Wear and high temperature resistant ball joint and method of manufacturing same

Abstract

A ball joint (1) includes an outer ring (2) and an inner ring (3), the outer ring (2) and the inner ring (3) respectively including a spherical inner surface (2a) and a spherical outer surface (3b) in contact with each other. The outer ring (2) comprises a nickel-based material and an outer layer obtained by carbonitriding at least the inner surface (2a) of the outer ring (2), and the inner ring (3) comprises a cobalt-based or nickel-based material.

Description

Technical Field

[0001] The present invention relates to the field of ball joints, and more particularly to the field of inner and outer race components of ball joints.

[0002] More specifically, the present invention relates to reducing wear on a ball joint by utilizing a special composition of the outer race of the ball joint.

[0003] The invention also relates to a support system for supporting an engine on its housing, and to a method for producing such a ball joint and such a support system.

[0004] The support system includes a conventional ball joint and / or a shackle incorporated into the ball joint to support the engine in its housing. These components are typically made of nickel or cobalt alloys, which are materials that are resistant to the high temperatures generated by combustion in the engine's combustion chamber. The ball joint allows the support system to be flexible during thermal expansion of the engine.

[0005] The ball joint comprises an inner ring and an outer ring, which respectively comprise an outer surface and an inner surface in contact with each other. However, the synergy between the inner and outer rings has limited advantages at high temperatures, since the material of the rings wears away over time. The outer ring of the ball joint can be a component added to the support system and fastened by any suitable means, such as by a nut or crimping, or can be formed directly in the support system. Background Art

[0006] To date, in order to limit the wear of ball joints, inner rings comprising cobalt alloys and outer rings comprising nickel alloys have generally been used. This combination of materials allows good sliding behavior of one ring relative to the other.

[0007] However, the wear is still too high for this component, so regular maintenance of the engine support system is required, which incurs costs. Summary of the invention

[0008] The invention therefore aims to significantly reduce the wear caused by friction between the rings of a ball joint and makes it possible to increase the fatigue life of the components.

[0009] A subject of the invention is a ball joint comprising an outer ring and an inner ring, the outer ring and the inner ring respectively comprising a spherical inner surface and a spherical outer surface in contact with each other. The outer ring comprises a nickel-based material and an outer layer obtained by carbonitriding at least the inner surface of the outer ring, and the inner ring comprises a cobalt-based or nickel-based material.

[0010] By this combination of materials, the wear caused by the friction between the outer and inner rings of the ball joint is reduced.

[0011] Advantageously, the outer ring comprises an outer surface radially opposite to the inner surface, said outer surface of the outer ring being obtained by carbonitriding at least the inner surface and the outer surface.

[0012] Advantageously, the outer ring is made of a nickel-based alloy, in particular of the formula NiCr19Fe18Nb.

[0013] According to one embodiment, the inner ring is made of a cobalt-based alloy, in particular a cobalt alloy of formula CoCr29W5. Alternatively, the inner ring can be made of a nickel-based alloy, in particular a nickel alloy of formula NiCr19Fe18Nb, and comprises a cobalt-based coating on all or part of the outer surface of the inner ring. Preferably, the inner ring is a solid-type ring made of a cobalt alloy or a nickel alloy. The term "solid-type ring" is understood to mean a ring whose shape is obtained by mechanical processing by removing material (turning, grinding) from a tube, a rod, or a forged and / or rolled blank.

[0014] Advantageously, the outer layer of the outer ring has a thickness of 2 to 20 µm, preferably 5 to 10 µm.

[0015] According to an embodiment, the inner ring comprises a hole radially opposite the spherical outer surface, and the ball joint comprises a sleeve mounted in the hole of the inner ring and comprising an outer surface radially in contact with the hole.

[0016] The sleeve may comprise a nickel-based material, more specifically an alloy of the formula NiCr19Fe18Nb.

[0017] Another subject of the invention is a method for manufacturing a ball joint as described above. The method comprises at least the following steps:

[0018] - the step of providing an outer ring comprising a nickel-based material and an inner ring comprising a cobalt-based or nickel-based material,

[0019] - a step of carbonitriding at least the inner surface of the outer ring,

[0020] - Steps to assemble the outer ring with the inner ring.

[0021] Advantageously, the method comprises a step of treating the inner ring, before the step of assembling the outer ring with the inner ring, said inner ring comprising an outer surface fully or partially covered with a cobalt-based coating, preferably an alloy of formula CoCr29W5. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other objects, features and advantages of the present invention will become apparent from a reading of the following description, given purely by way of non-limiting example and with reference to the accompanying drawings, in which:

[0023] Figure 1shows a ball joint according to an exemplary embodiment of the present invention;

[0024] Figure 2 yes Figure 1 A front view of a ball joint;

[0025] Figure 3 yes Figure 1 A cross-sectional view of a ball joint of FIG.

[0026] Figure 4 The steps of a method for producing a ball joint according to one embodiment of the invention are shown. DETAILED DESCRIPTION

[0027] Figure 1 , 2 3 show a ball joint 1 according to the invention in a reference system (X, Y, Z), comprising an outer ring 2 and an inner ring 3 coaxial along an axis X.

[0028] like Figure 2 As shown, the outer ring 2 includes a concave spherical inner surface 2a or a hole, an outer surface 2b radially opposite to the inner surface 2a, and two opposite radial end surfaces (not marked) axially defining the inner surface 2a and the outer surface 2b.

[0029] The inner ring 3 includes a convex spherical outer surface 3b for mounting the inner surface 2a of the outer ring 2, a cylindrical hole 3a radially opposite to the outer surface 3b, and two opposite radial end surfaces (not shown) axially defining the hole 3a and the outer surface 3b. The inner surface 2a of the outer ring 2 and the outer surface 3b of the inner ring 3 are in contact with each other and have complementary shapes.

[0030] The outer ring 2 comprises a nickel-based material, in particular an alloy of formula NiCr19Fe18Nb, and an outer layer obtained by carbonitriding at least its inner surface 2a. The outer layer has a thickness between 2 and 20 μm, preferably between 5 and 10 μm.

[0031] The outer surface 2 b and the end face of the outer ring 2 may also be treated by carbonitriding so that the outer ring 2 is completely covered with the outer layer.

[0032] The inner ring 3 comprises a cobalt alloy of formula CoCr29W5 or a nickel alloy of formula NiCr19Fe18Nb and in this case may comprise a cobalt-based coating, in particular of formula CoCr29W5. The coating covers the entire outer surface 3b of the inner ring 3 or only a portion thereof.

[0033] The sliding between the inner surface 2a of the outer ring including the carbonitrided layer and the inner ring 3 including the cobalt-based or nickel-based alloy results in very little wear.

[0034] In the exemplary embodiment shown, the ball joint 1 further comprises a sleeve 4 which is mounted in the bore 3a of the inner ring 3 and forms the bore of the ball joint 1. The sleeve 4 has an annular shape. The sleeve 4 has an outer surface 4a which is in radial contact with the bore 3a of the inner ring 3.

[0035] In a manner known per se, sleeve 4 and inner ring 3 are assembled by radially inserting an elastic retaining ring 5 in grooves formed on outer surface 4a of sleeve 4 and bore 3a of inner ring 3. Sleeve 4 comprises a nickel-based material, more particularly an alloy of formula NiCr19Fe18Nb.

[0036] In another embodiment, the ball joint 1 may be without the sleeve 4 .

[0037] In the exemplary embodiment shown, the outer ring 2 of the ball joint 1 comprises a fastening flange 6 which extends radially outwards from one axial end of the outer surface 2b. Alternatively, the outer ring 2 of the ball joint 1 may be free of the flange 6.

[0038] The present invention also proposes a method for manufacturing the ball joint 1 as described above.

[0039] The method for manufacturing the ball joint 1 comprises at least three steps, such as Figure 4 shown.

[0040] The method first comprises a step E1 of providing an outer ring 2 comprising a nickel-based material and an inner ring 3 comprising a cobalt-based or nickel-based material.

[0041] Next, the method comprises a step E2 of carbonitriding the inner surface 2a of the outer ring 2. It is also conceivable to carbonitrid the outer surface 2b and the end faces of the outer ring 2.

[0042] This carbonitriding step E2 may, for example, comprise two sub-steps, namely a first surface hardening sub-step E3 and a second nitriding sub-step E4, which are carried out simultaneously or successively with the first sub-step E3 and in the same heat treatment cycle. The heat treatment cycle is characterized by raising the temperature from a low initial temperature to a high temperature, maintaining the high temperature, and then reducing the temperature to a temperature close to the low initial temperature. For example, the heat treatment cycle corresponding to the step E2 of carbonitriding the inner surface 2a of the outer ring 2 starts with a first surface hardening sub-step E3, which uses acetylene to supply carbon, and continues with a second nitriding sub-step E4, which uses ammonia to supply nitrogen. The temperature of this heat treatment cycle may, for example, be 400° C. to 500° C. and maintained for the necessary time to achieve the desired carbon and nitrogen enrichment of the treated inner surface 2a. The carbonitriding step E2 ends with a rapid decrease in the temperature of the outer ring 2. For example, the treated outer ring 2 is returned to ambient temperature. Depending on the selected thickness, the carbonitriding treatment may last from 10 to 50 hours.

[0043] Finally, the method comprises a step E5 of assembling together the inner ring 3 and the outer ring 2 .

[0044] Optionally, the method for manufacturing the ball joint 1 may further comprise a step E6 of treating the inner ring 3. During this step, the outer surface 3b of the inner ring 3 may be completely or only partially covered with a cobalt-based coating, preferably an alloy of formula CoCr29W5.

[0045] The invention has been described based on a ball joint comprising an inner ring and an outer ring, which is to be added to the associated support system. It would not depart from the scope of the invention if the outer ring of the ball joint was directly formed from a component of the support system by machining to form the inner surface of said outer ring.

Claims

1. A ball joint (1), comprising an outer ring (2) and an inner ring (3), wherein the outer ring (2) and the inner ring (3) respectively comprise a spherical inner surface (2a) and a spherical outer surface (3b) in contact with each other, characterized in that: The outer ring (2) comprises a nickel-based material and an outer layer obtained by carbonitriding at least an inner surface (2a) of the outer ring (2), and the inner ring (3) comprises a cobalt-based or nickel-based material.

2. The ball joint (1) according to claim 1, wherein: The outer ring (2) comprises an outer surface (2b) radially opposite to the inner surface (2a), and the outer layer of the outer ring is obtained by carbonitriding at least the inner surface (2a) and the outer surface (2b).

3. The ball joint (1) according to any one of claims 1 and 2, wherein: The outer ring (2) comprises an alloy having a chemical formula of NiCr19Fe18Nb.

4. The ball joint (1) according to any one of claims 1 to 3, wherein: The inner ring (3) comprises a cobalt alloy having the chemical formula CoCr29W5.

5. The ball joint (1) according to any one of claims 1 to 3, wherein: The inner ring (3) comprises a nickel alloy of the chemical formula NiCr19Fe18Nb and comprises a cobalt-based coating located on all or part of the outer surface (3b) of the inner ring (3).

6. The ball joint (1) according to any one of claims 1 to 5, wherein: The outer layer of the outer ring (2) has a thickness of 2 µm to 20 µm, preferably 5 µm to 10 µm.

7. The ball joint (1) according to any one of claims 1 to 6, wherein: The inner ring (3) comprises a hole (3a) radially opposite to the spherical outer surface (3b), and the ball joint (1) further comprises a sleeve (4) mounted in the hole (3a) of the inner ring and comprising an outer surface (4a) in radial contact with the hole.

8. The ball joint (1) according to claim 7, wherein: The sleeve (4) comprises a nickel-based material, more specifically an alloy having the chemical formula NiCr19Fe18Nb.

9. A method for producing a ball joint (1) according to any one of claims 1 to 8, characterized in that The method comprises at least the following steps: - a step (E1) of providing an outer ring (2) comprising a nickel-based material and an inner ring (3) comprising a cobalt-based or nickel-based material, - a step (E2) of carbonitriding at least the inner surface (2a) of the outer ring (2), - Step (E5) of assembling the outer ring (2) and the inner ring (3).

10. The method for manufacturing a ball joint (1) according to claim 9 comprises a step (E6) of treating the inner ring (3) before a step (E5) of assembling the outer ring (2) with the inner ring (3), wherein the inner ring (3) comprises an outer surface (3b) completely or partially covered with a cobalt-based coating, preferably an alloy with the chemical formula CoCr29W5.

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