Joint structure of dissimilar metals and implant

Abstract

To provide a joining structure of dissimilar metals capable of firmly joining a cobalt chromium alloy and titanium or a titanium alloy.SOLUTION: A titanium or titanium alloy first material 1, a cobalt base alloy second material 2 and an intermediate layer 3 for joining the first material 1 and the second material 2 are provided, the intermediate layer 3 is composed of a first intermediate layer 4 in contact with the first material 1 and a second intermediate layer 5 in contact with the first intermediate layer 4 and the first intermediate layer 4 is composed of niobium and the second intermediate layer 5 is composed of copper. Preferably, second material 2 is a cobalt-chromium alloy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joint structure of dissimilar metals and an implant such as an artificial joint that uses this joint structure of dissimilar metals. [Background technology]

[0002] Cobalt-chromium alloy, a cobalt-based alloy, is a medical material with high strength and excellent wear resistance, and is widely used in artificial joints and dentures. However, its elastic modulus differs significantly from that of bone, and its biocompatibility is known to lead to complications. Titanium and titanium alloys, on the other hand, are known as excellent medical materials, being lightweight, with an elastic modulus close to that of bone, and highly biocompatible. However, their lower strength compared to cobalt-chromium alloys hinders the development of high-performance artificial joints. Joining these two materials, using cobalt-chromium alloys in areas requiring strength and titanium or titanium alloys in areas that interface with bone, would enable high-performance artificial joints. However, direct joining of these two materials presents a challenge, as brittle intermetallic compounds are formed, resulting in low joint strength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-340365 [Non-patent literature]

[0004] [Non-Patent Document 1] Laser welding of pure titanium and dental cobalt-chromium alloy, [online], [Retrieved July 3, 2024], Internet<URL: https: / / kaken.nii.ac.jp / ja / grant / KAKENHI-PROJECT-19926012 / > Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a dissimilar metal joint structure capable of firmly joining a cobalt-chromium alloy and titanium or a titanium alloy, and to provide an implant such as an artificial joint using this dissimilar metal joint structure. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have discovered a material that does not form brittle intermetallic compounds with cobalt-chromium alloys and titanium or titanium alloys, and have discovered that by interposing this material as an intermediate layer, cobalt-chromium alloys and titanium or titanium alloys can be firmly joined, leading to the present invention.

[0007] That is, the dissimilar metal joining structure of the present invention comprises a first material made of titanium or a titanium alloy, a second material made of a cobalt-based alloy, and an intermediate layer joining the first material and the second material, wherein the intermediate layer comprises a first intermediate layer in contact with the first material and a second intermediate layer in contact with this first intermediate layer and the second material, the first intermediate layer being made of niobium and the second intermediate layer being made of copper.

[0008] In the dissimilar metal joint structure of the present invention, the second material is a cobalt-chromium alloy.

[0009] The implant of the present invention also has the dissimilar metal joint structure of the present invention.

[0010] Furthermore, the implant of the present invention has a structure in which the second material is enclosed within the first material.

[0011] The implant of the present invention is an artificial hip joint stem, in which the second material is disposed in and near the neck. [Effects of the Invention]

[0012] According to the dissimilar metal joint structure of the present invention, a cobalt-chromium alloy and titanium or a titanium alloy can be firmly joined, and implants such as artificial joints can be provided using this dissimilar metal joint structure. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing the basic configuration of a joint structure of dissimilar metals according to the present invention, and its partially enlarged cross-sectional view. [Figure 2] 1 is a front view of an artificial hip joint stem showing one embodiment of the implant of the present invention. [Figure 3] FIG. [Figure 4] FIG. 10 is an explanatory diagram showing the joining of materials of the artificial hip joint stem. [Figure 5] Same as above, this is a photo of the artificial hip stem after manufacturing. [Figure 6] 10. The same as above, a micrograph of a cross section of a joint between materials of an artificial hip stem. DETAILED DESCRIPTION OF THE INVENTION

[0014] The dissimilar metal joint structure and implant of the present invention will be described based on the following examples. Note that the present invention is not limited to the following examples, and various modifications can be made without departing from the spirit of the present invention. [Example]

[0015] In FIG. 1, which shows the basic configuration of the dissimilar metal joining structure of the present invention, 1 denotes a first material, made of titanium or a titanium alloy. Here, titanium alloys with added elements such as aluminum, vanadium, and tin can be used. Also, 2 denotes a second material indirectly joined to the first material 1, made of a cobalt-based alloy. Here, cobalt-based alloys that can be used include cobalt-chromium alloys and those with added elements such as nickel, molybdenum, tungsten, tantalum, and niobium.

[0016] Between the first material 1 and the second material 2, there is an intermediate layer 3 that joins the first material 1 and the second material 2. The intermediate layer 3 further comprises a first intermediate layer 4 that contacts the first material 1, and a second intermediate layer 5 that contacts the first intermediate layer 4 and the second material 2. The first intermediate layer 4 is made of niobium, and the second intermediate layer 5 is made of copper. By configuring the intermediate layer 3 in this way, brittle intermetallic compounds are not generated when the first material 1 and the second material 2 are joined, and the first material 1 and the second material 2 can be firmly joined.

[0017] The joining between the first material 1 and the first intermediate layer 4, the first intermediate layer 4 and the second intermediate layer 5, and the second intermediate layer 5 and the second material 2 can be performed by known methods such as metal additive manufacturing, welding, casting, and forging. [Example]

[0018] Next, an embodiment of an implant having a dissimilar metal joint structure according to the present invention will be described, taking an artificial hip joint stem as an example.

[0019] 2 to 4, which show the artificial hip joint stem of this embodiment, the stem 11 comprises a stem body 12 inserted into the femur, a stem distal end 13 to which a spherical head (not shown) is attached, and a neck 14 that connects the stem body 12 and the stem distal end 13 and is thinner than the stem distal end 13. Because the stem body 12 is inserted into the femur, it must be highly biocompatible. Therefore, the outer surface of the stem body 12 is made of a highly biocompatible titanium alloy. Furthermore, in this embodiment, the entire outer surface of the stem 11 is also made of a titanium alloy. Furthermore, despite its thinness, the neck 14 must be strong because it connects the femur to the pelvis. For this reason, a reinforcing member 15 made of a high-strength cobalt-chromium alloy is embedded in and near the neck 14.

[0020] 4, the titanium alloy constituting the stem 11 and the cobalt-chromium alloy constituting the reinforcing member 15 are joined via an intermediate layer 16 by the dissimilar metal joining structure described in Example 1. That is, the intermediate layer 16 is formed on all outer surfaces of the reinforcing member 15, and the stem 11 and the reinforcing member 15 are joined via this intermediate layer 16. Although not shown, similar to Example 1, the intermediate layer 16 is composed of a first intermediate layer made of niobium and a second intermediate layer made of copper.

[0021] As described above, in this embodiment, the stem 11 has the dissimilar metal joint structure described in the first embodiment, and the stem 11 and the reinforcing member 15 can be firmly joined together.

[0022] Furthermore, in this embodiment, the stem 11 is made of a first material, a titanium alloy, which contains the second material, a cobalt-chromium alloy, which constitutes the reinforcing member 15. Since only the titanium alloy, which has high biocompatibility, is exposed, the structure is also excellent in biological safety.

[0023] In this embodiment, the cobalt chromium alloy, which is the second material constituting the reinforcing member 15, is disposed in the neck 14 and its vicinity, thereby imparting high strength to the neck 14 and its vicinity. [Example]

[0024] Next, an embodiment of the method for manufacturing a dissimilar metal joint structure according to the present invention will be described by taking the manufacture of an artificial hip joint stem of Example 2 as an example.

[0025] In this example, an artificial hip joint stem was manufactured using a deposition-based additive manufacturing technology called Directed Energy Deposition (DED). The deposition method involves simultaneously irradiating the target area with a material powder and a laser or electron beam, causing them to melt and solidify. This method allows for repair of parts because it processes the base material, and its fast manufacturing speed allows for the creation of large products. Furthermore, by integrally manufacturing different materials, it is possible to change the mechanical properties of the different materials.

[0026] The modeling device used was a powder DED 3D metal additive manufacturing machine, LAMDA200 (manufactured by Nidek Machine Tools). Copper (Cu), niobium (Nb), and titanium alloy (Ti6Al4V) were additively manufactured on a cobalt-chromium alloy (CoCr) substrate, resulting in the configuration shown in Figure 4. The material powders used were Cu powder (particle size 53-106 μm), Nb powder (particle size 63-100 μm), and Ti6Al4V alloy powder (particle size -150 μm). The manufacturing conditions were adjusted as follows: laser power 0.5-2.0 kW, scanning speed 200-4000 mm / min, powder feed rate 1-20 g / min, and layer pitch 0.1 mm-1.5 mm. Figure 5 shows a photograph of the stem obtained after cutting and polishing.

[0027] A micrograph of the cross section of the joint between dissimilar metals is shown in Figure 6. It was confirmed that the cobalt-chromium alloy and titanium alloy were joined via an intermediate layer made of copper and niobium, without the formation of brittle intermetallic compounds at the joint. [Explanation of symbols]

[0028] 1. First Ingredient 2. Second ingredient 3. Middle class 4. The first middle class 5. The second middle class 11 Stem (artificial hip stem) 14 neck

Claims

1. a first material comprising titanium or a titanium alloy; a second material comprising a cobalt-based alloy; an intermediate layer that bonds the first material and the second material; the intermediate layer comprises a first intermediate layer in contact with the first material, and a second intermediate layer in contact with the first intermediate layer and the second material; 1. A dissimilar metal joint structure, wherein the first intermediate layer is made of niobium, and the second intermediate layer is made of copper.

2. 2. A joint structure for dissimilar metals according to claim 1, wherein said second material is a cobalt-chromium alloy.

3. An implant having the dissimilar metal joint structure according to claim 2.

4. The implant according to claim 3, having a structure in which the first material encloses the second material.

5. 5. The implant according to claim 3 or 4, which is an artificial hip stem, wherein the second material is disposed at and near the neck.

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