Medical implant antibacterial cobalt-based alloy

Abstract

The medical implant antibacterial cobalt-based alloy has the mass percentage composition of Cr: 17-18, Mn: 10.5-11.5, Fe: 22-23.5, W: 4-5, N: 0.1-0.2, Mo: 1.5-1.9, Nb: 0.7-0.85, Zr: 0.05-0.11, Cu: 2.5-3.0, and the balance of Co and inevitable impurities. The alloy has excellent mechanical and processing properties, can be widely applied to the preparation of orthopedic implants, oral implant systems, cardiovascular stents and other medical devices, can effectively reduce the infection risk of implanted devices, and can obviously reduce the corresponding cost of the devices.

Description

Technical Field

[0001] This invention relates to a medical implant alloy material. Background Technology

[0002] Due to their excellent corrosion resistance, wear resistance, thermal fatigue resistance, and thermal conductivity, cobalt-based alloys are widely used in the field of implantable medical devices. CN103215475B discloses a cobalt-based alloy for surgical implantation, CN106319289B discloses a Co-Cr-W alloy, and CN111996415B discloses a cobalt-chromium alloy biomaterial; these cobalt-based alloys all avoid containing Ni as much as possible to prevent various toxic side effects that may occur after implantation into the human body.

[0003] However, further improvements are still needed to these implant alloys in order to reduce the risk of implantation infection, enhance biocompatibility, ensure safety of use, and reduce costs. Summary of the Invention

[0004] The purpose of this invention is to provide a cobalt-based alloy for medical implantation that has at least excellent antibacterial properties.

[0005] According to one aspect of the present invention, a medical implantable cobalt-based alloy is provided, having the following mass percentage composition: Cr: 17-18; Mn: 10.5-11.5; Fe: 22-23.5; W: 4-5; N: 0.1-0.2; Mo: 1.5-1.9; Nb: 0.7-0.85; Zr: 0.05-0.11; Cu: 2.5-3.0; with the balance being Co and unavoidable impurities.

[0006] According to a preferred embodiment of the alloy of the present invention, Cr: 17.4~17.6; Mn: 11.0~11.3; Fe: 22.1~22.5; W: 4.4~4.6; N: 0.15~0.18; Mo: 1.6~1.7; Nb: 0.72~0.75; Zr: 0.08~0.10; Cu: 2.78~2.80; the balance being Co and unavoidable impurities.

[0007] The Ni impurity content in the alloy of this invention is controlled to be <0.05%. By strictly controlling the Ni element, the alloy of this invention avoids potential sensitization and carcinogenic risks.

[0008] The cobalt-based alloy of the present invention uses a CoCrMnFe alloy matrix. By adding specific amounts of Nb and Zr elements, the biocompatibility of the alloy is further improved on the basis of improving the mechanical properties of the alloy. In particular, the antibacterial properties of the alloy are significantly improved by adding Cu elements.

[0009] In the alloy of this invention, nitrogen (N) not only strengthens the material but also maintains its plasticity and toughness. Furthermore, it works synergistically with molybdenum (Mo) to improve the alloy's corrosion resistance. Simultaneously, nitrogen and cobalt in the alloy synergistically reduce the stacking fault energy—the lower the stacking fault energy, the wider the spread dislocations, the greater the bundle energy, the more difficult the bundle formation, the greater the resistance to slip, and thus the higher the yield strength. Therefore, the alloy of this invention maintains good plasticity and toughness while enhancing corrosion resistance.

[0010] According to the alloy matrix designed in this invention, Fe and Mn elements can partially replace expensive Co elements, thereby reducing costs. Furthermore, Mn can further stabilize the austenitization of cobalt-based alloys, thus improving the alloy's machinability. In addition, Fe, Mn, and Mo elements in the alloy are all essential trace elements for the human body, participating in most aspects of human metabolism, thereby further improving the alloy's biocompatibility.

[0011] In summary, the medical implantable antibacterial cobalt-based alloy of the present invention has the characteristics of antibacterial, non-toxic, environmentally friendly, and low cost, and has excellent mechanical and processing properties.

[0012] According to another aspect of the present invention, a method for preparing the above-mentioned alloy is provided, comprising:

[0013] According to the melting point from high to low, the metal elements except Zr are added to the vacuum induction melting furnace in sequence until they are completely melted into a melt.

[0014] Then nitrogen gas is introduced into the melt to control the N content in the alloy between 0.1% and 0.2%.

[0015] Finally, add Zr;

[0016] After vacuum melting, the melt is cast into ingots, wherein the melting temperature is 1350–1450℃;

[0017] Homogenization heat treatment of ingots, wherein the temperature is 1205~1235℃ and the time is 3~5 hours;

[0018] Next, the ingot is hot-forged to obtain the corresponding blank. During the hot forging process, the temperature is controlled to be no less than 980℃.

[0019] The obtained preform is held at 940~960℃ for 0.5~2 hours and then water-cooled. After that, it is held at 630~670℃ for 1~3 hours and then naturally cooled to room temperature.

[0020] When metal elements are added, the burn-off rate of Cr is calculated as 5%, the burn-off rate of Zr is calculated as 40%, and the burn-off rate of other metal elements is calculated as 3%.

[0021] This invention reduces the resistance of materials during deformation by hot forging, thereby reducing the risk of cracking, and further improves the strength and elongation of the materials through heat treatment.

[0022] According to another aspect of the present invention, a medical device is also provided, which is made of the above-described alloy. The alloy of the present invention can be widely used in the preparation of medical devices such as orthopedic implants, dental implant systems, and cardiovascular stents, effectively reducing the risk of infection in implanted devices while significantly reducing the corresponding costs. Detailed Implementation

[0023] The present invention will be further explained and illustrated below through specific embodiments.

[0024] First, prepare the ingredients according to the corresponding examples shown in Table 1 below: the burn-off rate of Cr is calculated as 5%, the burn-off rate of Zr is calculated as 40%, and the burn-off rate of other metal elements is calculated as 3%.

[0025] Raw materials are added to the crucible of the vacuum melting furnace in descending order of melting point. Heating begins until complete melting, followed by the introduction of nitrogen gas. The nitrogen flow rate and time are controlled to maintain the N content in the alloy at approximately 0.15%. Finally, volatile Zr is added. The melting process is performed in a vacuum furnace at 1400℃ with an initial vacuum of 9.52 × 10⁻⁶. -4 Pa; Argon gas with a purity of 99.99% is used for protection during the smelting process, and the furnace pressure is controlled at 8 Pa. After all the ingredients are smelted until completely melted and stirred evenly, they are cast into ingots with a diameter of φ60*200mm.

[0026] Next, the ingot was homogenized at 1220 (±15)℃ for 4 hours, and then hot-forged into a billet. During the hot forging process, the temperature needed to be controlled not to be lower than 980℃. Finally, it was rolled into a 10mm thick plate. The samples were wire-cut into 10*10*5mm samples for heat treatment: held at 950℃ for 1.5 hours and then water-cooled, and then held at 650℃ for 2 hours and then cooled to room temperature in the furnace to obtain the corresponding alloy samples of the present invention, Examples 1-4.

[0027] Table 1 shows the mass percentage composition of the comparative example alloy L605 and the alloy samples 1-4 according to the present invention. Table 1: Alloy Composition (where Ni is an impurity)

[0028]

[0029] Alloy physical property testing and antibacterial property testing: The test results of tensile strength, yield strength and elongation of the above alloy examples and control examples are shown in Table 2 below.

[0030] This invention, based on relevant standards such as JIS Z 2801:2012 "Antibacterial Product Antibacterial Test Methods and Antibacterial Effects," used alloy L605 as a control to further determine the bactericidal effect of each alloy example against Staphylococcus aureus. The bactericidal rate was calculated using the formula: (Number of viable bacteria in the control alloy L605 sample - Number of viable bacteria in the cobalt-based alloy of this invention) / Number of viable bacteria in the control alloy L605 sample * 100%. Furthermore, cytotoxicity was tested using MTS reagent for each alloy example; according to the evaluation criteria, levels below 2 are sufficient to meet the requirements for biomedical materials. The bactericidal rate and cytotoxicity test results for each alloy example are also shown in Table 2. Table 2: Alloy Properties

[0031]

[0032] As shown in Table 2, compared with the comparative alloy L605, the alloy examples of the present invention show significant improvements in tensile strength, yield strength, and elongation. This is because in the alloys of the present invention, Nb can form Cr2Nb particles and CoNb compounds with the alloy matrix, respectively, while Zr can form CuZr compounds with Cu. These compounds play a dispersion strengthening role in the matrix, thereby improving the strength of the alloy without reducing its toughness.

[0033] Compared to the control alloys, all alloy examples of the present invention exhibited excellent antibacterial properties, with bactericidal rates exceeding 91%, especially the alloys of Examples 2 and 3, which achieved bactericidal rates exceeding 99.8%. This is because the dissolved Nb, Zr, and Cu ions can rapidly and synergistically kill bacteria, thereby enhancing the alloy's antibacterial properties. Furthermore, Cu ions also simultaneously promote and accelerate angiogenesis, inhibit smooth muscle cell proliferation, inhibit thrombus formation, and inhibit VSMC (arterial smooth muscle cell) proliferation. In addition, the cytotoxicity test results of all alloy examples fully met the requirements for biomedical materials.

Claims

1. A cobalt-based alloy for medical implantation, comprising the following composition by weight percentage: Cr:17~18; Mn:10.5~11.5;Fe:22~23.5; W：4~5； N: 0.1~0.2； Mo: 1.5~1.9; Nb ：0.7~0.85；Zr：0.05~0.11； Cu: 2.5~3.0; balance is Co and unavoidable impurities. Its preparation methods include: Metal elements other than Zr are added to the vacuum melting furnace in order of melting point from high to low until they are completely melted into a melt. Then nitrogen gas is introduced into the melt to control the N content in the alloy between 0.1% and 0.2%. Finally, add Zr; After vacuum melting, the melt is cast into ingots, wherein the melting temperature is 1350–1450℃; Homogenization heat treatment of ingots, wherein the temperature is 1205~1235℃ and the time is 3~5 hours; Next, the ingot is hot-forged to obtain the corresponding blank. During the hot forging process, the temperature is controlled to be no less than 980℃. The obtained preform is held at 940~960℃ for 0.5~2 hours and then water-cooled. After that, it is held at 630~670℃ for 1~3 hours and then naturally cooled to room temperature.

2. The alloy according to claim 1, wherein... Cr:17.4~17.6; Mn:11.0~11.3; Fe: 22.1~22.5; W：4.4~4.6； N: 0.15~0.18； Mo: 1.6~1.7; Nb ：0.72~0.75； Zr：0.08~0.10； Cu: 2.78~2.80; balance is Co and unavoidable impurities.

3. The alloy according to claim 1, wherein the content of metallic Ni impurities is controlled to be <0.05%.

4. A medical device made of an alloy according to any one of claims 1-3.

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