Wear-resistant and high-temperature resistant ball joint and manufacturing method of the ball joint

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) respectively having 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 resistant ball joint and manufacturing method of 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 the ball joints.

[0002] More specifically, the invention relates to reducing the wear of 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 on its casing, and to the method of manufacturing such a ball joint and such a support system.

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

[0005] A ball joint comprises an inner ring and an outer ring, respectively having an outer surface and an inner surface in contact with each other. The synergy of the inner ring and the outer ring nevertheless has limited advantages at high temperature, because there is wear of the materials of the rings over time. The outer ring of the ball joint can be an added part on the support system and fixed by any suitable means, for example by a nut or a crimping, or it can be formed directly in the support system. State of the prior art

[0006] Until now, to limit the wear of the ball joints, an inner ring comprising a cobalt alloy and an outer ring comprising a nickel alloy have been conventionally used. The combination of these materials allows good sliding behavior of one ring relative to the other.

[0007] However, wear and tear is still too high for this assembly and therefore requires regular maintenance of the engine support system, which generates 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 makes it possible to increase the fatigue life of the parts.

[0009] The subject of the invention is a ball joint comprising an outer ring and an inner ring respectively comprising a spherical inner surface and a 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 frictional wear of the outer and inner rings of the ball joint is reduced.

[0011] Advantageously, the outer ring comprises an outer surface radially 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 a nickel-based alloy, in particular of the 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 NiCrl9Fel8Nb and comprises 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 cobalt alloy or nickel alloy. By "solid type ring" is meant 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 of between 2 μm and 20 μm, preferably between 5 μm and 10 μm.

[0015] According to one embodiment, the inner ring comprises a bore, radially opposite the spherical outer surface and said ball joint comprises a sleeve mounted in the bore of the inner ring and comprising 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 also relates to a method for manufacturing a ball joint as defined above. The method comprises at least the following steps: - step of providing 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, - assembly step of the outer ring with the inner ring.

[0018] Advantageously, the method comprises, before the step of assembling the outer ring with the inner ring, a step of treating the inner ring, said inner ring comprising an outer surface covered entirely or partly with a cobalt-based coating, preferably an alloy of formula CoCr29W5. Brief description of the figures

[0019] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

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

[0021] [Fig.2] is a front view of the patella of [Fig.l];

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

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

[0024] Figures 1, 2 and 3 illustrate a ball joint 1 in a reference 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 opposite the inner surface 2a, and two opposite radial end faces (not referenced) axially delimiting the inner 2a and outer 2b surfaces.

[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 opposite the outer surface 3b, and two opposite radial end faces (not referenced) axially delimiting the bore 3a and the outer surface 3b. The inner 2a and outer 3b surfaces of the outer 2 and inner 3 rings are in contact with each other and of complementary shape.

[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 μm and 20 μm, preferably between 5 μm and 10 μm.

[0028] The outer surface 2b and the end 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 NiCrl9Fel8Nb 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.

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

[0031] In the illustrated embodiment, the ball joint 1 also comprises 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 against 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 devoid of the sleeve 4.

[0034] In the illustrated embodiment, the outer ring 2 of the ball joint 1 comprises a fixing flange 6 extending radially outwards one of the axial ends of the outer surface 2b. Alternatively, the outer ring 2 of the ball joint 1 could be devoid of the flange 6.

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

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

[0037] The method firstly 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.

[0038] Then, the method comprises 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 sub-steps, a first sub-step E3 of cementation and a second sub-step E4 of nitriding which is carried out simultaneously or successively with the first sub-step E3 and in the same heat treatment cycle. A heat treatment cycle is characterized by a rise in temperature from a low initial temperature to a high temperature, a maintenance at the high temperature, then a drop in temperature to a temperature close to the low initial temperature. For example, a heat treatment cycle corresponding to the step E2 of carbonitriding of the inner surface 2a of the outer ring 2, begins with the first sub-step E3 of cementation which uses acetylene to constitute a carbon supply, and continues with the second nitriding sub-step E4 which uses ammonia to provide a nitrogen supply. The temperature of this heat treatment cycle can, for example, be between 400°C and 500°C and is maintained for the time necessary for the desired enrichment in carbon and nitrogen 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 room temperature. The carbonitriding treatment can last from 10 to 50 hours depending on the thickness chosen.

[0040] Finally, the method comprises a step E5 of assembling the inner 3 and outer 2 rings together.

[0041] 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 entirely covered, or only partially, 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 which is intended to be attached to the associated support system. It does not depart from 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, the outer ring (2) more particularly comprising an alloy of formula NiCrl9Fel8Nb.

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 inner ring (3) comprises a cobalt alloy of formula CoCr29W5.

4. Ball joint (1) according to one of claims 1 and 2, 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).

5. Ball joint (1) according to any one of claims 1 to 4, 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.

6. Ball joint (1) according to any one of claims 1 to 5, 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.

7. Ball joint (1) according to claim 6, in which the sleeve (4) comprises a nickel-based material, more particularly an alloy of formula NiCrl9Fel8Nb.

8.

9. Method of manufacturing a ball joint (1) according to any one of claims 1 to 7, 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). Method for manufacturing a ball joint (1) according to claim 8, comprising, before 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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