METHOD FOR ADDITIVELY MANUFACTURING A COMPONENT, AND AN ADDITIVELY MANUFACTURED COMPONENT

Abstract

A process for the additive manufacture of a metallic and/or vitreous and/or ceramic component, a mixture of substrate particles and an at least two-phase binder is firstly provided. The mixture is preferably provided as composite particles, so that the substrate particles adhere to one another by the at least two-phase binder. The mixture is selectively melted layerwise by means of electromagnetic radiation so that a shaped part is additively produced. The shaped part is taken out from the mixture which has not been melted and the at least two-phase binder is subsequently removed, preferably successively. The process produces a microporous shaped part which after sintering leads to a component having a desired density and a desired mechanical and/or thermal stability.

Claims

1. A process for the additive manufacture of a component, the process comprising the steps: providing substrate particles and a binder, wherein the substrate particles comprise one or more of metallic substrate particles, vitreous substrate particles and ceramic substrate particles, wherein the binder comprises a thermoplastic polymer and at least one additives; producing a shaped part, wherein a layer of substrate particles and binder being produced and the binder being selectively melted by electromagnetic radiation to produce a shaped part layer, at least one further layer of substrate particles and binder being produced and the binder being selectively melted by the electromagnetic radiation to produce at least one further shaped part layers; taking the shaped part out from the layers produced; removing the binder from the shaped parts; and sintering the shaped part to obtain the component.

2. The process as claimed in claim 1, wherein the substrate particles and the binder form composite particles.

3. The process as claimed in claim 2, wherein each of the composite particles comprises a plurality of the substrate particles.

4. The process as claimed in claim 2, wherein the composite particles have a fluidity which is defined by a Hausner number in accordance with VDI Guideline VDI 3405 sheet 1, wherein the Hausner number H.sub.R is equal to or greater than one and less than or equal to one and a half.

5. The process as claimed in claim 2, wherein each of the composite particles has a maximum dimension and the maximum dimension of at least 80% of the composite particles equal to or greater than 0.005 mm and equal to or less than 0.3 mm.

6. The process as claimed in claim 2, wherein each of the composite particles has a minimum dimension and a maximum dimension and a ratio of the minimum dimension to the maximum dimension for at least 80% of the composite particles is equal to or greater than 0.6 and less than or equal to one.

7. The process as claimed in claim 2, wherein the substrate particles are present in a proportion of from 40% by volume to 70% by volume in the composite particles.

8. The process as claimed in claim 1, wherein the binder has a melt viscosity of from 10.sup.0 Pa.Math.s to 10.sup.6 Pa.Math.s at a temperature which is at least 10 C. above a temperature, wherein the temperature is one of a glass transition temperature and a crystallite melting temperature of the binder.

9. The process as claimed in claim 1, wherein the thermoplastic polymer is present in a proportion of from 10% to 70% in the binder.

10. The process as claimed in claim 1, wherein the at least one additive is present in a proportion of from 30% to 90% in the binder.

11. The process as claimed in claim 1, wherein each of the substrate particles has a maximum dimension and the maximum dimension of at least 80% of the substrate particles is equal to or greater than 1 m and equal to or less than 50 m.

12. The process as claimed in claim 1, wherein the thermoplastic polymer comprises at least one of polycondensates, polymerizates, polyadducts and thermoplastic elastomers.

13. The process as claimed in claim 1, wherein the at least one additive comprises a plasticizer.

14. The process as claimed in claim 1, wherein the layers are applied in a thickness equal to or greater than 0.05 mm and equal to or less than 0.3 mm.

15. The process as claimed in claim 1, wherein the substrate particles and the binder are distributed in a construction region to form a layer, wherein a temperature in a construction region is equal to or greater than 20 C. and equal to or less than one of a glass transition temperature and a crystallite melting temperature of the binder.

16. The process as claimed in claim 1, wherein the binder is removed successively from the shaped part.

17. The process as claimed in claim 1, wherein the at least one additive is dissolvable by a solvent and the thermoplastic polymer is insoluble in the solvent and the at least one additive is removed at least partially from the shaped part by the solvent.

18. The process as claimed in claim 1, wherein the shaped part is dipped into a solvent in order to remove the at least one additive, wherein a temperature of the solvent is equal to or greater than 20 C. and equal to or less than 100 C.

19. The process as claimed in claim 1, wherein from 30% to 100% of the at least one additive is removed from the shaped part by a solvent.

20. The process as claimed in claim 1, wherein the binder is at least partly removed thermally from the shaped part at a first temperature, wherein the first temperature is equal to or greater than 300 C. and equal to or less than 900 C.

21. The process as claimed in claim 1, wherein a thermal removal of the binder is carried out in one of an inert gas atmosphere, a reducing atmosphere and a high vacuum.

22. The process as claimed in claim 1, wherein at least 95% of the binder has been removed from the shaped part after sintering.

23. The process as claimed in claim 1, wherein sintering is carried out at a second temperature, wherein the second temperature is equal to or greater than 600 C. and equal to or less than 2400 C.

24. A component, comprising: a component structure comprising at least one of metal, glass and ceramic, wherein pores are present in an interior of the component structure and at a component surface of the component structure, wherein at least 80% of the pores have a maximum dimension in a range from 1 m to 100 m.

25. The component as claimed in claim 24, wherein a porosity is equal to or greater than 0.01 and equal to or less than 0.15.

26. The component as claimed in claim 24, wherein the component surface has a surface roughness, wherein the surface roughness is equal to or greater than 5 m and equal to or less than 200 m.

27. The component as claimed in claim 24, wherein the pores at the component surface at least partly form undercuts.

28. A component produced by: providing substrate particles and a binder, wherein the substrate particles comprise one or more of metallic substrate particles, vitreous substrate particles and ceramic substrate particles, wherein the binder comprises a thermoplastic polymer and at least one additive; producing a shaped part, wherein a layer of substrate particles and binder being produced and the binder being selectively melted by electromagnetic radiation to produce a shaped part layer, at least one further layer of substrate particles and binder being produced and the binder being selectively melted by the electromagnetic radiation to produce at least one further shaped part layer; taking the shaped part out from the layers produced; removing the binder from the shaped part; and sintering the shaped part to obtain the component.

29. The process as claimed in claim 13, wherein the at least one additive comprises an ester of an aromatic hydroxybenzoic acid.

30. The process as claimed in claim 16, wherein the binder is removed successively from the shaped part, with the at least one additive being removed from the shaped part at least partly before the thermoplastic polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the drawings:

[0038] FIG. 1 is a view of a flow diagram of a process for the additive manufacture of a component;

[0039] FIG. 2 is a schematic view of an apparatus for the additive manufacture of a shaped part, from composite particles;

[0040] FIG. 3 is an enlarged view of a construction space of the apparatus in FIG. 2;

[0041] FIG. 4 is a schematic view of a composite particle comprising substrate particles and a two-phase binder;

[0042] FIG. 5 is a view of a volume-based, cumulative distribution of the composite particles;

[0043] FIG. 6 is a view of a schematic view of a vessel with solvent for chemical removal of binder from the shaped part;

[0044] FIG. 7 is a view of a schematic temperature profile for thermal binder removal and for sintering of the shaped part; and

[0045] FIG. 8 is a view of an enlarged section of an additively manufactured component after sintering.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] For the additive manufacture of a component 1, composite particles 2 are provided in a process step S.sub.1. The composite particles 2 each comprise metallic and/or vitreous and/or ceramic substrate particles 3 which adhere to one another by means of a two-phase binder 4. The two-phase binder 4 in turn comprises an additive 5 in the form of a plasticizer, which can be dissolved by means of a solvent 6, and a thermoplastic polymer 7, which is insoluble in the solvent 6.

[0047] The composite particles 2 have a fluidity or flowability defined by a Hausner factor H.sub.R in accordance with VDI Guideline VDI 3405 sheet 1 (version: October 2013), wherein the Hausner factor H.sub.R is such that: 1H.sub.R1.5, in particular 1H.sub.R1.4, in particular 1H.sub.R1.3.

[0048] Furthermore, the composite particles 2 in each case have a minimum dimension A.sub.min and a maximum dimension A.sub.max. At least 80%, in particular at least 90%, in particular at least 95%, of a volume-based, cumulative distribution Q.sub.3 of the composite particles 2 obeys: 0.005 mmA.sub.max0.3 mm, in particular 0.008 mmA.sub.max0.2 mm, in particular 0.01 mmA.sub.max0.1 mm. The volume-based, cumulative distribution Q.sub.3 of the composite particles 2 as a function of a dimension A is shown by way of example in FIG. 5. Furthermore, the composite particles 2 are substantially spherical, so that at least 80%, in particular at least 90%, in particular at least 95%, of a volume-based, cumulative distribution of the composite particles 2 obeys: 0.6A.sub.min/A.sub.max1, in particular 0.7A.sub.min/A.sub.max1, in particular 0.8A.sub.min/A.sub.max1.

[0049] The substrate particles 3 are in each case present in a proportion of from 40% by volume to 70% by volume, in particular from 45% by volume to 65% by volume, in particular from 50% by volume to 60% by volume, in the composite particles 2. The substrate particles 3 in each case have a maximum dimension B.sub.max, wherein at least 80%, in particular at least 90%, in particular at least 95%, of a volume-based, cumulative distribution of the substrate particles 3 obeys: 1 mB.sub.max50 m, in particular 5 mB.sub.max40 m, in particular 10 mB.sub.max30 m.

[0050] The substrate particles 3 are held together by the two-phase binder 4 and thus form the pulverulent composite particles 2. The binder 4 has a melt viscosity of from 10 Pa.Math.s to 10.sup.6 Pa.Math.s, in particular from 10 Pa.Math.s to 10.sup.5 Pa.Math.s, in particular from 10 Pa.Math.s to 10.sup.4 Pa.Math.s at a temperature which is at least 10 C. above a temperature T.sub.S, wherein the temperature T.sub.S is in the case of an amorphous structure of the binder 4 the glass transition temperature and in the case of a partially crystalline binder 4 is the crystallite melting temperature of the binder 4. The determination of the melt viscosity is carried out in accordance with DIN EN ISO 3219 (version: October 1994) and in particular at a shear rate selected from the group consisting of 1.00 s.sup.1, 2.50 s.sup.1, 5.00 s.sup.1, 10.0 s.sup.1, 25.0 s.sup.1, 50.0 s.sup.1 and 100 s.sup.1. The indicated values of the melt viscosity apply, in particular, at a shear rate of 1.00 s.sup.1. In the two-phase binder 4, the thermoplastic polymer 7 is present in a proportion of from 10% by weight to 70% by weight, in particular from 15% by weight to 50% by weight, in particular from 20% by weight to 40% by weight, and the plasticizer 5 is present in a proportion of from 30% by weight to 90% by weight, in particular from 50% by weight to 85% by weight, in particular from 60% by weight to 80% by weight. The binder 4 can optionally contain additional additives.

[0051] The thermoplastic polymer 7 is selected from the group consisting of polycondensates, polymerizates, polyadducts and thermoplastic elastomers. The plasticizer 5 is an ester of an aromatic hydroxybenzoic acid, preferably a fatty alcohol ester of p-hydroxybenzoic acid, with a length of the carbon chain preferably being in the range C12-C26, in particular in the range C18-C22. The plasticizer 5 serves to adjust the melt viscosity and the rheological properties of the binder 4.

[0052] The composite particles 2 are, for example, produced by subjecting a suspension composed of the substrate particles 3 and an alcoholic medium in which the binder 4 has been dissolved to spray drying.

[0053] The composite particles 2 are provided by means of an apparatus 8 for the additive manufacture of a shaped part 9. For this purpose, 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 composite particles 2. The reservoir space 14 is open in the direction of the surface 11. The composite 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.

[0054] Next to the reservoir recess 12 in the x direction there is a construction recess 15 provided in the base body 10. 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 bound a construction space 17 which is open in the direction of the surface 11.

[0055] In a process step S.sub.2, a first layer L.sub.1 of composite 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. For this purpose, 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. To apply the first layer L.sub.1, the plate 13 is firstly moved in the z direction so that a desired amount of the composite 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 composite 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 L.sub.1 is applied in a thickness D which is determined by the distance of the construction base body 16 from the surface 11.

[0056] In a process step S.sub.3, the binder 4 of the composite particles 2 in the first layer L.sub.1 is selectively melted, so that a first shaped part layer F.sub.1 is formed. The first layer L.sub.1 is closest to the surface 11 in this process step and forms a construction region. The construction region is heated to a temperature T.sub.B by means of heating elements 23. The temperature T.sub.B in the construction region is such that: 20 C.T.sub.BT.sub.S, in particular 20 C.T.sub.B120 C., in particular 25 C.T.sub.B100 C., in particular 30 C.T.sub.B80 C. T.sub.S is in the case of an amorphous structure of the binder 4 the glass transition temperature or in the case of a partially crystalline or crystalline structure of the binder 4 the highest crystallite melting temperature 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. To produce the first shaped part layer F.sub.1, 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 electromagnetic radiation R melts the binder 4, so that the binder 4 spreads between the substrate particles 3 and on solidification forms the solid first shaped part layer F.sub.1.

[0057] In a process step S.sub.4, a further layer L.sub.2 of composite particles 2 is applied in the above-described manner to the previously applied layer L.sub.1. For this purpose, the plate 13 is moved in the z direction so that a desired amount of composite particles 2 is present above the surface 11 and can be transported by means of the application device 18 to the construction space 17. To apply the layer L.sub.2, the construction base body 16 is lowered by the thickness D in the z direction, so that the composite particles 2 can be distributed uniformly and homogeneously on top of the previously applied layer L.sub.1.

[0058] In a process step S.sub.5, the binder 4 of the composite particles 2 in the layer L.sub.2 are selectively melted in the above-described manner by means of the electromagnetic radiation R, so that a further shaped part layer F.sub.2 is produced. The molten binder 4 spreads between the substrate particles 3 and holds these together after solidification of the binder 4. The thickness D of the applied layers L.sub.1, L.sub.2 is such that: 0.05 mmD0.3 mm, in particular 0.07 mmD0.25 mm, in particular 0.09 mmD0.2 mm. The process steps S.sub.4 and S.sub.5 are repeated until the shaped part 9 has been additively manufactured in the desired way. In FIG. 3, three layers L.sub.1, L.sub.2 and L.sub.n and three shaped part layers F.sub.1, F.sub.2 and F.sub.n where n=3 are depicted by way of example. As an alternative, it is possible for a layer or a plurality of layers of composite 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 F.sub.1 is formed. The shaped part 9 is in this case arranged on at least one layer which has not been melted.

[0059] In a process step S.sub.6, the shaped part 9 is taken out from the composite 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 part.

[0060] In a process step S.sub.7, the shaped part 9 is subjected to chemical binder removal. For this purpose, the shaped part 9 is dipped into a vessel 24 filled with the solvent 6. This is shown in FIG. 6. Acetone, for example, serves as solvent 6. The solvent 6 dissolves the plasticizer 5 out from the shaped part 9, while the thermoplastic polymer 7 is insoluble and remains in the shaped part 9. The shaped part 9 acquires a microporous structure as a result of the removal of the plasticizer 5. The solvent 6 has a temperature T.sub.L. The temperature T.sub.L is such that: 20 C.T.sub.L100 C., in particular 25 C.T.sub.L80 C., in particular 30 C.T.sub.L60 C. From 30% to 100%, in particular from 50% to 90%, in particular from 60% to 80%, of the plasticizer 5 is removed from the shaped part 9 by means of the solvent 6. After the chemical binder removal, the shaped part 9 is also referred to as brown part. After a time t.sub.0, the chemical binder removal is stopped and the shaped part 9 is taken from the solvent 6. The time t.sub.0 is dependent on the component geometry and in particular is proportional to the square of the wall thickness of the shaped part 9.

[0061] In a process step S.sub.8, the shaped part 9 is, after the chemical binder removal, subjected to thermal binder removal and subsequently sintered in a process step S.sub.9. 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. To effect thermal binder removal, the shaped part 9 is brought to a first temperature T.sub.1. The first temperature T.sub.1 is such that: 300 C.T.sub.1900 C., in particular 400 C.T.sub.1800 C., in particular 550 C.T.sub.1750 C. In the thermal binder removal, the binder 4, i.e. the thermoplastic polymer 7 and optionally residual plasticizer 5, is burnt out from the shaped part 9 at the first temperature T.sub.1 and the binder 4 is thus thermally removed. Here, the substrate particles 3 partly form sintering necks, so that the shaped part 9 is held together despite removal of the thermoplastic polymer 7. Owing to the microporous structure of the shaped part 9, thermal binder removal occurs quickly and uniformly. The thermal removal of the binder 4 is carried out over a time t.sub.1. The time t.sub.1 is dependent on the component geometry and in particular is proportional to the square of the wall thickness of the component 1 to be produced. The time t.sub.1 is preferably selected so that at least 95%, in particular at least 99%, in particular at least 99.9% of the binder 4 is removed.

[0062] The shaped part 9 is subsequently brought, in the process step S.sub.9, to a second temperature T.sub.2 which is higher than the first temperature T.sub.1. Sintering of the shaped part 9 occurs at the temperature T.sub.2. The second temperature T.sub.2 is such that: 600 C.T.sub.22400 C., in particular 800 C.T.sub.22200 C., in particular 1100 C.T.sub.22000 C. Sintering is carried out for a time t.sub.2. The time t.sub.2 is dependent on the component geometry and in particular is proportional to the square of the wall thickness of the component 1 to be produced. The time t.sub.2 is preferably so long that no relevant change in a porosity of the component 1 can be achieved by subsequent further sintering. The sintering is preferably carried out until the porosity P obeys: 0.01P0.15, in particular 0.03P0.12, in particular 0.05P0.09.

[0063] After sintering, at least 90%, in particular at least 95%, in particular at least 99.9%, of the binder 4 has been removed from the shaped part 9. The additively manufactured component 1 is present after sintering.

[0064] The component 1 is, dependent on the use of metallic and/or vitreous and/or ceramic substrate particles 3, composed of metal and/or glass and/or ceramic. In an interior 25 of the component, the component 1 has closed pores 26. At a component surface 27, the component 1 has open pores 28. The component 1 has a microporous structure which is such that at least 80%, in particular at least 85%, in particular 90%, of the pores 26, 28 have a maximum dimension d.sub.max in the range from 1 m to 100 m, in particular from 10 m to 80 m, in particular from 20 m to 60 m. The component 1 has a porosity P which is defined as the ratio of a pore volume to a component volume. The component volume comprises the material volume and the volumes of the closed pores 26. The porosity P is such that: 0.01P0.15, in particular 0.03P0.12, in particular 0.05P0.09.

[0065] Owing to their shape, the open pores 28 at the component surface 27 at least partly form undercuts 29. For example, the open pores 28 have a droplet-like shape extending from the component surface 27, so that these pores widen in the direction of the interior 25 of the component and form the undercuts 29. Owing to the open pores 28, the component surface 27 has a surface roughness r.sub.Z. The surface roughness r.sub.Z is such that: 5 mr.sub.Z200 m, in particular 10 mr.sub.Z120 m, in particular 15 mr.sub.Z100 m. The surface roughness r.sub.Z is defined in accordance with DIN EN ISO 4287 (version: October 1998) and is measured by the profile method in accordance with DIN EN ISO 4288 (version: April 1998).

[0066] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.