Contact layer on the surface of a metal element in relative movement against another metal element and an articulation joint provided with such a contact layer

Abstract

A contact layer is formed by a deposition method on an inner surface of a first metal element by a centrifuging process, and preferably includes an inner layer of copper alloy and an outer layer of tin alloy. Such a contact layer is used in an articulation joint including a first metal element having a surface provided with the contact layer, and a second metal element with a second surface. The first and second elements are relatively movable such that first and second surfaces slide against each other.

Claims

1. A method of forming a contact layer on a surface of a first metal element, the surface being intended to be slidable against a surface of a second metal element, the method comprising the steps of: providing a copper alloy, a tin alloy and the first metal element formed of titanium or a titanium alloy and having an inner surface; inserting the first metal element into a mold without removal of oxidation from the inner surface such that the surface is spaced from the interior of the mold; introducing the copper alloy into the mold; rotating the mold such that the copper alloy is impregnated on the surface of the first element by centrifugal force to form a first layer on the surface; hardening the first layer on the first element; introducing the tin alloy into the mold; rotating the mold such that the tin alloy is impregnated on the first layer by centrifugal force to form a second, outer layer; and hardening the second layer on the first layer.

2. The method of claim 1, wherein the step of providing the copper alloy includes providing a copper alloy having a copper content of between fifty percent (50%) by weight and ninety percent (90%) by weight.

3. The method of claim 1 further comprising the step of extracting the first metal element from the mold prior to the step of introducing the tin alloy into the mold.

4. The method of claim 1 wherein the first layer has a thickness of between one hundred micrometers (100 μm) and three hundred micrometers (300 μm) and the second layer has a thickness between two micrometers (2 μm) and twenty micrometers (20 μm).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIGURES

(1) The invention will be better understood on reading the following description given purely as a nonlimiting example. The description is given with reference to the attached drawings in which:

(2) FIG. 1 is a transverse cross section of a ball joint according to an embodiment of the invention, mounted on a shaft; and

(3) FIG. 2 is a larger scale schematic view of the detail III of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows an articulation part of ball-type joint 1, the ball joint 1 comprising an internal ring 3 and an external ring 7. The internal and external rings 3, 7, respectively, are each composed of a titanium alloy, for example of TA6V type. Alternatively, the two rings 3, 7 may each be composed of a nickel alloy or of steel.

(5) The external ring 7 has a substantially cylindrical outer surface 7A, a spherical or partially spherical inner surface 7B, more specifically in the form of sphere sections, which is connected to the outer surface 7A by lateral walls 7C.

(6) The internal ring 3 has a substantially cylindrical inner surface 3A, which is designed to be disposed about the outer periphery of a corresponding cylindrical shaft 9. The internal ring 3 also has an outer surface 3B having a spherical profile, more specifically in the form of sphere sections, corresponding or complementary to that of the inner surface 7B of the external ring 7. Thus, the internal ring 3 and the external ring 7 each have, relative to one another, three degrees of rotational freedom. The inner surface 3A and the outer surface 3B of the internal ring 3 are connected to each other by lateral walls 3C. These lateral walls 3C of the internal ring 3 protrude, in axial cross section, on either side of the lateral walls 7C of the external ring 7 in the position depicted in FIG. 1, in which the cylindrical surface 7A of the external ring 7 is coaxial with the shaft 9. Although not depicted, the internal ring 3 may also have a cylindrical sleeve fitted between the ring inner surface 3A and the outer periphery of the shaft 9. Such a sleeve may be formed, for example, of bronze or another appropriate material.

(7) The ball joint 1 also comprises a first contact layer 8 and a second contact layer 4 deposited respectively on the spherical surfaces 7B, 3B of the external ring 7 and the internal ring 3, respectively. Specifically, the first contact layer 8 is deposited on the inner surface 7B so as to form part of the external ring 7 and provides the contact surface of the external ring 7, which is intended to cooperate with the internal ring 3 within an interface or cooperation zone Z. Likewise, the second contact layer 4 is deposited on the outer surface 3B so as to form part of the internal ring 3 and provides the contact surface of the internal ring 3, and is intended to cooperate with the external ring 7 in the interface/cooperation zone Z.

(8) The contact layers 4 and 8 each have specific properties adapted to improve the friction coefficient at the interface Z between the internal ring 3 and the external ring 7. More specifically, the second contact layer 4, which is provided on the outer surface 3B of the internal ring 3, preferably has a hardness greater than the hardness of the first contact layer 8 on the inner surface 7B of the external ring 7.

(9) Preferably, the second contact layer 4 provided on the outer surface 3B of the internal ring 3 has a dry slip friction coefficient of less than 0.5, most preferably less than 0.2, and a lubricated slip friction coefficient of less than 0.2, most preferably less than 0.12.

(10) According to a first embodiment (not depicted), the second contact layer 4 on the outer surface 3B of the internal ring 3 is deposited by a thermal spraying method on the second or outer surface 3B of the second element or internal ring 3, in particular by plasma spraying, by high velocity oxy-fuel (“HVOF”) spray coating, or by cold spray.

(11) The second contact layer 4 comprises tungsten carbide, the content of which is about fifty percent (50%) by weight to about ninety percent (90%) by weight. The second contact layer 4 may also comprise cobalt, the content of which is about five percent (5%) by weight to about twenty-five percent (25%) by weight, and may also include other elements such as chromium, the content of which may between about zero percent (0%) by weight and about ten percent (10%) by weight, and/or nickel, the content of which may be between about zero percent (0%) by weight and about thirty percent (30%) by weight.

(12) According to this first embodiment, the second contact layer 4 has a surface hardness of between 500 HB (i.e., Brinell hardness number) and 2000 HB, preferentially between 800 HB and 1500 HB, and has a thickness of between ten micrometers (10 μm) and two thousand micrometers (2000 μm), preferably between 50 μm and 200 μm.

(13) According to a second embodiment, the second contact layer 4 is preferably deposited on the internal ring 3 by a gaseous phase condensation method, or physical vapor deposition (“PVD”).

(14) According to a first variant of the second embodiment (not shown), the second contact layer 4 consists of a carbon coating of a diamond type, or diamond-like carbon (“DLC”). The second contact layer 4 formed of DLC may further comprise additional metal(s), such as tungsten, titanium, silicone, or nickel, the concentration of which may be between about three percent (3%) by weight and about twenty percent (20%) by weight.

(15) According to this variant, the second contact layer 4 of DLC has a surface hardness of between 800 HB and 5000 HB, preferably between 1200 HB and 2500 HB, and has a thickness of between one micrometer (1 μm) and twenty micrometers (20 μm), preferably between two micrometers (2 μm) and five micrometers (5 μm).

(16) According to a second variant of this second embodiment that is not illustrated, the second contact layer 4 comprises chromium nitride. The second contact layer 4 has a surface hardness of between about 100 HB and about 2800 HB, preferably between about 1500 HB and about 2300 HB, and has a thickness of between one micrometer (1 μm) and about fifty micrometers (50 μm), preferably between 5 μm and 25 μm.

(17) According to a third variant of this second embodiment shown in FIG. 2, the second contact layer 4 comprises a bottom or inner, first layer 6 comprising a metal, and a top or outer, second layer 41 applied to the first layer 6, and composed of DLC. For example, the bottom or inner first layer 6 can comprise chromium nitride, or the bottom first layer 6 may consist of a metal link layer comprising chromium, titanium, or silicone, of a thickness of between 0.02 μm and 5 μm, and advantageously between 0.1 μm and 1 μm.

(18) According to a third embodiment that is not illustrated, the outer surface 3B of the internal ring 3 is not provided with a contact layer, the base material of the internal ring 3 being in direct contact with the contact layer 8 on the inner surface 7B of the external ring 7.

(19) According to the present invention, the first contact layer 8 is deposited on the inner surface 7B of the external ring 7 according to a method comprising the following steps: introducing and fixing or retaining the external metal ring 7 within a cylindrical mold, the inner surface 7B for receiving the contact layer 8 being free from, i.e., spaced from, the interior of the mold; introducing the material used to form the contact layer 8 into the mold; rotating the mold with progressively increasing rotational speed, such that the impregnation of the surface 7B is accomplished under the effect of centrifugal force; that is, the alloy material is impregnated on the surface 7B by centrifugal force; hardening the layer 8 and cooling the external ring 7; and extracting or removing the external ring 7 from the mold.

(20) According to a first embodiment of the present invention, such a contact layer 8 is a copper alloy, preferably having a copper content of between about fifty percent (50%) by weight and about ninety percent (90%) by weight.

(21) The first layer 8 can further comprise other elements, including aluminum, the content of which may be between about five percent (5%) by weight and fifteen percent (15%) by weight, nickel, the content of which may be between about two percent (2%) by weight and about eight percent (8%) by weight, and iron, the content of which may be between about one percent (1%) by weight and seven percent (7%) by weight.

(22) Alternatively, the first contact layer 8 may be a copper alloy, the copper content of which is between about seventy percent (70%) by weight and about ninety percent (90%) by weight, and comprising other elements, including nickel, the content of which is between about ten percent (10%) by weight and about twenty percent (20%) by weight, and tin of a content between about five percent (5%) by weight and twelve percent (12%) by weight. As another alternative, the contact layer 8 is a copper alloy, the copper content of which is between about seventy percent (70%) by weight and about ninety percent (90%) by weight, and comprising other elements, including nickel, the content of which is between about thirty percent (30%) by weight and about forty percent (40%) by weight, and indium, the content of which is about two percent (2%) by weight and about eight percent (8%) by weight. According to yet another alternative, the contact layer is a copper alloy, the copper content of which is about seventy percent (70%) by weight and about ninety percent (90%) by weight, and comprising other elements, including aluminum, the content of which is between about five percent (5%) by weight and about fifteen percent (15%) by weight, iron, with a content substantially equal to about (1%) by weight, and graphite.

(23) According to this first embodiment, the contact layer 8 has a surface hardness of between 50 HB and 400 HB, preferably between 150 HB and 300 HB, and has a thickness of between twenty micrometers (20 μm) and two thousand micrometers (2000 μm), preferably between 100 μm and 300 μm.

(24) According to a second embodiment, the contact layer 8 is a tin alloy, the tin content of which is between seventy-five percent (75%) by weight and about ninety-five percent (95%) by weight. The contact layer 8 can also comprise other elements such as antimony, the content of which is five percent (5%) by weight and about fifteen percent (15%) by weight, and copper, the content of which is between about two percent (2%) by weight and about ten percent (10%) by weight.

(25) According to this second embodiment, the contact layer 8 has a surface hardness of between 20 HB and about 40 HB, and has a thickness of between about fifty micrometers (50 μm) and about three hundred micrometers (300 μm).

(26) According to a third embodiment (not depicted), the contact layer 8 on the external ring 7 comprises a bottom or inner, first layer formed of a copper alloy according to any one of the above-described embodiments, and a top or outer, second layer applied to the first layer and formed of a tin alloy according to any one of the above-described embodiments. The bottom or inner, first layer is preferably formed of a copper alloy with a copper content of about fifty percent (50%) by weight and ninety percent (90%) by weight and has a thickness of between about one hundred micrometers (100 μm) and about three hundred micrometers (300 μm). The top or outer, second layer is formed of a tin alloy and preferably has a thickness of between about two micrometers (2 μm) and about twenty micrometers (20 μm).

(27) Further, the bottom or inner, first layer is preferably formed of a copper alloy in a process that includes the following steps: introducing and fixing the first metal element (e.g., the external ring 7) in a cylindrical mold, the surface 7B receiving the first layer of copper alloy being spaced from the interior of the mold; introducing the material for forming the first layer of copper alloy into the mold; rotating the mold with progressively increasing rotational speed such that the copper alloy material is impregnated on the surface of the first metal element/ring 7 by centrifugal force; hardening the layer of copper alloy and cooling the first metal element/ring 7; and extracting the first metal element/ring from the mold; and

(28) Furthermore, the top or outer, second layer is preferably formed of a tin alloy in a process that includes the following steps: introducing and fixing the first metal element (e.g., the ring 7) with the first layer into a cylindrical mold, the surface for receiving the second layer of tin alloy being spaced from the interior of the mold; introducing the material for forming the second layer of tin alloy into the mold; rotating the mold with progressively increasing rotational speed such that the tin alloy material is impregnated on the surface of the first metal element by centrifugal force; hardening the second layer of tin alloy and cooling the first metal element; and extracting of the first metal element from the mold.

(29) Furthermore, the technical features of the different embodiments can be, wholly and only for some of them, combined with one another. Thus, the ball joint can be adapted in terms of costs, performance, and simplicity of implementation.

(30) The present invention has been described for an articulation part of ball joint type as an exemplary embodiment. The present invention can be applied to any type of articulation part, and more generally to any device comprising a first metal element with a first surface, and a second metal element with a second surface, the two elements being in relative contact movement.

(31) Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved contact layers.

(32) Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

(33) All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.