Method for manufacturing objects from Ti / Nb / Ta alloy powder

Abstract

The present invention relates to a method for manufacturing an object from Ti / Nb / Ta alloy powder, an object manufactured by this method, and the use of Ti / Nb / Ta alloy powder for manufacturing an object by laser-based powder bed melting.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an object from Ti / Nb / Ta alloy powder, an object manufactured by this method, and the use of Ti / Nb / Ta alloy powder for manufacturing an object by laser-based powder bed melting.

[0002] Ti / Nb / Ta alloys have great potential for medical applications, particularly as implants in dentistry and orthopedics. Here, advances in additive manufacturing technology, in particular, offer the possibility of producing implants individually tailored to patient needs.

[0003] A challenge in manufacturing three-dimensional objects using additive manufacturing techniques is determining process parameters essential for obtaining high-quality parts. In particular, in the case of laser-based powder bed fusion (LB-PBF), a preferred method in the field of metal powder processing, a series of different parameters must be correlated and optimized. For example, the influence of parameters such as laser power, the speed at which the laser is guided across the powder bed, the distance of the melt marks (Schmelzspuren), the laser focus, and the powder bed thickness on the resulting microstructure during the printing process can only be evaluated through systematic changes in the constituent elements during a complex process and subsequent assessment.

[0004] In their paper "Highly Anisotropic steel Processed by Selective Laser Melting," published in Met. Mat. Trans. 44b (2013) 795, T. Niendorf et al. describe the fabrication of samples made of austenitic stainless steel using a high-energy laser system. The resulting microstructure is characterized by the formation of a highly anisotropic structure at extremely high laser energy inputs, which forms a coarse-grained columnar structure with a (001) texture in the building direction. In contrast, a finer-grained, relatively isotropic structure is produced at lower energy inputs.

[0005] The article "The effect of laser energy input on the microstructure, physical and mechanical properties of Ti-6Al-4V alloys by selective laser melting," published in Virt. Phys. Protoyping, 11 (2016) 41 by DK Do et al., describes the microstructure development and mechanical properties of L-PBF-treated Ti-6Al-4V. Here, the laser power is kept constant, and the energy input is controlled by the scan speed.

[0006] In "Influence of the Energy Density for Selective Laser Melting on the Microstructure and Mechanical Properties of Stainless Steel" in Metals 10 (2020) 919, C. Donik et al. describe the influence of laser power on microstructure (density) and several mechanical properties such as UTS, YS, and elongation at break in L-PBF.

[0007] In "Microstructure and mechanical characterization of SLM processed Haynes® 2300", T. Bauer et al. (ETH Zuerich Library, https: / / doi.org / 10.3929 / ethz-a-010584903) describe the mechanical properties of Haynes 230, a Ni / Cr / W / Mo alloy, as a function of the laser energy introduced.

[0008] F. Dorsch summarizes the results of his own investigation on the influence of printing parameters on the shape of components in SLM in his paper "High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications III" published in PROCEEDINGS OF SPIE, V. 8963.

[0009] M. Xia et al. introduce a model for investigating the process during the printing of Ti / Nb / Ta powder mixtures by laser-based powder bed fusion (LPBF) in "Multi-material model for mesoscopic analysis of porosity evolution during laser powder-bed fusing TiNbTa powder mixture" published in Computational Material Science 198 (2021) 110674.

[0010] A. Gatto et al. describe in their paper "Influence of laser powder bed fusion process parameters on the properties of CuZn42 components: case study of the laser surface energy density" published in Progess in Additive Manufacturing (2023) 8:843-855 a model for predicting the density, hardness and relative ratio of brass phases in the reported system depending on the surface energy density (SED). According to this model, a linear dependence can be recognized between hardness and density.

[0011] In the methods described in the prior art, the energy introduced by the laser always also affects the porosity of the manufactured sample, so that, for example, the production of components with a high density such as required in implant technology can only be achieved by extremely special and strictly limited process parameters, which is a drawback.

[0012] Therefore, there is a further need for a method that allows precise adjustment of the properties of three-dimensional components while applying different process parameters and simultaneously increasing the density. In particular, it is desired that when the density of the material is complete, the phase composition and thus properties such as strength and elongation at break can be adapted to the requirements of a specific application of the component.

[0013] Surprisingly, within the scope of the present invention, it has been found that by additive manufacturing, the phase composition of titanium-based alloys can be precisely adjusted, and at the same time, properties such as strength and elongation at break can be precisely adjusted by the introduced energy, while at the same time components with consistently extremely high density are obtained.

[0014] Therefore, a first object of the present invention is a method for manufacturing an object, a) Prepare a first layer composed of Ti / Nb / Ta alloy powder and treat this layer by melting with a laser beam supplying energy having a surface energy \(E_A\). i b) Form a further layer composed of Ti / Nb / Ta alloy powder on the treated first layer and treat this further layer by melting with a laser beam supplying energy having a surface energy \(E_A\). i c) Repeat step b) to obtain an additively manufactured object. In a method comprising: At least one of the properties consisting of the phase composition, and the elongation at break \(A(E_A\) i ), the hardness \(VH(E_A\) i ), the tensile strength \(R\) m (E_A i ), and the yield strength \(R\) p02 ) is adjusted according to the surface energy \(E_A\) of the object, respectively. i A method characterized in that.

[0015] The surface energy \(E_A\) in the sense of the present invention i is understood to be the energy provided by the laser beam per unit area. This can be represented by Equation 1:

Number

[0016] Here, \(P\) L is the laser output quantified in watts (W), \(v\) s is the scan speed of the laser inducing the laser on the powder bed quantified in mm / s, \(H\) s is the hatch width, that is, the distance between individual lines traversed by the laser quantified in mm. \(E_A\) i can be similarly specified in the case of a pulsed system, and the scan speed mentioned above can be replaced by the product of the pulse duration and the pulse interval. ​​​

[0017] The method according to the present invention enables the additive manufacturing of dense components having a precisely controlled phase composition and precisely controlled properties such as elongation at break, ductility, hardness, tensile strength, and / or yield strength, without observing the changes or fluctuations in the density of the components that are normally observed.

[0018] Within the scope of the present invention, the density of additively manufactured components may be determined, unless otherwise specified, by optical methods, gravimetric methods, or using a pycnometer. In the case of determination by optical methods, for example, micrographs (Schliffaufnahmen) of the object may be used.

[0019] In the context of this invention, "dense" is understood to mean an object having a porosity of less than 1%, as determined by optical porosity analysis.

[0020] The elongation at break A, which represents a measure of the ductility of a constructed object, can be determined by a tensile test of a metal or metallic material according to DIN EN ISO6892-1 or ASTM E8.

[0021] The hardness VH can be determined by a Vickers hardness test in accordance with ISO 6507 / ASTM E384.

[0022] Tensile strength R m and yield strength R p02 This can be determined by a tensile test of a metal or metallic material in accordance with DIN EN ISO6892-1 or ASTM E8.

[0023] The method according to the present invention is particularly intended for the manufacture of components having high density. Therefore, embodiments in which the object has a density of more than 99.0%, preferably more than 99.6%, and particularly preferably more than 99.9%, as determined by a micrograph of the object, are preferred.

[0024] Within the scope of the method according to the present invention, the mechanical properties of the constituent members, such as hardness, tensile strength, elongation at break, and yield strength, are controlled by the energy introduced. The energy introduced can be varied to achieve changes in the properties of the object. Therefore, the surface energy E_A used to process the layer... i Embodiments that vary the properties are preferred. In this way, it is possible to make a gradient in an object, for example, with respect to its mechanical properties, or to precisely strengthen areas exposed to a particular load or increase their ductility.

[0025] The method according to the present invention is suitable for Ti / Nb / Ta alloys, and in particular, embodiments are preferred in which the Ti / Nb / Ta alloy powder has a composition xTi / yNb / zTa, and based on the total mass of the alloy powder, the mass fraction x of titanium (Ti) is preferably 61 to 72 mass%, the mass fraction y of niobium (Nb) is preferably 21 to 32 mass%, and the mass fraction z of tantalum (Ta) is preferably 3 to 11 mass%.

[0026] Surprisingly, within the scope of the method according to the present invention, it has been found that the introduced energy can adjust not only the mechanical properties but also the crystallographic composition of an object while keeping its chemical composition constant, and that this does not adversely affect the density of the object. Therefore, the object, when subjected to the introduced surface energy E_A i The corresponding crystalline phase composition Z(FA i Embodiments having ) are preferred. Furthermore, adjusting the phase composition of the material allows for surface energy E_A i An embodiment of the method according to the present invention, carried out by the present invention, is preferred.

[0027] The method according to the present invention enables the manufacture of high-precision three-dimensional objects by layered construction. In a preferred embodiment, the powder is formed with a layer thickness of 10 to 90 μm, preferably 15 to 35 μm.

[0028] Suitable powders that can be used in powder bed-based methods are known to those skilled in the art. For example, International Publication No. 2019 / 197376 describes Ti / Nb / Ta alloy powders for additive manufacturing. Spherical powders with sufficient fluidity to form a powder layer have been found to be particularly suitable. Therefore, in preferred embodiments, the alloy powder is spherical powder. Suitable powders can be obtained, for example, by EIGA (Electrode Induction-melting Gas Atomization), plasma spheroidization, ultrasonic atomization, or wire atomization.

[0029] The alloy powder used may contain further components so that the further properties of the object produced by the method according to the present invention can be adapted. Preferably, these are one or more metals selected from the group consisting of Zr, Hf, Mo, W, and Sn. In preferred embodiments, their proportions are 2 to 10% by mass, preferably 3 to 7% by mass, and particularly preferably 4 to 6% by mass, based on the total weight of the alloy powder. In even more preferred embodiments, the alloy powder used according to the present invention has 10% by mass or less of further components other than Ti, Nb, and Ta.

[0030] In particular, in the field of orthopedic implants, it is sometimes necessary to adapt implants so that different areas of the implant have different mechanical properties. This is within the scope of the method according to the present invention, in particular the surface energy E_A i This can be achieved by changing the surface energy E_A, and thus objects having mechanical properties that vary across their cross-sections are available. Therefore, in this context, embodiments in which an object has a gradient with respect to at least one of the properties selected from the group consisting of elongation at break, ductility, hardness, yield strength, and tensile strength are preferred. The gradient is preferably the surface energy E_A i This is achieved by changing [something].

[0031] A further subject of the present invention is an object obtained by the method according to the present invention, wherein the object has a phase composition and elongation at break A(E_Ai ), hardness VH(E_A i ), tensile strength R m (E_A i ), and yield strength R p02 At least one of the properties selected from the group consisting of the following is the surface energy E_A i The object is such that, as determined by optical porosity analysis based on a micrograph of the object, it has a density of over 99.0%, preferably over 99.6%, and particularly preferably over 99.9%.

[0032] In a preferred embodiment, the object according to the present invention preferably has a gradient with respect to at least one of the properties selected from the group consisting of elongation at break, ductility, hardness, and tensile strength.

[0033] In a particularly preferred embodiment, the object is an implant, preferably a dental, orthopedic, craniofacial, and / or spinal implant.

[0034] A further subject of the present invention is the use of Ti / Nb / Ta alloy powder for manufacturing an object by laser-based powder bed melting, wherein the object has a phase composition and elongation at break A(E_A) i ), hardness VH(E_A i ), tensile strength R m (E_A i ), and yield strength R p02 At least one of the properties selected from the group consisting of the following is the surface energy E_A i The material is used in a way that the object has a density of over 99.0%, preferably over 99.6%, and particularly preferably over 99.9%, as determined by optical porosity analysis based on a micrograph of the object.

[0035] Surprisingly, within the scope of the present invention, it has been found that the phase composition and mechanical properties of an object made of Ti / Nb / Ta alloy powder can be adjusted by energy input during processing by selective laser beam melting, while maintaining the same composition. Therefore, a further subject of the present invention is a method for adjusting at least one of the properties selected from the group consisting of tensile strength, elongation at break, ductility, yield strength, and hardness of an optically dense object made of Ti / Nb / Ta alloy powder by selective laser beam melting, wherein the adjustment of the property is performed by the surface energy E_A during laser beam melting. i This method is characterized by being performed by changing [something].

[0036] Furthermore, surprisingly, the surface energy E_A of the introduced laser beam i It was found that this significantly affects the development of the phase. This generally depends, in particular, on the chemical composition of the alloy. Titanium-rich Ti / Nb / Ta alloys usually crystallize in a hexagonal or orthorhombic martensitic crystal structure, which is preferable. In contrast, niobium-rich and / or tantalum-rich Ti / Nb / Ta alloys usually crystallize in a body-centered cubic crystal structure, which is preferable. Surprisingly, in this case, the formation of the crystalline phase occurred at a surface energy E_A i It was found that the surface energy E_A is affected by the energy into which the laser beam is introduced. i The lower the surface energy E_A, the more favorable the formation of crystal structures with a large proportion of hexagonal or orthorhombic crystals. In contrast, the surface energy E_A of the laser beam i The higher the surface energy E_A, the more favorable the formation of a body-centered cubic crystal structure. Therefore, a further subject of the present invention is a method for adjusting the crystalline phase composition of an optically dense object made of Ti / Nb / Ta alloy powder by selective laser beam melting, wherein the adjustment of properties is performed by the surface energy E_A during laser beam melting. i This method is characterized by being carried out by adjusting and / or changing the following. [Brief explanation of the drawing]

[0037] [Figure 1]These are the tensile strength and fracture elongation values ​​of the manufactured test specimen, derived from the stress diagram / elongation diagram corresponding to the surface energy E_Ai. [Figure 2] These are X-ray diffraction patterns of powders from three samples manufactured differently. [Figure 3a] These are the corresponding diffraction patterns of additively manufactured Ti-27Nb-6Ta produced at E_Ai = 1.45 J / mm², E_Ai = 2.05 J / mm², and E_Ai = 2.78 J / mm². [Figure 3b] This is an enlarged view of Figure 3a.

[0038] The present invention will be described in more detail based on the following examples, but these examples should not be understood as limiting the concept of the invention.

[0039] An alloy with the composition Ti-27Nb-6Ta was processed by laser-based powder bed melting, and a sample with a density exceeding 99.94% was obtained by optical porosity analysis, and its properties were determined. Figure 1 shows the surface energy E_A. i The tensile strength values ​​and fracture elongation of the manufactured test specimens, derived from the stress diagram / elongation diagram, are shown accordingly. i = 1.5 J / mm 2 From approximately 770 MPa, E_A i = 2.85 J / mm 2 While the fracture elongation decreases to approximately 700 MPa, conversely, E_A = 1.5 J / mm 2 From approximately 22% in E_A i = 2.85 J / mm 2 It will increase to approximately 34%.

[0040] As shown in Figure 2, a comparison of the X-ray diffraction patterns of powders from three differently manufactured samples reveals that higher energy input is clearly associated with an increase in the body-centered cubic phase (the so-called beta phase). The powder crystallizes orthorhombic in the α'' phase, while E_A i = 1.45 J / mm 2The additively fabricated material exhibits, in addition to the orthorhombic phase, a small amount of reflection suggesting the formation of a body-centered cubic β phase. The intensity of the corresponding reflection assigned to the β phase increases significantly with increasing energy input. Furthermore, a strong texture effect is observed, which is particularly evident in the increased intensity of the 200 reflection in the β phase material.

[0041] High-energy synchrotron diffraction experiments will allow for further detailed conclusions about the phase structure of the addition-fabricated Ti-27Nb-6Ta structure. Figure 3a shows E_A i = 1.45 J / mm 2 , E_A i =2.05 J / mm 2 , and E_A i = 2.78 J / mm 2 The corresponding diffraction patterns of addition-produced Ti-27Nb-6Ta are shown. All diffractograms show the presence of a bcc-β equilibrium phase and a martensite non-equilibrium α'' phase with an orthorhombic structure. The lattice parameters are a β = 0.3286 nm or a α’’ = 0.2930 nm / c α’’ The value is determined to be 0.4694 nm. Aside from these two phases, no other components such as hexagonal close-packed (hcp) α-martensite or hexagonal α'-martensite are detected.

[0042] From the diffraction patterns, particularly as can be seen from the magnified view in Figure 3b, both the number and position of the diffraction peaks are constant, suggesting an α''+β two-phase microstructure for all processed Ti-27Nb-6Ta materials. However, considering different sets of processing parameters, the diffraction peaks are clearly distinguishable in intensity. In general, differences in signal intensity are due not only to considerable differences in the volume fractions of the phases present, but also to differences in their texture components. The phase composition was evaluated by Rietveld analysis, which allowed for a detailed and quantitative evaluation of the phase proportions. Therefore, E_A i = 1.45 J / mm 2In the case of Ti-27Nb6Ta manufactured using [method / technology], a balanced phase composition was obtained in which α'' martensite was slightly dominant in proportion. In contrast, parameter set E_A i = 2.78 J / mm 2 The Ti-27Nb-6Ta structure after processing consists mainly of body-centered cubic β phase. In other words, the volume fraction of martensite α'' phase decreases as the energy input in PBF-LB / M increases.

Claims

1. A method for manufacturing a dense object, a) Prepare a first layer made of Ti / Nb / Ta alloy powder, and set the surface energy E_A of the layer. ｉ A step of processing by a laser beam that supplies an energy input having the following characteristics: b) A further layer made of Ti / Nb / Ta alloy powder is formed on the treated first layer, and the surface energy E_A ｉ A step of processing by a laser beam that supplies an energy input having the following characteristics: c) Repeat step b) to obtain the added-manufactured object. In a method including, Phase composition, and elongation at break A(E_A) ｉ ), hardness VH (E_A ｉ ), tensile strength R ｍ (E_A ｉ ), and yield strength R ｐ０２ At least one adjustment of the characteristics selected from the group consisting of the following is the surface energy E_A ｉ Features that it is checked in accordance with method.

2. The method according to claim 1, characterized in that the object has an optical density of more than 99.0%, preferably more than 99.6%, and particularly preferably more than 99.9%, and the optical density is determined by a micrograph of the object.

3. The surface energy E_A used to process the layer ｉ The method according to claim 1, characterized in that it comprises varying the surface energy E_A used to process the layer

4. The method according to at least one of claims 1 to 3, characterized in that the Ti / Nb / Ta alloy powder has a composition xTi / yNb / zTa with 61 < x < 72, 21 < y < 32, and 3 < z < 11, where x, y, and z represent mass percentages based on the total mass of the alloy powder.

5. The method according to at least one of claims 1 to 4, characterized in that the powder is formed into a layer with a thickness of 10 to 90 μm, preferably 15 to 35 μm.

6. The method according to at least one of claims 1 to 5, characterized in that the alloy powder is spherical powder.

7. The method according to at least one of claims 1 to 6, characterized in that the alloy powder further comprises one or more metals selected from the group consisting of Zr, Hf, Mo, W, and / or Sn.

8. The method according to claim 7, characterized in that the proportion of one or more metals in the alloy powder is 10% by mass or less based on the total mass of the alloy powder.

9. The method according to at least one of claims 1 to 8, characterized in that the object has a gradient with respect to at least one of the properties selected from the group consisting of phase composition, elongation at break, hardness, and tensile strength.

10. An object obtained by a method according to at least one of claims 1 to 9, wherein the object has a phase composition and an elongation at break A (E_A ｉ ), hardness VH (E_A ｉ ), tensile strength R ｍ (E_A ｉ ), and yield strength R ｐ０２ At least one of the properties selected from the group consisting of the following is the surface energy E_A ｉ An object having, in accordance with, the object having a density of more than 99.0%, preferably more than 99.8%, and particularly preferably more than 99.97%, as determined based on a micrograph of the object.

11. The object according to claim 10, characterized in that the object is an implant, preferably a dental, orthopedic, craniofacial, and / or spinal implant.

12. The use of Ti / Nb / Ta alloy powder for producing a dense object by laser-based powder bed melting, wherein the object has a phase composition and elongation at break A(E_A) ｉ ), hardness VH (E_A ｉ ), tensile strength R ｍ (E_A ｉ ), and yield strength R ｐ０２ At least one of the properties selected from the group consisting of the following is the surface energy E_A ｉ The material is used in accordance with the following conditions, wherein the material has a density of more than 99.0%, preferably more than 99.6%, and particularly preferably more than 99.9%, as determined based on a micrograph of the material.

13. A method for adjusting at least one of the properties selected from the group consisting of phase composition, tensile strength, elongation at break, yield strength, and hardness of an optically dense object made of Ti / Nb / Ta alloy powder by selective laser beam melting, characterized in that the adjustment of the property is performed by changing the surface energy during the laser beam melting.

14. A method for adjusting the phase composition of an optically dense object made of Ti / Nb / Ta alloy powder by selective laser beam melting, characterized in that the adjustment of the phase composition is performed by changing the surface energy during laser beam melting.

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