WO2023111037A1 - Procédé de fabrication d'un élément ayant des parties poreuses et élément fritté ayant une porosité non uniforme - Google Patents

Procédé de fabrication d'un élément ayant des parties poreuses et élément fritté ayant une porosité non uniforme Download PDF

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Publication number
WO2023111037A1
WO2023111037A1 PCT/EP2022/085892 EP2022085892W WO2023111037A1 WO 2023111037 A1 WO2023111037 A1 WO 2023111037A1 EP 2022085892 W EP2022085892 W EP 2022085892W WO 2023111037 A1 WO2023111037 A1 WO 2023111037A1
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WO
WIPO (PCT)
Prior art keywords
layer
compound particles
binder
volume
wax
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PCT/EP2022/085892
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English (en)
Inventor
Christian STAUDIGEL
Christian Fischer
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Headmade Materials Gmbh
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Publication of WO2023111037A1 publication Critical patent/WO2023111037A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1103—Making porous workpieces or articles with particular physical characteristics
    • B22F3/1109—Inhomogenous pore distribution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2027—Metallic material
    • B01D39/2031—Metallic material the material being particulate
    • B01D39/2037—Metallic material the material being particulate otherwise bonded
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2068—Other inorganic materials, e.g. ceramics
    • B01D39/2072—Other inorganic materials, e.g. ceramics the material being particulate or granular
    • B01D39/2079—Other inorganic materials, e.g. ceramics the material being particulate or granular otherwise bonded, e.g. by resins
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    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/10—Formation of a green body
    • B22F10/14—Formation of a green body by jetting of binder onto a bed of metal powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/10—Formation of a green body
    • B22F10/16—Formation of a green body by embedding the binder within the powder bed
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    • B22F10/30—Process control
    • B22F10/34—Process control of powder characteristics, e.g. density, oxidation or flowability
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    • B22F10/38—Process control to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
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    • B22F3/10—Sintering only
    • B22F3/1017—Multiple heating or additional steps
    • B22F3/1021—Removal of binder or filler
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    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1121—Making porous workpieces or articles by using decomposable, meltable or sublimatable fillers
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    • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • B22F7/002—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of porous nature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/001—Rapid manufacturing of 3D objects by additive depositing, agglomerating or laminating of material
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    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/008—Producing shaped prefabricated articles from the material made from two or more materials having different characteristics or properties
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    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/40—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material
    • B28B7/46—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material for humidifying or dehumidifying
    • B28B7/465—Applying setting liquid to dry mixtures
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    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
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Definitions

  • the invention relates to a process for the manufacture of an element having porous portions and elements integrally formed from a sinterable material, having a non-uniform controlled porous architecture.
  • Porous structures metallic as well as ceramic and glass, occupy an important role in technology particularly as materials of construction, heat exchangers, high temperature filters, catalyst supports, and artificial bone and many methods are presently utilized for producing these porous structures.
  • powder metallurgical techniques involve the steps of shaping metal powder into green compacts by such techniques as loose packing, tamping, compaction, extrusion, rolling or the like and then consolidating the green compacts so formed by sintering. Porosity is controlled mainly by particle size, particle size distribution, particle shape, compacting pressure techniques and sintering temperature.
  • it is difficult to control important physical parameters such as pore size, density and surface area by this technique.
  • the porosity in the element or at least a portion thereof is as designed rather than random.
  • control of properties at different locations within the element, to produce for example a gradient of porosity through the element is a desired feature.
  • the porosity may also be ordered meaning that it is also regular or periodic at least in one direction if not in two, three or more directions through at least part of the element, or having a predetermined orientation relative to the external shape of the element.
  • the porosity is interconnected meaning that at least a major fraction or substantially all open pores intersect with at least some other open pores which extend in a different direction.
  • Methods have been known comprising the steps of computationally designing a product including a controlled porous architecture of interconnected porosity within the product, and producing a three dimensional positive model of the product including said controlled porous architecture using rapid prototyping, also referred to as layered manufacturing.
  • WO 2017/117527 utilizes laser additive manufacturing technologies for the creation of porous media that can be used in filtration devices, flow control devices, drug delivery devices and similar devices.
  • Porous structures result from interconnected pores between fused powder particles.
  • a decrease in laser power results in a larger pore size resulting from less particle sintering and/or melting.
  • the porous media are not subject to a sintering step and pore sizes well below the spatial resolution of the laser mesh can hardly be obtained.
  • WO 2018/197082 discloses a method for additively manufacturing a metal and/or glass-type and/or ceramic component.
  • Compound particles are prepared from substrate particles and an at least two-phase binder.
  • the compound particles are melted selectively in layers by means of electromagnetic radiation, such that a moulded part is additively manufactured.
  • the moulded part is removed from the unmelted mixture, and the at least two-phase binder is then preferably successively removed. Finally, the debound moulded part is sintered.
  • the invention relates to a process for the manufacture of an element having porous portions, the process comprising the steps of
  • the sinterable material powder is inhomogeneously distributed in the green part, and/or (a-2) the sintering activity of the sinterable material powder is inhomogeneous throughout the green part, and
  • thermoplastic and/or wax-type material is intended to encompass both “thermoplastic and/or wax-type material” and “plasticized thermoplastic and/or wax-type material”.
  • the sinterable material powder is inhomogeneously distributed in the green part.
  • the sinterable material powder particles are spaced apart by either the binder or voids resulting from incomplete densification of the green part.
  • the inhomogeneous distribution is such that the regions in the green part with a lower volume concentration of sinterable material powder give rise to porous portions in the element.
  • the regions in the green part with a higher volume concentration of sinterable material powder give rise to less porous, i.e. more dense, portions in the element.
  • the sintering activity of the sinterable material powder is inhomogeneous throughout the green part.
  • the higher the “sintering activity” the lower the temperature necessary to achieve full sintering. This in turn implies that, at a given temperature, portions of the green part having a higher sintering activity sinter in a faster and more complete way than portions of the green part having a lower sintering activity.
  • Sintering activity can be influenced by various means, including variation of particle size of the sinterable material powder, and incorporation of flux agents or flux-reducing agents.
  • the dependence of sintering activity from the particle size is due to the different surface energy of a material, e.g. of the sinterable material powder particle.
  • a material e.g. of the sinterable material powder particle.
  • This reaction generally occurs early on by the diffusion of surface atoms that form a neck region between the particles.
  • the particles connected by the neck have a smaller surface area than the unconnected particles, and these necks form conductive and ductile bridges.
  • the total surface area is reduced and the surface energy is reduced which is the main thermodynamic driving mechanism during sintering.
  • smaller powder particles have a higher surface compared to bigger powder particles; i.e. , smaller powder particles also have a higher surface energy compared to bigger powder particles.
  • Flux agents or flux-reducing agents are agents that increase or decrease sintering activity of the sinterable material powder. Flux agents or flux-reducing agents can enhance or inhibit grain growth and diffusion processes during sintering. The suitability and efficacy of flux agents or flux-reducing agents is strongly dependent on the sinterable material powder.
  • very small particles e.g. nanoparticles of the sinterable material powder, or metal-organic compounds of the sinterable material powder can increase the sintering activity and act as flux agent.
  • the addition of other elements and/or compounds can act as flux agents, e.g. for iron alloys such as stainless steel 316L, carbon or carbon compounds can increase the sintering activity and act as flux agent.
  • iron alloys such as stainless steel 316L
  • carbon or carbon compounds can increase the sintering activity and act as flux agent.
  • boron or boron compounds can increase the sintering activity.
  • impurities and/or interstitials are known to inhibit grain growth and diffusion processes during sintering and can act as flux reducing agents.
  • oxides and carbides are known to inhibit grain growth and diffusion processes.
  • the dependence of sintering activity from flux agents or flux-reducing agents is due to the different mechanisms to enhance or inhibit grain growth and diffusion processes of a material, e.g. of the sinterable material powder particle, during sintering.
  • a flux agent is added, this results in a high thermodynamic potential that drives the particles to a low surface energy state during sintering, e.g. to densification at lower sintering temperatures.
  • a flux-reducing agent is added, this results in a low thermodynamic potential.
  • the inhomogeneous sintering activity is such that the regions in the green part with a lower sintering activity give rise to porous portions in the element.
  • a fine powder i.e. a powder having a high surface, and/or the addition of a flux agent gives rise to high sintering activity resulting in dense regions in the green part; and vice versa.
  • the green part is manufactured in a layer-by-layer wise manner.
  • layer-by-layer denotes that a first layer of the green part is manufactured, followed by one or more further layers.
  • manufacturing in layer-by-layer wise manner is accomplished by an additive manufacturing process.
  • Such additive manufacturing processes may either use pre-formed compound particles containing a sinterable material powder and a binder.
  • the additive manufacturing processes may use sinterable material powder, wherein the binder is selectively deposited to the sinterable material powder during the process.
  • Some additive manufacturing processes may use both pre-formed compound particles containing a sinterable material powder and a binder, and further binder or solvent may be selectively deposited.
  • the process comprises the steps of: providing compound particles containing a sinterable material powder and a binder; providing a first layer of compound particles; selectively densifying the first layer of compound particles to bind the compound particles to each other in a predefined manner so as to produce a first shaped part layer, optionally, providing at least one further layer of compound particles on the first shaped part layer; selectively densifying the further layer of compound particles to bind the compound particles to each other in a predefined manner so as to produce at least one further shaped part layer, the first shaped part layer and the further shaped part layers forming a green part.
  • “Selectively densifying” means that the compound particles are bound to each other in a target area, with substantially no particle bonding outside the target area. Selective densification can be accomplished by known methods of additive manufacturing. Selective densification may involve selectively melting the binder, e.g. by means of electromagnetic radiation, and/or dissolving the binder in a fluid that is selectively deposited on a compound particle layer.
  • Selectively densifying the first and further layer of compound particles may involve
  • a functional agent e.g. a fusing agent and/or a detailing agent
  • a functional agent e.g. a fusing agent and/or a detailing agent
  • exposing the whole first or at least one further layer to radiation generally referred to as multi jet fusion (MJF) or High Speed Sintering (HSS), or
  • binder jetting BJ
  • the compound particles are bound to each other without full densification, for example.
  • the compound particles are bound to each other only at their points of contact, and gaps or voids, for example tetrahedral or octahedral gaps, remain between the joint compound particles.
  • Ambient gas atmosphere under which the process is carried out generally air or an inert gas such as nitrogen, remains in the gaps that are not occupied by the joint compound particles.
  • the gaps are largely interconnected and form extended channels. These gaps persist even after the debinding and sintering steps, and the green bodies are not densely sintered.
  • the compound particles are bound to each other with full densification.
  • the fully densified portions in the green part no or essentially no gaps are filled with gas atmosphere are present.
  • the sinterable material powder is homogeneously distributed in the fully densified portions. The fully densified portions contribute to a higher stability of the green part.
  • the not fully densified portions in the green part have a void fraction of at least 10% by volume, preferably at least 15% by volume, more preferably at least 20% by volume, most preferably at least 25% by volume, in particular at least 30% by volume, in particular at least 35% by volume, in particular at least 40% by volume, in particular at least 45% by volume, in particular at least 50% by volume, and the fully densified portions have a void fraction of 5% by volume or less, preferably 4% by volume or less, more preferably 3% by volume or less, most preferably 2% by volume or less.
  • void(s) is used synonymously for “gaps”.
  • “Void fraction” is defined as the ratio of the void volume, i.e.
  • the void fraction is defined as the ratio of the void volume to the sum of the void volume plus the volume occupied by the joint compound particles, incorporating the sinterable material powder and the binder.
  • the fully densified portions may result in massive portions or portions of limited porosity, e.g. porosity characterized by comparatively smaller pores in the final element.
  • the not fully densified portions may result in portions of higher porosity, e.g. porosity characterized by comparatively larger pores, than the limited porosity.
  • the average pore diameter of the pores located within the portions of limited porosity is 2 times, preferably 5 times, more preferably 7 times, most preferably 10 times, in particular 13 times, in particular 15 times, in particular 17 times, in particular 20 times smaller than the average pore diameter of the pores located within the portions of higher porosity.
  • Porosity is a measure of the void, i.e. “empty”, spaces in the relevant portions of the sintered element, i.e. the massive portions or portions of limited porosity and the portions of higher porosity, respectively, and is a fraction of the volume of voids over the total volume, between 0 and 1 , or as a percentage between 0% and 100%.
  • the porosity of the portions of higher porosity is higher by at least 5 percentage points, preferably at least 10 percentage points, more preferably at least 15 percentage points, most preferably at least 20 percentage points, in particular at least 25 percentage points, in particular at least 30 percentage points, in particular at least 35 percentage points, in particular at least 40 percentage points than the porosity of the massive portions or portions of limited porosity.
  • the degree of porosity in the portions of the final element resulting form the fully densified portions in the green part may be controlled by the choice of the sintering temperature and/or particle size of the sinterable material powder. At high sintering temperatures or fine particle sizes, the sintering results in the formation of massive portions in the final element. On the other hand, at comparatively low sintering temperatures or comparatively larger particle sizes, the sintering results in the formation of portions of limited porosity in the final element.
  • fully densified portions are located in the vicinity of at least a part of the outer surface of the green part.
  • the outer surface of the green part is converted to the outer surface of the final element during sintering.
  • the fully densified portions located in the vicinity of at least a part of the outer surface of the green part may consititute the outer surface, or at least parts thereof.
  • the fully densified portions may constitute burrs, reinforcing struts, reinforcing arches etc.
  • Full densification means that the sinterable material powder particles having as high a packing density as attainable under the conditions of processes (i), (ii) or (iii) above.
  • full densification means that the binder essentially completely occupies the space between the sinterable material powder particles. This results in regions within the shaped part having a low porosity or a porosity characterized by isolated, i.e. , non-interconnected pores, after sintering.
  • a first layer of compound particles is provided, for example as a powder bed in a construction space, and the first layer is selectively densified.
  • the construction space is positioned in a horizontal x direction and a horizontal y direction relative to the electromagnetic radiation.
  • the construction space is positioned in a vertical z direction relative to an application direction of the compound particles.
  • the second layer is once again selectively densified.
  • the construction space is positioned in the x direction and the y direction relative to the electromagnetic radiation.
  • the layers are applied by means of an application device to a construction base body or a previously applied layer.
  • the application device is, for example, configured as a doctor blade and/or roller.
  • the layers are applied in a thickness D in the range: 0.01 mm ⁇ D ⁇ 0.3 mm, in particular 0.05 mm ⁇ D ⁇ 0.25 mm, in particular 0.09 mm ⁇ D ⁇ 0.2 mm. Reliable densification of the layers is ensured by the thickness D, so that the molten binder becomes uniformly and homogeneously distributed between the sinterable material powder particles and the shaped part is formed after solidification of the binder.
  • the molten binder becomes distributed between the sinterable material powder particles and holds these together after solidification, so that a comparatively strong shaped part having a low porosity is formed.
  • the porosity is dependent on the proportion, the composition and the viscosity of the molten binder.
  • the shaping step of laser sintering (LS) processes involves providing a powder bed of a compound particles in a construction space which is usually heated to an elevated temperature, e.g. to 50 to 60 °C.
  • the compound particles in the powder bed can absorb the energy, e.g., from an energy beam from a radiation source, such as a laser beam, and as a result, a localized region of the powder material increases in temperature.
  • the local increase in temperature allows for selectively melting the compound particles to bind the compound particles to each other in a predefined manner.
  • selectively irradiating with electromagnetic radiation involves directing an electromagnetic radiation beam on the first and the at least one further layer and moving said electromagnetic radiation beam over the layers whereby the energy input is locally varied.
  • Variation of the energy input by electromagnetic radiation over portions of the first and the at least one further layer may be accomplished by varying the power of the electromagnetic radiation beam and/or speed of movement and/or hatch distance of the electromagnetic radiation beam over the layers.
  • the gaps remaining between the joint compound particles in the not fully densified regions are sub-resolution gaps.
  • the resolution is limited both by a voxel volume and particle size of the compound particles.
  • sub-resolution gap denotes a gap having a gap volume which is smaller than a resolvable volume element VR.
  • VR is either a voxel volume V vox or a particle size-dependent volume V p tci, whichever value is larger.
  • V p tci is defined
  • the Dv90 (by volume) corresponds to the 90 th percentile of the particle size distribution of the compound particles, meaning that 90% of the particles have a size of the Dv90 or smaller and 10% have a size larger than the Dv90.
  • a “voxel volume” may be the smallest volume element which can be indivually addressd in the selective densification. Selective densification occurs either by electromagnetic radiation, i.e. by an electromagnetic radiation beam, or by deposition of the functional agent and/or the application of the patterning agent.
  • electromagnetic radiation the voxel volume is defined as pixel area, or cross-sectional area of the radiation beam, multiplied by the thickness of the first or further layer.
  • the voxel volume depends on the resolution, of e.g. the inkjet printing head, with which the functional agent or the patterning agent may be applied.
  • the process comprises the further steps of defining a desired three-dimensional porosity field of the element and programming the energy input by the electromagnetic radiation for the two-dimensional coordinates of the first and the at least one further layer.
  • a process for (ii), such as a multi jet fusion or high speed sintering process an entire layer of compound particles is exposed to radiation, such as infrared radiation, but a selected region of the layer is fused and hardened to become a shaped part layer.
  • a functional agent e.g. a fusing agent and/or a detailing agent, is selectively deposited in contact with the selected region of the particle layer.
  • the construction space is positioned in a horizontal x direction and a horizontal y direction relative to an applicator of the fluid.
  • the construction space is positioned in a vertical z direction relative to an application direction of the compound particles. After application of the second layer on top of the first layer, the second layer is once again selectively densified.
  • the construction space is positioned in the x direction and the y direction relative to the applicator of the fluid.
  • the functional agent(s) are capable of penetrating into the layer of compound particles and spreading onto the exterior surface of the compound particles.
  • the fusing agent is capable of absorbing radiation and converting the absorbed radiation to thermal energy, which in turn melts or sinters the compound particles that are in contact with the fusing agent.
  • the detailing agent is capable of reflecting radiation and/or reduce the conversion of the absorbed radiation to thermal energy and/or cooling the compound particles, which in turn does not melt or sinter the compound particles that are in contact with the detailing agent. This causes the compound particles to fuse, bind, cure, etc. selectively to form the shaped part layer. Further layers are applied and selectively densified in a manner analogous to applying and selectively densifying the second layer, until the desired shape part has been produced.
  • the layers are applied by means of an application device to a construction base body or a previously applied layer.
  • the application device is configured as a doctor blade and/or roller.
  • the layers are applied in a thickness D in the range: 0.01 mm ⁇ D ⁇ 0.3 mm, in particular 0.05 mm ⁇ D ⁇ 0.25 mm, in particular 0.09 mm ⁇ D ⁇ 0.2 mm. Reliable densification of the layers is ensured by the thickness D, so that the molten binder becomes uniformly and homogeneously distributed between the sinterable material powder particles and the shaped part is formed after solidification of the binder.
  • the molten binder becomes distributed between the sinterable material powder particles and holds these together after solidification, so that a comparatively strong shaped part having a low porosity is formed.
  • the porosity is dependent on the proportion, the composition and the viscosity of the molten binder.
  • the shaping step of multi jet fusion (MJF) processes involves providing a powder bed of a compound particles in a construction space which is usually heated to an elevated temperature, e.g. to 50 to 60 °C.
  • the functional agents e.g. a fusing agent and/or a detailing agent, is applied.
  • the compound particles with fusing agent in the powder bed can absorb the energy, e.g., an energy from a radiation source, such as an infrared radiation, and as a result, a localized region of the powder material increases in temperature.
  • the local increase in temperature allows for selectively melting the compound particles to bind the compound particles to each other in a predefined manner.
  • the compound particles in the powder bed wetted with detailing agent can reflect the energy and/or absorb less energy, e.g., from a radiation source, such as an infrared radiation.
  • the detailing agent can effectively cool the compound particles.
  • the temperature increase in a localized region of the powder material is limited. The limited lower local temperature increase allows for selectively protecting the compound particles from melting and to maintain the compound particles as a powder bed.
  • selectively melting involves directing an radiation on the first and the at least one further layer and moving said radiation over the layers whereby the thermal temperature increase, e.g. by functional agents, is locally varied.
  • Variation of the thermal temperature increase over portions of the first and the at least one further layer may be accomplished by varying the ratio of functional agents influencing the temperature by the adsorption and/or reflection and/or cooling effects over the layers.
  • the process comprises the further steps of defining a desired three-dimensional porosity field of the element and programming the thermal temperature increase by adsorption and/or reflection and/or cooling for the two- dimensional coordinates of the first and the at least one further layer.
  • a patterning agent is selectively applied to a layer of compound particles.
  • the binder of the compound particles is selected so that it is at least partially soluble in a patterning agent that is used during printing. Dissolution of the binder physically breaks up the compound particles and converts them into layer of thick slurry of the sinterable material powder.
  • the slurry is a layer of adequate structural uniformity that is composed of the sinterable material powder, which can be densified as a result of binder dissolution and redistribution, fluid evaporation, and capillary forces to form a densified green part. Further layers are applied and selectively densified in a manner analogous to applying and selectively densifying the second layer, until the desired shape part has been produced.
  • the layers are applied by means of an application device to a construction base body or a previously applied layer.
  • the application device is, for example, configured as a doctor blade and/or roller.
  • the layers are applied in a thickness D in the range: 0.01 mm ⁇ D ⁇ 0.3 mm, in particular 0.05 mm ⁇ D ⁇ 0.25 mm, in particular 0.09 mm ⁇ D ⁇ 0.2 mm. Reliable densification of the layers is ensured by the thickness D, so that the dissolved binder becomes uniformly and homogeneously distributed between the sinterable material powder particles and the shaped part is formed after solidification of the binder.
  • the dissolved binder becomes distributed between the sinterable material powder particles and holds these together after solidification, so that a comparatively strong shaped part having a low porosity is formed.
  • the porosity is dependent on the proportion, the composition and the viscosity of the dissolved binder.
  • the shaping step of binderjetting (BJ) processes involves providing a powder bed of a compound particles in a construction space which is usually heated to an elevated temperature, e.g. to 30 to 80 °C.
  • the compound particles in the powder bed can absorb the patterning agent and the binder is at least partially soluble in a patterning agent.
  • the dissolution of the binder physically breaks up the compound particles and converts them into a layer of thick slurry of the sinterable material powder.
  • the local dissolution of the binder allows for selectively breaking up the compound particles to bind the compound particles to each other in a predefined manner.
  • selectively applying a patterning agent involves applying a patterning agent on the first and the at least one further layer whereby the amount and/or composition of the patterning agent is locally varied.
  • the process comprises the further steps of defining a desired three-dimensional porosity field of the element and programming the composition and/or amount of patterning agent for the two-dimensional coordinates of the first and the at least one further layer.
  • the process comprises providing a first type of compound particles having a first volume concentration of sinterable material powder and a second type of compound particles having a second volume concentration of sinterable material powder, at least a portion of the first or further layers comprises the first type of compound particles and at least a portion of the first or further layers comprises the second type of compound particles.
  • further type(s) of compound particles may be provided, at least a portion of the first or further layers comprises the further type(s) of compound particles.
  • the process comprises providing a first type of compound particles having a first average particle size of sinterable material powder and a second type of compound particles having a second average particle size of sinterable material powder, at least a portion of the first or further layers comprises the first type of compound particles and at least a portion of the first or further layers comprises the second type of compound particles.
  • the process comprises providing a first type of compound particles having a first volume concentration of flux agent and a second type of compound particles having a second volume concentration of flux agent or no flux agent, at least a portion of the first or further layers comprises the first type of compound particles and at least a portion of the first or further layers comprises the second type of compound particles.
  • the process comprises selectively applying a flux agent or flux-reducing agent to a first and/or further layer of compound particles, wherein to at least a portion of the first or further layers, the flux agent or fluxreducing agent is applied in a first concentration, and to at least a portion of the first or further layers, no flux agent or flux-reducing agent is applied or the flux agent or flux-reducing agent is applied in a concentration different from the first concentration.
  • Flux agents and flux-reducing agents are dependent on the sinterable material powder.
  • Suitable flux agents may be selected from fine particles, e.g. nanoparticles, of sinterable material.
  • carbon or boron may be suitable flux agents.
  • suitable flux-reducing agents may be selected from ceramics such as oxides or carbides.
  • the additive manufacturing processes may use sinterable material powder, wherein the binder is selectively deposited to the sinterable material powder during the process.
  • the process comprises the steps of providing a first layer of sinterable material powder; selectively depositing a binder liquid onto the first layer of sinterable material powder to bind the sinterable material powder together in a predefined manner so as to produce a first shaped part layer, providing at least one further layer of sinterable material powder on the first shaped part layer; selectively depositing the binder liquid onto the further layer of sinterable material powder to bind the sinterable material powder together in a predefined manner so as to produce at least one further shaped part layer, the first shaped part layer and the further shaped part layers forming a green part.
  • binder jetting process initially using uncompounded sinterable material powder.
  • binder jetting process (iii) utilizes compound particles containing the sinterable material powder and the binder.
  • the first layer is provided from sinterable material powder without binder.
  • the binder is added to said first layer in the form of a binder liquid.
  • the binder liquid is a mixture of the binder and a liquid, e.g. a solvent which allows for dissolving the binder.
  • the liquid may be selected from water or organic solvents such as alcohols, ketones or aldehydes.
  • the layers are applied by means of an application device to a construction base body or a previously applied layer.
  • the application device is, for example, configured as a doctor blade and/or roller.
  • the layers are applied in a thickness D in the range: 0.01 mm ⁇ D ⁇ 0.3 mm, in particular 0.05 mm ⁇ D ⁇ 0.25 mm, in particular 0.09 mm ⁇ D ⁇ 0.2 mm.
  • Reliable densification of the layers is ensured by the thickness D, so that the dissolved binder becomes uniformly and homogeneously distributed between the sinterable material powder particles and the shaped part is formed after solidification of the binder.
  • the dissolved binder becomes distributed between the sinterable material powder particles and holds these together after solidification, so that a comparatively strong shaped part having a low porosity is formed.
  • the porosity is dependent on the proportion, the composition and the viscosity of the dissolved binder.
  • the solid shaped part is taken out of the loose, i.e. not densified, uncompounded sinterable material powder.
  • the shaped part in this state is referred to as green body.
  • the shaping step of binderjetting (BJ) processes involves providing a powder bed of an uncompounded sinterable material powder in a construction space which is usually heated to an elevated temperature, e.g. to 30 to 80 °C.
  • the uncompounded sinterable material powder in the powder bed can absorb the binder liquid, and as a result, in a localized region the binder liquid converts the powder material into layer of thick slurry of the sinterable material powder.
  • the local application of the binder liquid allows for selectively binding the uncompounded sinterable material powder to each other in a predefined manner.
  • selectively applying a binder liquid involves applying a binder liquid on the first and the at least one further layer and applying the binder liquid over the layers whereby the amount and/or composition of the binder liquid is locally varied.
  • the process comprises the further steps of defining a desired three-dimensional porosity field of the element and programming the composition and/or amount of binder liquid for the two-dimensional coordinates of the first and the at least one further layer.
  • the amount and/or composition of binder liquid deposited is varied over portions of the first and the at least one further layer. Doing so allows for providing green parts having portions with varying packing density of sinterable material powder. For example, regions in the green part a low volume concentration of binder, i.e. regions in the green part with a high volume concentration of sinterable material powder, give rise to less porous, i.e. more dense, portions in the element.
  • the process comprises providing a first type of sinterable material powder having a first average particle size and a second type of sinterable material powder having a second average particle size, at least a portion of the first or further layers comprises the first type of sinterable material powder and at least a portion of the first or further layers comprises the second type of sinterable material powder.
  • the process comprises selectively applying a flux agent or flux-reducing agent to a first and/or further layer of compound particles, wherein to at least a portion of the first or further layers, the flux agent or fluxreducing agent is applied in a first concentration, and to at least a portion of the first or further layers, no flux agent or flux-reducing agent is applied or the flux agent or flux-reducing agent is applied in a concentration different from the first concentration.
  • Flux agents and flux-reducing agents are dependent on the sinterable material powder.
  • Suitable flux agents may be selected from fine particles, e.g. nanoparticles, of sinterable material.
  • carbon or boron may be suitable flux agents.
  • suitable flux-reducing agents may be selected from ceramics such as oxides or carbides.
  • elements with a controlled porous architecture are obtained.
  • the pore structure within a product can be varied for customization and unique properties.
  • the properties at different locations within the element can be controlled, e.g. to produce a gradient of porosity through the element.
  • the porosity is interconnected or consists of “open pores”, meaning that at least a major fraction or substantially all pores intersect with at least some other pores which extend in a different direction.
  • the present invention also allows for the manufacturing of products that have porous portions and solid portions, i.e., essentially non-porous portions, within one integrally formed sintered element. Hence, joints between porous and solid product portions, which result from the joining of multiple product components required by conventional manufacturing techniques, can be eliminated.
  • the invention further relates to a process for the manufacture of a porous element or an element having porous portions, the process comprising the steps of:
  • the sintering activity of the sinterable material powder is inhomogeneous throughout the integral part, and debinding the green part and sintering the debound part to obtain the element having porous portions, such that regions in the green part with a lower volume concentration of sinterable material powder and/or lower sintering activity give rise to porous portions in the element.
  • the above process comprises
  • the above process comprises
  • the process comprises providing a first type of compound particles having a first volume concentration of sinterable material powder and a second type of compound particles having a second volume concentration of sinterable material powder, at least a portion of the first or further layers comprises the first type of compound particles and at least a portion of the first or further layers comprises the second type of compound particles.
  • further type(s) of compound particles may be provided, at least a portion of the first or further layers comprises the further type(s) of compound particles.
  • the process comprises providing a first type of compound particles having a first average particle size of sinterable material powder and a second type of compound particles having a second average particle size of sinterable material powder, at least a portion of the first or further layers comprises the first type of compound particles and at least a portion of the first or further layers comprises the second type of compound particles .
  • the process comprises providing a first type of compound particles having a first volume concentration of flux agent and a second type of compound particles having a second volume concentration of flux agent or no flux agent, at least a portion of the first or further layers comprises the first type of compound particles and at least a portion of the first or further layers comprises the second type of compound particles .
  • the process comprises selectively applying a flux agent or flux-reducing agent to a first and/or further layer of compound particles, wherein to at least a portion of the first or further layers, the flux agent or fluxreducing agent is applied in a first concentration, and to at least a portion of the first or further layers, no flux agent or flux-reducing agent is applied or the flux agent or flux-reducing agent is applied in a concentration different from the first concentration.
  • the first green part may be a sheet which after sintering yields a metallic foil, e.g. a permeable metallic foil, e.g. made from titanium.
  • a metallic foil e.g. a permeable metallic foil, e.g. made from titanium.
  • the thin foils need to be supported in order to withstand the high pressure differences encountered during application, e.g. by additional support frames or mesh fabric.
  • Such supporting structures are generally not permanently connected to the foils.
  • the process of the present invention allows for the provision of a solid, i.e. non-porous, supporting structures and/or a supporting structure with different porosity, preferably a higher porosity, on the foil which forms an integral structure with the foil.
  • the shaped part After the shaped part has been taken out of the bed of non-densified or “loose” compound particles, the shaped part is subjected to debinding to partly remove the binder.
  • Suitable methods for partial removal of the binder depend on the nature of the binder comprised in the compound particles. Solvent debinding, thermal debinding and chemical debinding are techniques frequently used.
  • binder components having different solvent solubility and/or different thermal degradability and/or different reactant degradability and/or different volatility allows for selective removal of one or more binder components, during the debinding step.
  • the solvent treatment process is preferred.
  • the partial removal of the binder or removal of a binder ingredient results in a microporous structure of the shaped part.
  • the sinterable material powder particles are held together by the remaining binder.
  • the remaining binder components retained in the brown part provide a brown part that is stable and sufficiently strong to be handled and transported between the debinding and sintering steps.
  • Suitable solvents are selected from alcohols such as ethanol or propanol; aromatic compounds such as benzene, toluene or xylenes; esters such as ethyl acetate; ethers such as diethylether or tetrahydrofuran; ketones such as acetone; alkanes such as hexane or heptane; halogenated hydrocarbons such as n-propyl bromide, trichloroethylene, perchloroethylene, n-methyl pyrrolidine; water; gases in supercritical state; and mixtures thereof.
  • the solvent is preferably kept at a temperature TL in the range of 20 to 100 °C, preferably 25 to 80 °C, more preferably 30 to 60 °C.
  • the green part to be debound is treated in a reactive gas atmosphere.
  • a reactive gas atmosphere may comprise a gas, preferably nitric acid.
  • the chemical treatment process is carried out at elevated temperature levels.
  • the temperature in the chemical treatment process may be in the range of 40 to 150 °C, preferably 60 to 140 °C, more preferably 80 to 130 °C.
  • a drying and/or curing step may be necessary. During this step, the strength of the green the green part is increased for an easier handling in the post processing steps.
  • a drying process residual solvents from the patterning fluid is removed, e.g. in an oven at elevated temperature for a period of several hours.
  • a curing process the parts a hardened in an oven at elevated temperature, e.g. 200 °C, for a period of several hours. The drying and/or curing step results in much stronger green parts.
  • the sintering step serves to drive out the residual binder and sinter the debound part to obtain the final sintered element.
  • shrinkage occurs.
  • the resulting element is homogeneous and has a high density.
  • porosity prevails after sintering.
  • the residual binder is driven out at a first temperature Ti which is in the range of 100 to 750 °C, preferably 150 to 700 °C, more preferably 200 to 650 °C, most preferably 300 to 600 °C.
  • a suitable temperature Ti may also be dependent on the atmosphere.
  • the first temperature Ti is selected as a function of the residual binder components. Binder which is not removed is not available as polymeric binder in the part but is diffused, e.g. as carbon, into the metal part and increases the carbon content in the metal part.
  • the sinterable material powder particles partly form sintering necks, so that the shaped part is held together despite removal of the remaining binder. Owing to the microporous structure of the shaped part, thermal binder removal occurs quickly and uniformly.
  • Undesirable chemical reactions during the thermal binder removal may be avoided by means of an inert gas atmosphere or a reducing atmosphere or high vacuum.
  • the inert gas atmosphere comprises, in particular, at least one noble gas which noble gas may suitably be selected from, e.g., nitrogen, helium and argon.
  • the reducing atmosphere may include gases such as hydrogen, carbon dioxide, and/or carbon monoxide.
  • sintering is carried out at a second temperature T2 which is in the range of 600 to 2000 °C, preferably 800 to 1800 °C, more preferably 900 to 1500 °C.
  • the second temperature T2 is preferably in the range of 600 to 2400 °C, more preferably 800 to 2200 °C, most preferably 1100 to 2000 °C.
  • the sintering temperature T2 is below the melting temperature of the sinterable material powder.
  • the sintering at the second temperature T2 is carried out for a period of time At2 which is dependent on the geometry of the part and the material to be sintered and in particular is proportional to the square of the wall thickness of the component to be produced.
  • the period of time At2 is so long that no significant change in the porosity of the part can be achieved by subsequent further sintering.
  • Sintering may be carried out at more than one temperature T2, e.g. a sintering step at the temperature T2a is carried out for a period of time At2a and another sintering step at the temperature T2b is carried out for a period of time At2b.
  • the molded part will shrink essentially without affecting the shape of the molded part.
  • the powder particles will fuse together and the open space between the powder particles disappears.
  • the density of the product increases and the product shrinks.
  • the sintering step is commonly completed when the product has reached a density of about 90 to 100% by volume of the solid of which the powder is made, depending on the material and later use of the product.
  • the part is completely free of binder.
  • the component forms an integral structure having a desired pore architecture which includes porous portions and may in addition include portions of high density.
  • the sinterable material powder is a metal powder and the sintering temperature is below the solidus temperature of the metal powder.
  • the solidus of a material is the locus of temperatures below which the material is completely solid. Said locus of temperatures may be determined from a curve on a phase diagram.
  • feedstock compound denotes a composition of matter constituting the compound particles, and which contains the sinterable material powder and the binder.
  • the process involves compound particles containing a sinterable material powder and a binder.
  • the compound particles contain (i) sinterable material powder dispersed throughout the compound particle, the sinterable material powder preferably having a particle size distribution such that at least 80% of the particles have a maximum particle size Amax in the range of 100 nm to 400 pm; and
  • the compound particles are, for example, produced by subjecting a suspension of the sinterable material powder and a solvent, e.g. an alcoholic solvent, in which the binder has been dissolved to spray drying.
  • a solidified melt of the binder component having dispersed therein the sinterable material powder may be milled. Larger compound particles may also be compounded by an extruder with subsequent granulation.
  • the compound particles may be composed of particles of arbitrary shape such as irregular, cylindrical, rotational ellipsoid or essentially spherical, or filaments, but are preferably essentially spherical.
  • the sinterable material powder includes conventionally known sinterable materials.
  • the sinterable material is selected from metals, alloys, vitreous materials and ceramic materials.
  • metals are selected from iron, stainless steel, steel, copper, bronze, aluminum, tungsten, molybdenum, silver, gold, platinum, titanium, nickel, cobalt, chromium, zinc, niobium, tantalum, yttrium, silicon, magnesium, calcium and combinations thereof.
  • the metal particles have a particle size distribution such that at least 85%, preferably at least 90%, more preferably at least 95%, most preferably at least 99% of the particles have a maximum particle size Amax in the range of 500 nm to 400 pm, preferably 1 pm to 150 pm, more preferably 3 pm to 50 pm, most preferably 5 pm to 25 pm.
  • alloys are selected from steels such as stainless steels (316 L, 17-4 PH), chromium-nickel steels, bronzes, copper alloys such as Hovadur, nickel-base alloys such as Hastelloy or Inconel, cobalt and cobalt-chromium alloys such as stellite, aluminum alloys such as Aluminum 6061 , tungsten heavy alloys, titanium alloys such as grade 1 via grade 5 (Ti-6AI-4V) to grade 38 according to ASTM.
  • steels such as stainless steels (316 L, 17-4 PH)
  • chromium-nickel steels such as bronzes
  • copper alloys such as Hovadur
  • nickel-base alloys such as Hastelloy or Inconel
  • cobalt and cobalt-chromium alloys such as stellite
  • aluminum alloys such as Aluminum 6061
  • tungsten heavy alloys titanium alloys such as grade 1 via grade 5 (Ti-6AI-4V) to grade 38 according to ASTM.
  • ceramic particles are selected from oxides such as aluminum oxides, silicon oxides, zirconium oxides, titanium oxides, magnesium oxides, yttrium oxides; carbides such as silicon carbides, tungsten carbides; nitrides such as boron nitrides, silicon nitrides, aluminum nitrides; silicates such as steatite, cordierite, mullite; and combinations thereof.
  • oxides such as aluminum oxides, silicon oxides, zirconium oxides, titanium oxides, magnesium oxides, yttrium oxides
  • carbides such as silicon carbides, tungsten carbides
  • nitrides such as boron nitrides, silicon nitrides, aluminum nitrides
  • silicates such as steatite, cordierite, mullite; and combinations thereof.
  • the ceramic particles have a particle size distribution such that at least 85%, preferably at least 90%, more preferably at least 95%, most preferably at least 99% of the particles have a maximum particle size Amax in the range of 200 nm to 25 pm, preferably 300 nm to 10 pm, more preferably 400 nm to 7 pm, most preferably 500 nm to 3 pm.
  • vitreous particles are selected from non-oxide glasses such as halogenide glasses, chalcogenide glasses; oxide glasses such as phosphate glasses, borate glasses, silicate glasses such as aluminosilicate glasses, lead silicate glasses, boron silicate glasses, soda lime silicate glasses, quartz glasses, alkaline silicate glasses; and combinations thereof.
  • the vitreous particles have a particle size distribution such that at least 85%, preferably at least 90%, more preferably at least 95%, most preferably at least 99% of the particles have a maximum particle size Amax in the range of 200 nm to 25 pm, preferably 300 nm to 10 pm, more preferably 400 nm to 7 pm, most preferably 500 nm to 3 pm.
  • the sinterable material powder may contain combinations of more than one of metals, alloys, vitreous particles and ceramic particles as described above, for example hard metals or metal matrix composites (also referred to as metal ceramic composites).
  • the particulate feedstock compound contains the sinterable material powder in an amount of about 0.70 to 0.99 ⁇ (
  • the remainder is comprised of binder component.
  • critical solids loading is referred to as the amount of sinterable material powder by volume in a feedstock compound at a critical limit. Said “critical limit” is reached when the feedstock compound becomes stiff and does not flow due to the relative viscosity becoming infinite upon addition of sinterable material powder to the feedstock compound. Physically, “critical solids loading” defines the maximum packing arrangement of particles while still retaining a continuous material and it is the limit above which it is not possible to continue loading the binder matrix with solid powders.
  • relative viscosity denotes the viscosity of the feedstock compound in relation to the viscosity of the neat binder in order to isolate the effect of the sinterable material powder. The viscosity of the feedstock compound increases upon addition of sinterable material powder.
  • the critical solids loading There are several ways to determine the critical solids loading. For example, one can determine the peak in the torque of a kneader when more and more metal powder is added to the binder. After critical solids loading is reached, the torque usually decreases again as the feedstock compound becomes more friable.
  • a pycnometer measurement may be used: up to the critical solids loading, the theoretical density is in agreement with the measured density at the pycnometer, above the critical solids loading, the measured density is below the theoretical density due to pores (see also: 1990, R. M. German, Powder Injection Molding, Metal Powder Industries Federation 1990, p.129-130).
  • Rheological measurements may also be used to estimate the value of the critical solids loading by plotting ⁇ r
  • r denotes the relative viscosity.
  • the compound particles comprise the sinterable material powder in an amount of about 20 to 90% by volume, preferably 30 to 80% by volume, more preferably 40 to 75% by volume, most preferably 45 to 70% by volume, in particular 50 to 65% by volume, and the binder component in an amount of about 10 to 80% by volume, preferably 20 to 70% by volume, more preferably 25 to 60% by volume, most preferably 30 to 55% by volume, in particular 35 to 50% by volume.
  • Each compound particle comprises a plurality of sinterable material powder particles dispersed within a matrix of the binder and held together by the binder.
  • a plurality of sinterable material powder particles per compound particle makes it possible for the shape of the compound particles to be independent of the shape of the sinterable material powder particles.
  • substantially spherical compound particles can be produced without the necessity of the sinterable material powder particles being spherical. This reduces the production costs since sinterable material powders with arbitrary or irregular particle geometry are more readily available than powders having a particular, e.g., spherical, powder particle geometry.
  • the average number of sinterable material powder per composite particle is, in particular, at least 2, in particular at least 5, in particular at least 10, in particular at least 50, in particular at least 100, in particular at least 500, in particular at least 1000, in particular at least 5000, in particular at least 10000, in particular at least 50000, in particular at least 100,000.
  • the average number of sinterable material powder particles per composite particle is, in particular, not more than 20,000,000, in particular not more than 10,000,000, in particular not more than 5,000,000, in particular not more than 1 ,000,000, in particular not more than 500,000, in particular not more than 100,000, in particular not more than 50,000, in particular not more than 10,000, in particular not more than 5000.
  • the particulate feedstock compounds have a particle size distribution such that at least 80% by volume, preferably at least 90% by volume, more preferably at least 95% by volume, most preferably at least 99% by volume, of the particulate feedstock compounds have a maximum particle size Bmax in the range of 0.005 to 0.3 mm, preferably 0.008 to 0.2 mm, more preferably 0.01 to 0.2 mm, most preferably 0.015 to 0.15 mm.
  • Laser Sintering is a preferred method for carrying out the present invention and is described in more detail below.
  • Compound particles amenable to selectively irradiating with electromagnetic radiation comprise a binder which is a thermoplastic and/or wax-type material.
  • the binder component comprises at least one first thermoplastic and/or wax-type material, preferably at least one semi-crystalline first thermoplastic and/or wax-type material, and at least one second thermoplastic and/or wax-type material.
  • the first thermoplastic and/or wax-type material and the second thermoplastic and/or wax-type material differ in at least one property which property is selected from
  • a solvent preferably selected from alcohols such as ethanol, or propanol; aromatic compounds such as benzene, toluene, or xylene; esters such as ethyl acetate; ethers such as diethylether, or tetrahydrofuran; ketones such as acetone; alkanes such as hexane, or heptane; halogenated hydrocarbons such as n-propyl bromide, trichloroethylene, perchloroethylene, n-methyl pyrrolidine; and mixtures thereof; water; and gases in supercritical state;
  • alcohols such as ethanol, or propanol
  • aromatic compounds such as benzene, toluene, or xylene
  • esters such as ethyl acetate
  • ethers such as diethylether, or tetrahydrofuran
  • ketones such as acetone
  • alkanes such as hexane, or
  • thermoplastic and/or wax-type material is less soluble, less degradable, or less volatile than the second thermoplastic and/or wax-type material.
  • the binder components are selected such that the temperature transition from solid or semi-solid to fluid is very narrow, leading to less influence on adjacent feedstock compound particles in 3D printing.
  • the feedstock compound particles irradiated with an energy beam can be converted from solid to fluid at comparably low temperature and form a dense green part without affecting adjacent feedstock compounds.
  • This narrow temperature transition from solid or semi-solid to fluid is reflected by a small difference between TP and T cr oss as explained in more detail below.
  • the melting process results in an endothermic peak in the DSC curve and the melting temperature refers to the melt peak temperature TP in said DSC curve where the rate of change of endothermic heat flow is maximum.
  • the DSC curve may comprise a single melt peak.
  • the DSC curve may comprise several melt peaks, i.e. several local maxima.
  • the melt peak temperature TP is defined as the temperature at the global maximum.
  • the binder component preferably exhibits a single melt peak.
  • the binder component exhibits a melt peak temperature TP below 180 °C, preferably in the range of 10 °C to 180 °C, more preferably 20 °C to 160 °C, most preferably 30 °C to 140 °C, in particular 35 °C to 120 °C, in particular 40 °C to 100 °C, in particular 45 °C to 90 °C, in particular 50 °C to 85 °C.
  • Melt peak temperatures TP within these ranges allow for selective densifying or melting with as little additional energy (e.g. laser energy) as possible, and low energy laser sources can conveniently be used.
  • TP is determined in accordance with DIN EN ISO 11357-3 in the second heating after a first heating/cooling cycle.
  • a sample is heated in a first heat ramp from -20 °C to a temperature which is 20 K above completion of all thermal events, cooled to -20 °C afterwards and finally heated again in a second heat ramp from -20 °C to the temperature which is 20 K above completion of all thermal events, each with a heating and cooling rate of 10 K/min.
  • “Thermal events” for the purpose herein means thermal events other than decomposition, or in other words, essentially reversible thermal events.
  • dynamic viscoelasticity measurements allow for the determination of dynamic viscoelasticity properties including storage modulus G’ and loss modulus G” of a material.
  • the storage modulus G‘ represents the elastic proportion of a material. It is proportional to the proportion of deformation energy which is stored in the material and which may be recovered from the material after relief of stress.
  • the loss modulus G represents the viscous portion of a material. It corresponds to the proportion of energy loss which is converted into heat by internal friction.
  • Tcross is the temperature at the intersection between the storage modulus G’ curve and the loss modulus G” curve in a dynamic viscoelasticity measurement of the binder component. This temperature is also referred to as “cross-over” temperature in the literature and refers to a state of the material at which the transition from the molten state to the viscous state of said material takes place. If the G’ and the G” curves intersect more than once, Tcross is the intersection at the highest temperature. It is understood by the skilled person that the expression “highest temperature” refers to the highest temperature below a temperature where decomposition occurs.
  • Tcross may be determined in a heating step or a cooling step.
  • Kinetic effects such as supercooling or suspended thermal transitions, may interfere with the determination of Tcross.
  • it may be advisable to determine Tcross in a heating step or a cooling step. In the event that Tcross measured during heating differs from Tcross measured during cooling, the higher value of T cross is used.
  • the storage modulus G’ curve and the loss modulus G” curve are recorded in a dynamic viscoelasticity measurement during heating of a material starting from a temperature below its melting temperature, e.g. 20 K below TP to a temperature where the material is completely molten.
  • the geometry is heated to a temperature at which the sample of binder component is fully liquefied, i.e. a temperature of about 20 K above the presumed T cr oss of the binder component, and the sample is placed on the hot lower plate.
  • a temperature at which the sample of binder component is fully liquefied i.e. a temperature of about 20 K above the presumed T cr oss of the binder component
  • the sample is placed on the hot lower plate.
  • it is cooled from the temperature of about 20 K above Tcross of the binder component to a temperature of about 10 K below the first intersection temperature, then heated to the temperature of about 20 K above the melting temperature of the binder component, each with a cooling and heating rate of 1 K/min.
  • the trigger point is located in the transition between the solid and the liquid state. Between both states, the shear modulus changes significantly which results in the necessity of different control modes in the measurement needs.
  • a change of the measurement mode is necessary to stay in the linear viscoelastic range.
  • the specimen changes from a liquid to a rigid state.
  • the deformation in the liquid state must not be too large, otherwise the specimen is no longer in the linear viscoelastic range. If the liquid is exposed to a certain deformation, upon releasing the imposing force or stress, the liquid completely takes the new shape or position. Since the specimen will reach the selected deformation in the liquid state, the measurement in this phase is deformation controlled. In the rigid state, the deformation would not be achieved and the limit of the torque of the rheometer will be reached. That is why measuring mode has to be switched to shear stress controlled mode.
  • the switch of the measurement of deformation controlled mode to shear stress controlled mode is set by a trigger point.
  • the trigger point is located in the transition between the solid and the liquid state. Between both states, the shear modulus changes significantly which results in the necessity of different control modes in the measurement needs.
  • the trigger point can be any specific point or criteria that allows the change of measuring mode in the linear viscoelastic range. In the heating ramp, it is the same way round.
  • the binder component satisfies a condition such that T cr oss is higher by not more than 60 K than TP, preferably by not more than 50 K, more preferably by not more than 45 K, most preferably by not more than 40 K, in particular by not more than 35 K.
  • T cr oss is higher by not more than 60 K than TP, preferably by not more than 50 K, more preferably by not more than 45 K, most preferably by not more than 40 K, in particular by not more than 35 K. This also includes a situation where Tcross is lower than Tp.
  • the binder component exhibits a percentage of melting enthalpy measured by DSC between Tinit and [TP + 25 K], of at least 94%, preferably at least 95%, more preferably at least 96%, most preferably at least 97%, in particular at least 98%, in particular at least 99% of the total melting enthalpy, wherein Tinit is the initial melting temperature.
  • total melting enthalpy refers to the sum of any endothermic DSC peaks in the range of 10 °C to 20 K above completion of all thermal events, for example in the range of 10 °C to 200 °C. Melting enthalpy is usually reported as J/g and can be derived from the area which is enclosed by an endothermic DSC peak curve and the baseline.
  • the initial melting temperature (Tinit) is the first cross-over point between the baseline and the thermogram at a temperature below TP and refers to the initial melting temperature of the binder component.
  • the melting temperature TP is the temperature at maximum height of the peak.
  • the binder component comprises 3 to 70% by volume, preferably 5 to 60% by volume, more preferably 7 to 50% by volume, most preferably 10 to 40% by volume, in particular 12 to 35% by volume, in particular 15 to 30% by volume, of the first thermoplastic and/or wax-type material, based on the total volume of the binder component.
  • the binder component further comprises 30 to 97% by volume, preferably 40 to 95% by volume, more preferably 50 to 93% by volume, most preferably 60 to 90% by volume, in particular 65 to 88% by volume, in particular 70 to 85% by volume, of a second (plasticized) thermoplastic and/or wax-type material, based on the total volume of the binder component.
  • one binder component is removed (in the context of the present patent application: the second thermoplastic and/or wax-type material) wherein at the same time another binder component (the first thermoplastic and/or wax-type material) remains within the part to be manufactured, holding together the sinterable material powder.
  • debinding processes e.g. solvent debinding, thermal debinding, chemical debinding etc., are known per se.
  • one binder component may be selectively removed from a green part by means of dissolving said binder component in a solvent, wherein a second binder component remains within the green part. Therefore, the binder components need to differ in e.g. molecular weight or polarity in order to exhibit different solubilities in the solvent.
  • any given polymer or wax may be fairly soluble in one solvent, e.g., a non-polar solvent, and may be poorly soluble or insoluble in another solvent, e.g., a more polar solvent.
  • a given polymer or wax qualifies as a first thermoplastic and/or wax-type material or second thermoplastic and/or wax-type material depends on the solvent intended for the debinding step.
  • solvents e.g. from polar solvents to less polar or non-polar solvents or vice versa
  • the categorization of the binder components into first thermoplastic and/or waxtype material or second thermoplastic and/or wax-type material may be reversed.
  • the material remaining in the part to be debound may be a polymer or wax which is poorly soluble or insoluble in acetone
  • binder component to be removed may be a polymer or wax which is soluble in acetone
  • solubility of the first thermoplastic and/or wax-type material is lower than 0.1 g, preferably lower than 0.05 g, more preferably lower than 0.01 g, most preferably lower than 0.005 g in 100°g solvent, in particular insoluble in the solvent
  • the solubility of the second thermoplastic and/or wax-type material is in the range of 0.1 g to 500 g, preferably 0.5 g to 300 g, more preferably 1 g to 200 g, most preferably 2 g to 175 g, in particular 3 g to 150 g, in particular 5 g to 100 g, in 100 g solvent at a predetermined temperature.
  • the predetermined temperature may be in the range of 10 °C to [TP - 5°K], preferably 20 °C to 80 °C, more preferably 30 °C to 70 °C, most preferably 35 °C to 65 °C, in particular 40 °C to 60 °C.
  • a chemical debinding (also referred to as “catalytic debinding”) process is e.g. described in DE 10 2005 027 216 A1.
  • a molded article to be debound is positioned in a debinding furnace in which the molded article is brought to an appropriate process temperature.
  • a process gas which includes a reactant such as nitric acid
  • a reactant such as nitric acid
  • the first thermoplastic and/or wax-type material is semicrystalline.
  • semicrystalline characterizes those polymers which possess high degrees of inter- and/or intra-molecular order.
  • the semi-crystal line nature of a polymer can be verified by a first order transition or crystalline melting point (T m ) as determined by differential scanning calorimetry (DSC).
  • the first thermoplastic and/or wax-type materials is semi-crystal line because they exhibit a sharp transition separating the fluid and solidified states. Further, they are characterized by a strength increase by crystallization upon solidification.
  • the first thermoplastic and/or wax-type material and the second thermoplastic and/or wax-type material may be selected from a variety of materials.
  • Suitable polymers include: polyolefins such as polyethylene such as Lupolen 2420, Lupolen 5261 Z (available from
  • polyamides can be produced by a reaction of carboxylic acids and amines to amides or by reaction of moieties/derivatives of carboxylic acids and amines.
  • Polyamide homopolymers can be produced by reaction of one monomer, i.e. amino acids or lactames having 4 to 25 carbon atoms, such as Polyamide 6 by ring opening polymerization of s-caprolactam.
  • Polyamides can be produced by polycondensation reaction of diamines having 4 to 25 carbon atoms and dicarboxylic acids having 4 to 25 carbon atoms or their salts, such as Polyamide 6.6 by polycondensation reaction of hexamethylenediamine and adipic acid or by reaction of hexamethylenediamine adipate.
  • Copolyamides can be produced by polycondensation reaction of different amines with different carboxylic acids, preferably diamines having 4 to 25 carbon atoms such as hexamethylenediamine, preferably dicarboxylic acids having 4 to 25 carbon atoms such as adipic acid, azelaic acid, dodecandioic acid, preferably amino-carboxylic acids having 4 to 25 carbon atoms such as aminoundecanoic acid, or their salts.
  • carboxylic acids preferably diamines having 4 to 25 carbon atoms such as hexamethylenediamine, preferably dicarboxylic acids having 4 to 25 carbon atoms such as adipic acid, azelaic acid, dodecandioic acid, preferably amino-carboxylic acids having 4 to 25 carbon atoms such as aminoundecanoic acid, or their salts.
  • a melting point of 110 to 120 °C can be reached in mixtures with 20 to 40% PA6.6, 20 to 40% PA6 and 30 to 50% PA12, while the melting points of pure PA6.6, PA6 and PA12 are 250 °C, 215 °C and 176 °C, respectively.
  • Polyolefins are the group of thermoplastic polymers formed by the polymerization of olefins such as propylene, ethylene, isoprenes, and butenes which are commonly obtained from natural carbon sources such as crude oil and gas. Polyolefins contain only carbon and hydrogen atoms attached together with or without side branches. Properties of polyolefins primarily depend on the type of monomers and route of polymerization, resulting in various molar mass and degree of crystallinity. They can be simply modified by introducing various functional groups or mixed with other polymers and fillers to get tailored properties for required applications.
  • olefins such as propylene, ethylene, isoprenes, and butenes which are commonly obtained from natural carbon sources such as crude oil and gas. Polyolefins contain only carbon and hydrogen atoms attached together with or without side branches. Properties of polyolefins primarily depend on the type of monomers and route of polymerization, resulting in various molar mass and degree of crystallinity
  • Polyolefins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), medium-density polyethylene (MDPE), metallocene polyethylene (mPE); cross-linked polyethylenes (xPE); cyclic polyolefins (COC); syndiotactic, isotactic and atactic polypropylene (sPP, iPP, aPP); random and homopolypropylene (rPP, hPP); thermo-elastic polyolefins (TPO), as well as other special type of polyolefins as for example polybutene (PB), polymethylpentene (P4MP), (EP), ethylene vinyl acetate (EVA), and mixtures (blends) and copolymers thereof can be used.
  • polyolefins are characterized by high chemical resistance (unaffected by alkalis and diluted acids) and low solvent solubility (unaffected by most
  • Vistamaxx 8880, AchieveTM Advanced PP6936G2 (available from Exxon Mobile), is particularly preferred.
  • Water soluble or water-dispersible thermoplastic polymers such as polyalkylene glycols, or polyvinyl polymers selected from polyvinyl alcohol, polyvinyl lactams, and copolymers contain functional groups which render the polymer soluble or dispersible in common solvents such as acetone and ethanol and water.
  • polyalkylene glycols polyethylene glycols are preferred, such as polyethylene glycol 200 to polyethylene glycol 20.000 (available from Carl Roth GmbH + Co. KG).
  • polyvinyl alcohols may be produced by saponification of polyvinyl acetate; the properties of the polyvinyl alcohol such as solubility in water are affected by the degree of saponification.
  • polyvinyl lactams polyvinyl pyrrolidone is particularly preferred. Copolymers of polyvinyl pyrrolidone and polyvinyl alcohol may also be used.
  • polyesters are polymers obtained by condensation reactions of difunctional reactants, e.g. diols and diacids, and are characterized by the presence of ester functions (-COO-) along the chain.
  • Linear polyesters can be classified into three classes of aliphatic, partly aromatic and aromatic polymers.
  • Aliphatic polyesters are obtained from aliphatic dicarboxylic acids (or esters) and aliphatic diols.
  • Partly aromatic polyesters are obtained from aromatic dicarboxylic acids (or esters) and aliphatic diols.
  • Aromatic polyesters have all ester functions attached to aromatic rings.
  • copolyesters can be obtained.
  • at least partially multifunctional, i.e. more than difunctional, reactants branched polyesters can be obtained.
  • polyethers are polymers with ether linkage in the “backbone” of the polymer chain.
  • thermoplastic elastomers are multiblock copolymers built up from so-called short crystallizable hard segments and long flexible segments. Owing to such chemical structure, thermoplastic elastomers exhibit an unusual combination of thermoplastic and elastomeric behavior, which might be beneficial.
  • Thermoplastic elastomers based on polystyrene, polyolefines, polyvinyls, polyurethanes, polyester and polyamides are known per se.
  • wax is a collective technological term for a group of organic substances that can generally be described in terms of their physical and technical properties.
  • waxes are characterized by the fact that they are solids with a melting point above 40 °C (usually between 50 °C and 160 °C), a low melt viscosity (below 10 Pa s at 10 °C above the melting point). Waxes melt without decomposing.
  • Waxes can be also divided in natural waxes of fossil origin such as paraffin, montan wax; natural waxes of natural origin such as beeswax, carnauba wax; semi-synthetic waxes (also referred to as chemically modified natural waxes) such as ethylene-bis-stearamide; synthetic waxes such as polyolefin waxes.
  • waxtype materials is intended to include waxes as well as wax-type substances such as ester-type waxes, higher or polyhydric alcohols, higher fatty acids showing wax-like properties, and mixtures thereof.
  • Suitable wax-type materials include: paraffin waxes such as microcrystalline wax; ester-type waxes such as beeswax, candelilla wax, carnauba wax, esters of organic acids such as sulfonic acids or carboxylic acids, preferably of fatty acids having 6 to 40 carbon atoms or esters of aromatic carboxylic acids such as benzoic acid, phthalic acid or hydroxybenzoic acid; amide waxes such as amides of organic acids such as sulfonic acids or carboxylic acids, preferably of fatty acids having 6 to 40 carbon atoms such as oleamide such as Deurex A 27 P (available from Deurex AG), erucamide such as Deurex A 26 P (available from Deurex AG), ethylene-bis-stearamide such as Deurex A 20 K (available from Deurex AG); sulfonamide such as N-ethyltoluene- 4-sulfonamide; polyolefinic waxes such as polyethylene
  • Fischer-Tropsch wax such as VESTOWAX EH 100, VESTOWAX H 2050 MG, VESTOWAX SH 105, Shell GTL Sarawax SX 105, Shell GTL Sarawax SX 80 (available from Evonik Industries AG); higher organic acids such as fatty acids having 10 to 40 carbon atoms; higher or polyhydric alcohols such alcohols having 10 to 40 carbon atoms; polyethylene glycol; and mixtures thereof.
  • the wax-type material is a mixture of different wax-type materials.
  • the binder component b-ii) is a plasticized thermoplastic and/or wax-type material.
  • “Plasticized thermoplastic and/or wax-type material” means the combination of a thermoplastic and/or wax-type material with a plasticizer.
  • a plasticizer is a high-boiling liquid with a boiling point generally above 180 °C which is compatible with the thermoplastic and/or waxtype material to decrease its melt viscosity.
  • plasticizers are polar compounds which means that their chemical structure comprises at least one highly electronegative heteroatom such as an oxygen atom or a nitrogen atom.
  • the plasticized plasticized thermoplastic and/or wax-type material b-ii) comprises the plasticizer in an amount of up to 50 vol.-%, preferably up to 40 vol.-%, more preferably up to 30 vol.-%, most preferably up to 20 vol.-%, in particular up to 15 vol.-%, in particular up to 10 vol.-%, relative to the total volume of b-ii).
  • Suitable plasticizers include liquid esters of aliphatic carboxylic acids such as dimethyl sebacate, di-n-octyl sebacate, dimethyl succinate, dimethyl adipate, dibutyl adipate, dioctyl adipate, dimethyl azelate, dioctyl azelate, di-n-butyl maleic ester, dioctyl maleate, butyl oleate, dimethyl hexanedioate, benzyl laurate, methyl laurate, ethyl myristate, diacetyl triethyl citrate, acetyl tributyl citrate; liquid esters of aromatic carboxylic acids such as dimethyl phthalate, methyl 2- hydroxybenzoate, butyl 4-hydroxybenzoate, butyl benzoate, 2-ethylhexyl benzoate, bis(2-ethylhexyl) terephthalate; al
  • paraffin waxes such as microcrystalline wax are derived from petroleum.
  • microcrystalline wax is obtained as a refined mixture of solids mainly containing saturated aliphatic hydrocarbons produced by de-oiling of certain fractions from the petroleum refining process.
  • the ester-type waxes may be waxes occurring naturally or produced synthetically.
  • naturally occurring ester-type waxes are selected from beeswax, candelilla wax, and carnauba wax; and synthetically produced ester- type waxes are suitably selected from esters of carboxylic acids, preferably of fatty acids having 5 to 34 carbon atoms, more preferably of fatty acids having 10 to 28 carbon atoms, or esters of a hydroxybenzoic acid.
  • the ester- type waxes comprise the esters of a hydroxybenzoic acid such as esters of 4-hydroxybenzoic acid.
  • polyolefin waxes can be produced by thermally decomposing branched high molecular weight polyolefins or directly polymerizing olefins.
  • Suitable polyolefin waxes include, for example, homopolymers of propylene or higher 1 -olefins, copolymers of propylene with ethylene or with higher 1 -olefins or their copolymers with one another.
  • the higher 1 -olefins are preferably linear or branched olefins having 4 to 20, preferably 4 to 6 carbon atoms.
  • olefins may have an aromatic substitution conjugated to the olefinic double bond. Examples of these are 1 -butene, 1 -hexene, 1 -octene or 1 -octadecene, and styrene.
  • the polyolefin waxes may be oxidized. Polyethylene waxes such as Deurex E 06 K (available from Deurex AG) are particularly preferred.
  • amide waxes such as amides of sulfonic acids or carboxylic acids, preferably fatty acids can be produced by condensation reactions of amides such as ethylenediamine and sulfonic acids or carboxylic acids, preferably fatty acids having 5 to 34 carbon atoms, preferably 10 to 28 carbon atoms.
  • Oleamide such as Deurex A 27 P (available from Deurex AG), erucamide such as Deurex A 26 P (available from Deurex AG), ethylene-bis-stearamide such as Deurex A 20 K (available from Deurex AG) are particularly preferred.
  • the first thermoplastic and/or wax-type material and the second thermoplastic and/or wax-type material differ in at least one property which property is selected from solubility in a solvent, degradability induced by heat and/or a reactant, and volatility.
  • the binder component ingredients i.e. the first thermoplastic and/or wax-type material and the second thermoplastic and/or wax-type material differ in their solubility in a solvent and the first thermoplastic and/or wax-type material is less soluble than the second thermoplastic and/or wax-type material
  • debinding is carried out as a solvent debinding step using a suitable solvent.
  • thermoplastic and/or wax-type material (b-i) provides the necessary shape retention of the debound part
  • first thermoplastic and/or wax-type material (b-i) is hereinafter also called “backbone polymer”.
  • the first thermoplastic and/or wax-type material (b-i) is a backbone polymer selected from polyolefins, polyolefinic waxes, polyamides, poly(meth)acrylates, polyesters, polyethers, and mixtures thereof.
  • Suitable polyolefins include polyethylenes, polypropylenes, polyolefinic copolymers with different monomers, polyolefinic copolymers with non-olefinic monomers (such as ethylene vinyl acetate or ethylene n-butyl acrylate copolymer), modified polyolefins, polyolefinic waxes, and mixtures thereof.
  • suitable polymer that are commercially available are those mentioned above.
  • the backbone polymers comprise a DSC melt peak temperature TP below 160 °C, preferably below 150 °C, more preferably below 140 °C, most preferably below 130 °C, in particular below 120 °C, in particular below 110 °C, in particular below 100 °C, in particular below 90 °C.
  • the backbone polymers comprise a melt viscosity below 1500 Pa s, preferably below 1300 Pa s, more preferably below 1000 Pa s, most preferably below 800 Pa s, in particular below 600 Pa s, in particular below 500 Pa s, in particular below 400 Pa s, in particular below 300 Pa s, in particular below 200 Pa s, in particular below 100 Pa s, according to ISO 1133 with 2.16 kg at 160 °C.
  • the backbone polymers comprise a melt viscosity below 1500 Pa s, preferably below 1300 Pa s, more preferably below 1000 Pa s, most preferably below 800 Pa s, in particular below 600 Pa s, in particular below 500 Pa s, in particular below 400 Pa s, in particular below 300 Pa s, in particular below 200 Pa s, in particular below 100 Pa s, according to ISO 1133 with 2.16 kg at 190 °C.
  • the backbone polymers comprise a melt volume-flow rate of at least 5 cm 3 /10 min, preferably at least 10 cm 3 /10 min, more preferably at least 20 cm 3 /10 min, most preferably at least 30 cm 3 /10 min, in particular at least
  • cm 3 /10 min in particular at least 50 cm 3 /10 min, in particular at least 60 cm 3 /10 min, in particular at least 70 cm 3 /10 min, in particular at least 80 cm 3 /10 min, in particular at least 90 cm 3 /10 min, in particular at least 100 cm 3 /10 min, in particular at least 110 cm 3 /10 min, in particular at least 120 cm 3 /10 min, in particular at least 130 cm 3 /10 min, in particular at least 140 cm 3 /10 min, in particular at least 150 cm 3 /10 min, in particular at least 160 cm 3 /10 min, in particular at least 170 cm 3 /10 min, in particular at least 180 cm 3 /10 min, in particular at least 190 cm 3 /10 min, in particular at least
  • the backbone polymers comprise a melt volume-flow rate of at least
  • cm 3 /10 min in particular at least 50 cm 3 /10 min, in particular at least 60 cm 3 /10 min, in particular at least 70 cm 3 /10 min, in particular at least 80 cm 3 /10 min, in particular at least 90 cm 3 /10 min, in particular at least 100 cm 3 /10 min, in particular at least 110 cm 3 /10 min, in particular at least 120 cm 3 /10 min, in particular at least 130 cm 3 /10 min, in particular at least 140 cm 3 /10 min, in particular at least 150 cm 3 /10 min, in particular at least 160 cm 3 /10 min, in particular at least 170 cm 3 /10 min, in particular at least
  • b-ii) is selected from polar waxes, or a plasticized thermoplastic and/or wax-type material containing a polar plasticizer.
  • polar wax means a wax whose chemical structure is formed essentially from, or even constituted by, carbon and hydrogen atoms, and comprising at least one highly electronegative heteroatom such as an oxygen, nitrogen or sulfur atom.
  • the polar wax is selected from polyolefinic waxes, ester-type waxes, amide waxes, higher organic acids, higher or polyhydric alcohols, polyethylene glycol, and mixtures thereof.
  • the ester-type waxes include esters of organic acids.
  • the amide waxes include amides of organic acids such as sulfonic acids or carboxylic acids. Representatives of suitable waxes that are commercially available are those mentioned above.
  • the polar wax has a drop point in the range of from 20 to 160 °C, more preferably in the range of from 30 to 150 °C, still more preferred in the range of from 35 to 140 °C, in particular in the range of from 40 to 130 °C, in particular in the range of from 40 to 120 °C, in particular in the range of from 40 to 110 °C, in particular in the range of from 40 to 100 °C, and most preferred in the range of from 40 to 90 °C, according to DIN ISO 2176.
  • the polar wax comprises a melt viscosity below 30 Pa s, preferably below 20 Pa s, more preferably below 10 Pa s, most preferably below 5 Pa s, in particular below 3 Pa s, in particular below 1 Pa s, in particular below 700 mPa s, in particular below 300 Pa s, in particular below WO mPa s, in particular below 50 mPa s, according to DIN EN ISO 3104 at 160 °C.
  • the polar wax comprises a melt viscosity below 40 Pa s, preferably below 30 Pa s, more preferably below 20 Pa s, most preferably below 10 Pa s, in particular below 5 Pa s, in particular below 3 Pa s, in particular below 1 Pa s, in particular below 700 mPa s, in particular below 300 Pa s, in particular below 100 mPa s, according to DIN EN ISO 3104 at 120 °C.
  • b-ii) is a wax-type material selected from aromatic esters and aromatic sulfonamides, or a plasticized thermoplastic and/or wax-type material containing a plasticizer selected from aromatic esters and aromatic sulfonamides.
  • the alcohol of the aromatic ester may be an alcohol having 1 to 40 carbon atoms.
  • the aromatic sulfonamides may carry at least one organic moiety having 1 to 40 carbon atoms at the amide nitrogen atom.
  • (b-i) is a polyamide, preferably a copolyamide; and (b-ii) is a wax-type material selected from an ester of an organic acid and/or an amide of an organic acid, preferably aromatic esters and aromatic sulfonamides, or a plasticized thermoplastic and/or wax-type material containing a plasticizer selected from aromatic esters and aromatic sulfonamides.
  • the polyamide preferably meets the limitations with regard to DSC melt peak temperature TP, melt viscosity and melt volume-flow rate defined above for the “backbone polymer”.
  • (b-i) is a polyester, preferably polycaprolactone, or a copolyester, preferably poly (hydroxybutyrat-co-hydroxyvalerat), and/or a polyester-based thermoplastic elastomer; and (b-ii) is an ester-type wax, an ester of an organic acid, an amide wax, a higher organic acid, and/or a higher or polyhydric alcohol.
  • the polyester or the copolyester preferably meets the limitations with regard to DSC melt peak temperature TP, melt viscosity and melt volume-flow rate defined above for the “backbone polymer”.
  • (b-i) is a polyolefin such as polyethylene; polypropylene; a polyolefinic copolymer of monomers such as ethene, propene, butene, hexane; a polyolefinic copolymer with non-olefinic monomers such as an ethylene n-butyl acrylate copolymer and/or an ethylene vinyl acetate copolymer; and/or a polyolefin wax; and/or a modified polyolefin; and (b-ii) is an ester-type wax, an ester of an organic acid, an amide wax, a higher organic acid, and/or a higher or polyhydric alcohol.
  • a polyolefin such as polyethylene; polypropylene; a polyolefinic copolymer of monomers such as ethene, propene, butene, hexane; a polyolefinic copolymer with non-olefini
  • the polyolefin preferably meets the limitations with regard to DSC melt peak temperature TP, melt viscosity and melt volume-flow rate defined above for the “backbone polymer”.
  • the first thermoplastic and/or wax-type material is a polyethylene wax and the second thermoplastic and/or wax-type material is an amide wax.
  • the combination of a polyethylene wax and an amide wax lends itself to solvent debinding using ethanol or acetone as a solvent.
  • the first thermoplastic and/or wax-type material is a polyamide and the second thermoplastic and/or wax-type material is a wax, preferably an ester-type wax.
  • the combination of a polyamide and a wax lends itself to solvent debinding using acetone as a solvent.
  • the first thermoplastic and/or wax-type material is a polypropylene wax and the second thermoplastic and/or wax-type material is an amide wax.
  • the combination of a polypropylene wax and an amide wax lends itself to solvent debinding using ethanol as a solvent.
  • the first thermoplastic and/or wax-type material is a polyethylene wax and the second thermoplastic and/or wax-type material is a water soluble or water-dispersible thermoplastic polymer such as polyethylene glycol.
  • a polyethylene wax and a water soluble or water- dispersible thermoplastic polymer lends itself to solvent debinding using water or an aqueous solution as a solvent.
  • thermoplastic and/or wax-type material examples include thermoplastic and/or wax-type material, second thermoplastic and/or wax-type material and solvents that have proven useful in implementing the invention; various further combinations are possible and the table shall not be limiting:
  • the first thermoplastic and/or wax-type material and the second thermoplastic and/or wax-type material, respectively, may be comprised of a single material or of a mixture of materials which meet the requirements of a difference in at least one property as defined above.
  • the binder component may comprise a dispersant.
  • One material constituting, for example, the second thermoplastic and/or wax-type material may act as a dispersant. Otherwise, an extraneous dispersant may additionally be incorporated.
  • the dispersant acts as an adhesion promotor and/or compatibilizer between the binder components, i.e. the first thermoplastic and/or wax-type material and/or second thermoplastic and/or wax-type material; and/or between the non-organic particles and the binder component.
  • the dispersant is selected from fatty acids having 10 to 24 carbon atoms such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, or oleic acid, preferably stearic acid.
  • fatty acids having 10 to 24 carbon atoms such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, or oleic acid, preferably stearic acid.
  • the extraneous dispersant is selected from metal salts of fatty acids.
  • the metal may be selected from alkali metals, alkaline earth metals or transition metals such as lithium, sodium, potassium, magnesium, calcium, strontium, barium, and zinc.
  • the fatty acid may be selected from the fatty acids having 5 to 34 carbon atoms, preferably 10 to 28 carbon atoms as described above.
  • Preferred metal salts of fatty acids are selected from sodium stearate, magnesium stearate, zinc stearate or magnesium oleate.
  • the binder component Due to the viscosity of the binder component in the abovementioned ranges, the latter becomes, in the molten state, uniformly and homogeneously distributed between the sinterable material powder and joins the individual sinterable material powder or the individual compound particles.
  • a thinning agent or thickening agent serves to increase the viscosity of the binder component when molten. This enhanced viscosity prevents the sag of the sinterable material powder and facilitates uniform flow of the particles and imparts resistance to segregation and sedimentation.
  • the viscosity of the binder component is adjusted, i.e. reduced or increased, by means of the thickening or thinning agent.
  • Thinning agents are employed to lower the viscosity of the overall binder component.
  • Thickening agents are employed to increase the viscosity of the overall binder component.
  • the thinning agent can act as a plasticizer to allow control of the rheological properties and the fluidity of the first thermoplastic and/or wax-type material or the second thermoplastic and/or wax-type material.
  • the thickening or thinning agent is selected from waxes and/or thermoplastic polymers such as polyolefins and polyolefin waxes, polyamides and amide waxes, paraffin waxes, ester-type waxes; vinyl esters such as ethylene vinyl acetate; abietates; adipates; alkyl sulfonates; amines and amides such as formamide, hydroxylalkylformamide, amine, diamine; azelates; benzoates; citrates; chlorinated paraffins; ether-ester plasticizers; glutarates; hydrocarbon oils; isobutyrates; maleates; oleates; phosphates; phthalates; sulfonamides; oily liquids such as peanut oil, fish oil, castor oil; and mixtures thereof.
  • waxes and/or thermoplastic polymers such as polyolefins and polyolefin waxes, polyamides and amide waxes
  • polyethylene wax Deurex E 09 K having a viscosity of ⁇ 40 mPa s at 140 °C can be used as a thinning agent, while Deurex E 25 having a viscosity of 4000 mPa s at 140 °C or even higher molecular weight polyolefinic compounds can be used as thickening agent.
  • the thickening or thinning agent and/or dispersant may be present in an amount of 0 to 15% by volume, preferably 0.01 to 10% by volume, more preferably 0.02 to 8% by volume, most preferably 0.5 to 6% by volume, based on the total volume of the binder component.
  • the binder component exhibits a viscosity, as determined at a temperature of 130 °C; and at a shear rate of 1 s -1 , of below 6 Pa s, preferably below 5 Pa s, more preferably below 4 Pa s, most preferably below 3 Pa s, in particular below 2 Pa s, in particular below 1 Pa s, in particular below 700 mPa s, in particular below 400 mPa s, in particular below 200 mPa s.
  • the determination of the viscosity is carried out in accordance with EN ISO 3219:1994.
  • the binder component exhibits a viscosity, as determined at a temperature of 110 °C; and at a shear rate of 1 s -1 , of below 10 Pa s, preferably below 8 Pa s, preferably below 6 Pa s, more preferably below 5 Pa s, most preferably below 4 Pa s, in particular below 3 Pa s, in particular below 2 Pa s, in particular below 1 Pa s, in particular below 600 mPa s, in particular below 300 mPa s.
  • the determination of the viscosity is carried out in accordance with EN ISO 3219:1994.
  • the binder component exhibits a viscosity, as determined at a temperature of 100 °C; and at a shear rate of 1 s -1 , of below 10 Pa s, preferably below 8 Pa s, more preferably below 6 Pa s, most preferably below 5 Pa s, in particular below 4 Pa s, in particular below 3 Pa s, in particular below 2 Pa s, in particular below 1 Pa s, in particular below 500 mPa s.
  • the determination of the viscosity is carried out in accordance with EN ISO 3219:1994.
  • the feedstock compound exhibits a viscosity, as determined at a temperature of 130 °C, and a shear rate of 1 s -1 , of below 600 Pa s, preferably below 400 Pa s, more preferably below 350 Pa s, most preferably below 250 Pa s, in particular below 150 Pa s, in particular below 50 Pa s, in particular below 10 Pa s.
  • the determination of the viscosity is carried out in accordance with EN ISO 3219:1994.
  • the feedstock compound exhibits a viscosity, as determined at a temperature of 110 °C, and a shear rate of 1 s -1 , of below 800 Pa s, preferably below 550 Pa s, more preferably below 450 Pa s, most preferably below 350 Pa s, in particular below 200 Pa s, in particular below 100 Pa s, in particular below 60 Pa s.
  • the determination of the viscosity is carried out in accordance with EN ISO 3219:1994.
  • the feedstock compound exhibits a viscosity, as determined at a temperature of 100 °C, and a shear rate of 1 s -1 , of below 1000 Pa s, preferably below 850 Pa s, more preferably below 700 Pa s, most preferably below 550 Pa s, in particular below 400 Pa s, in particular below 250 Pa s, in particular below 100 Pa s.
  • the determination of the viscosity is carried out in accordance with EN ISO 3219:1994.
  • the process according to the invention allows for the manufacture of sintered elements having a non-uniform, controlled porous architecture not obtainable by conventional powder metallurgical processes.
  • the method of the invention also enables control of properties at different locations within the element, to produce for example a desired gradient of porosity through the product, or otherwise to optimise the product design for requirements of different applications.
  • the step of selectively densifying the first and the at least one further layer of compound particles is carried out so that the element has a variable porosity, wherein
  • the porosity function along a gradient direction has at least one point of inflection.
  • the invention also relates to a sintered element integrally formed from a sinterable material, the element having non-uniform porosity, wherein
  • the porosity function along a gradient direction has at least one point of inflection.
  • the porosity varies along a first gradient direction, said first gradient direction is oriented in the direction of largest increase of porosity, characterized in that
  • the porosity additionally varies along at least a second direction, said second direction is oriented perpendicular to the first gradient direction;
  • the porosity function along the first gradient direction has at least one point of inflection.
  • the porosity of the element is assumed to be a scalar-valued differentiable function of the specific coordinates of the element. Each point in the bulk volume of the element is assigned to a value of porosity. Even if the porosity of the element varies abruptly from one point to a neighbouring point, it is still assumed that the function of porosity is differentiable.
  • the gradient of the porosity function of the element is a vector field.
  • Each specific coordinate of the element is assigned to a gradient vector.
  • the orientation of this vector defines the direction of largest increase of porosity.
  • the absolute value of the gradient vector shows the rate of largest increase of the porosity. Therefore, if the porosity of the element is homogeneous, the gradient vector field is zero.
  • the sintered element of the present invention shows a porosity that varies along a first gradient direction. This means that at least in one direction within the element the porosity varies. Only such a direction is designated as gradient direction. In other directions, the porosity may be homogeneous.
  • the porosity of the element shows at least one of the following properties: There exists a second gradient direction that is different from the first gradient direction such that the porosity additionally varies along this second gradient direction. Therefore, there is an angle between the second and the first gradient directions meaning that both gradient directions are not parallel to each other, so that the angle is not 0° or 180°.
  • the porosity function along the first gradient direction has at least one point of inflection. If the porosity function is considered only with respect to the first gradient direction, the variable of the porosity function is onedimensional. This means that the curvature of the function changes its sign, meaning that the second derivative of the function becomes zero and changes its sign.
  • the porosity repeatedly varies along the first gradient direction.
  • This embodiment includes the situation that a recurring structure of high or low porosity is embedded within a structure having essentially a homogeneous porosity.
  • the porosity function is strongly rising or falling, almost defining a step function.
  • the porosity function is differentiable. For example, a grid-like structure may be formed having a porosity being different from the remaining structure of the element.
  • At least two gradient vectors of the three-dimensional porosity function at two different positions of the element include an angle not equal to 0° or 180°.
  • the gradient vector field of the three-dimensional porosity function of the element comprises a plurality of gradient vectors showing in different directions.
  • the three dimensional porosity function may be formed in a defined manner and not randomly. Therefore, a broad range of the porosity within the element may be accomplished.
  • the three-dimensional porosity function may suitably be designed for the desired application of the element.
  • the sintered element having non-uniform porosity is useful as biomedical implant, filtration device, or battery separator.
  • the sintered element has at least one first region having a porosity of less than 5%, preferably less than 4%, more preferably less than 3%, most preferably less than 2%, and at least one second region having a porosity of more than 5%, preferably more than 10%, more preferably more than 15%, most preferably more than 20%, in particular more than 25%, in particular more than 30%, wherein the porosity in the second region is interconnected.
  • the porosity may be determined by optical methods or computer tomography.
  • the process and the element of the present invention that an isotropic microstructure and a part without tension is obtained.
  • the microstructure On the mesoscale, the microstructure is characterized by an equiaxed, uniform morphology and no layer-wise structures in the microstructure are obtained.
  • the grain structure does not show a preferential direction.
  • the microstructure for austenitic steels suchs as stainless steel 316L is characterised by twins and equiaxed grain structure, with an average grain size ranging from 1 pm to 100 pm, preferable from 3 pm to 80 pm, more preferably from 5 pm to 60 pm, most preferably from 8 pm to 40 pm, in particular from 10 pm to 30 pm.
  • Existing closed pores in the microstructure usually are very small and rounded with an average diameter of 0.5 pm to 5 pm, and are located preferentially within the grains and not on the grain boundaries.
  • the microstructure for titanium alloys with a (a+!3>) structure such as Ti6AI4 is characterised by lamellar (a+!3>) structure with a !3>-grain size of approximately 150 to 250 pm produced at sintering temperatures of approximately 1100 to 1400 °C with a sintering duration of approximately 2 to 5 h.
  • Fig. 1 is a view of a flow diagram of a process for the additive manufacture of a component
  • Fig. 2 is a schematic view of an apparatus for the additive manufacture of a shaped part, from composite particles, and
  • Fig. 3 shows the application of electromagnetic radiation to the shaped part layer.
  • Fig. 4A depicts the cubic testing specimen (green part) obtained with a laser output of 8 W.
  • Fig. 4B depicts the cubic testing specimen (green part) obtained with a laser output of 12 W.
  • Fig. 4C depicts the cubic testing specimen (green part) obtained with a laser output of 16 W.
  • Fig. 4D depicts the cubic testing specimen (green part) obtained with a laser output of 20 W.
  • Fig. 5A depicts the cubic testing specimen (sintered part) obtained with a laser output of 8 W.
  • Fig. 5B depicts the cubic testing specimen (sintered part) obtained with a laser output of 12 W.
  • Fig. 5C depicts the cubic testing specimen (sintered part) obtained with a laser output of 16 W.
  • Fig. 5D depicts the cubic testing specimen (sintered part) obtained with a laser output of 20 W.
  • Fig. 6 shows a micro graph section of a cubic test specimen with varying porosity.
  • Fig. 7 shows a typical microstructure of stainless steel 316L after sintering.
  • Fig. 8 shows a filter unit with porous hexagons made of titanium Ti6AI4V.
  • Fig. 9A and Fig. 9B show a hip cup for medical application.
  • Fig. 10A and Fig. 10B show another filter unit.
  • Fig. 11 shows a sphere consisting of different shells with varying porosities.
  • Fig. 12 shows a highly porous cubic testing specimen (sintered element).
  • Fig. 13A shows a cubic testing specimen (sintered element) with limited porosity.
  • Fig. 13B shows a magnified excerpt of Fig. 13A.
  • the compound particles 2 are provided by means of an apparatus 8 for the additive manufacture of a shaped part 9.
  • the apparatus 8 has a base body 10 which has a flat surface 11 running in a horizontal x direction and in a horizontal y direction.
  • a reservoir recess 12 is formed in the base body 10 and together with a plate 13 which can be moved in a vertical z direction gives a reservoir space 14 for the compound particles 2.
  • the reservoir space 14 is open in the direction of the surface 1 1 .
  • the compound particles 2 are provided in the reservoir space 14.
  • the pulverulent composite particles 2 are also referred to as feedstock powder.
  • the x, y and z directions form a Cartesian coordinate system.
  • the construction recess 15 extends in the x direction and the y direction and defines a construction field.
  • a construction base body 16 which can be moved in the z direction is arranged in the construction recess 15.
  • the construction base body 16 is preferably configured as construction platform.
  • the construction recess 15 and the construction base body 16 define a construction space 17 which is open in the direction of the surface 11.
  • compound particles 2 are provided in a process step S1 .
  • the compound particles 2 each comprise a sinterable material powder 3 which is dispersed in a binder 4.
  • a first layer L1 of compound particles 2 is applied to the construction base body 16 by means of an application device 18.
  • the application device 18 is arranged above the surface 11 in the z direction and conveys composite particles 2 provided into the construction space 17.
  • the application device 18 has, for example, a doctor blade 19 which extends in the y direction and can be moved in the x direction along the surface 11 .
  • the plate 13 is firstly moved in the z direction so that a desired amount of the compound particles 2 is present above the surface 11 .
  • the doctor blade 19 is subsequently moved in the x direction so that the doctor blade 19 carries along the compound particles 2 located above the surface 11 and conveys them into the construction space 17 and distributes them uniformly there.
  • the movement of the plate 13, the doctor blade 19 and the construction base body 16 is controlled by means of a control device 20.
  • the first layer L1 is applied in a thickness D which is determined by the distance of the construction base body 16 from the surface 11 .
  • the binder 4 of the compound particles 2 in the first layer L1 is selectively melted, so that a first shaped part layer F1 is formed.
  • the first layer L1 is closest to the surface 11 in this process step and forms a construction region.
  • the construction region is heated to a temperature TB by means of heating elements 23.
  • the temperature TB is lower than the glass transition temperature in the case of an amorphous structure of the binder 4 or lower than the highest crystallite melting temperature of the binder 4 in the case of a partially crystalline or crystalline structure of the binder 4.
  • the selective melting is carried out by means of electromagnetic radiation R, in particular by mean of laser radiation.
  • the electromagnetic radiation R is generated by means of an electromagnetic radiation source 21 and directed by means of a mirror device 22 onto the construction field.
  • the mirror device 22 allows the electromagnetic radiation R striking the construction field to be moved in the x direction and the y direction.
  • the electromagnetic radiation R is moved in the x direction and/or the y direction according to the shaped part 9 to be produced.
  • the energy input by the electromagnetic radiation is a function of the x-y-coordinate within the first shaped part layer F1 . At least in portions of the first shaped part layer, the energy input by the electromagnetic radiation has been adjusted to bind the component particles to each other without fully melting them. In the following, it is described how the energy input is controlled as a fuction of the x-y-coordinate where the laser beam is applied to the layer:
  • the laser beam scans the plain of the shaped part layer F1 formed in x-y- direction. For example, as shown in Fig. 2, the laser beam is moved with an exposure speed v s in x direction. At the end, the laser beam is moved in y direction by a defined hatch distance h s . Then, the laser beam is moved in opposite x direction with the defined exposure speed v s . During movement of the laser beam, a defined laser power is input to the layer.
  • the mean energy density e m results from the superposition of the energy input of single tracks exposed side by side. It is calculated as follows:
  • the hatch distance h s is smaller than the sintering width w s .
  • the sintering width w s is defined as the diameter of the laser spot, i.e. around 250 pm in case for EOS Formiga P110.
  • the hatch distance h s can also be larger than sintering width w s .
  • the energy input may be varied at a resolution of the cross-section of the laser beam as it hits the shaped part layer F1 .
  • the laser input may be varied by varying the laser power PL, the exposure speed v s and/or the hatch distance h s .
  • the hatch distance h s is constant while scanning the shaped part layer F1 . Therefore, the energy input is adjusted by varying the laser power PL and/or the exposure speed v s as a function of the x-y-coordinate at which the laser beam hits the shaped part layer F1. Varying laser power PL will also result in varying beam penetration depth 6 that also results in varying sintering depth.
  • the electromagnetic radiation R melts the binder 4, so that the binder 4 spreads between the sinterable material powder particles 3 and on solidification forms the solid first shaped part layer F1 .
  • a further layer L2 of compound particles 2 is applied in the above-described manner to the previously applied layer L1 .
  • the plate 13 is moved in the z direction so that a desired amount of compound particles 2 is present above the surface 11 and can be transported by means of the application device 18 to the construction space 17.
  • the construction base body 16 is lowered by the thickness D in the z direction, so that the compound particles 2 can be distributed uniformly and homogeneously on top of the previously applied layer L1 .
  • a process step S5 the binder 4 of the compound particles 2 in the layer L2 are selectively melted in the above-described manner by means of the electromagnetic radiation R, so that a further shaped part layer F2 is produced.
  • the energy input is again varied at a resolution of the cross-section of the laser beam as it hits the shaped part layer F2.
  • the molten binder 4 spreads between the sinterable material powder particles 3 and holds these together after solidification of the binder 4.
  • the process steps S4 and S5 are repeated until the shaped part 9 has been additively manufactured in the desired way.
  • a layer or a plurality of layers of compound particles 2 firstly to be applied before the binder 4 is melted by means of the electromagnetic radiation R and a solid first shaped part layer F1 is formed.
  • the shaped part 9 is in this case arranged on at least one layer which has not been melted.
  • the shaped part 9 is taken out from the compound particles 2 which have not been melted and out of the construction space 17 and cleaned.
  • the shaped part 9 is also referred to as green body.
  • a process step S7 the shaped part 9 is subjected to chemical binder removal.
  • the shaped part 9 is dipped into a vessel filled with the solvent.
  • the shaped part 9 is, after the chemical binder removal, subjected to thermal binder removal and subsequently sintered in a process step S9.
  • the thermal binder removal and the sintering are carried out by means of a heating device under inert gas atmosphere or in a reducing atmosphere or in the high vacuum.
  • the shaped part 9 is subsequently brought, in the process step S9, to a second temperature T2 which is higher than the first temperature T1
  • the variation of the energy input by the laser beam results in a variation of the porosity of the final element 1 .
  • the sintered specimen is ground on a grinding and polishing machine, e.g. a LaboPol-25 from Struers.
  • the grinding process may be executed starting with grid size of P180 and subsequently fine grid sizes such as P360, P600 and P1200.
  • the polishing step is executed with with a polycrystalline diamond suspension with a particle size of 3 pm followed by an aluminum oxide suspension with a particle size of 0.04 pm.
  • the micrographs are created by a digital microscope Dino-Lite AM7915MZT.
  • the microstructure is obtained by etching and taking a micrograph.
  • Binder component 1-B was produced according to table 1.
  • Feedstock compound 1-F of binder component 1 -B was produced according to table 2.
  • Binder component 1 -B Binder component 1 -B; vol.-% relative the total volume of the binder component (b).
  • copolyamide having a DSC melting range of 115 to 125 °C, available from EMS-CHEMIE HOLDING AG
  • Table 2 Feedstock compound 1 -F; vol.-% relative the total volume of the particulate feedstock compound.
  • Cubic testing specimen were produced by a laser additive manufacturing process using a Formiga P110 (available from EOS GmbH).
  • the feedstock compound 1 -F of table 2 was used as starting material.
  • the hatch distance was 0.13 mm at a laser speed of 4450 mm/s and the powder bed surface temperature was 50 °C.
  • the laser output was varied (8 W, 12 W, 16 W, 20 W) resulting in a different energy input: A laser output of 8 W resulted in an energy input of 20.5 mJ/mm 2 ; a laser output of 12 W resulted in an energy input of 30.8 mJ/mm 2 ; a laser output of 16 W resulted in an energy input of 41 .0 mJ/mm 2 ; and a laser output of 20 W resulted in an energy input of 51 .3 mJ/mm 2 .
  • feedstock compound 1-F was used as starting material at a laser output of 8 W, a laser speed of 3000 mm/s and a hatch spacing of 0.13 mm resulting in an energy input of 20.5 mJ/mm 2
  • feedstock compound 1-F was used as starting material at a laser output of 12 W, a laser speed of 3000 mm/s and a hatch spacing of 0.13 mm resulting in an energy input of 30.8 mJ/mm 2
  • feedstock compound 1-F was used as starting material at a laser output of 16 W, a laser speed of 3000 mm/s and a hatch spacing of 0.13 mm resulting in an energy input of 41 .0 mJ/mm 2
  • feedstock compound 1-F was used as starting material at a laser output of 20 W, a laser speed of 3000 mm/s and a hatch spacing of 0.13 mm resulting in an energy input of 51 .3 mJ/mm 2
  • the cubic testing specimen were examined for their density.
  • Fig. 4A to Fig. 4D show the resulting cubic testing specimens at varying laser output.
  • the use of feedstock compound 1-F applying a laser output of 8 W resulted in a manual density of 74.6% (Fig. 4A).
  • Applying a laser output of 12 W, and thus a higher energy input resulted in a manual density of 85.9% (Fig. 4B).
  • Said cubic test specimens were then subjected to a solvent debinding step and a sintering step.
  • the green parts were dipped into acetone at a temperature of 45 °C for 16 h.
  • Sintering was carried out in a cycle with a heating and cooling rate of 5 K/min, holding times of 2 h at 380 °C, of 1 h at 600 °C, of 30 min at 1100 °C and of 2 h at a final sintering temperature of 1380 °C in a hydrogen atmosphere.
  • Fig. 5A to Fig. 5D show the resulting cubic testing specimens after sintering at varying laser output.
  • the use of feedstock compound 1-F applying a laser output of 8 W resulted in a manual density of 86.5% (Fig. 5A).
  • Applying a laser output of 12 W, and thus a higher energy input resulted in a manual density of 91.6% (Fig. 5B).
  • Applying a laser output of 16 W, and thus a higher energy input, resulted in a manual density of 93.5% (Fig. 5C).
  • Applying a laser output of 20 W, and thus a higher energy input resulted in a manual density of 94.7% (Fig. 5D).
  • Fig. 6 shows a micro graph section of a cubic test specimen with varying porosity.
  • the hatch distance was 0.13 mm at a laser speed of 3500 mm/s and a laser output of 6 W at a powder bed surface temperature of 50 °C.
  • the hatch distance was 0.13 mm at a laser speed of 4450 mm/s and a laser output of 15 W at a powder bed surface temperature of 50 °C. After debinding and sintering, a sintered metal part with gradient porosity was obtained.
  • Fig. 7 shows a typical microstructure of stainless steel 316L after sintering. On the mesoscale, the microstructure is characterized by an equiaxed, uniform morphology and no layer-wise structures in the microstructure are obtained.
  • FIG. 8 shows a filter unit 8.1 made of titanium Ti6AI4V.
  • the filter unit 8.1 exhibits porous regions 8.2 which have hexagonal shapes.
  • the massive webs 8.3 connecting the porous regions 8.2 which have hexagonal regions act as supporting structures.
  • Fig. 9A and Fig. 9B show a hip cup 9.1 for medical application.
  • the hip cup 9.1 has a generally curved structure and is comprised of three layers 9.2, 9.3, 9.4 of different porosity.
  • the inner layer 9.2 of the hip cup 9.1 is less porous than the intermediate layer 9.3 of the hip cup 9.1.
  • the outer layer 9.4 of the hip cup 9.1 has the highest porosity.
  • a boundary face 9.5 delimits the inner layer 9.2 from the intermediate layer 9.3.
  • This boundary face 9.5 is curved, i.e. has an essentially spherical shape.
  • Another boundary face 9.6 delimits the intermediate layer 9.3 from the outer layer 9.4.
  • This boundary face 9.6 is also curved, i.e. has an essentially spherical shape.
  • Fig. 10A and Fig. 10B show another filter unit 10.1 having an essentially hollow cylindrical shape.
  • the upper end 10.2 and the lower end 10.3 of the filter unit 10.1 are massive.
  • the inner layer 10.4 of the filter unit 10.1 is massive and perforated.
  • the intermediate layer 10.5 of the filter unit 10.1 has the highest porosity.
  • the outer layer 10.6 of the filter unit 10.1 has a lower porosity than the intermediate layer 10.5.
  • a boundary face 10.7 delimits the inner layer 10.4 from the intermediate layer 10.5.
  • This boundary face 10.7 is curved, i.e. has an essentially cylindrical shape.
  • Another boundary face 10.8 delimits the intermediate layer 10.5 from the outer layer 10.6.
  • This boundary face 10.8 is also curved, i.e. has an essentially cylindrical shape.
  • Fig. 11 shows a sphere consisting of shells with varying porosities.
  • Cubic testing specimen were produced by a laser additive manufacturing process using a Formiga P110 (available from EOS GmbH).
  • a first test specimen (green part) was manufactured using a hatch distance of 0.13 mm at a laser speed of 3000 mm/s, a laser diameter of 250 pm and a laser output of 11 W.
  • the powder bed surface temperature was 40 °C.
  • the obtained green part was sintered under a hydrogen atmosphere at a temperature of 1100 °C.
  • a second test specimen (green part) was manufactured using a hatch distance of 0.13 mm at a laser speed of 3000 mm/s, a laser diameter of 250 pm and a laser output of 25 W.
  • the powder bed surface temperature was 50 °C.
  • the obtained green part was sintered under a hydrogen atmosphere at a temperature of 1380 °C.
  • Fig. 12 shows the first cubic testing specimen (sintered element) as a porous structure with interconnected pores in dark color. Light areas represent the metal.
  • Fig. 13A shows the second cubic testing specimen (sintered element).
  • Fig. 13B shows a magnified excerpt of Fig. 13A. Only very few isolated pores are visible.

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Abstract

L'invention concerne un procédé de fabrication d'un élément ayant des parties poreuses, comprenant les étapes consistant à (a) fournir une partie verte composée d'une poudre de matériau frittable et d'un liant d'une manière couche par couche, en fournissant des particules de composé contenant une poudre de matériau frittable et un liant; fournir une première couche de particules composites; densifier sélectivement la première couche de particules de composé pour lier les particules de composé l'une à l'autre d'une manière prédéfinie de manière à produire une première couche de partie façonnée, éventuellement, fournir au moins une autre couche de particules de composé sur la première couche de partie façonnée; densifier sélectivement l'autre couche de particules de composé pour lier les particules de composé l'une à l'autre d'une manière prédéfinie afin de produire au moins une autre couche de partie façonnée, la première couche de partie façonnée et les autres couches de partie façonnées formant une partie verte, au moins dans des parties de la première et/ou de la ou des autres couches, les particules de composé étant liées l'une à l'autre sans densification totale et des espaces restants entre les particules de composé jointes; et (b) délianter la partie verte et fritter la partie déliantée pour obtenir l'élément ayant des parties poreuses. Le procédé permet la fabrication d'un élément fritté ayant des parties poreuses dans lesquelles la porosité varie d'une manière définie.
PCT/EP2022/085892 2021-12-14 2022-12-14 Procédé de fabrication d'un élément ayant des parties poreuses et élément fritté ayant une porosité non uniforme WO2023111037A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1382408A2 (fr) * 2002-07-15 2004-01-21 Hitachi Metals, Ltd. Métal poreux, filtre construit avec ce métal et son procédé de fabrication
DE102005027216A1 (de) 2005-06-13 2006-12-21 Basf Ag Vorrichtung und Verfahren zum kontinuierlichen katalytischen Entbindern mit verbesserten Strömungsbedingungen
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