Wear-resistant and high-temperature resistant ball joint and ball joint manufacturing process

Abstract

Wear-resistant and high-temperature resistant ball joint and method for manufacturing the ball joint. Ball joint (1) comprising an outer ring (2) and an inner ring (3) having respectively 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 said outer ring (2), and the inner ring (3) comprises a cobalt-based or nickel-based material. Reference: Figure 2

Description

Title of the invention: Wear-resistant and high-temperature ball joint and method for manufacturing the ball joint Technical field of the invention

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

[0002] More specifically, the invention relates to the reduction of wear on a ball joint, by exploiting a particular composition of the outer ring of a ball joint.

[0003] The invention also relates to a system for supporting an engine to its casing, and to the method of manufacturing such a ball joint and such a support system.

[0004] A support system comprises conventional ball joints and / or shackles incorporating ball joints to support the engine within its housing. These parts are generally made of nickel or cobalt alloy, materials resistant to the high temperatures generated by combustion in the engine's combustion chamber. The ball joints allow the support system to remain flexible during the engine's thermal expansion.

[0005] A ball joint comprises an inner ring and an outer ring, having respectively an outer surface and an inner surface in contact with each other. The synergy between the inner and outer rings nevertheless offers limited advantages at high temperatures, as the ring materials wear over time. The outer ring of the ball joint can be an added component on the support system and fixed by any suitable means, for example by a nut or a crimp, or it can be formed directly within the support system. Prior art

[0006] To date, to limit wear on ball joints, a conventional method has been used: an inner ring made of a cobalt alloy and an outer ring made of a nickel alloy. The combination of these materials allows for good sliding behavior of one ring relative to the other.

[0007] However, wear remains too significant for this assembly and therefore requires regular maintenance of the engine support system, which incurs costs. Summary of the invention

[0008] The invention thus aims to significantly reduce wear due to friction between the rings of a ball joint and to increase the fatigue life of the parts.

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

[0010] With such a combination of materials, the wear by friction of the outer and inner rings of the ball joint is reduced.

[0011] Advantageously, the outer ring has an outer surface radically opposite the inner surface, said outer layer of the outer ring being obtained by carbonitriding at least the inner and outer surfaces.

[0012] Advantageously, the outer ring is made of nickel-based alloy, in particular of formula NiCrl9Fel8Nb.

[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 may be made of a nickel alloy, in particular a nickel alloy of formula NiCr9Fel8Nb, and has a cobalt-based coating, said coating being positioned on all or part of the outer surface of the inner ring. Preferably, the inner ring is solid, made of a cobalt alloy or a nickel alloy. A "solid ring" is defined as a ring whose shape is obtained by machining with chip removal (turning, grinding) from tubes, bars, forged and / or rolled blanks.

[0014] Advantageously, the outer layer of the outer ring has a thickness between 2 pm and 20 pm, preferably between 5 pm and 10 pm.

[0015] According to one embodiment, the inner ring has a bore, radially opposed to the spherical outer surface and said ball joint includes a sleeve mounted in the bore of the inner ring and having an outer surface radially in contact against the bore.

[0016] The sleeve may comprise a nickel-based material, more particularly an alloy of formula NiCrl9Fel8Nb.

[0017] The invention further relates to a method for manufacturing a ball joint as defined above. The method comprises at least the following steps: - a step of supplying an outer ring comprising a nickel-based material, and an inner ring comprising a cobalt-based or nickel-based material, - carbonitriding step of at least the inner surface of the outer ring, - step of assembling the outer ring with the inner ring.

[0018] Advantageously, the process includes, prior to the step of assembling the outer ring with the inner ring, a step of processing the inner ring, said Inner ring comprising an outer surface covered entirely or partially with a cobalt-based coating, preferably an alloy of formula CoCr29W5. Brief description of the figures

[0019] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0020] [Fig-1] illustrates a ball joint according to an example of an embodiment of the invention;

[0021] [Fig.2] is a front view of the ball joint of [Fig. 1];

[0022] [Fig.3] is a cross-sectional view of the ball joint of [Fig.1]; and

[0023] [Fig.4] illustrates the steps of the manufacturing process of a ball joint according to one embodiment of the invention. Detailed description of the invention

[0024] Figures 1, 2 and 3 illustrate a ball joint 1 in a frame (X, Y, Z) according to the invention, comprising an outer ring 2 and an inner ring 3 coaxial along the X axis.

[0025] As illustrated in [Fig.2], the outer ring 2 comprises a concave spherical inner surface 2a or bore, an outer surface 2b radially opposed to the inner surface 2a, and two opposing radial (not referenced) front faces axially delimiting the inner surface 2a and outer surface 2b.

[0026] The inner ring 3 comprises a convex spherical outer surface 3b on which the inner surface 2a of the outer ring 2 is mounted, a cylindrical bore 3a radially opposed to the outer surface 3b, and two opposing radial (not referenced) front faces axially delimiting the bore 3a and the outer surface 3b. The inner surfaces 2a and outer surfaces 3b of the outer ring 2 and inner ring 3 are in contact with each other and have complementary shapes.

[0027] The outer ring 2 comprises a nickel-based material, particularly an alloy of formula NiCrl9Fel8Nb, and an outer layer obtained by carbonitriding at least its inner surface 2a. This outer layer has a thickness of between 2 pm and 20 pm, preferably between 5 pm and 10 pm.

[0028] The outer surface 2b and the front faces of the outer ring 2 can also be treated by carbonitriding so that the outer ring 2 is completely covered with the outer layer.

[0029] The inner ring 3 comprises a cobalt alloy of formula CoCr29W5, or a nickel alloy of formula NiCr9Fel8Nb and may in this case comprise a cobalt-based coating, particularly of formula CoCr29W5. The coating covers the entire outer surface 3b of the inner ring 3 or only a part of it.

[0030] The sliding between the inner surface 2a of the outer ring which includes a The carbonitriding layer and the inner ring 3, which comprises a cobalt-based or nickel-based alloy, cause very little wear.

[0031] In the illustrated embodiment, the ball joint 1 also includes a sleeve 4 mounted in the bore 3a of the inner ring 3 and which forms the bore of the ball joint 1. The sleeve 4 has an annular shape. The sleeve 4 has an outer surface 4a radially in contact with the bore 3a of the inner ring 3.

[0032] In a manner known per se, the sleeve 4 and the inner ring 3 are assembled together by radial interposition of an elastic retaining ring 5 inside grooves formed on the outer surface 4a of the sleeve 4 and on the bore 3a of the inner ring 3. The sleeve 4 comprises a nickel-based material, more particularly an alloy of formula NiCrl9Fel8Nb.

[0033] In another embodiment, the ball joint 1 could be without the sleeve 4.

[0034] In the illustrated embodiment, the outer ring 2 of the ball joint 1 includes a mounting flange 6 extending radially outwards from one of the axial ends of the outer surface 2b. Alternatively, the outer ring 2 of the ball joint 1 could be without the flange 6.

[0035] The invention also proposes a method for manufacturing a ball joint 1 as described above.

[0036] The manufacturing process for a ball joint 1 comprises at least three steps illustrated by [Fig.4].

[0037] The process first includes a step El of supplying an outer ring 2 comprising a nickel-based material and an inner ring 3 comprising a cobalt-based or nickel-based material.

[0038] Next, the process includes a step E2 of carbonitriding the inner surface 2a of the outer ring 2. It may also be envisaged to carry out carbonitriding of the outer surface 2b as well as the front faces of the outer ring 2.

[0039] This carbonitriding step E2 may, for example, comprise two substeps: a first carburizing substep E3 and a second nitriding substep E4, which is carried out simultaneously or successively with the first substep E3 and within the same heat treatment cycle. A heat treatment cycle is characterized by a temperature increase from a low initial temperature to a high temperature, a holding period at the high temperature, and then a decrease in temperature to a temperature close to the low initial temperature. For example, a heat treatment cycle corresponding to the carbonitriding step E2 of the inner surface 2a of the outer ring 2 begins with the first carburizing substep E3, which uses acetylene to provide carbon, and continues with the second nitriding substep E4, which uses... Ammonia is used to provide nitrogen. The temperature of this heat treatment cycle can, for example, be between 400°C and 500°C and is maintained for the duration necessary to achieve the desired carbon and nitrogen enrichment of the treated inner surface 2a. The carbonitriding step E2 ends with a rapid drop in the temperature of the outer ring 2. The treated outer ring 2 is, for example, brought back to ambient temperature. The carbonitriding treatment can last from 10 to 50 hours depending on the chosen thickness.

[0040] Finally, the process includes a step E5 of assembling the inner ring 3 and outer ring 2 together.

[0041] Optionally, the manufacturing process for the ball joint 1 may further include a step E6 of processing the inner ring 3. During this step, the outer surface 3b of the inner ring 3 may be fully coated, or only partially coated, with a cobalt-based coating, preferably an alloy of formula CoCr29W5.

[0042] The present invention has been illustrated on the basis of a ball joint comprising an inner ring and an outer ring intended to be attached to the associated support system. It remains within the scope of the invention when the outer ring of the ball joint is formed directly from a part of the support system by machining to form the inner surface of said outer ring.

Claims

Claims

1. Ball joint (1) comprising an outer ring (2) and an inner ring (3) respectively comprising 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 the inner surface (2a) of said outer ring (2), and in that the inner ring (3) comprises a cobalt-based or nickel-based material.

2. Ball joint (1) according to claim 1, in which the outer ring (2) comprises an outer surface (2b) radially opposite the inner surface (2a), said outer layer of the outer ring being obtained by carbonitriding at least the inner (2a) and outer (2b) surfaces.

3. Ball joint (1) according to one of claims 1 and 2, in which the outer ring (2) comprises an alloy of formula NiCrl9Fel8Nb.

4. Ball joint (1) according to any one of claims 1 to 3, in which the inner ring (3) comprises a cobalt alloy of formula CoCr29W5.

5. Ball joint (1) according to any one of claims 1 to 3, in which the inner ring (3) comprises a nickel alloy of formula NiCrl9Fel8Nb, and comprises a cobalt-based coating, said coating being positioned on all or part of the outer surface (3b) of the inner ring (3).

6. Ball joint (1) according to any one of claims 1 to 5, in which the outer layer of the outer ring (2) has a thickness of between 2 pm and 20 pm, preferably between 5 pm and 10 pm.

7. Ball joint (1) according to any one of claims 1 to 6, in which the inner ring (3) comprises a bore (3a) radially opposite the spherical outer surface (3b), and said ball joint (1) further comprises a sleeve (4) mounted in the bore (3a) of the inner ring and comprising an outer surface (4a) radially in contact against said bore.

8. Ball joint (1) according to claim 7, in which the sleeve (4) comprises a nickel-based material, more particularly an alloy of formula NiCrl9Fel8Nb.

9. Method of manufacturing a ball joint (1) according to any one of claims 1 to 8, characterized in that it comprises at least the following steps: - step (El) of providing an outer ring (2) comprising a nickel-based material, and an inner ring (3) comprising a cobalt-based or nickel-based material, - step (E2) of carbonitriding at least the inner surface (2a) of the outer ring (2), - step (E5) of assembling the outer ring (2) with the inner ring (3).

10. Method of manufacturing a ball joint (1) according to claim 9, comprising, before the step (E5) of assembling the outer ring (2) with the inner ring (3), a step (E6) of treating the inner ring (3), said inner ring (3) comprising an outer surface (3b) covered entirely or partly with a cobalt-based coating, preferably an alloy of formula CoCr29W5.

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