A method for preparing a high-performance medical tantalum coating

Abstract

The present application relates to the field of medical materials, in particular to a preparation method of high-performance medical tantalum coating. A thin-size-low-diffusion tantalum coating is prepared on the surface of a porous titanium alloy substrate by a chemical vapor deposition method through a halide reaction of hydrogen reduction of metallic tantalum; there is an alloy element interdiffusion zone between the tantalum coating and the porous titanium alloy substrate, and the thickness of the interdiffusion zone is less than the thickness of the tantalum coating. The present application obtains a high-performance thin-size tantalum coating with high purity, small grain size and controllable transition layer suitable for the porous titanium alloy substrate, has higher preparation efficiency and lower cost, realizes high bonding strength of the coating and simultaneous improvement of the strength and plasticity of the porous titanium alloy, avoids dissolution of toxic metal ions such as Al and V, and improves biocompatibility and osteogenic performance. The new tantalum coating porous titanium alloy implant device has obvious advantages of higher mechanical, chemical and biological safety and lower cost, and is suitable for the fields of orthopedics, dental implants and tissue defect fillers.

Description

Technical Field

[0001] This invention relates to the field of medical materials, specifically a method for preparing a high-performance medical tantalum coating, which is particularly suitable for orthopedic and dental implants and tissue defect fillers. Background Technology

[0002] Titanium alloys are widely used in bone tissue repair implants. However, titanium alloys such as Ti6Al4V contain elements like Al and V, which are harmful to the human body. Metal corrosion is unavoidable in the human body, easily leading to the dissolution of toxic metal ions, especially after long-term implantation, significantly increasing the potential biocompatibility risks. In recent years, the widespread use of 3D-printed porous Ti6Al4V has further exacerbated the dissolution of toxic ions due to its high specific surface area, reducing the biocompatibility of implants. Simultaneously, titanium alloys lack the ability to induce bone formation. Considering the difficulty of developing new alloys, surface modification is an effective means to improve the biocompatibility and bioactivity of titanium alloys.

[0003] Tantalum metal possesses excellent biocompatibility, corrosion resistance, ductility, and radioactivity, making it widely used in hard tissue repair. Porous tantalum implants prepared using chemical vapor deposition on a brittle carbon foam matrix have demonstrated excellent osseointegration advantages in clinical practice, but suffer from drawbacks such as thick coatings, high cost, and high density. However, using a stronger porous titanium alloy as the matrix promises to achieve the advantages of thinner coatings, lower cost, and lower density in porous tantalum. Simultaneously, the tantalum coating prevents the titanium alloy from leaching toxic ions such as Al and V, while maintaining tantalum's excellent biocompatibility and bioactivity.

[0004] Current research on tantalum coating preparation mainly focuses on physical deposition methods, but this method is not suitable for porous materials. Chemical vapor deposition (CVD), on the other hand, is not limited by the shape of the workpiece and is more suitable for coating deposition on the surface of implants with complex shapes. Patent CN 109338329 B develops a method for preparing tantalum coatings on the surface of titanium-based implants with non-porous structures; patent CN 116014163 A develops a method for preparing tantalum coatings on the surface of pure titanium (TA1, TA2) or titanium alloy (TA10) fuel cell bipolar plates. Clearly, coating preparation methods suitable for simple plate-shaped workpieces are not suitable for porous implants, especially titanium alloy implants that are entirely porous. Ensuring the uniformity of the tantalum coating on the surface of the deep pores is a crucial and extremely challenging feature.

[0005] Patents CN 110090072 B and CN 113210625 A describe methods for preparing tantalum coatings on porous titanium alloy implants, but the preparation time is extremely long, ranging from 7 to 10 hours. This long preparation cycle not only leads to low efficiency but, more importantly, causes severe diffusion of alloying elements, making it impossible to achieve a uniformly composed pure tantalum coating. As mentioned in patent CN 116014163 A, the tantalum element in the coating exhibits a gradient distribution from the inside out. Considering that tantalum is a rare metal, its raw material cost is high (more than 10 times that of titanium). Compared to thick tantalum coatings, thin tantalum coatings have a significant cost advantage. However, for thin tantalum coatings, the requirements for controlling the transition layer thickness and grain size are more stringent, and the lengthy preparation process cannot achieve these coating characteristics.

[0006] In summary, current chemical vapor deposition (CVD) tantalum coatings and their preparation methods are either only applicable to simple plate-shaped workpieces or, due to their excessively long preparation times, fail to produce thin-sized pure tantalum coatings with uniform composition and fine grains. Therefore, these methods cannot achieve the preparation of thin-sized, low-diffusion, high-performance pure tantalum coatings on porous titanium alloy substrates. Summary of the Invention

[0007] The purpose of this invention is to provide a high-performance medical tantalum coating deposited on the surface of titanium alloy implants and its preparation method. By rapidly depositing the tantalum coating and controlling the metallurgical reaction at the interface between the coating and the substrate, a high-purity, fine-grained, and controllable transition layer high-performance thin-size-low-diffusion tantalum coating suitable for porous titanium alloy substrates is obtained, enabling porous titanium alloys to obtain the excellent corrosion resistance, biocompatibility, and osteogenic properties of tantalum metal.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing a high-performance medical tantalum coating is disclosed. The method employs chemical vapor deposition to prepare a thin-size, low-diffusion tantalum coating on the surface of a porous titanium alloy substrate by reducing the halide of metallic tantalum with hydrogen. An interdiffusion region of alloying elements exists between the tantalum coating and the porous titanium alloy substrate, and the thickness of the interdiffusion region is less than the thickness of the tantalum coating.

[0010] The method for preparing the high-performance medical tantalum coating describes a tantalum coating surface with a silvery-gray metallic luster, a single-phase α-Ta phase composition, an interdiffusion region thickness less than 1 / 2 of the tantalum coating thickness, and titanium and its alloying elements existing only in the porous titanium alloy matrix and the interdiffusion region.

[0011] The method for preparing the high-performance medical tantalum coating has a tantalum coating thickness of 1–20 μm, a tantalum coating purity of ≥99 wt.%, and a tantalum coating grain size of less than 1 / 4 of the tantalum coating thickness.

[0012] The method for preparing the high-performance medical tantalum coating involves using tantalum halide as the reaction source, hydrogen as the reducing gas, and argon as the carrier gas during chemical vapor deposition. The ratio of tantalum halide evaporation rate to hydrogen flow rate is 2–40 g / ml, the reaction temperature is 800–1050℃, the reaction time is shortened by 0.1–2 h, and the reaction chamber pressure is greater than 20 Pa.

[0013] The method for preparing the high-performance medical tantalum coating has a uniform composition and dense structure. The integrity of the coating on the porous titanium alloy surface is 100%, the coating bonding strength is greater than 100 MPa, and the strength and plasticity of the porous titanium alloy with tantalum coating are improved at the same time, while the leaching of toxic metal ions is reduced by more than 99%.

[0014] The method for preparing the high-performance medical tantalum coating describes a porous titanium alloy substrate with a porosity of 60-90% and an average pore size of 100-800 μm.

[0015] The design concept of this invention is:

[0016] This invention proposes the construction of a thin-size, low-diffusion tantalum coating on a porous titanium alloy substrate. This achieves the advantages of a pure tantalum layer, including high corrosion resistance, biocompatibility, low cost, and high bonding strength, while avoiding the toxicity caused by severe diffusion of transition layer elements leading to metal ion dissolution and excessive brittle phases that degrade mechanical properties. However, due to the infinite miscibility of tantalum and titanium, traditional long-duration, high-temperature chemical vapor deposition methods easily lead to severe diffusion of alloying elements, making it difficult to construct the aforementioned ideal structure. This invention proposes leveraging the synergistic effect of controlling the dosage ratio of tantalum halide and hydrogen, as well as the reaction chamber pressure, to achieve controllable coating growth mode and rate, significantly shortening the reaction time, i.e., the alloying element diffusion time. By controlling the metallurgical reaction at the tantalum coating-substrate interface, a high-purity, fine-grained, high-performance thin-size tantalum coating with a controllable transition layer, suitable for porous titanium alloy substrates, is obtained.

[0017] The advantages and beneficial effects of this invention are:

[0018] 1. This invention proposes a method for preparing a high-performance medical tantalum coating. By rapidly depositing the tantalum coating and controlling the metallurgical reaction at the coating-substrate interface, a high-purity, fine-grained, and controllable transition layer (interdiffusion region) high-performance thin-size low-diffusion tantalum coating suitable for porous titanium alloy substrates is obtained. This improves preparation efficiency and reduces raw material costs. In particular, it has a significant cost advantage compared with traditional foamed carbon matrix porous tantalum and 3D printed porous tantalum used in clinical applications.

[0019] 2. The pure tantalum coating on the porous titanium alloy surface of this invention achieves high bonding strength through a metallurgically bonded transition layer at the interface with the substrate, thereby improving the strength and plasticity of the porous titanium alloy. Its performance indicators are as follows: compressive plastic strain of 20-30%, compressive strength of 80-150 MPa, and bonding strength of 120-300 MPa. Simultaneously, it improves corrosion resistance, prevents the dissolution of toxic metal ions such as Al and V, and enhances biocompatibility and osteogenic properties. Therefore, the tantalum-coated porous titanium alloy can achieve significantly higher mechanical, chemical, and biological safety, greatly improving the clinical therapeutic effect of porous titanium alloy implants. Attached Figure Description

[0020] Figure 1 The figures show the phase composition of the tantalum coatings in different embodiments and comparative examples. In the figures, the horizontal axis 2θ represents the diffraction angle (°), and the vertical axis Intensity represents the relative intensity (au).

[0021] Figure 2 These are microscopic images of the tantalum coating surfaces in different embodiments and comparative examples.

[0022] Figure 3 The images show the microstructure of the tantalum coating interface in different embodiments and comparative examples.

[0023] Figure 4 This is an analysis diagram of the elemental distribution at the interface of the tantalum coating in Example 3. Detailed Implementation

[0024] In the specific implementation process, the tantalum coating on the porous titanium alloy substrate of this invention is prepared by chemical vapor deposition. Tantalum pentachloride is used as the reaction source, and hydrogen is used as the reducing gas. The porous titanium alloy (Ti6Al4V) substrate is prepared by 3D printing metal powder, with a porosity ≥65% and an average pore size of 100–800 μm. The porous titanium alloy substrate needs to be pretreated and dried before being placed in the high-temperature deposition reaction chamber of the chemical vapor deposition equipment. Afterwards, the reaction chamber is sealed, an inert gas is introduced, and a high vacuum environment is obtained using a vacuum device. The reaction chamber is then heated until the deposition temperature is reached. The tantalum reaction source and reducing gas are then introduced to begin tantalum coating deposition. After deposition, the tantalum coating sample is cooled and removed.

[0025] The tantalum coating has a silvery-gray metallic luster and is composed of a single-phase α-Ta. The thickness of the interdiffusion zone is less than 1 / 2 of the thickness of the tantalum coating. The Ti element and alloying elements such as Al and V are only present in the titanium alloy matrix and the interdiffusion zone. The thickness of the tantalum coating is 1 to 20 μm, the purity of the tantalum coating is ≥99 wt.%, and the grain size of the tantalum coating is less than 1 / 4 of the thickness of the tantalum coating.

[0026] The following embodiments further illustrate the present invention. These embodiments are only some embodiments of the present invention and do not limit the scope of the present invention in any way.

[0027] Example 1

[0028] In this embodiment, the deposition reaction temperature was set to 1000℃, the reaction time to 0.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 5g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and its flow rate was 1200sccm.

[0029] Example 2

[0030] In this embodiment, the deposition reaction temperature was set to 1000℃, the reaction time to 0.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 35g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and its flow rate was 1200sccm.

[0031] Example 3

[0032] In this embodiment, the deposition reaction temperature was set to 850℃, the reaction time to 0.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 15g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and its flow rate was 1200sccm.

[0033] Example 4

[0034] In this embodiment, the deposition reaction temperature was set to 850℃, the reaction time to 1.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 15g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and its flow rate was 1200sccm.

[0035] Example 5

[0036] In this embodiment, the deposition reaction temperature was set to 850℃, the reaction time to 1.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 15g / ml, with a reaction chamber pressure of 100Pa. The carrier gas was argon, and its flow rate was 1200sccm.

[0037] Comparative Example 1

[0038] In this comparative example, the deposition reaction temperature was set at 750℃, the reaction time was 0.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 15g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and the flow rate was 1200sccm.

[0039] Comparative Example 2

[0040] In this comparative example, the deposition reaction temperature was set at 850℃, the reaction time was 0.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 1g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and the flow rate was 1200sccm.

[0041] Comparative Example 3

[0042] In this comparative example, the deposition reaction temperature was set at 1100℃, the reaction time was 0.5h, and the evaporation temperature of tantalum pentachloride, the carrier gas flow rate, and the hydrogen flow rate were adjusted to achieve an evaporation rate to hydrogen flow rate ratio of 5g / ml, with a reaction chamber pressure of 50Pa. The carrier gas was argon, and the flow rate was 1200sccm.

[0043] like Figure 1 As shown, macroscopic observation revealed that the surfaces of the above-mentioned examples and comparative samples all exhibited a silvery-gray metallic luster, and XRD analysis showed that their phase composition was single-phase α-Ta. Figure 2 As shown, the microstructure of the coating surface reveals that the coating in the example is uniform, free of pores and cracks, and intact; while Comparative Example 1 exhibits obvious pores, and Comparative Example 2 exhibits obvious cracks. Figure 3 As shown, the microscopic morphology of the coating cross-section reveals that the coating thickness of the embodiments is uniform, the transition layer is thin, and the interface with the substrate is tight. In contrast, the coatings of Comparative Examples 1 and 2 are too thin and have obvious cracks at the interface with the substrate, while the coating of Comparative Example 3 is extremely thin and the transition layer is too thick. Figure 4 As shown, electron probe microanalysis of the cross-section of Example 3 revealed that Ti and alloying elements such as Al and V exist only in the titanium alloy matrix and interdiffusion region. The diffusion layer has a bilayer structure rich in tantalum and titanium, and aluminum is enriched in the titanium-rich layer.

[0044] As shown in Table 1, the purity of the tantalum coating in the examples was significantly higher than that in the comparative examples, and the thickness of the coating and transition layer was more controllable. Analysis of the compressive properties of the 3D-printed porous titanium alloy substrate after tantalum coating deposition showed that, compared to the 3D-printed porous titanium alloy substrate with a compressive strength of 50.3 MPa and a compressive plasticity of 16.9%, both compressive strength and compressive plasticity were significantly improved after tantalum coating deposition; while the comparative examples showed a slight decrease. The bonding strength at the point of coating failure was tested using the scratch test, and the examples showed significantly higher strength than comparative examples 1 and 2. Immersion tests were used to evaluate the reduction in the leaching of toxic ions such as Al and V in physiological saline at 37°C after tantalum coating deposition. The results showed that the reduction in the leaching rate of the examples was significantly higher than that of comparative examples 1 and 2 with incomplete coatings and comparative example 3 with an excessively thick transition layer.

[0045] Table 1. Characteristics and properties of tantalum coating on titanium alloy surfaces

[0046]

[0047]

[0048] In summary, this invention proposes a method for preparing a high-performance medical tantalum coating. Chemical vapor deposition (CVD) is used to obtain a high-purity, fine-grained, and controllable transition layer of a high-performance thin-size tantalum coating suitable for porous titanium alloy substrates, resulting in higher preparation efficiency and lower cost. By controlling the metallurgical bonding between the coating and the substrate interface, high bonding strength of the coating is achieved, simultaneously improving the strength and plasticity of the porous titanium alloy, preventing the dissolution of toxic metal ions such as Al and V, and enhancing biocompatibility and osteogenic properties. Therefore, the tantalum-coated porous titanium alloy proposed in this invention exhibits significantly higher mechanical, chemical, and biological safety and lower cost, which will greatly improve the clinical therapeutic effect of porous titanium alloy implants and has broad application prospects in the fields of orthopedic implants, dental implants, and tissue defect filling materials.

[0049] The above embodiments are only used to illustrate the present invention, and do not limit the scope of application of the present invention.

Claims

1. A method for producing a high performance medical tantalum coating, characterized by, The thin size-low diffusion tantalum coating is prepared on the surface of the porous titanium alloy substrate by the chemical vapor deposition method through the halide reaction of the hydrogen reduction of the metal tantalum, the thickness of the tantalum coating is 1-20 μm; the alloy element interdiffusion zone exists between the tantalum coating and the porous titanium alloy substrate, and the thickness of the interdiffusion zone is less than 1 / 2 of the thickness of the tantalum coating, and the titanium and the alloy elements only exist in the porous titanium alloy substrate and the interdiffusion zone; In the chemical vapor deposition process, the tantalum halide is used as the reaction source, the hydrogen is used as the reducing gas, the argon is used as the carrier gas, the ratio of the evaporation speed of the tantalum halide to the flow rate of the hydrogen is 2-40 g / ml, the reaction temperature is 800-1050 ℃, the reaction time is shortened to 0.1-2 h, and the reaction chamber pressure is greater than 20 Pa. The porosity of the porous titanium alloy substrate is 60-90%, and the average pore diameter is 100-800 μm.

2. The method of claim 1, wherein the high performance medical tantalum coating is prepared by, The surface of the tantalum coating has a silver gray metallic luster, and the phase composition is a single-phase α-Ta.

3. The method of claim 1, wherein the high performance medical tantalum coating is prepared by, The purity of the tantalum coating is greater than or equal to 99 wt.%, and the grain size of the tantalum coating is less than 1 / 4 of the thickness of the tantalum coating.

4. The method of producing high performance medical tantalum coatings according to one of claims 1 to 3, characterized in that The coating composition is uniform, the structure is dense, the integrity of the porous titanium alloy surface coating is 100%, the coating bonding strength is greater than 100 MPa, and the strength and plasticity of the tantalum coating porous titanium alloy are simultaneously improved, and the toxic metal ion dissolution amount is reduced by more than 99%.

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