A Co-based superelastic alloy for orthodontic wires and its preparation method

Abstract

This invention discloses a Co-based superelastic alloy for orthodontic wire and its preparation method. The alloy comprises the following components by mass percentage: Co 26-49%, Mo 9-29%, Cr 4-17%, Ga 7-30%, and Ge 11-33%. Ingots are prepared using vacuum induction melting followed by electroslag remelting, and wires are obtained through forging and drawing. The wires are further processed using a cyclic heat treatment process to obtain the final product. The alloy of this invention exhibits excellent superelasticity, good corrosion resistance, and no harmful ion leaching, effectively improving the effectiveness and safety of orthodontic treatment.

Description

Technical Field

[0001] This invention belongs to the field of shape memory alloys, specifically relating to a Co-based superelastic alloy for orthodontic wires and its preparation method. Background Technology

[0002] Fixed orthodontic appliances are widely used in the correction of various malocclusions, enabling precise control of tooth position in three dimensions. The archwire is a crucial component of fixed orthodontic appliances. During orthodontic treatment, the corrective force is generated by the archwire, transmitted through brackets, teeth, and the periodontal ligament, and finally to the alveolar bone, causing tooth movement and inducing tissue remodeling in the periodontal tissues. Since the magnitude of the corrective force on the periodontal tissues largely depends on the archwire, an ideal orthodontic archwire needs excellent shape memory and hyperelasticity to release a gentle yet continuous corrective force on the periodontal tissues. Therefore, selecting appropriate materials for archwire fabrication is fundamental to successful orthodontic treatment.

[0003] Currently, nickel-titanium alloy archwires, which possess shape memory effect, superelasticity, and biocompatibility, are widely used in clinical practice. Through continuous research and improvement, three generations of nickel-titanium archwires, classified according to their phase transition temperature, are now available: the first-generation conventional nickel-titanium archwire, the second-generation superelastic nickel-titanium archwire, and the third-generation thermally activated nickel-titanium archwire. These three generations exhibit different characteristics at oral temperatures and are widely used in orthodontic clinical treatment. However, nickel-titanium archwires suffer from problems such as limited superelastic deformation and the potential for nickel ion release and sensitization, directly affecting the correction of malocclusion. Therefore, there is an urgent need to develop a new type of alloy archwire with large superelastic deformation and minimal ion dissolution. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a Co-based superelastic alloy for orthodontic wires and its preparation method. This alloy has good superelastic effect, good corrosion resistance, and no harmful ion leaching, which can effectively improve the effect and safety of orthodontic treatment.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Co 26–49%, Mo 9–29%, Cr 4–17%, Ga 7–30%, and Ge 11–33%. Further, a preferred range of alloy composition is: Co 27–29%, Mo 17–23%, Cr 8–12%, Ga 15–22%, and Ge 20–27%.

[0007] Specifically, the orthodontic wire uses a Co-based superelastic alloy, whose typical preferred composition is as follows (in weight percentages):

[0008] (1) Cr 8%, Mo 23%, Ga 15%, Ge 27%, balance Co;

[0009] (2) Cr 10%, Mo 20%, Ga 19%, Ge 24%, balance Co;

[0010] (3) Cr 12%, Mo 17%, Ga 22%, Ge 20%, balance Co.

[0011] The preparation method of the Co-based superelastic alloy for orthodontic wire includes the following steps:

[0012] (1) Using a composition system based on mass percentage: Co 26-49%, Mo 9-29%, Cr 4-17%, Ga 7-30%, Ge 11-33%, alloy ingots were prepared by vacuum induction melting + electroslag remelting process;

[0013] (2) The alloy ingot is forged and drawn to produce alloy wire;

[0014] (3) The alloy wire is subjected to cyclic heat treatment to improve the microstructure and enhance the superelastic effect;

[0015] (4) The alloy wire is chemically polished to remove the surface oxide scale and obtain Co-based superelastic alloy for orthodontic wire.

[0016] In step (3), the cyclic heat treatment process is as follows: ① Heat to 1000℃~1150℃ and hold for 0.5~1.5h; ② Cool with the furnace to 700℃~900℃ and hold for 0.5~1.5h; ③ Repeat steps ① and ② 4-14 times; ④ Water cooling.

[0017] The principle of this invention is as follows: (1) Through innovative alloy design, this invention uses Co as the base and adds alloying elements such as Cr, Mo, Ga, and Ge to form an ordered body-centered cubic (BCC) Heusler structure. When subjected to stress, it undergoes stress-induced martensitic transformation, transforming into a hexagonal close-packed (HCP) structure. The stress-induced phase transformation brings additional deformation, which macroscopically exhibits superelasticity. (2) Due to the unique ordered structure of this alloy, this invention further carries out a cyclic heat treatment process, which further improves the orderliness of the BCC Heusler structure of the alloy and stabilizes the superelastic properties. (3) Cr, Co, and Mo in the alloy are all easily passivated elements, and their content is above 58%. In the solution, they can form a passivation film with good protective effect, avoiding the dissolution of ions and ensuring the corrosion resistance of the alloy.

[0018] Compared with the prior art, the present invention has the following advantages and effects:

[0019] (1) The alloy in this invention has good room temperature superelasticity, which can obtain a relatively gentle orthodontic force when used in orthodontic wire.

[0020] (2) The Co-based alloy of the present invention has excellent corrosion resistance. In simulated saliva, the ion dissolution of Cr ions, Co ions, Mo ions, Ga ions and Ge ions did not reach the detection limit, the dissolution was almost zero, and there were no toxic side effects.

[0021] (3) Compared with existing TiNi alloy wires, the present invention does not contain the sensitizing and teratogenic element Ni, and has good biocompatibility when used in orthodontic wires.

[0022] (4) The alloy of the present invention has good technical application and market prospects in the field of biomedicine, especially in the field of orthodontics. Detailed Implementation

[0023] To facilitate understanding of the present invention, specific embodiments will be described in detail below. These embodiments will help those skilled in the art to further understand the present invention; however, they are not intended to limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements to the present invention without departing from its conceptual framework, and these modifications and improvements all fall within the scope of protection of the present invention.

[0024] Example 1

[0025] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 23%, Cr 8%, Ga 15%, Ge 27%, with the balance being Co.

[0026] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following steps: ① Heating to 1000℃ and holding for 1 hour; ② Furnace cooling to 700℃ and holding for 1 hour; ③ Repeating steps ① and ② four times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0027] Example 2

[0028] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 20%, Cr 10%, Ga 19%, Ge 24%, with the balance being Co.

[0029] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following steps: ① Heating to 1100℃ and holding for 1 hour; ② Furnace cooling to 800℃ and holding for 1 hour; ③ Repeating steps ① and ② nine times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0030] Example 3

[0031] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 17%, Cr 12%, Ga 22%, Ge 20%, with the balance being Co.

[0032] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following process: ① Heating to 1150℃ and holding for 1 hour; ② Furnace cooling to 900℃ and holding for 0.5 hours; ③ Repeating steps ① and ② 14 times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0033] Example 4

[0034] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 29%, Cr 4%, Ga 30%, Ge 11%, with the balance being Co.

[0035] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following steps: ① Heating to 1000℃ and holding for 0.5 hours; ② Furnace cooling to 700℃ and holding for 1 hour; ③ Repeating steps ① and ② four times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0036] Example 5

[0037] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 9%, Cr 17%, Ga 7%, Ge 33%, with the balance being Co.

[0038] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following steps: ① Heating to 1150℃ and holding for 1 hour; ② Furnace cooling to 900℃ and holding for 1.5 hours; ③ Repeating steps ① and ② 14 times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0039] Example 6

[0040] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 16%, Cr 8%, Ga 12%, Ge 15%, with the balance being Co.

[0041] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following steps: ① Heating to 1120℃ and holding for 1.5 hours; ② Furnace cooling to 760℃ and holding for 1 hour; ③ Repeating steps ① and ② seven times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0042] Example 7

[0043] A Co-based superelastic alloy for orthodontic wire comprises the following components by mass percentage: Mo 27%, Cr 6%, Ga 15%, Ge 16%, with the balance being Co.

[0044] The manufacturing method of orthodontic wire is as follows: An alloy ingot is prepared by vacuum induction melting followed by electroslag remelting according to the alloy weight ratio. The ingot is then forged and drawn into wire. The wire undergoes cyclic heat treatment, with the following process: ① Heating to 1050℃ and holding for 1 hour; ② Furnace cooling to 840℃ and holding for 1 hour; ③ Repeating steps ① and ② 11 times; ④ Water cooling. After heat treatment, the surface oxide layer is removed by chemical polishing. The material properties of the wire before and after heat treatment are shown in Table 1.

[0045] Test example: The performance of the orthodontic wires of Examples 1 to 7 using Co-based superelastic alloy was tested, and the results are detailed in Table 1.

[0046] Table 1 Performance tests of Co-based superelastic alloys used for orthodontic wires in Examples 1-7

[0047]

[0048]

[0049] As shown in Table 1, the Co-based alloy for orthodontic wire of the present invention has good superelasticity, which reflects the great advantages of the alloy element design and cyclic heat treatment process of the present invention; moreover, the present invention does not leach harmful ions, thus improving the safety of use.

[0050] The above description is merely an embodiment of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention are equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A Co-based superelastic alloy for orthodontic wires, characterized in that: It is composed of the following components in mass percentage: Co 26~49%, Mo 9~29%, Cr 4~17%, Ga 7~30%, Ge 11~33%.

2. The Co-based superelastic alloy for orthodontic wire according to claim 1, characterized in that: It is composed of the following components in mass percentage: Co 27~29%, Mo 17~23%, Cr 8~12%, Ga 15~22%, Ge 20~27%.

3. The Co-based superelastic alloy for orthodontic wire according to claim 1, characterized in that: Its components are any one of the following (1) to (3) by mass percentage: (1) Cr 8%, Mo 23%, Ga 15%, Ge 27%, balance Co; (2) Cr 10%, Mo 20%, Ga 19%, Ge 24%, balance Co; (3) Cr 12%, Mo 17%, Ga 22%, Ge 20%, balance Co.

4. A method for preparing a Co-based superelastic alloy for orthodontic wire as described in claim 1, characterized in that... Includes the following steps: (1) Using a composition system based on mass percentage: Co 26~49%, Mo 9~29%, Cr 4~17%, Ga 7~30%, Ge 11~33%, alloy ingots were prepared by vacuum induction melting + electroslag remelting process; (2) The alloy ingot is forged and drawn to prepare alloy wire; (3) Perform cyclic heat treatment on the alloy wire; (4) The alloy wire is chemically polished to remove the surface oxide scale and obtain Co-based superelastic alloy for orthodontic wire.

5. The method for preparing the Co-based superelastic alloy for orthodontic wire according to claim 4, characterized in that: In step (3), the process of the cyclic heat treatment is as follows: ① heat to 1000℃~1150℃ and hold for 0.5~1.5h; ② cool with the furnace to 700℃~900℃ and hold for 0.5~1.5h; ③ repeat steps ① and ② 4~14 times; ④ water cooling.

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