Metal powder for 3D printing

Abstract

The invention relates to a metal powder for 3D printing. In particular, the invention relates to a metal powder suitable for use in a 3D printing process and to a process for producing said powder. The metal powder of the present invention is characterized in that the particles of the metal powder have an average aspect ratio [Psi] A of 0.7 to 1, where [Psi] A = x Feret, min / x Feret, max. The method comprises: a) pressing or pressing and sintering powdered components of the powder to obtain a metal body; b) powdering the metal body to obtain a metal powder; c) separating the particles having a particle size of less than 10 [mu] m as determined according to ASTM B822 to obtain the metal powder according to the invention; and d) classifying the particle size of the metal powder according to the invention via screening in order to obtain the desired particle size distribution.

Description

This application is a divisional application of the patent application with the original application date of April 9, 2019, application number 201980025283.6 (international application number PCT / EP2019 / 058901), and invention name “Metal powder for 3D printing”. Technical Field

[0001] The present invention relates to metal powders suitable for use in 3D printing methods, and methods for producing such powders. Background Art

[0002] 3D printing refers to a method in which materials are joined or solidified under computer control to produce a three-dimensional object, wherein the materials are added together (e.g., liquid molecules or powder particles are fused together). 3D printing is used in both rapid prototyping and additive manufacturing (AM). Objects can have almost any shape or geometry and are typically produced using digital model data from a 3D model or another electronic data source such as an additive manufacturing file (AMF) file (typically in sequential layers). There are many different technologies, such as stereolithography (STL) or fused deposition modeling (FDM). Therefore, unlike traditional machining processes where material is removed from a raw material (i.e., subtractive manufacturing), 3D printing or AM typically builds a three-dimensional object from a computer-aided design (CAD) model or AMF file by continuously adding material layer by layer.

[0003] In the current situation, 3D printing or AM has been used in manufacturing, medical, industrial and socio-cultural industries, which has promoted 3D printing or AM to become a successful commercial technology.

[0004] One application area for 3D-printed devices is the medical industry, where precise manufacturing of surgical instruments and customized medical devices are highly demanding. Virtual planning and guidance of surgeries using 3D-printed personalized instruments has been successfully applied in many surgical areas, including total joint replacement and craniomaxillofacial reconstruction. An example of this is the bioresorbable tracheal splint developed at the University of Michigan for treating neonates with tracheobronchomalacia. The hearing aid and dental industries are expected to be the largest areas for future development using customized 3D printing technology.

[0005] Patient-matched implants are a natural extension of this work, creating truly personalized implants that fit a unique individual. The use of additive manufacturing for serial production of orthopedic implants (metal) is also increasing due to its ability to effectively create porous surface structures that promote osseointegration.

[0006] However, despite ongoing developments in this area, there are still problems that need to be addressed, particularly regarding the production of patient-matched implants.

[0007] Plastic implant materials are exposed to high mechanical loads. Although conventional materials based on stainless steel or cobalt-chromium alloys exhibit sufficient mechanical strength, their use raises toxicological concerns due to the release of toxic or allergenic elements, leading to inflammatory reactions in adjacent tissues. Metals and metal alloys based on titanium, tantalum and niobium show high biocompatibility and suitable mechanical properties to avoid stress shielding and subsequent implant loosening. However, most available metal powders suffer from the disadvantage that, to date, their use as materials in 3D printing methods does not produce products of the expected quality.

[0008] US2016 / 0074942 discloses a method for producing a substantially spherical metal powder. The method comprises providing a particulate source metal comprising primary particles and having an average initial particle size; mixing the particulate source metal with a binder and optionally a solvent to form a slurry; granulating the slurry to form substantially spherical granules, wherein each granule comprises an agglomerate of the particulate source metal; debinding the granules at a debinding temperature to reduce the binder content of the granules to form debinded granules; at least partially sintering the debinded granules at a sintering temperature such that the particles within each granule fuse together to form partially or completely sintered granules; and recovering the sintered granules to form a substantially spherical metal powder.

[0009] WO 2017 / 048199 discloses a titanium-tantalum alloy having a titanium content ranging from 10 wt.% to 70 wt.%, wherein the alloy has a body-centered cubic structure. Furthermore, a method for forming a titanium-tantalum alloy is described, comprising the following steps: (a) slicing a 3D CAD model of a component to be formed into a plurality of 2D image layers; (b) preparing a homogeneous powder mixture of titanium powder and tantalum powder; (c) distributing the powder mixture layer onto a processing bed; (d) performing powder bed fusion of the powder mixture layer in one of a vacuum environment and an inert gas environment according to one of the 2D image layers; and sequentially performing steps (c) and (d) for each of the plurality of 2D image layers.

[0010] However, despite these efforts, there remains a need for metal powders suitable for 3D printing that address the following issues: The use of metal powders in 3D printing methods requires that the powders possess certain properties. For example, the powders must be flowable in order to produce uniform and non-porous products. Furthermore, a certain particle size distribution is generally required, which may vary depending on the specific 3D printing method used. Therefore, the particle size distribution required for powders used in selective laser melting methods may be different from those intended for use in electron beam melting methods. In addition, low levels of oxygen, nitrogen, and hydrogen in the powders can help improve the mechanical properties of the subsequent products. Last but not least, the powders used should have sufficient absorption to laser or electron beams of different wavelengths to allow sufficient melting, which is required to produce mechanically stable and non-porous products. Therefore, there remains a need for powders specifically designed for use in 3D printing methods and methods for producing such powders. Summary of the Invention

[0011] The present invention addresses this need by providing metal powders suitable for 3D printing and methods for producing the powders.

[0012] Therefore, a first object of the present invention is a metal powder suitable for use in a 3D printing method, characterized in that the particles of the metal powder have an average aspect ratio Ψ of 0.7 to 1, preferably 0.8 to 1, more preferably 0.9 to 1, even more preferably 0.95 to 1 A , where Ψ A =x Feret,min / x Feret,max .

[0013] Another object of the present invention is a method for producing the powder of the present invention. The method of the present invention comprises the following steps: a) pressing or pressing and sintering the powdered components of the powder to obtain a metal body; b) pulverizing the metal body to obtain metal powder; c) separating particles having a particle size of less than 2 μm, preferably less than 5 μm, even more preferably less than 10 μm, as determined according to ASTM B822, to obtain the metal powder of the present invention; and d) Classifying the particle size of the metal powder of the present invention by screening to obtain a desired particle size distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a graphic representation of the definition of Ferret's diameter as explained above.

[0015] Figure 2 Shown is an SEM image of the inventive powder according to Example 2. As can be clearly seen, the particles have a uniform sphericity and size distribution.

[0016] Figure 3Shown is an SEM image of the powder according to Comparative Example 4. In contrast to the powder of the present invention, this conventional powder exhibits a high degree of agglomeration and is therefore unsuitable for use in 3D printing.

[0017] Figure 4 A SEM (cross-sectional) image of the inventive powder according to Example 11 is shown, which clearly demonstrates the homogeneity of the powder and the absence of any unwanted particles of a size that would render the powder unsuitable for 3D printing methods.

[0018] Figure 5 Shown is an SEM image of the powder according to the invention according to Example 12 after treatment with HF, which leads to a roughening of the powder surface.

[0019] Figure 6 Shown is an SEM image / EDX cross section of a powder particle of the powder according to the invention according to Example 11. The image clearly shows the dendritic nature of the powder, where: 1: Ti 70.8 wt%, Nb 26.3 wt%, Ta 2.9 wt% 2: Ti 72.4 wt%, Nb 25.4 wt%, Ta 2.2 wt% 3: Ti 54.0 wt%, Nb 38.2 wt%, Ta 7.8 wt% 4: Ti 54.6 wt%, Nb 38.0 wt%, Ta 7.4 wt% Figure 7 Shown is an SEM image / EDX cross section of a powder particle of the powder according to the invention according to Example 13. The image clearly shows the dendritic nature of the powder, where: 1: Ti 56.4 wt%, Nb 40.0 wt%, Ta 3.6 wt% 2: Ti 64.4 wt%, Nb 32.1 wt%, Ta 3.4 wt% 3: Ti 67.4 wt%, Nb 31.4 wt%, Ta 1.2 wt% 4: Ti 53.7 wt%, Nb 41.4 wt%, Ta 4.9 wt% 5: Ti 53.5 wt%, Nb 42.0 wt%, Ta 4.5 wt% Figure 8 The X-ray diffraction patterns of the powders according to the invention are shown according to Example 1 (Nb), Example 7 (Ti42Nb) and Example 13 (Ti40Nb4Ta). As can be clearly seen, only one crystal phase is identified in each figure, even for the binary and ternary systems. DETAILED DESCRIPTION

[0020] The present invention provides a metal powder suitable for use in a 3D printing method, characterized in that the particles of the metal powder have an average aspect ratio Ψ of 0.7 to 1, preferably 0.8 to 1, more preferably 0.9 to 1, even more preferably 0.95 to 1 A , where Ψ A =x Feret,min / x Feret,max .

[0021] Feret's diameter is a measure of the size of an object along a specified direction. Generally speaking, it can be defined as the distance between two parallel planes that constrain the object to be perpendicular to that direction. This measure is used in the analysis of particle size (e.g., in microscopy), where it is applied to the projection of a three-dimensional (3D) object onto a 2D plane. In such cases, Feret's diameter is defined as the distance between two parallel tangent lines rather than planes (see Figure 1 ). Regarding the present invention, Ψ A Defined as the ratio of the smallest Feret diameter of a particle in μm to the largest Feret diameter of the corresponding particle in μm. Average aspect ratio Ψ within the meaning of the present invention A Refers to the distribution of aspect ratios of the particles of a powder as determined by statistical analysis by scanning electron microscopy (SEM).

[0022] Surprisingly, it was found that particles having an average aspect ratio within the claimed range are particularly suitable for use in 3D printing methods and have good flowability.

[0023] Metals such as tantalum (Ta), titanium (Ti) and niobium (Nb) are advantageous materials for the production of orthopedic implants due to their low toxicity, high biocompatibility and high mechanical stability of the resulting objects. Therefore, preferred are embodiments of the present invention in which the powder comprises or consists of a metal selected from tantalum, titanium, niobium and their alloys. In a particularly preferred embodiment, the powder according to the present invention comprises an alloy of titanium and niobium. In an especially preferred embodiment, the alloy further comprises tantalum. In an alternative preferred embodiment, the powder comprises an alloy of tantalum and niobium.

[0024] The composition of the powder can be adjusted according to the requirements of the specific case. In a preferred embodiment, the metal powder of the present invention comprises an alloy powder comprising Ti in an amount of 50 to 75 wt%, preferably 57 to 61 wt%, based on the total weight of the powder.

[0025] In a further preferred embodiment, the powder according to the invention comprises an alloy powder which comprises Nb in an amount of 25 to 50% by weight, preferably 39 to 43% by weight, based on the total weight of the powder.

[0026] In a particularly preferred embodiment, the powder comprises an alloy powder comprising Ti in an amount of 50 to 75 wt. %, preferably 57 to 61 wt. %, and Nb in an amount of 25 to 50 wt. %, preferably 39 to 43 wt. %, respectively, based on the total weight of the powder.

[0027] Further preferred are embodiments of the present invention in which the powder comprises an alloy of Ti, Nb, and Ta. In this case, preferably, the amount of Ta is 2 to 20% by weight, preferably 2 to 15% by weight, and in particular 2 to 6% by weight, based on the total weight of the powder. Preferably, the alloy comprises Ti in an amount of 50 to 75% by weight, more preferably 55 to 70% by weight, even more preferably 55 to 61% by weight, and Nb in an amount of 25 to 50% by weight, preferably 27 to 43% by weight, respectively, based on the total weight of the powder, for a total of 100% by weight.

[0028] It has been found that the mechanical properties (e.g., elasticity) of objects, particularly orthopedic implants, can be significantly improved if the content of certain impurities is kept as low as possible. In a preferred embodiment, the oxygen level in the powder according to the invention is less than 3000 ppm, particularly less than 1500 ppm, and especially less than 1000 ppm, more particularly less than 500 ppm, and even more particularly less than 300 ppm, ppm being the mass of the powder. The nitrogen level in the powder according to the invention is preferably less than 200 ppm, particularly less than 100 ppm, especially less than 50 ppm, and even more particularly less than 30 ppm.

[0029] The content of lithium (Li), sodium (Na), and potassium (K) in the powder according to the invention is preferably less than 80 ppm. Surprisingly, it has been found that the quality of the resulting product can be significantly improved if the content of these elements is kept below the claimed levels. In a preferred embodiment, the content of Li in the powder according to the invention is less than 80 ppm, preferably less than 50 ppm, and in particular less than 30 ppm. In another preferred embodiment, the content of Na in the powder according to the invention is less than 80 ppm, preferably less than 50 ppm, and in particular less than 30 ppm. In a preferred embodiment of the invention, the content of K is less than 80 ppm, preferably less than 50 ppm, and in particular less than 30 ppm. In a particularly preferred embodiment, the total content of Li, Na, and K in the powder according to the invention is less than 100 ppm, preferably less than 50 ppm.

[0030] In order for a metal powder to be suitable for use in a 3D printing method, the powder must have a certain flowability and a certain tap density. In a preferred embodiment, the powder of the present invention has a tap density of 40-80%, preferably 60-80%, of its theoretical density as measured according to ASTM B527.

[0031] In the case where the powder of the present invention is a Ta, Nb or Ti metal powder or an alloy powder thereof, it is preferred that the powder has a g / cm 3 , preferably 2.7 to 13.3 g / cm 3 For example, fully dense tantalum has a tap density of 16.65 g / cm 3 Therefore, in a preferred embodiment, the Ta powder of the present invention has a density of 6.6 to 13.3 g / cm 3 , preferably 10.0 to 13.3 g / cm 3 In addition, fully dense niobium has a tap density of 8.58 g / cm 3 Therefore, in a preferred embodiment, the Nb powder of the present invention has a density of 3.4 to 6.9 g / cm 3 , preferably 5.1 to 6.9 g / cm 3 In the case where the powder of the present invention comprises a binary alloy (especially a Ti / Nb alloy), the tap density is preferably 2.2 to 5.2 g / cm 3 , preferably 3.3 to 5.2 g / cm 3 In the case where the powder comprises a ternary alloy (particularly a Ti / Nb / Ta alloy), the powder preferably has a density of 2.3 to 6.5 g / cm 3 , preferably 3.5 to 6.5 g / cm 3 The tap density.

[0032] In a further preferred embodiment, the powder according to the invention has a flowability of less than 25 s / 50 g, in particular less than 20 s / 50 g, even more preferably less than 15 s / 50 g, measured according to ASTM B 213. Surprisingly, it has been found that the powder according to the invention can be applied easily while still exhibiting adequate fixation to allow the production of precise and well-defined articles.

[0033] As mentioned above, the particle size distribution of the powders of the present invention can be adjusted as needed, in particular according to the specific printing method used. Due to the different processing and requirements for the printed products, the requirements regarding the properties of the powders may vary depending on the method used. For example, selective laser melting (SLM) uses fine powders to obtain accurately formed products with well-resolved structural features. Electron beam melting (EBM) requires coarser particles, which is mainly the result of the repulsion of electrostatically charged particles due to their interaction with the electron beam. Such repulsion is obviously significant for very fine powders. Laser cladding (LC) requires even coarser powders to avoid overspray and the associated large amount of powder loss.

[0034] In a preferred embodiment, the powder of the present invention has the following particle size distribution, as measured according to ASTM B822: D10 greater than 2 μm, preferably greater than 5 μm, D90 less than 80 μm, preferably less than 70 μm, even more preferably less than 62 μm, and D50 between 20 and 50 μm, preferably between 25 and 50 μm. In a preferred embodiment, the powder fraction obtained by sieving is less than 63 μm. Such powders are particularly suitable for use in selective laser melting (SLM).

[0035] In an alternative preferred embodiment, the powder of the present invention has a particle size distribution, as measured according to ASTM B822, of D10 greater than 20 μm, preferably greater than 50 μm, and even more preferably greater than 65 μm, and D90 less than 150 μm, preferably less than 120 μm, and even more preferably less than 100 μm, with a D50 of 40 to 90 μm, preferably 60 to 85 μm. In a preferred embodiment, the powder fraction obtained by sieving is 63 to 100 μm. Such powders are particularly suitable for use in electron beam melting (EBM).

[0036] In another alternative preferred embodiment, the powder of the present invention has a particle size distribution, as measured according to ASTM B822, of D10 greater than 50 μm, preferably greater than 80 μm, and even more preferably greater than 100 μm, and D90 less than 240 μm, preferably less than 210 μm, and D50 of 60 to 150 μm, preferably 100 to 150 μm. In a preferred embodiment, the powder fraction obtained by sieving is 100 to 300 μm. Such powders are particularly suitable for use in laser cladding methods (LC).

[0037] Surprisingly, it was found that the mechanical stability of the articles produced by the 3D printing method and the uniformity of the elemental distribution can be greatly improved if the particles of the metal powder used have a dendritic microstructure. Therefore, the following embodiment of the powder according to the invention is preferred: in which the powder has a dendritic microstructure with local deviations in the chemical composition. Analysis of the invention by X-ray diffraction surprisingly showed that the dendritic microstructures in the powders, although different in composition, all have the same crystal structure, in contrast to conventional powders, in which local deviations in composition are usually associated with different crystal structures, which give rise to more than one phase in the X-ray diffraction, while in the case of the powder according to the invention only one phase was detected. By Figure 8 Confirmed this, Figure 8 Powder X-ray diffraction patterns of exemplary inventive powders are depicted.

[0038] The present invention also provides a method for producing the powder of the present invention. The method of the present invention comprises the following steps: a) pressing or pressing and sintering the powdered components of the powder to obtain a metal body; b) pulverizing the metal body to obtain metal powder; c) separating particles having a particle size of less than 2 μm, preferably less than 5 μm, even more preferably less than 10 μm, as determined according to ASTM B822, to obtain the metal powder of the present invention; and d) Classifying the particle size of the metal powder of the present invention by screening to obtain a desired particle size distribution.

[0039] Surprisingly, it has been found that the method according to the invention allows the production of metal powders which are particularly suitable for 3D printing methods.

[0040] In a preferred embodiment, the separation in step c) of the process according to the invention is achieved by sieving, in particular air classification, of the powder.

[0041] In an alternative preferred embodiment, the separation in step c) of the process of the invention is achieved by deagglomeration using ultrasound in a water bath followed by decantation. In an alternative preferred embodiment, the deagglomeration is achieved by stirring in a water bath followed by decantation. In another alternative preferred embodiment, the deagglomeration is achieved via high power dispersion in a water bath followed by decantation. -Ultra- by Werke GmbH & Co. KG (Germany) for high power dispersion.

[0042] In a preferred embodiment, the degree of decanting of the fine particles can be adjusted by controlling the zeta potential of the dispersion. This can be achieved, for example, by adjusting the pH value. Therefore, preferred are embodiments of the process according to the invention in which the degree of decanting of the particles is adjusted by adjusting the pH of the water bath used for deagglomeration.

[0043] It is desirable to obtain a metal powder with a low oxygen content. Therefore, in a preferred embodiment, the method of the present invention further comprises a deoxidation step. Deoxidation of the powder of the present invention is preferably carried out after step c) of the powder of the present invention. Preferably, the deoxidation is carried out in the presence of a reducing agent, which is preferably selected from Li, Na, K, Mg and Ca and mixtures thereof. In a further preferred embodiment, the powder of the present invention is subjected to a leaching step after deoxidation to remove any unwanted impurities generated during the deoxidation. Preferably, the leaching is carried out using an inorganic acid. In order to adjust the properties of the powder to match the requirements of a specific application, the surface of the powder can be doped. Therefore, the following embodiment is preferred: wherein the surface of the powder is preferably doped with a dopant selected from phosphorus, boron, silicon, yttrium, calcium, magnesium and mixtures thereof. Methods of doping are well known to those skilled in the art. Therefore, those skilled in the art are familiar with how to introduce dopants.

[0044] The powders of the present invention can be further treated to improve their performance during 3D printing. Therefore, preferred embodiments are those in which the powders of the present invention are further treated with an acid, preferably hydrofluoric acid or a complex-forming carboxylic acid. Surprisingly, it has been found that such acid treatment of the powder improves the absorption of laser radiation during the printing process. Without being bound by theory, it is believed that this treatment may result in roughening of the powder surface, thereby increasing the surface absorption of radiation.

[0045] In a preferred embodiment, the complex-forming carboxylic acid is selected from the group consisting of carboxylic acids, dicarboxylic acids and alpha-hydroxy acids, and mixtures thereof.

[0046] The powders of the present invention are particularly suitable for use in 3D printing methods. Therefore, a further object of the present invention is the use of the powders of the present invention in an additive manufacturing method. Preferably, the method is selected from selective laser melting (SLM or LBM), electron beam melting (EBM), and laser cladding (LC).

[0047] Another object of the present invention is a method for producing a three-dimensional article using the powder according to the invention, wherein the three-dimensional article is built up layer by layer.

[0048] A further object of the present invention is a three-dimensional article obtained by the process according to the invention and / or comprising the powder according to the invention. This three-dimensional article is characterized by its advantageous properties, which make it particularly suitable for medical applications. The requirements for articles for medical purposes are varied and range from biocompatibility to mechanical strength. Surprisingly, it has been found that three-dimensional articles produced from the powder according to the invention, in particular using a 3D printing method, exhibit particularly advantageous properties. It was found that the elastic modulus (Young's modulus m E ) is close to the case of natural bone, which has an elastic modulus of approximately 40 GPa. Common materials currently used exhibit a much higher elastic modulus of more than 100 GPa, which leads to poor compatibility with implants. It is therefore desirable to obtain an implant (the object obtained in the process of the invention) whose properties are much closer to those of natural bone. Therefore, in a preferred embodiment, the three-dimensional article according to the invention has an elastic modulus m of 20 to 100 GPa, preferably 40 to 90 GPa, in particular 40 to 80 GPa, measured according to DIN EN ISO 6892-1. E .

[0049] In a further preferred embodiment, the three-dimensional article according to the invention has an ultimate strength (R 200) of 600 to 1400 MPa, preferably 600 to 1200 MPa, in particular 600 to 699 MPa, determined according to DIN EN ISO 6892-1. m ).

[0050] Also preferred are embodiments in which the three-dimensional article according to the invention has a yield strength R of 500 to 1200 MPa, preferably 500 to 1000 MPa, in particular 500 to 699 MPa, measured according to DIN EN ISO 6892-1. p0.2 .

[0051] In a particularly preferred embodiment, the three-dimensional article of the invention has: Modulus of elasticity m of 20 to 100 GPa, preferably 40 to 90 GPa, in particular 40 to 80 GPa, determined according to DIN EN ISO 6892-1 E ; An ultimate strength R of 600 to 1400 MPa, preferably 600 to 1200 MPa, in particular 600 to 699 MPa, determined according to DIN EN ISO 6892-1 m ;as well as Yield strength R of 500 to 1200 MPa, preferably 500 to 1000 MPa, in particular 500 to 699 MPa, determined according to DIN EN ISO 6892-1 p0.2 .

[0052] In a further preferred embodiment, the three-dimensional article according to the invention is characterized in that the ultimate strength R m The strain value A under g They are respectively greater than 0.5%, preferably greater than 1%, in particular greater than 4%.

[0053] Further preferred are embodiments of the three-dimensional article according to the invention wherein the three-dimensional article has a strain at break value A of greater than 2%, preferably greater than 4%, in particular greater than 10%, measured according to DIN EN ISO 6892-1. 30 .

[0054] Preferably, the article is an implant, in particular a medical implant, such as a dental implant, hip implant, knee implant, shoulder implant, craniofacial implant or spinal implant. In another preferred embodiment, the article is used in high temperature applications, such as furnaces and reactors.

[0055] The present invention will be explained in more detail with the aid of the following examples, which should not be construed as limiting the invention.

[0056] Example: Several powders were prepared according to steps a) and b) of the described method. The results are summarized in Table 1: The powder obtained is subjected to a separation step as described in step c) of the process of the invention by: 1) Screening / wind classification 2) Ultrasonic treatment 3) Water decantation (at pH 5 to 8) The powder was subsequently deoxidized and classified by sieving according to the fractions given in Table 2. The results are summarized in Table 2: The powders according to the invention of Examples 9, 12, 13 and 14 were used in a selective laser melting process to produce three-dimensional test articles 1, 2, 3 and 4, respectively, whose properties were tested in accordance with DIN EN ISO 6892-1: 2016. The respective results are summarized in Table 3, the values ​​given being the average results obtained from a series of tests.

[0057] m E : Modulus of elasticity, determined according to DIN EN ISO 6892-1:2016 R p0.2 : Yield strength, measured according to DIN EN ISO6892-1:2016 R m : Ultimate strength, determined according to DIN EN ISO 6892-1:2016 F m : Maximum force, measured according to DIN EN ISO 6892-1:2016 A g :R m Strain under load, determined according to DIN EN ISO 6892-1:2016 A 30 : Breaking strain, determined according to DIN EN ISO 6892-1:2016 S0: cross-sectional area, determined according to DIN EN ISO 6892-1:2016 Table 3:

Claims

1. A metal powder suitable for use in a 3D printing method, wherein the powder comprises or consists of a metal selected from the group consisting of tantalum, titanium, niobium and alloys thereof, and wherein the particles of the metal powder have an average aspect ratio Ψ of 0.7 to 1, preferably 0.8 to 1, more preferably 0.9 to 1, even more preferably 0.95 to 1. A , where Ψ A =x Feretmin / xFeret max. 2 . The powder according to claim 1 , wherein the powder comprises or consists of an alloy of titanium and niobium.

3. The powder according to any one of claims 1 and 2, wherein the alloy further contains tantalum. 4 . The powder according to claim 1 , wherein the powder comprises or consists of a metal alloy of titanium, niobium and tantalum.

5. Powder according to any one of the preceding claims, wherein the powder has a tap density of 40-80% of its theoretical density, preferably 60-80% of its theoretical density, measured according to ASTM B527.

6. Powder according to any one of the preceding claims, wherein the powder has a flowability of less than 25 s / 50 g, in particular less than 20 s / 50 g, even more preferably less than 15 s / 50 g, measured according to ASTM B213.

7. Powder according to one or more of claims 1 to 6, wherein the powder has the following particle size distribution, measured according to ASTM B822: D10 greater than 2 μm, preferably greater than 5 μm, and D90 less than 80 μm, preferably less than 70 μm, and D50 between 20 and 50 μm, preferably between 25 and 50 μm.

8. Powder according to one or more of claims 1 to 6, wherein the powder has the following particle size distribution, measured according to ASTM B822: D10 greater than 20 μm, preferably greater than 50 μm, and D90 less than 150 μm, preferably less than 120 μm, and D50 is from 40 to 90 μm, preferably from 60 to 85 μm.

9. Powder according to one or more of claims 1 to 6, wherein the powder has the following powder distribution, measured according to ASTM B822: D10 greater than 50 μm, preferably greater than 80 μm, and D90 less than 240 μm, preferably less than 210 μm, and D50 between 60 and 150 μm, preferably between 100 and 150 μm.

10. Powder according to any one of the preceding claims, wherein the oxygen level in the powder is less than 3000 ppm, particularly less than 1500 ppm and especially less than 1000 ppm, more especially less than 500 ppm, even more especially less than 300 ppm.

11. Process for producing a powder according to one or more of claims 1 to 10, comprising the steps of: a) pressing or pressing and sintering the powdered components of the powder to obtain a metal body; b) pulverizing the metal body of step a) to obtain metal powder; c) separating particles having a particle size of less than 2 μm, preferably less than 5 μm, even more preferably less than 10 μm, as determined according to ASTM B822, to obtain the metal powder of the present invention; and d) Classifying the particle size of the metal powder of the present invention by screening.

12. The method according to claim 11, wherein the separation in step c) of the method is achieved by sieving the powder.

13. The process according to claim 11, wherein the separation in step c) of the process is achieved by deagglomeration using ultrasound in a water bath followed by decantation.

14. The process according to claim 11, wherein the separation in step c) of the process is achieved by stirring in a water bath and subsequent decantation.

15. The method according to claims 11 to 14, wherein the method further comprises a deoxygenation step.

16. The method according to claims 11 to 15, wherein the powder is further subjected to an acid treatment.

17. Use of the powder according to one or more of claims 1 to 10 in an additive manufacturing method.

18. Method for producing a three-dimensional article using a powder according to one or more of claims 1 to 10, wherein the three-dimensional article is built up layer by layer.

19. The method according to claim 18, wherein the method is selected from the group consisting of selective laser melting (SLM, LBM), electron beam melting (EBM) and laser cladding (CL).

20. Three-dimensional article obtained by the method according to claim 18.

21. The three-dimensional article according to claim 20, characterized in that The three-dimensional article has an elastic modulus m of 20 to 100 GPa, preferably 40 to 90 GPa, in particular 40 to 80 GPa, measured according to DIN EN ISO 6892-1. E .

22. The three-dimensional article according to any one of claims 20 and 21, characterized in that The three-dimensional article has an ultimate strength R of 600 to 1400 MPa, preferably 600 to 1200 MPa, in particular 600 to 699 MPa, measured according to DIN EN ISO 6892-1. m .

23. The three-dimensional article according to any one of claims 20 to 22, characterized in that The three-dimensional article has a yield strength R of 500 to 1200 MPa, preferably 500 to 1000 MPa, in particular 500 to 699 MPa, measured according to DIN EN ISO 6892-1. p0.2 .

24. The three-dimensional article according to any one of claims 20 to 23, characterized in that The three-dimensional article has: Modulus of elasticity m of 20 to 100 GPa, preferably 40 to 90 GPa, in particular 40 to 80 GPa, determined according to DIN EN ISO 6892-1 E ; An ultimate strength R of 600 to 1400 MPa, preferably 600 to 1200 MPa, in particular 600 to 699 MPa, determined according to DIN EN ISO 6892-1 m ;as well as Yield strength R of 500 to 1200 MPa, preferably 500 to 1000 MPa, in particular 500 to 699 MPa, determined according to DIN EN ISO 6892-1 p0.2 .

25. The three-dimensional article according to any one of claims 20 to 24, characterized in that The three-dimensional article is a medical article, in particular a medical implant.

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