METHOD FOR CONNECTING WORKPIECES WHICH ARE PRODUCED FROM A RAW MATERIAL USING AN ADDITIVE MANUFACTURING PROCESS`

Abstract

A method for the additive manufacturing of a workpiece from a raw material, having at least one metal, wherein a geometric model of the workpiece is produced and the model is divided into a plurality of individual parts. Each individual part is manufactured in stages from the raw material. In a manufacturing step, a respective amount of the raw material is locally fused to an already manufactured part of the respective individual part using localized application of heat, and solidified in the same place, and wherein the individual parts are joined by a diffusion process using the application of pressure and the local application of heat at the contact surfaces, and in this way the finished workpiece is joined. A workpiece is manufactured from a raw material by a method of this type.

Claims

1.-9. (canceled).

10. A method for the additive manufacture of a workpiece from a raw material which comprises at least one metal, the method comprising: generating a geometric model of the workpiece and splitting the model into a plurality of individual parts, wherein each individual part is produced stepwise from the raw material wherein, in each production step, a unit of quantity of the raw material is locally melted, with localized introduction of heat, and solidified onto an already finished part of the respective individual part, and joining the plurality of individual parts together by a diffusion process under unidirectional pressure and localized heat input at the contact surfaces, whereby the finished workpiece is joined.

11. The method as claimed in claim 10, wherein the local introduction of heat at the adjoining contact surfaces of any two individual parts is achieved by an externally applied current via the ohmic resistance arising at the contact surfaces.

12. The method as claimed in claim 10, wherein at least one of the plurality of individual parts is joined by spark plasma sintering.

13. The method as claimed in claim 10, wherein the plurality of individual parts is created in each case layer by layer from the raw material.

14. The method as claimed in claim 13, wherein the plurality of individual parts is manufactured in parallel in an installation for layered production.

15. The method as claimed in claim 13, wherein the raw material is provided in powder form.

16. The method as claimed in claim 15, wherein the raw material is melted locally by selective laser melting.

17. A workpiece, wherein the workpiece is created from a raw material using a method as claimed in claim 10, whereby in the workpiece, problems in the material structure of the workpiece, which stem from individual melting and solidification processes, and/or stresses, are not present to a noteworthy degree.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] There follows a more detailed explanation of an exemplary embodiment of the invention, with reference to a drawing, in which, schematically:

[0029] FIG. 1 shows, in a diagram, the sequence of a method for additive manufacturing of a workpiece from a raw material,

[0030] FIG. 2 shows, in an oblique view, the parallel production of multiple individual parts in the same installation, and

[0031] FIG. 3 shows, in an oblique view, the joining of individual parts to give a finished workpiece as shown in FIG. 1.

[0032] Mutually corresponding parts and variables are in each case provided with identical reference signs in all figures.

DETAILED DESCRIPTION OF INVENTION

[0033] FIG. 1 shows, in a schematic diagram, the sequence of a method 1 for producing a workpiece 2. In that context, the workpiece 2 is designed as a turbine blade 4 of a gas turbine (not shown in greater detail). The turbine blade 4 has two platforms 6a, 6b and a profiled airfoil 8. Now, a first method step involves establishing a geometric model 10 of the workpiece 2. Now, this geometric model 10 is first divided into individual parts 12a -12f, wherein the conditions in the installation provided for manufacturing the individual parts 12a -12f are also to be taken into account for advantageous division.

[0034] In the next method step, the individual parts 12a -12f are then manufactured layer by layer from a raw material 14 in an installation (not shown in greater detail). To that end, the raw material 14, which in this case is in the form of a powdered metal alloy, is locally melted by selective laser melting 16 in a multiplicity of individual manufacturing steps, such that a quantity of powder melted in one manufacturing step by the local heat input of the laser solidifies on an already-finished part 13b, 13c of an individual part 12b, 12c, and thus the next layer is formed step by step. The geometric model 10 of the workpiece 2 can be used in this case for the layered buildup of the individual parts 12a -12f. Depending on their geometry, certain groups of individual parts 12b, 12c are manufactured in parallel here. Details of this manufacture are explained in greater detail with reference to FIG. 2.

[0035] The individual parts 12a -12f are finally joined by spark plasma sintering 18. To that end, a unidirectional pressure 20a is first exerted on the individual parts 12a -12f in the direction of the layered buildup, and a current 22 is applied through the individual parts 12a -12f. The spark plasma sintering 18 produces, at the contact surfaces 24a -24d of the individual parts 12a -12f provided by the geometric model 10, sufficient diffusion of the alloy such that any two adjacent individual parts 12a -12f are thereby solidly connected to one another, and can thus be joined to give the finished workpiece 2. Details of this joining process are explained in greater detail with reference to FIG. 3.

[0036] FIG. 2 shows, schematically in an oblique view, an installation 26 for selective laser melting. The already-finished parts 13b-13e of the individual parts 12b -12e, which have a similar geometry in each case, are in a powder bed 28. A laser 30 scans the powder bed28 according to the geometry of the individual parts 12b -12e, with each individual laser pulse corresponding to a manufacturing step 32 in which a unit of quantity 34 of powder grains is melted. The raw material 14 melted in this manner solidifies on the already-finished part 13b of the individual part 12b, and so a next layer 36b is deposited on the already-finished part 13b of the individual part 12b by a multiplicity of such manufacturing steps 32. Before another layer of raw material 14 is deposited onto this layer 36b, a layer is first deposited onto the already-finished part 13c-13e of every other individual part 12c -12e, such that the individual parts 12b -12e are formed by layers that are parallel in the buildup direction 38, and at any stage of the manufacture in the installation 26 any two individual parts 12b -12e arising simultaneously there differ in the buildup direction 38 by at most one layer 36b.

[0037] Manufacturing the individual parts 12b -12e in parallel in this manner makes it possible to save manufacturing time which is necessary at every new layer for preparation and smoothing of the powder bed 28, since the parallel manufacturing now means that, overall, fewer layers and thus fewer individual preparation processes of this type are required. In addition, in the buildup direction 38 heat dissipation from an already-finished part 13b-13e is better than in the case of one-piece manufacturing of a workpiece, since the time for the laser 30 to return to irradiate the same location after one manufacturing step 32 for a layer 36b when manufacturing the next-higher layer is greater due to the other individual parts that are still to be processed beforehand.

[0038] FIG. 3 shows, schematically in an oblique view, the joining of individual parts 12a -12f to give a finished turbine blade 4. In a first step, individual parts 12b -12e, which in the geometric model of the turbine blade 4 represent a disk-like division of an internal structure of the airfoil 8, and the platforms 6a, 6b, which are not shown in greater detail here, are joined together by a first spark plasma sintering process in which the pressure 20a acts perpendicular to the contact surfaces 24a -24d provided on the individual parts. In a second step, a second spark plasma sintering process adds external airfoil surfaces 12a, 12f to the internal structure formed by the individual parts 12b -12e, wherein the pressure 20b used for this, or the arrangement of the individual parts defined by the geometric model 10, acts perpendicular to the pressure 20a used in the first spark plasma sintering process.

[0039] Although the invention has been described and illustrated in greater detail by means of the preferred exemplary embodiment, the invention is not limited by this exemplary embodiment. Other variants can be derived herefrom by a person skilled in the art without departing from the protective scope of the invention.