Electron beam additive manufacturing method for zirconium alloy implants

Abstract

The present application is about an electron beam additive manufacturing method for zirconium alloy implants. It includes: controlling the energy source to preheat the substrate to a preset temperature with a step-changing surface energy input density within the total surface energy input time; controlling the substrate to descend to a preset height, and laying the zirconium alloy powder on the preheated substrate; controlling the energy source to preheat the zirconium alloy powder on the substrate with a first body energy input density within the first body energy input time; controlling the energy source to selectively melt the preheated zirconium alloy powder with a second body energy input density; and controlling the energy source to thermally compensate the powder bed after selective melting with a third body energy input density within the second body energy input time. The present application ensures the stability of the printing process and the quality consistency of the target parts by controlling the energy source with coupled parameters such as the surface energy input density, the first body energy input density, the second body energy input density, and the third body energy input density.

Description

Technical Field

[0001] The present application relates to the technical field of additive manufacturing, and in particular to an electron beam additive manufacturing method for zirconium alloy implants. Background Art

[0002] As the aging population intensifies, the market demand and registration volume of knee joint products continue to rise. According to statistics, the number of total knee replacement surgeries in China reached more than 400,000 in 2020, and it is still growing at a rate of 20% per year. In addition, the number of registered knee joint products is also increasing. The number of domestically registered and imported knee joint prosthesis products approved by the State Food and Drug Administration has exceeded 160.

[0003] From the perspective of product materials, more than 95% of knee prosthesis products are made of cobalt-chromium-molybdenum alloy. Although cobalt-chromium-molybdenum alloy has good wear resistance, corrosion resistance and high strength performance, and is widely used in the joint surface components and load-bearing components of artificial joints, cobalt-chromium-molybdenum alloy still has many problems to be improved, such as: high alloy density, nearly twice that of titanium alloy; high elastic modulus, about ten times that of cortical bone; high cobalt, chromium and nickel content, easy to cause metal allergies; and aseptic loosening caused by accumulation of wear particles. The emergence of zirconium-niobium alloy has become an effective means to improve the clinical problems of cobalt-chromium-molybdenum alloy knee prosthesis. The density of zirconium-niobium alloy is only 75% of that of cobalt-chromium-molybdenum alloy, with low elastic modulus, significantly improved stress shielding effect and good biocompatibility. Compared with cobalt-chromium-molybdenum alloy, after the surface oxidation modification forms a dense oxide film with a thickness of more than 5 μm, the material surface is harder, more wear-resistant, has good wettability and a lower friction coefficient, which greatly reduces the patient's inflammatory response.

[0004] Among the related technologies, there are relatively few types of zirconium-niobium alloy joint products, and they are usually prepared by forging zirconium-niobium alloy. Limited by traditional processing capabilities, there are great deficiencies in the design freedom of the load-bearing part of the prosthesis and the design of the porous structure bone integration interface. Additive manufacturing technology provides a new idea for solving the above problems. The concept of free forming of additive manufacturing technology breaks the limitations of traditional technology on the structural design of knee prosthesis, and its natural advantages in the preparation of porous structures enable it to support the new design and development of joint bone integration interfaces. It can also build knee prostheses that are more compatible with human body mechanics from aspects such as structural gradient design and process gradual regulation. However, most of the additive manufacturing methods for zirconium alloys reported so far use powder bed laser additive manufacturing, laminated additive manufacturing, and laser cladding additive manufacturing methods. The cleanliness and forming quality of the alloy components prepared by these methods cannot meet the application requirements of medical joint implants.

[0005] Moreover, current forged zirconium-niobium joint products, taking the knee joint as an example, are usually based on big data of foreign patient anatomy and are limited by traditional processing capabilities. They are greatly limited in product design. In clinical applications, they have poor matching with Chinese anatomy, low prosthesis coverage, irritation of the ligaments around the joint, pain caused by abnormal patellar pulley, and joint instability. Secondly, current knee joint products are basically fixed with bone cement, which results in poor bone integration performance of the prosthesis biological fixation interface.

[0006] Therefore, it is necessary to provide a new technical solution to improve one or more problems existing in the above solutions.

[0007] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0008] The purpose of the present application is to provide an electron beam additive manufacturing method for zirconium alloy implants, thereby overcoming one or more problems caused by limitations and defects of related technologies to a certain extent.

[0009] According to an embodiment of the present application, an electron beam additive manufacturing method for a zirconium alloy implant is provided, the method comprising:

[0010] During the total surface energy input time, the energy source is controlled to preheat the substrate to a preset temperature with a step-wise surface energy input density; wherein the step number n of the step-wise surface energy input density is ≥ 3, the surface energy input density of the second step is less than the surface energy input density of the first step, and the surface energy input density gradually increases from the second step to the nth step, and the surface energy input density of the third step is greater than the surface energy input density of the first step;

[0011] Controlling the substrate to descend to a preset height, and laying the zirconium alloy powder on the preheated substrate;

[0012] During a first energy input time, controlling the energy source to preheat the zirconium alloy powder on the substrate at a first energy input density;

[0013] Controlling the energy source to selectively melt the preheated zirconium alloy powder at a second energy input density;

[0014] During the second body energy input time, controlling the energy source to perform thermal compensation on the powder bed after the selected area is melted with a third body energy input density;

[0015] Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

[0016] In an embodiment of the present application, the total surface energy input time includes the surface energy input time of the 1st step to the surface energy input time of the nth step; wherein, the total surface energy input time is less than or equal to 60 minutes, and the surface energy input time of the nth step is 5-20 minutes.

[0017] In the embodiment of the present application, the calculation formula of the surface energy input density is:

[0018] (1);

[0019] In the formula, represents the surface energy input density, represents the input power, represents the output power loss rate, represents the scanning speed of the energy source, Indicates the scanning distance, Represents the energy conversion rate.

[0020] In the embodiment of the present application, the surface energy input density is 0.01-0.2 J / mm 2 .

[0021] In the embodiment of the present application, the calculation formulas for the first body energy input density, the second body energy input density and the third body energy input density are all:

[0022] (2);

[0023] In the formula, when calculating the first body energy input density, represents the first body energy input density; when calculating the second body energy input density, represents the second body energy input density; when calculating the third body energy input density, represents the third body energy input density; represents the input power, represents the output power loss rate, Indicates the looseness of powder particles, represents the scanning speed of the energy source, Indicates the scanning distance, represents the energy conversion rate, Indicates the preset altitude.

[0024] In the embodiment of the present application, the first body energy input density and the third body energy input density are both 0.3-1.5 J / mm 3 , the sum of the first body energy input time and the second body energy input time is 8-30s.

[0025] In the embodiment of the present application, the energy input density of the second body is 9.0-35.0 J / mm 3 .

[0026] In the embodiment of the present application, the preset height is 0.05-0.1 mm.

[0027] In an embodiment of the present application, the beam spot size of the energy source corresponding to the surface energy input density, the beam spot size of the energy source corresponding to the first body energy input density, and the beam spot size of the energy source corresponding to the third body energy input density are all 300-2000μm, and the beam spot size of the energy source corresponding to the second body energy input density is 50-500μm.

[0028] In an embodiment of the present application, at least 80 wt % of the zirconium alloy powder has a particle size range of 45-170 μm, and a median particle size range of the zirconium alloy powder is 80-120 μm; wherein wt % represents the weight content percentage.

[0029] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0030] In one embodiment of the present application, through the above method, within the total surface energy input time, the energy source is controlled to preheat the substrate to a preset temperature with a step-varying surface energy input density, thereby achieving uniform preheating of the substrate, providing a stable temperature field for subsequent powder laying, and maintaining the flatness of the substrate at a preset temperature as much as possible; the energy source is controlled to preheat the zirconium alloy powder on the substrate with a first body energy input density, thereby achieving uniform preheating of the powder, preventing powder blowing or powder over-sintering, and facilitating better subsequent selective melting; the energy source is controlled to selectively melt the preheated zirconium alloy powder with a second body energy input density, thereby achieving sintering of the zirconium alloy powder; the energy source is controlled to perform thermal compensation on the powder bed with a third body energy input density, which not only prevents powder blowing due to low powder bed temperature, but also reduces thermal stress and improves the forming quality of the target parts, thereby meeting the application requirements of medical joint implants. In each step of additive manufacturing, the present application controls the energy source to ensure the stability of the printing process and the quality consistency of the target parts by coupling parameters such as surface energy input density, first body energy input density, second body energy input density and third body energy input density. The present application allows the selection of a suitable process within a more free process window according to the requirements of the target parts, and seeks a balance between the quality and economy of the target parts.

[0031] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A flowchart schematically showing a method for electron beam additive manufacturing of a zirconium alloy implant in an exemplary embodiment of the present application;

[0034] Figure 2 A schematic diagram of a target part printed by conventional method embodiment 1 is shown;

[0035] Figure 3 A schematic diagram of a physical image of a target part printed using Example 2 of the method of the present application is shown;

[0036] Figure 4 A schematic diagram of a physical image of a target part printed using Example 3 of the method of the present application is shown;

[0037] Figure 5 A schematic diagram of a target part printed using Example 4 of the method of the present application is shown;

[0038] Figure 6 The metallographic image of the target part printed by the conventional method embodiment 1 is schematically shown;

[0039] Figure 7 The metallographic diagram of the target part printed by the method embodiment 2 of the present application is schematically shown;

[0040] Figure 8 The metallographic diagram of the target part printed by the method embodiment 3 of the present application is schematically shown;

[0041] Fig. 9 The metallographic diagram of the target part printed by the method embodiment 4 of the present application is schematically shown. DETAILED DESCRIPTION

[0042] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0043] This example embodiment provides a method for electron beam additive manufacturing of a zirconium alloy implant. Figure 1As shown in , the method includes: steps S101 to S106.

[0044] Among them, step S101: within the total surface energy input time, control the energy source to preheat the substrate to a preset temperature with a step-by-step changing surface energy input density; wherein, the step number n of the step-by-step changing surface energy input density is ≥3, the surface energy input density of the second step is less than the surface energy input density of the first step, and the surface energy input density gradually increases from the second step to the nth step, and the surface energy input density of the third step is greater than the surface energy input density of the first step.

[0045] It should be noted that the substrate is a rigid platform, and in the process of printing the zirconium alloy implant (i.e., the target part), the substrate needs to be preheated to a preset temperature. The present application controls the energy source to preheat the substrate with a stepped surface energy input density, thereby achieving uniform preheating of the substrate during preheating, which not only provides a stable temperature field for the subsequent laying of powder, but also maintains the flatness of the substrate at a preset temperature, ensuring that the powder can be evenly spread, thereby avoiding problems such as powder blowing or over-sintering caused by local thickness differences during the printing process. In addition, when the present application preheats the substrate, if the preset temperature is too high, it is easy to cause the powder bed to overheat and sinter, and the powder is not easy to recover. If the preset temperature of the substrate is too low, it will also cause the powder subsequently laid on the substrate to be loose, which is easy to cause powder blowing or powder splashing during the forming process, thereby affecting the forming quality of the final target part. Therefore, the present application sets the preset temperature to 600-800°C, and the method of preheating the substrate with a stepped surface energy input density can improve the forming quality of the subsequent target parts.

[0046] Furthermore, the total surface energy input time includes the surface energy input time of the 1st step to the surface energy input time of the nth step; wherein, the total surface energy input time is less than or equal to 60 minutes, and the surface energy input time of the nth step is 5-20 minutes.

[0047] In this application, the total time of surface energy input is represented by t, t≤60min, t=t1+t2+…+t n , where t1 represents the surface energy input time of the first step, t2 represents the surface energy input time of the second step, and t n Indicates the surface energy input time of the nth step.

[0048] It should be noted that in the present application, the number of steps n≥3, so the value of the number of steps n can be 3, 4 or 5, etc., and the present application does not impose any restrictions on this.

[0049] The following describes the specific process of controlling the energy source in the present application to preheat the substrate to a preset temperature with a step-varying surface energy input density when the step number n is 4:

[0050] During the surface energy input time t1 of the first step, the substrate is preheated using the surface energy input density of the first step;

[0051] During the surface energy input time t2 of the second step, the substrate is continued to be preheated using the surface energy input density of the second step;

[0052] During the surface energy input time t3 of the third step, the substrate is continued to be preheated using the surface energy input density of the third step;

[0053] During the surface energy input time t4 of the fourth step, the substrate is continuously preheated using the surface energy input density of the fourth step.

[0054] By controlling the energy source to preheat the substrate with a stepped surface energy input density, the substrate can be preheated uniformly, providing a stable temperature field for subsequent powder laying, and the substrate can be preheated to the preheating temperature within the total surface energy input time. The value of the preset temperature can be set according to actual conditions, and this application does not limit this.

[0055] The substrate is preheated with a stepped surface energy input density. The surface energy input density of the first step preheats the substrate from a cold plate to a lower temperature range, for example, usually 200-400°C, and the substrate will not produce a large deformation. The surface energy input density of the second step is lower than that of the first step in order to keep the substrate as warm as possible at 200-400°C, so that the temperature of each area of ​​the substrate is uniform and the deformation is uniform. The surface energy input density from the second step to the nth step is gradually increased, and the surface energy input density of the third step is greater than that of the first step, so as to achieve uniform preheating and uniform deformation of the substrate within a preset temperature range.

[0056] It is understandable that directly using a larger surface energy input density for preheating from the beginning will have the highest efficiency in increasing the temperature. However, due to the problem of synchronous heat dissipation of the substrate, it is difficult to achieve uniform temperature distribution of the substrate, and there will usually be serious warping problems around the substrate. The step preheating in this application can not only enable the substrate to quickly reach the preset temperature, but also ensure that the substrate temperature and deformation are uniform, so as to ensure that after the powder is spread, the powder thickness is uniform in the entire substrate area, and the powder will not be blown or over-sintered due to the local powder layer being too thick or too thin, thereby affecting the forming quality.

[0057] Step S102: Control the substrate to descend to a preset height, and spread the zirconium alloy powder on the preheated substrate.

[0058] It should be noted that the preset height of the substrate is 0.05-0.1 mm. When the substrate is controlled to descend by the preset height of 0.05-0.1 mm, the amount of zirconium alloy powder laid in each layer can be indirectly controlled, thereby facilitating the subsequent printing of the target parts.

[0059] Step S103: During the first energy input time, controlling the energy source to preheat the zirconium alloy powder on the substrate at a first energy input density.

[0060] It should be noted that after the zirconium alloy powder is laid on the preheated substrate, the energy source is controlled to preheat the zirconium alloy powder with the first energy input density to achieve powder preheating. The present application adopts the first energy input density to preheat the zirconium alloy powder, so that the preheated zirconium alloy powder can better achieve a certain degree of pseudo-sintering and have a certain strength, thereby facilitating the subsequent selective melting and forming, and avoiding powder blowing during the selective melting process, or powder splashing causing melting quality problems.

[0061] Step S104: controlling the energy source to selectively melt the preheated zirconium alloy powder at a second energy input density.

[0062] It should be noted that after the zirconium alloy powder on the substrate is preheated, the energy source is controlled to selectively melt the preheated zirconium alloy powder with the second body energy input density to obtain a forming plane. The present application adopts the second body energy input density to selectively melt the preheated zirconium alloy powder, so that the surface of the forming plane is smooth and flat without defects, so as to facilitate the subsequent good repetition of powder spreading, powder preheating, selective melting and thermal compensation steps, forming a virtuous cycle, and obtaining the target part.

[0063] Step S105: During the second body energy input time, the energy source is controlled to perform thermal compensation on the powder bed after the selected area is melted with a third body energy input density.

[0064] It should be noted that after the preheated zirconium alloy powder is selectively melted, the present application uses a third body energy input density to perform thermal compensation on the powder bed after the selective melting, which not only prevents the powder blowing phenomenon caused by low powder bed temperature, but also reduces thermal stress, thereby improving the forming quality of the target parts.

[0065] Step S106: Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

[0066] It should be noted that after obtaining the target part, the target part is cooled to room temperature and then taken out, and the powder is recovered.

[0067] It should be noted that, in the present application, the energy source may be, in addition to an electron beam, a laser or an electric arc.

[0068] In one embodiment of the present application, through the above method, within the total surface energy input time, the energy source is controlled to preheat the substrate to a preset temperature with a step-varying surface energy input density, thereby achieving uniform preheating of the substrate, providing a stable temperature field for subsequent powder laying, and maintaining the flatness of the substrate at a preset temperature as much as possible; the energy source is controlled to preheat the zirconium alloy powder on the substrate with a first body energy input density, thereby achieving uniform preheating of the powder, preventing powder blowing or powder over-sintering, and facilitating better subsequent selective melting; the energy source is controlled to selectively melt the preheated zirconium alloy powder with a second body energy input density, thereby achieving sintering of the zirconium alloy powder; the energy source is controlled to perform thermal compensation on the powder bed with a third body energy input density, which not only prevents powder blowing due to low powder bed temperature, but also reduces thermal stress and improves the forming quality of the target parts, thereby meeting the application requirements of medical joint implants. In each step of additive manufacturing, the present application controls the energy source to ensure the stability of the printing process and the quality consistency of the target parts by coupling parameters such as surface energy input density, first body energy input density, second body energy input density and third body energy input density. The present application allows the selection of a suitable process within a more free process window according to the requirements of the target parts, and seeks a balance between the quality and economy of the target parts.

[0069] Next, we will refer to Figure 1 Each step of the above method in this example implementation is described in more detail.

[0070] In one embodiment, the calculation formula for the surface energy input density is:

[0071] (1);

[0072] In the formula, represents the surface energy input density, represents the input power, represents the output power loss rate, represents the scanning speed of the energy source, Indicates the scanning distance, Represents the energy conversion rate.

[0073] It should be noted that the surface energy input density can be calculated using the above formula (1). Indicates the energy conversion rate, which refers to the proportion of energy reaching the material surface absorbed by the powder material. The value range is 30%-95%. It indicates the loss rate of output power, specifically refers to the loss rate of theoretical output power of additive manufacturing before reaching the material surface after being accelerated, focused and deflected in the electron gun of electron beam additive manufacturing equipment. ≤20%.

[0074] It should also be noted that , is the accelerating voltage, is the output melting current.

[0075] In one embodiment, the surface energy input density is 0.01-0.2 J / mm 2 .

[0076] It should be noted that the range of surface energy input density is 0.01-0.2J / mm 2 , within the range of this surface energy input density, the step-change preheating of the substrate can be better achieved.

[0077] Furthermore, the surface energy input density can be 0.01 J / mm 2 , 0.1J / mm 2 , 0.15J / mm 2 or 0.2J / mm 2 The specific settings can be made according to the actual situation, and this application does not impose any restrictions on this.

[0078] In one embodiment, the calculation formulas for the first body energy input density, the second body energy input density, and the third body energy input density are all:

[0079] (2);

[0080] In the formula, when calculating the first body energy input density, represents the first body energy input density; when calculating the second body energy input density, represents the second body energy input density; when calculating the third body energy input density, represents the third body energy input density; represents the input power, represents the output power loss rate, Indicates the looseness of powder particles, represents the scanning speed of the energy source, Indicates the scanning distance, represents the energy conversion rate, Indicates the preset altitude.

[0081] It should be noted that, through the above formula (2), the first body energy input density, the second body energy input density and the third body energy input density can be calculated.

[0082] In one embodiment, the first body energy input density and the third body energy input density are both 0.3-1.5 J / mm 3 , the sum of the first body energy input time and the second body energy input time is 8-30s.

[0083] It should be noted that the range of the first body energy input density and the range of the third body energy input density are both 0.3-1.5 J / mm 3 , the sum of the first energy input time and the second energy input time is 8-30s, and usually the first energy input time ≥ the second energy input time. Within this range of the first energy input density and the first energy input time, the zirconium alloy powder on the substrate can be better preheated. Within this range of the third energy input density and the second energy input time, the powder bed after the selective melting can be better thermally compensated to prevent the powder bed from blowing due to low temperature, while reducing thermal stress, thereby improving the forming quality of the target parts.

[0084] In this application, when the values ​​of the relevant parameters in formula (2) change, the powder bed can still be well preheated and thermally compensated by limiting the value range of the first body energy input density and the third body energy input density, and adding the requirements of the first body energy input time and the second body energy input time, so as to facilitate the subsequent selective melting and forming, and avoid powder blowing during the selective melting process, or powder splashing causing melting quality problems. For example, the loose powder ratio in formula (2) The value can be 0.5, 0.55, 0.6, etc. The scanning interval The value can be 0.08mm, 0.1mm, 0.12mm, etc. The preset height The value of can be 0.05mm, 0.06mm, 0.08mm or 0.1mm, etc., as long as the range of the first body energy input density and the range of the third body energy input density are both 0.3-1.5J / mm 3 , the sum of the first body energy input time and the second body energy input time is 8-30s, and other parameters in formula (2) can be set according to actual conditions, and this application does not impose any restrictions on this.

[0085] Furthermore, the first body energy input density can be 0.3 J / mm 3 , 0.8J / mm 3 , 1.2J / mm 3 or 1.5J / mm 3 The specific settings can be made according to the actual situation, and this application does not impose any restrictions on this.

[0086] The setting of the third body energy input density is similar and can be set according to actual conditions, and this application does not impose any restrictions on this.

[0087] The setting of the first body energy input time and the second body energy input time only needs to satisfy that the sum of the two times is 8-30s, and the first body energy input time ≥ the second body energy input time, and this application will not elaborate on this.

[0088] In one embodiment, the second body energy input density is 9.0-35.0 J / mm 3 .

[0089] It should be noted that the second body energy input density ranges from 9.0 to 35.0 J / mm 3 , within the range of the second energy input density, the preheated zirconium alloy powder can be better melted in a selective manner to obtain a smooth and defect-free forming plane, which is convenient for the subsequent repeated powder spreading, powder preheating, selective melting and thermal compensation steps to form a virtuous cycle and obtain the target parts with good forming quality. It should be noted that the powder particle bulk ratio in formula (2) is The value can be 0.5, 0.55, 0.6, etc. The scanning interval The value can be 0.08mm, 0.1mm, 0.12mm, etc. The preset height The value of can be 0.05mm, 0.06mm, 0.08mm or 0.1mm, etc., as long as the second body energy input density range is 9.0-35.0J / mm 3 , good forming quality can be obtained. Other parameters in formula (2) can be set according to actual conditions, and this application does not impose any restrictions on this.

[0090] Furthermore, the second body energy input density can be 9.0 J / mm 3 , 12.0J / mm 3 、20.0J / mm 3 、25.0J / mm 3 、30.0J / mm 3 or 35.0J / mm 3 The specific settings can be made according to the actual situation, and this application does not impose any restrictions on this.

[0091] In one embodiment, the preset height is 0.05-0.1 mm.

[0092] It should be noted that the preset height is 0.05-0.1mm. Within the range of this preset height, the setting range of the first body energy input density, the second body energy input density, and the third body energy input density, as well as the setting range of the first body energy input time and the second body energy input time, can better match the thickness of the laid powder to obtain a more stable powder bed, avoid problems such as powder blowing and splashing, and obtain better internal metallurgical quality, and obtain a forming plane with a smooth surface and no defects, so as to facilitate repeated powder laying, powder preheating, selective melting and thermal compensation steps to form a virtuous circle.

[0093] Further, the preset height may be 0.05 mm, 0.06 mm, 0.08 mm or 0.1 mm, etc. The preset height may be set according to actual conditions, and the present application does not impose any limitation thereto.

[0094] In one embodiment, the beam spot size of the energy source corresponding to the surface energy input density, the beam spot size of the energy source corresponding to the first body energy input density, and the beam spot size of the energy source corresponding to the third body energy input density are all 300-2000μm, and the beam spot size of the energy source corresponding to the second body energy input density is 50-500μm.

[0095] It should be noted that the beam spot size of the energy source corresponding to the surface energy input density, the beam spot size of the energy source corresponding to the first body energy input density, and the beam spot size of the energy source corresponding to the third body energy input density are all 300-2000μm, and the beam spot size of the energy source corresponding to the second body energy input density is 50-500μm. Within this beam spot size range, the input of each energy input density can be better achieved. The size of the beam spot also directly affects the amount of energy obtained by the powder from the energy source. Within this beam spot size range, the energy source can preheat the substrate to a preset temperature with a step-changing surface energy input density; within this beam spot size range, the energy source can preheat and thermally compensate the zirconium alloy powder on the substrate with the first body energy input density and the third body energy input density, thereby achieving uniform preheating and thermal compensation of the powder; within this beam spot size range, the energy source selectively melts the preheated zirconium alloy powder with the second body energy input density to obtain good internal metallurgical quality.

[0096] Further, in the present application, the beam spot size of the energy source corresponding to the surface energy input density, the beam spot size of the energy source corresponding to the first body energy input density, and the beam spot size of the energy source corresponding to the third body energy input density can be 300μm, 500μm, 700μm, 1000μm or 2000μm, etc., and the beam spot size of the energy source corresponding to the second body energy input density can be 50μm, 100μm, 300μm or 500μm, etc. The specific setting can be made according to the actual situation, and the present application does not limit this.

[0097] In one embodiment, at least 80 wt % of the zirconium alloy powder has a particle size range of 45-170 μm, and a median particle size range of the zirconium alloy powder is 80-120 μm; wherein wt % represents weight content percentage.

[0098] It should be noted that zirconium alloy powder is spherical particles, and its sphericity is ≥95%. The median particle size is generally expressed as D50, which mainly refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% in zirconium alloy powder. The particle size condition of the powder is matched with the first body energy input density in powder preheating, the second body energy input density in selective melting, and the third body energy input density of thermal compensation, so as to ensure the forming quality of the target part.

[0099] It should be noted that during the additive manufacturing and cooling process, the oxygen content in the environment needs to be controlled to ≤0.05ppm, and the water content and oxygen content need to be controlled below 100ppm during the powder recovery process, so as to ensure that the interstitial element content of the constructed orthopedic implant (i.e., the target part) meets the following requirements: C≤0.027%, O≤0.13%, H≤0.0025%, and N≤0.008%. It should be noted that zirconium alloy powder is a highly active material, and it is very easy to produce surface adsorption due to contact with water and oxygen in the air during the additive manufacturing process, which further leads to changes in the composition of the target part after forming. As an orthopedic implant material, zirconium alloy powder has very strict composition range requirements in order to be compatible with its mechanical properties and biocompatibility. Taking Zr2.5Nb alloy as an example, according to ASTM F2384 "Standard Specification for Forged Zirconium-2.5 Niobium Alloy for Surgical Implants", its interstitial elements should meet C≤0.027%, 0.09%≤O≤0.13%, H≤0.0025%, N≤0.008%, and GB / T43360 "Zirconium and Zirconium Alloy Powders for Additive Manufacturing" also requires C≤0.027%, 0.09%≤O≤0.12%, H≤0.0025%, N≤0.008%. Usually, the control of interstitial elements in the additive manufacturing process is achieved by controlling the element content of the raw materials, but it is difficult to avoid the increment in the process. This application realizes the process control of interstitial elements in additive manufacturing by controlling the core influencing factors of the environment, namely water content and oxygen content, to meet the application requirements of electron beam additive manufacturing of zirconium alloy orthopedic implants. Among them, ASTM is the abbreviation of American Society of Testing Materials, which means the American Society for Testing and Materials.

[0100] Furthermore, at least 98 wt % of the zirconium alloy powder has a particle size ranging from 53 to 150 μm, and a median particle size D50 of the zirconium alloy powder ranges from 90 to 110 μm.

[0101] It should be noted that the zirconium alloy powder in the present application is prepared by a plasma rotating electrode method. The process parameters used in the plasma rotating electrode method include: the rotation speed of the rod, the melting current of the rod, the feed speed of the rod and the oxygen content. Among them, the rotation speed of the rod is 20000-26000r / min, the melting current of the rod is 1500-2200A, the feed speed of the rod is 2.0-4.0mm / s, and the oxygen content is ≤5ppm, and a zirconium alloy powder for additive manufacturing is obtained.

[0102] The present application is further described below through the following examples.

[0103] Embodiment 1 is a process of printing a target part using a conventional method, and embodiments 2 to 4 are all processes of printing a target part using the method of the present application.

[0104] The zirconium alloy powders used in the following four embodiments of the present application are all Zr2.5Nb alloy powders, and the powders are prepared by a plasma rotating electrode method. During the preparation of the powders, the rotation speed of the rod is 23000r / min, the melting current of the rod is 1900A, the feed speed of the rod is 2.0mm / s, and the oxygen content is 1ppm. The parameters of the zirconium alloy powders used in Examples 1 to 4 of the present application are as follows: the particle size range of the zirconium alloy powder is 45-170μm, accounting for 90.3%, and the median particle size D50 of the zirconium alloy powder is in the range of 99μm.

[0105] Embodiment 1:

[0106] Step 1: Control the energy source to a constant preheating current of 30 mA, a scanning speed of 18 m / s, a preheating time of 30-45 min, and control the substrate temperature to about 750°C.

[0107] Step 2: Control the substrate to descend to a preset height of 0.05 mm, and spread the zirconium alloy powder on the preheated substrate;

[0108] Step 3: Control the energy source to preheat the zirconium alloy powder on the substrate with a preheating current of 35 mA, a preheating speed of 17.6 m / s, and a preheating time of 8 s;

[0109] Step 4: Control the energy source to have a melting current of 6 mA and a scanning speed of 6 m / s to selectively melt the preheated zirconium alloy powder;

[0110] Step 5: Control the energy source to preheat current of 32 mA and preheat speed of 17.6 m / s to perform thermal compensation on the powder bed after melting in the selected area. The compensation time is 5 s.

[0111] Step 6: Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

[0112] Embodiment 2:

[0113] Step 1: During the total surface energy input time, control the energy source to preheat the substrate to a preset temperature with a step-wise surface energy input density; wherein the total surface energy input time is 40 min, the step number of the step-wise surface energy input density is n=3, and the surface energy input density of the first step is 0.056 J / mm 2 The surface energy input time of the first step is t1=20min, and the surface energy input density of the second step is 0.018J / mm 2 The surface energy input time of the second step is t2 = 10min, and the surface energy input density of the third step is 0.07J / mm 2 , the surface energy input time of the third step is t3=10min, t=t1+t2+t3=40min, and the preset temperature is 700℃;

[0114] Step 2: Control the substrate to descend to a preset height, and spread the zirconium alloy powder on the preheated substrate; wherein the preset height is 0.05 mm;

[0115] Step 3: During the first energy input time, control the energy source to preheat the zirconium alloy powder on the substrate with the first energy input density; wherein the first energy input time is 10s, and the first energy input density is 1.5J / mm 3 ;

[0116] Step 4: Control the energy source to selectively melt the preheated zirconium alloy powder with a second body energy input density; wherein the second body energy input density is 16.3 J / mm 3 ;

[0117] Step 5: During the second body energy input time, control the energy source to perform thermal compensation on the powder bed after the selected area is melted with the third body energy input density; wherein the second body energy input time is 5s, and the third body energy input density is 0.4J / mm 3 ;

[0118] Step 6: Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

[0119] Embodiment 3:

[0120] Step 1: During the total surface energy input time, control the energy source to preheat the substrate to a preset temperature with a step-wise surface energy input density; wherein the total surface energy input time is 50 min, the number of steps of the step-wise surface energy input density is n=4, and the surface energy input density of the first step is 0.05 J / mm 2 The surface energy input time of the first step is t1=20min, and the surface energy input density of the second step is 0.018J / mm 2 The surface energy input time of the second step is t2 = 10min, and the surface energy input density of the third step is 0.06J / mm 2 The surface energy input time of the third step is t3 = 10min, and the surface energy input density of the fourth step is 0.075J / mm 2 , the surface energy input time of the 4th step is t4=10min, t=t1+t2+t3+t4=50min, and the preset temperature is 750℃;

[0121] Step 2: Control the substrate to descend to a preset height, and spread the zirconium alloy powder on the preheated substrate; wherein the preset height is 0.05 mm;

[0122] Step 3: During the first energy input time, control the energy source to preheat the zirconium alloy powder on the substrate with the first energy input density; wherein the first energy input time is 12s, and the first energy input density is 1.4J / mm 3 ;

[0123] Step 4: Control the energy source to selectively melt the preheated zirconium alloy powder with a second body energy input density; wherein the second body energy input density is 25.9 J / mm 3 ;

[0124] Step 5: During the second body energy input time, control the energy source to perform thermal compensation on the powder bed after the selected area is melted with the third body energy input density; wherein the second body energy input time is 5s, and the third body energy input density is 0.5J / mm 3 ;

[0125] Step 6: Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

[0126] Embodiment 4:

[0127] Step 1: During the total surface energy input time, control the energy source to preheat the substrate to a preset temperature with a step-wise change in surface energy input density; wherein the total surface energy input time is 35 min, the step number of the step-wise change in surface energy input density is n=3, and the surface energy input density of the first step is 0.04 J / mm 2The surface energy input time of the first step is t1=15min, and the surface energy input density of the second step is 0.028J / mm 2 The surface energy input time of the second step is t2 = 10min, and the surface energy input density of the third step is 0.085J / mm 2 , the surface energy input time of the third step is t3=10min, t=t1+t2+t3=35min, and the preset temperature is 680℃;

[0128] Step 2: Control the substrate to descend to a preset height, and spread the zirconium alloy powder on the preheated substrate; wherein the preset height is 0.05 mm;

[0129] Step 3: During the first energy input time, control the energy source to preheat the zirconium alloy powder on the substrate with the first energy input density; wherein the first energy input time is 10s, and the first energy input density is 1.2J / mm 3 ;

[0130] Step 4: Control the energy source to selectively melt the preheated zirconium alloy powder with a second body energy input density; wherein the second body energy input density is 34.2 J / mm 3 ;

[0131] Step 5: During the second body energy input time, control the energy source to perform thermal compensation on the powder bed after the selected area is melted with the third body energy input density; wherein the second body energy input time is 3s, and the third body energy input density is 0.3J / mm 3 ;

[0132] Step 6: Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

[0133] It should be noted that in Examples 2 to 4 of the present application, the beam spot size of the energy source corresponding to the surface energy input density, the beam spot size of the energy source corresponding to the first volume energy input density, and the beam spot size of the energy source corresponding to the third volume energy input density are all 500 μm. The beam spot size of the energy source corresponding to the second volume energy input density is 300 μm.

[0134] Combine the following Figures 2 to 9 , and Table 1, further illustrate the above embodiments.

[0135] Figures 2 to 5 The following are the physical pictures of the target parts printed by Example 1, Example 2, Example 3, and Example 4. It can be seen from the physical pictures that: Figure 2 The actual picture shows an uneven surface with many visible holes indicating poor fusion. Figures 3 to 5The surfaces of the actual images are flat and smooth, without visible holes due to poor fusion or warping.

[0136] Figures 6 to 9 The metallographic images of the target parts printed by Example 1, Example 2, Example 3, and Example 4 are shown respectively. It can be seen from the metallographic images that: Figure 6 There are a lot of poor fusion defects inside the metallographic diagram. Figures 7 to 9 There are no visible defects of poor fusion inside the metallographic images, and the interior is very dense.

[0137] The mechanical property test data in Table 1 include the data of ASTM F2384 standard, and the data obtained after tensile test of the target parts in Examples 2, 3, and 4. It can be seen from Table 1 that the tensile strength, yield strength, and elongation in Examples 2 to 4 are significantly higher than the ASTM F2384 standard. This indicates that the mechanical properties of the target parts printed by the method of the present application meet the forging standards and meet the application requirements of orthopedic implants.

[0138] Table 1 Mechanical properties test data of target parts

[0139]

[0140] It should be noted that in each step of electron beam additive manufacturing, the present application controls the energy source to ensure the stability of the printing process with coupled parameters such as surface energy input density, first body energy input density, second body energy input density and third body energy input density. As long as there is good coupling between the parameters, the target parts with good internal quality can be stably formed, and the quality consistency of the target parts is good. The present application allows electron beam additive manufacturing to be within a more free process window, rather than locking a single parameter, and selects a suitable process according to the requirements of the target parts, seeking a balance between the quality and economy of the target parts.

[0141] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application.

Claims

1. An electron beam additive manufacturing method for a zirconium alloy implant, characterized in that: The method includes: During the total surface energy input time, the energy source is controlled to preheat the substrate to a preset temperature with a step-by-step surface energy input density; wherein the step number n of the step-by-step surface energy input density is ≥ 3, the surface energy input density of the second step is less than the surface energy input density of the first step, and the surface energy input density gradually increases from the second step to the nth step, and the surface energy input density of the third step is greater than the surface energy input density of the first step; wherein the surface energy input density is 0.01-0.2 J / mm 2 ; The total surface energy input time includes the surface energy input time of the first step to the surface energy input time of the nth step; wherein the total surface energy input time is less than or equal to 60 minutes, and the surface energy input time of the nth step is 5-20 minutes; Controlling the substrate to descend to a preset height, and laying the zirconium alloy powder on the preheated substrate; During a first energy input time, controlling the energy source to preheat the zirconium alloy powder on the substrate at a first energy input density; Control the energy source to selectively melt the preheated zirconium alloy powder with a second body energy input density; wherein the second body energy input density is 9.0-35.0 J / mm 3 ; During the second energy input time, the energy source is controlled to perform thermal compensation on the powder bed after the selected area is melted with a third energy input density; wherein the first energy input density and the third energy input density are both 0.3-1.5 J / mm 3 , the sum of the first body energy input time and the second body energy input time is 8-30s; Repeat the steps of powder spreading, powder preheating, selective melting and thermal compensation until the target part is obtained.

2. The electron beam additive manufacturing method for zirconium alloy implants according to claim 1, characterized in that: The calculation formula of the surface energy input density is: （1）； In the formula, represents the surface energy input density, represents the input power, represents the output power loss rate, represents the scanning speed of the energy source, Indicates the scanning distance, Represents the energy conversion rate.

3. The electron beam additive manufacturing method for zirconium alloy implants according to claim 1, characterized in that: The calculation formulas for the first body energy input density, the second body energy input density and the third body energy input density are all: （2）； In the formula, when calculating the first body energy input density, represents the first body energy input density; When calculating the second body energy input density, represents the second body energy input density; When calculating the third body energy input density, represents the third body energy input density; represents the input power, represents the output power loss rate, Indicates the looseness of powder particles, represents the scanning speed of the energy source, Indicates the scanning distance, represents the energy conversion rate, Indicates the preset altitude.

4. The electron beam additive manufacturing method for zirconium alloy implants according to claim 1, characterized in that: The preset height is 0.05-0.1 mm.

5. The electron beam additive manufacturing method for zirconium alloy implants according to claim 1, characterized in that: The beam spot size of the energy source corresponding to the surface energy input density, the beam spot size of the energy source corresponding to the first body energy input density and the beam spot size of the energy source corresponding to the third body energy input density are all 300-2000μm, and the beam spot size of the energy source corresponding to the second body energy input density is 50-500μm.

6. The electron beam additive manufacturing method for zirconium alloy implants according to claim 1, characterized in that: At least 80 wt % of the zirconium alloy powder has a particle size range of 45-170 μm, and a median particle size range of the zirconium alloy powder is 80-120 μm; wherein wt % represents weight content percentage.

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