EP3194097A1

EP3194097A1 - Method for connecting workpieces which are produced from a raw material using an additive manufacturing process

Info

Publication number: EP3194097A1
Application number: EP15816378.2A
Authority: EP
Inventors: Michael Ott; Steffen Walter
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2014-12-18
Filing date: 2015-12-02
Publication date: 2017-07-26
Also published as: DE102014226370A1; US20170333995A1; WO2016096417A1; CN107107192A

Abstract

The invention provides a method (1) for the additive manufacturing of a workpiece (2) from a raw material (14), comprising at least one metal, wherein a geometric model (10) of the workpiece (2) is produced and the model (10) is divided into a plurality of individual parts (12a-12f), wherein each individual part (12a-12f) is manufactured in stages from the raw material (14), in that in a manufacturing step (32), a respective amount (34) of the raw material (14) is locally fused to an already manufactured part (13b-13e) of the respective individual part (12a-12f) using localized application of heat, and solidified in the same place, and wherein the individual parts (12a-12f) are joined by a diffusion process using the application of pressure (20a, b) and the local application of heat at the contact surfaces (24a-d), and in this way the finished workpiece (2) is joined. The invention additionally provides a workpiece (2) manufactured from a raw material (14) by means of a method (1) of this type.

Description

description

METHOD FOR CONNECTING WORKPIECES PRODUCED IN THE GENERATIVE MANUFACTURING PROCESS FROM A RAW MATERIAL

The invention relates to a process for the generative manufacturing a part made of a raw material which tens comprises Wenig ^¬ a metal, wherein a mathematical model of the workpiece is created, and in each case in a production step, a unit amount of the raw material under local heat input to an already manufactured part locally melted on ^¬ and solidified there.

Generative manufacturing processes represent a novel approach for producing workpieces with a high geometric complexity, and have recently gained in importance. An essential feature of generative manufacturing processes is that a raw material based on virtual data models of a workpiece in low-dimensional form (for example as wire or as foil) or informal (for example as powder or as liquid) by means of chemical and / or physical processes is gradually formed to the finished workpiece. In particular, in the field of internal combustion engines Eger ^¬ ben generative manufacturing processes on one hand the production of improved, conventionally impossible or very laborious prepared components, such as workpieces measured ^¬ tailored material properties, light weight or inner surfaces for better cooling. This thus allows an increase in efficiencies, respectively, a cost reduction for new parts. On the other hand, due to the possibility of individual, decentralized and instantaneous production, generative manufacturing processes promise great simplifications in service and repair.

Of particular interest here are laser-based transmission method Ferti ^¬, the processing of the typical constructive tion materials in the hot zone of a combustion engine equipped ^¬ ge. The production is typically carried out by scanning a powder bed with a laser beam, wherein selectively the metallic particles of the starting material through which the powder is formed - usually a nickel-based alloy - piece by piece and layer by layer are fused together until the finished component is shaped. Although with an additive manufacturing process

Geometries for workpieces to be produced can be realized, which can be realized by conventional manufacturing only with significantly increased production costs, such. Undercuts or cavities are also limited here. In particular, in the simultaneous production of thick-walled and thin-walled structures in a workpiece may be due to occurring in the workpiece during the production process residual stresses. These residual stresses are due to the different thermodynamic conditions for the classification of the atoms in the respective local crystal structure, which on thick-walled or

thin-walled structures prevail: the local heat dissipation of the heat introduced for the addition of the particles takes place almost completely through the already manufactured part of a workpiece. A larger thermal gradient is thus possible at a thick-walled structure, whereby the heat is dissipated fast ^¬ ler than a thin-walled structure to which molten material remains longer in the liquid phase. This can also lead to deposition processes of the alloy used.

The thus "frozen" during solidification in the different structures voltages in a workpiece can thereby be greater than the yield strength of the workpiece, can thereby cracks occur. Moreover, the delay of the production can already currency ^¬ rend result in damage to the manufacturing plant. The invention is therefore based on the object, a method for manufacturing a workpiece from a raw material suits ^¬ ben to produce that complex geometries it possible ^¬ laubt and thereby causes a lowest possible gen delay in the finished workpiece.

The above object is achieved by a method for the generative production of a workpiece from a raw material comprising at least one metal, wherein a geometric model of the workpiece created and the Mo ^¬ dell is divided into a plurality of individual parts, each item gradually from the Raw material is produced by each in a manufacturing ^step a Mengen ^¬ unit of the raw material with local heat input to an already manufactured part of each item is locally melted and solidified there, and wherein the individual ^¬ parts under the action of pressure and local heat on the Contact surfaces are joined together by a diffusion process and thereby the finished workpiece is joined.

Advantageous and partly per se inventive exporting ^¬ insurance forms are the subject of the dependent claims. The raw material is present given by a metal or a Le ^¬ government. A unit of quantity of the raw material in particular comprises a powder or granule grain. The local melting of the unit of quantity of the raw material under local heat input comprises in particular a complete melting, as well as a melting, in which the melting process remains reduced to the surface of the respective unit of quantity, ie in particular also a sintering process. The contact surfaces are each joined at which the items under the action of pressure and under local to warmth, are predetermined by the geometric ^¬ specific model of the workpiece. In particular, the geometric model of the workpiece for individual manufacturing Steps for adding a respective unit of quantity of the raw material used.

The invention is in a first step, assume that with increasing geometric complexity of the to be produced workpiece, a conventional production, in ^¬ play, of a forging or casting process, with closing at ^¬ post usually at a disproportionately high expenditure and thereby unacceptable costs leads. The problems which occur in the generative production of a workpiece with complex geometry, in particular with ^{respect to} the material ^stresses , should therefore be solved as far as possible in the context of a generative manufacturing process. In this connection, it is recognized that in particular for the reduction of material stresses in the molten and solidified raw material, which result from a different insertion of the atoms thus added into the crystal structure of the workpiece, the individual production steps or the respective local heat input in the spatial ^{sequence are} optimized can be. On the basis of a spatial arrangement of local melting points given by the geometry of the workpiece, such an optimization of the temporal distribution of respective local melting processes means, inter alia, a multiple, coupled application and simulation of the heat conduction equation, whereby the effort here also increases disproportionately. This is all the more true for workpieces with complex geometry, the production of which is particularly convenient here.

Likewise, a subsequent processing of a workpiece by means of heat and pressure, where appropriate, fix certain distortions and / or deformations in the finished workpiece, but are usually necessary to remedy occurring by such tension damage to a crystal structure, such as cracks, the structure can affect the finished workpiece. Such post-processing is therefore discarded. In contrast, the invention proposes different individual ^¬ parts of the workpiece by means of the separately-described ^¬ NEN manufacturing steps to produce. In a second step, the invention recognizes that this procedure makes it possible to select the dimensioning of the individual parts in such a way that problems of the material structure of the workpiece, in particular tension, arising from the individual melting and solidification processes do not yet occur to any appreciable extent. The division of the workpiece into different individual parts he ^¬ follows this by means of a geometric model, which in each case for the spatial division of the single manufacturing steps, each adding a unit of quantity of the raw material, is present anyway.

In particular, with a simultaneous production of thick and thin-walled structures in the workpiece, a different delay of the respective structures occur, so that here the division of the workpiece into individual parts, which are later joined together, due to the easier to suppress in smaller parts delay significantly improved manufacturing quality allowed ,

As a further advantageous here when, in each case, the local heat generation is considered for the diffusion processes for together ^¬ menfügen of the items, the off-closing assembly is carried out at a pressure which only causes a slight elastic deformation of the to be joined work ^¬ piece.

Preferably, a plurality of individual parts is assembled under the action of unidirectionally acting pressure. In particular, all items are assembled under the action of unidirectional pressure. In particular, this can also be done in stages, so that initially ver ^¬ different groups of items are packed under pressure to unidirektio- nalem rough structures, and then the coarse structures once again under the action of unidirectional pressure, which is not acting along the joining axis of the coarse structures, are assembled to the finished workpiece. Unidirectional printing is particularly easy to implement in the production process.

Conveniently, the local application of heat to the adjoining ^¬ contact surfaces of each pair of items by means of an externally applied current flow through the occurring at the adjoining contact surfaces ohmic resistance is achieved. Depending on the raw material have the items in ih ^¬ rem internal each have a high electrical conductivity. Is now through two items to which a is Kontaktflä ^¬ che provided, a current flow is created, the ohm ^¬ specific resistance at the contact surface is significantly higher than in the respective interior of the items. As a result, the applied current flow leads to a noticeable local effect of heat on the contacting contact surfaces. This heat development is maintained with applied current flow until the two individual parts have entered into a material connection at their contact surfaces by sufficient diffusion of the atoms and thus due to the improved mobility of the line carrier there the ohmic resistance decreases again. By thus limiting the reach loka ^¬ len heat on the provided on the items contact surfaces the final assembly of the items for manufacturing workpiece is particularly energy efficient. In addition, can be dispensed with excessive external heat, which could affect the external shape and / or structure of the items.

Conveniently, in this case a plurality of individual parts is assembled by means of spark plasma sintering. Spark plasma sintering is a process established in the industry, the application of which in the present method for joining the individual parts results in a particularly homogeneous structure of the finished workpiece. As a further advantage, it has proven when a plurality of individual parts in each case layers ge ^¬ made of the raw material. In particular, in production method in which a workpiece manufactured in layers generative of a metallic raw material, stresses may occur in the material during the manufacturing ^¬ this process are in already manufactured part of the workpiece in Schich ^¬ power direction. These stresses can lead to distortion or warpage of the already manufactured part of the workpiece, by means of which, inter alia, the plant ge ^¬ may be at risk for the manufacturing process. Against this background, is giving ^¬ ne manufacturing processes in a layered structure of the individual parts is particularly advantageous. In particular, a one ^¬ parts right here may also include additional auxiliary structures, which, given the geometry of the single part, which should allow the layered structure of the raw material be ^¬ low or at all concerned ^¬. These auxiliary structures are preferably to be removed before joining the individual parts to the finished workpiece.

In this case, a plurality of individual parts is preferably manufactured in parallel in a plant for layered production. Under such a parallel production is to be understood that a layer is added to an already manufactured part of an item, and before there another

Layer is added, at least one layer is added to an already manufactured part of another item.

This procedure has the following advantages: On the one hand, the plant is often subjected to a preparation process after a single production step or a plurality of production steps. This preparation process may consist, for example, in the correct placement of the raw material on the already manufactured part of a single part. If the raw material in powder form, the Vorbe ^¬ preparatory process includes providing a layer of powder wel ^¬ surface completely covers the already manufactured part of a workpiece and to have a very smooth surface has, for which the powder is still pulled apart separately. The parallel Customize number of individual parts of the same workpiece in the same plant, the time for a preparatory process of a manufacturing step or a layer for a plurality of items is thus used simultaneously, thereby IMP EXP ^¬ together with the time can be substantially shortened for manufacturing.

On the other hand, in the case of a simultaneous, parallel production of several individual parts in the same installation, improved heat dissipation of the quantity of heat registered locally to produce a layer is possible. In a one-piece

layer-by-layer production of the workpiece, each individual layer is added to raw material in a multiplicity of production steps with a respective local heat input for melting the relevant unit of quantity. Spatially considered, the sum of all local heat inputs required for adding a layer forms a maximum of simple coverage of the already manufactured part of the workpiece. If a workpiece is now manufactured in one piece in layers, the next local heat input takes place at a specific point on the surface of the already manufactured part much earlier than if corresponding parallel layers of other individual parts had previously been to be produced. The items thus retain during the layered Ferti ^¬ supply better heat dissipation than that of a single piece manufactured workpiece, which can have an advantageous effect on the solidification process, depending on the raw material. Among other things, in a faster solidification, the unwanted deposition of individual material phases of the raw material can be better prevented.

Particularly preferably, the raw material is provided in powder form. In this case, the local heat input is concentrated substantially point-like, so that the improved heat dissipation can have a particularly advantageous effect. Conveniently, for this purpose, the raw material is melted locally by means of selective laser melting. Selective ^laser melting is a particularly widespread process in order to provide the local heat input for a generative production process with a powdery raw material.

The invention further specifies a workpiece which is made of a raw material by means of the above-described method. Responsible for the procedure and its Weiterbildun ^¬ gen-mentioned advantages can thereby be applied analogously to the work ^¬ tee. In particular, the workpiece is designed as a component of an internal combustion engine.

An embodiment of the invention will be explained in more detail with reference to a drawing. Here, each specific ^¬ matically show:

1 shows a diagram of the sequence of a method for the generative production of a workpiece from a raw material,

2 shows an oblique view of the parallel production of meh ^¬ rerer items in the same system, and

3 shows an oblique view of the assembly of individual parts to a finished workpiece according to FIG. 1

Corresponding parts and sizes are provided in all figures with the same reference numerals.

In FIG. 1, the sequence of a method 1 for producing a workpiece 2 is shown in a schematic diagram. The workpiece 2 is designed as a turbine blade 4 of a gas turbine, not shown. The ^turbine blade 4 in this case has two platforms 6a, 6b and a profiled wing. 8 In a first method step, a geometric model 10 of the workpiece 2 will now he provides ^¬. This geometric model 10 is now first in Parts 12a-12f divided, the circumstances in the system provided for the production of the items 12a-12f system for an advantageous distribution are to be considered. In the next method step, the individual parts 12a-12f are then manufactured in layers in a plant, not shown, from a raw material 14. For this purpose, the raw material 14, which is designed here as a powdery Me ^¬ talllegierung, locally melted in a plurality of individual production steps by means of selective laser melting 16 so that a melted in a manufacturing step by the local heat input of the laser Pul ^¬ is confusing to an already fabricated part 13b, 13c of an item 12b, 12c solidifies, and thereby gradually the next layer is formed. For the layered structure of the individual parts 12a-12f, the geometric model 10 of the workpiece 2 can be used. Depending on their geometry, certain groups of individual parts 12b, 12c are manufactured in parallel. Details of this production will be explained with reference to FIG 2.

The individual parts 12a-12f are finally joined together by means of spark plasma sintering 18. For this purpose, a unidirectionally acting pressure 20a is first exerted on the individual parts 12a-12f in the direction of the layer structure, and a flow of current 22 is applied through the individual parts 12a-12f. The spark plasma sintering 18 produces sufficient diffusion of the alloy at the contact surfaces 24a-24d of the individual parts 12a-12f provided by the geometric model 10 so that each two adjacent individual parts 12a-12f are firmly connected to one another, and thus to the finished the workpiece 2 are joined together. Details of this joining process will be explained in more detail with reference to FIG 3. FIG. 2 schematically shows, in an oblique view, a system 26 for selective laser melting. In a Pul ^¬ verbett 28 already manufactured parts are 13b-13e of the individual parts 12b-12e, each having a similar geometry exhibit. A laser 30 scans the powder bed 28 according to the geometry of the individual parts 12b-12e, each individual laser pulse corresponding to a production step 32 in which a unit of quantity 34 of powder grains is melted. The thus-molten raw material 14 solidifies on the already produced ge ^¬ part 13b of the item 12b, and by a plurality ^¬ number of such production steps 32 a next layer is applied to the already made part 13b of the A ^¬ zelteils 12b 36b. Before being applied to this layer 36b, a further layer of raw material 14, 13c-13e to the already manufactured part of each individual ^¬ part 12c-12e applied only other a layer, so that the parallel A ^¬ individual parts 12b-12e through in assembly direction 38 Schich ^¬ th are formed, and at each time of manufacturing in the system 26 each two simultaneously arising therefrom individual parts 12b-12e in the direction of construction 38 differ by a maximum of one layer 36b.

By this parallel manufacture of the items 12b-12e manufacturing time can be saved, which is required for each new layer for the preparation and smooth drawing of the powder bed 28, since now due to the parallel manufacturing a total of fewer layers and thus less individual sol ^¬ cher preparation processes are required. In addition, in the construction direction 38, the heat dissipation from an already manufactured part 13b-13e compared to a one-piece production of a workpiece improved since the time until the laser 30 after a production step 32 for a layer 36b in Fer ^¬ tion of the next higher layer again on the same Spot irradiates, due to the previously still to be processed further items is higher.

In FIG. 3, the assembly of individual parts 12a-12f into the finished turbine blade 4 is schematically illustrated in an oblique view. In a first step, this single ^¬ parts 12b-12e, which constitute a disk-like dividing an internal structure of the wing 6 in the geometrical model of the turbine blade 4, and here not shown in detail platforms 8a, 8b 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, by egg NEN second Spark plasma sintering process, the outer through the A ^¬ individual parts 12b-12e formed inside structure Flügelflä ^¬ surfaces 12a, added 12f, the used for this purpose pressure 20b respect. By the geometric model 10 defi ^¬ nierten arrangement of the items acts perpendicular to the pressure 20a, which was used in the first spark plasma sintering process ver ^¬ .

Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by this embodiment ^¬ limits. Other variations can be deduced therefrom by those skilled in the art without departing from the scope of the invention.

Claims

claims

A method (1) for generatively producing a workpiece (2) from a raw material (14) comprising at least one metal,

wherein a geometric model (10) of the workpiece (2) it provides ^¬ and the model (10) is divided into a plurality of individual parts (12a-12f)

wherein each item (12a-12f) step by step from the raw material (14) is manufactured by each in a produc- ^¬ tion step (32) a unit of mass (34) of the raw material (14) under local heat input to an already manufactured part (13b -13e) of the respective item (12a-12f) is locally melted and solidified there, and

wherein the items (12a-12f) under the action of

Pressure (20a, b) and under local heat at the contact surfaces (24a-d) by a diffusion process ^{zusammenge ¬} adds and thereby the finished workpiece (2) is joined.

2. Method (1) according to claim 1,

wherein a plurality of individual parts (12a-12f) are joined together under the action of unidirectional pressure (20a, b).

3. Method (1) according to claim 1 or claim 2,

wherein the local effect of heat at the adjacent contact surfaces (24a-24d) of each of two individual parts (12a-12f) is achieved by means of egg ^¬ nes externally applied current flow (22) on the contact surfaces (24a-24d) occurring ohmic resistance.

4. Method (1) according to claim 2 or claim 3,

wherein at least a plurality of individual parts (12a-12f) are joined together by spark plasma sintering (18).

5. Method (1) according to one of the preceding claims, wherein a plurality of individual parts (12a-12f) are each made in layers of the raw material (14).

6. Method (1) according to claim 5,

wherein in a plant (26) for the layered production, a plurality of individual parts (12b-12e) is made in parallel.

7. Method (1) according to claim 5 or claim 6,

wherein the raw material (14) is provided in powder form

8. Method (1) according to claim 7,

wherein the raw material (14) is locally melted by selective laser melting (16).

9. workpiece (2), made of a raw material (14) with ^{¬ means of} a method (1) according to one of the preceding claims.