a contact layer, the base material of the ring being in direct contact with the contact layer 8 of the inner surface 7B of the outer ring 7 .

[0092] According to the invention, the first contact layer 8 is deposited on the inner surface 7B of the outer ring 7 according to a method comprising the following steps:

[0093] (a) an outer metal ring 7 is introduced and fixed in a cylindrical mould, the inner surface 7B to receive the layer 8 being away from the inside of the mould;

[0094] (b) introducing the material to form layer 8 into the mould;

[0095] (c) rotating the mould at a gradually increasing speed, the impregnation of the surface 7B being carried out under the action of centrifugal force;

[0096] (d) hardening the layer 8 and cooling the outer ring 7; and

[0097] (e) The outer ring 7 is removed from the mold.

[0098] According to a first embodiment of the invention, this contact layer is a copper alloy having a copper content of 50 to 90% by weight.

[0099] The layer 8 may further include other elements, including aluminum in an amount of 5 to 15% by weight, nickel in an amount of 2 to 8% by weight, and iron in an amount of 1 to 7% by weight. Alternatively, the contact layer 8 is a copper alloy having a copper content of 70 to 90% by weight and including other elements, including nickel in an amount of 10 to 20% by weight and tin in an amount of 5 to 12% by weight. Alternatively, the contact layer 8 is a copper alloy having a copper content of 70 to 90% by weight and including other elements, including nickel in an amount of 30 to 40% by weight and indium in an amount of 2 to 8% by weight. According to yet another alternative, the contact layer is a copper alloy having a copper content of 70 to 90% by weight and including other elements, including aluminum in an amount of 5 to 15% by weight, iron in an amount substantially equal to 1% by weight, and graphite.

[0100] According to the first embodiment, the surface hardness of the contact layer 8 is 50 to 400 HB, preferably 150 to 300 HB, and the thickness is 20 to 2000 μm, preferably 100 to 300 μm.

[0101] According to a second embodiment, this contact layer 8 is a tin alloy with a tin content of 75 to 95% by weight. The contact layer 8 may also include other elements, such as antimony with a content of 5 to 15% by weight and copper with a content of 2 to 10% by weight.

[0102] According to the second embodiment, the contact layer has a surface hardness of 20 to 40 HB and a thickness of 50 to 300 μm.

[0103] According to a third embodiment not shown, the contact layer 8 comprises a bottom first layer formed of a copper alloy according to any of the previous embodiments, and a top second layer applied to the first layer and formed of a tin alloy according to any of the previous embodiments. The bottom first layer has a thickness of 100 to 300 μm, while the top second layer has a thickness of 2 to 20 μm.

[0104] Furthermore, the technical features of the different embodiments may all be combined, or only some of them may be combined. Thus, the ball joint may be adjusted in terms of cost, performance and simplicity of implementation.

[0105] As an exemplary embodiment, the invention has been described for a spherical joint type articulation. The invention can be applied to any type of articulation component and more generally to any device comprising a first metal element having a first surface and a second metal element having a second surface, the two elements moving in contact with each other.

Claims

1. A contact layer (8) located on an inner surface (7B) of a first metal element (7), said inner surface (7B) being intended to move relative to a second surface (3B) of a second metal element (3), It is characterized by: The contact layer (8) comprises: - a bottom first layer made of a copper alloy having a copper content of 50-90% by weight and formed by the following successive steps according to the following process: (a) introducing and fixing a first metal element (7) into a cylindrical mold, with the inner surface (7B) to receive the copper alloy layer facing away from the interior of the mold; (b) introducing a material to form a copper alloy layer into a mold; (c) rotating the mold at a gradually increasing speed, the impregnation of the inner surface (7B) being carried out under the action of centrifugal force; (d) hardening the copper alloy layer and cooling the first metal element (7); (e) removing the first metal element (7) from the mold; and - a top second layer made of a tin alloy, which is applied onto the first layer and is formed by the following successive steps according to the following process: (f) introducing and fixing the first metal element (7) into a cylindrical mold, with the inner surface (7B) to receive the tin alloy layer facing away from the interior of the mold; (g) introducing a material to form a tin alloy layer into a mold; (h) rotating the mold at a gradually increasing speed, the impregnation of the inner surface (7B) being carried out under the action of centrifugal force; (i) hardening the tin alloy layer and cooling the first metal element (7); (j) Taking out the first metal element (7) from the mold.

2. A hinged component (1), comprising a first metal element (7) having an inner surface (7B) and a second metal element (3) having a second surface (3B), wherein the inner surface (7B) is provided with a contact layer (8) according to claim 1, and the first metal element (7) and the second metal element (3) move relative to each other through the inner surface (7B) and the second surface (3B).

3. The hinge component according to claim 2, wherein: The first metal element (7) and the second metal element (3) are formed of titanium alloy, nickel alloy or steel.

4. The hinge component according to claim 2 or 3, wherein: The second surface (3B) of the second metal element (3) is provided with a second contact layer (4), the hardness of which is greater than the hardness of the contact layer (8) of the inner surface (7B) of the first metal element (7).

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