AT525599A1 - Process for producing a component from a metal powder and/or ceramic powder - Google Patents

Abstract

The invention relates to a method for producing a component (6) from a metal powder (3) and/or ceramic powder, after which the metal powder (3) and/or ceramic powder is processed into a molded part (1) by means of an additive method, and preferably thereafter is sintered. The component (6) is produced from the optionally sintered molding (1) by mechanical post-compacting, in particular by rolling or compression molding, of at least part of the molding surface (7).

Description

powder is processed into a molded part using an additive process.

The invention further relates to a device produced by means of an additive method

Component comprising a metallic component body.

Additive processes per se are known from the prior art. A three-dimensional component is built up in layers from at least one material. These processes have found their way into industrial production in recent years, since these processes can be used to achieve a very high degree of customization without incurring expensive tooling costs. The process control

tion is computer controlled using CAD data.

The problem of this method in industrial application is very well described in DE 102017 007 178 A1. While high-quality components can be produced using conventional sintering technology (powder metallurgical processes) by applying high pressure, such compaction cannot be used in 3D printers. The addition of additives that melt and thus fill the pores in the component is not always applicable, as mixed materials are produced with it. The same applies to the impregnation of such

tiger components with low-melting metal alloys.

Hot isostatic pressing (HIP) is known from the prior art for the post-compacting of components that are produced by means of additive processes, as is described, for example, in DE 10 2020 107 105 A1. The hot-

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is.

DE 10 2018 102 616 A1 discloses a method for producing hard metal bodies, in which a hard metal green body is produced using a laser-based additive manufacturing method with energy input by means of a laser at each location of the energy input to achieve a temperature of 800 °C to a maximum of <2735 °C with a density of at least 30% and a maximum of 70% of the theoretical density of the hard metal body, and which is subsequently sintered at temperatures up to a maximum of 1600 °C by means of vacuum sintering at partial pressures of 100 to 90,000 Pa and/or gas pressure sintering and pressures of up to a maximum of 10 MPa up to a compaction of the hard metal body of 98% of the theoretical

cal density is subjected.

The present invention is based on the object of creating an industrially easier feasible way with which the performance of a

component manufactured by means of an additive process can be improved.

The object is achieved with the method mentioned at the outset, according to which it is provided that the component is produced from the molded part by (exclusively) mechanical

cal post-compacting, in particular by rolling or compression molding, at least a part of the molding surface is produced. There is no thermal

momechanical post-compression is used, as is the case with the HIP.

The object of the invention is also achieved in that the component body has, at least in sections, a surface which is higher than that produced by mechanical recompression, in particular by rolling or compression molding

density as a subsurface core layer.

The advantage here is that the post-compaction is carried out with one method

that is simply integrated into the process chain for the production of the

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can be begotten.

According to one embodiment variant of the invention, provision can be made for the post-compression to be carried out as cold compression. On the one hand, energy can be saved in this way. On the other hand, with the appropriate choice of material, further hardening of the component is also possible by increasing the strength of the

Component material accessible.

As already mentioned, it is possible with the invention to provide a component that has compressed and non-compacted surface areas. According to a further embodiment variant of the invention, provision can also be made to provide a component which has surface regions of different densities, with which a component can be produced which can have properties adapted to the respective application. It is thus also possible to reduce the tool costs, since these are due to a lower compression

have a longer service life.

Also to extend the service life of the tool, according to another embodiment variant of the invention, provision can be made for the molding to be produced with a maximum density of 80% of the full density. Thus, due to the higher porosity, lower forming forces are required for the compaction of the surface of the component, which means that the tool is also subject to less stress, compared to a post-compaction of a component with a

Density greater than 80% of full density has been produced.

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Edge zone compressions against liquid ingress can be improved.

According to further embodiment variants of the invention, it can be provided that a blasting method using electromagnetic radiation or a sinter-based additive method or a blasting-based powder bed method, such as in particular the cold metal fusion method, is used as the additive method, with the blasting method preferably being a blasting-based powder bed method, such as in particular selective laser sintering. Especially with these additive processes, the above-mentioned at least partial densification of the building

partial surface turned out to be advantageous.

For the same reasons, according to a further embodiment variant of the invention, a sintered steel powder, a metal injection molding powder or a mixture thereof is preferably used as the metal powder as the raw material for the production of the component. In particular, with the invention, a water-atomized or ground metal powder, which is usually used for additive processes due to the

Morphology and flowability can only be used to a limited extent.

According to another embodiment variant of the invention, it can be provided that the section of the surface with the higher density compared to the core layer is free of open pores. The component can thus be provided in a liquid-tight manner in this compressed area. A residual porosity can thus also be retained in the component, with which the component weight can be reduced or the component also has a storage capacity for liquid, as in

for example lubricants.

For a better understanding of the invention, this is based on the following

Figures explained in more detail.

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Fig. 1 the production of a molded part by means of powder bed laser sintering, in particular

special cold metal fusion;

Fig. 2 shows a first embodiment of a post-compression of a

component manufactured using an additive process;

Fig. 3 shows a second embodiment of a post-compression of a means

a component manufactured using an additive process; 4 shows a component with surface areas of different densities.

As an introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numbers or the same component designations, it being possible for the disclosures contained throughout the description to be applied to the same parts with the same reference numbers or the same component designations. The position information selected in the description, such as top, bottom, side, etc., is related to the figure directly described and shown and these position

information to be transferred to the new position in the event of a change in position.

Fig. 1 shows a molding 1 during its production by means of an additive

procedure. The molding 1 has a three-dimensional molding body 2 .

The shape of the molding 1 shown has no restrictive meaning but is only to be understood as an example. In principle, the method according to the invention can be used to produce moldings 1 with a wide variety of shapes, for example gears, sliding sleeves, clutch bodies, synchronizer rings, connecting rods, bearing caps for a split bearing arrangement, bearing elements, a

balancing components, torsional vibration dampers, filter structures, etc.,

The molded body 2 preferably comprises or consists of at least one metallic material and/or ceramic material. But it is also possible for the molded body 2 at least partially another material, such as

for example a polymeric plastic. It's still possible that

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stands or has it.

A water-atomized or ground metal powder is preferably used as the metallic material, in particular a sintered steel powder, a metal injection molding powder or mixtures. However, other

tall powder can be used as an alternative or in addition to this.

The molding 1 is produced using an additive manufacturing process. For example, the component 1 can be made with any of the previously known additive methods such as selective laser sintering, laser powder bed fusion, electron beam powder bed fusion, binder jetting, powder bed laser sintering, in particular cold metal fusion, direct energy deposition, wire arc additive manufacturing, stereolithography methods and other processes. In particular, such additive methods are used to produce the molding 1 in which the raw material is not completely melted, since with these methods with complete melting of the powder moldings are already produced whose density is greater than 99%. According to a preferred embodiment of the method, a blasting method using electromagnetic radiation or a sinter-based additive method is used as the additive method

deployed.

Since these methods are known per se, reference is made (to avoid repetition) to the relevant prior art for further details. As an example, selective laser sintering is shown schematically in FIG. A metal powder 3 or a powder containing this metal powder 3 (which can also contain a binder and/or at least one other additive in addition to the metal powder) is applied in layers over the entire surface of a platform 4. The layers of the molded part 1 are applied using a laser beam 5 in accordance with Shape of the blank is gradually "sintered" into the powder bed or the powder particles are connected by softening and solidifying the binder. Between the individual steps (layered application steps), the platform 4 is lowered and a

new layer applied. The energy supplied by the laser beam 5

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bordered sintering of the powder particles.

In the special case of using plastic powder particles containing metal powder, the laser-based printing process is not laser sintering, but a laser fusion process (cold metal fusion process), since the plastic matrix melts under the action of the laser energy and begins to flow and does not sinter.

The plastic matrix is then removed again during debinding.

Other processes are binder jetting or lithography-based metal manufacturing or in general all additive processes with which metallic green parts are produced

can be produced. Purely metallic or metallic/ceramic green bodies produced using the bulk sintering process can be

binding and sintering.

A component 6 is subsequently produced from the molding 1 by mechanically post-compacting at least a part or section of a molding surface 7 of the molding 1 by rolling or compression molding, preferably after the molding 1 has been sintered beforehand. A gear wheel is shown as component 6 in FIG. 2 as an example. Generally, for the post-compaction means

Rolling rotationally symmetrical components 6 preferred.

It should be mentioned at this point that the term “post-compression” means that this compression takes place after the molding 1 has been produced. For the purposes of the invention, the term does not necessarily mean that compaction of the molded body 1 has already taken place before this post-compression. A multi-step densification of at least a part or section of the molding

However, surface 7 is possible within the scope of the invention.

When compacting the surface 7 of the molded article by means of rollers, a roller tool with at least one molding wheel, for example a gear wheel, is used

8 when, as shown in FIG

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Component 6 is adjusted.

For the re-compaction of the molding surface 7, the rolling tool is preferably delivered, ie pressed against the molding 1. But it can also

Forming 1 are delivered to the rolling tool.

For the post-compacting of the surface 7 of the molding, either the molding 1 or preferably the rolling tool or the molding 1 and the rolling tool can be driven. The drive causes the rolling tool and the blank to rotate in opposite directions, so that the corresponding surface of the rolling tool slides off the surface 1 of the blank. Depending on the pressure with which the rolling tool and the blank 1 are pressed together, a greater or lesser degree of post-compaction of the blank surface can

che 7 can be achieved.

The relative movement of blank 1 and rolling tool to each other can

shaped, with or without reversal of direction of rotation, alternating, etc.

It is also possible that the distance between the rolling tool and the surface 7 of the molded article is reduced during the post-compaction in order to achieve a higher density in the area of the surface 7 of the molded article. This reduction

can be carried out stepwise or continuously.

Although only one rolling tool is shown in FIG. 2, it is possible within the scope of the invention to use more than one rolling tool simultaneously or one after the other in order to achieve the desired density of the molded surface 7.

are sufficient. For example, two or three rolling tools can be used.

The rolling tool can have an outer diameter that is larger than that of the blank 1. However, the rolling tool preferably has a small

ren outer diameter than the molding 1.

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Wave are arranged or clamped.

With this design variant of the post-compacting, a density can be achieved at least in the area of the molding surface 7 which corresponds to between 95% and 100% of the full density of the respective material. This density can decrease in the direction of the core layers of the component 6, ie inwards, so that the core layers of the component 6 have a lower density than its surface layer. The surface layer can have a layer thickness of between 1 μm and 1500 μm, in particular between 1 μm and 1000 μm, measured from the surface of the component 6 . Within this post-compacted surface layer, the density of the component 6 is preferably not less than 98% of the full density of the material used. In the case of the formation of a density gradient in the compacted surface layer, this value refers to the maximum density on the surface or the adjoining partial layer of the surface layer, with the maximum density starting from the

Surface of the component 6 into the component interior becomes smaller.

The statements on the maximum density can be general within the scope of the invention

apply, regardless of the compression method used.

3 shows a variant of a tool for post-compaction. The densification of the molding surface 7 of the molding 1

followed by compression molding.

In the context of the invention, the term "compression molding" means that

the molding 1 is pressed through or into a die tool 9 .

In the embodiment shown, the die tool 9 has three compression stages 10 . A compression level 10 is characterized in that you

Inner diameter 11 is smaller than an outer diameter 12 of the molding 1.

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The molding 1 is pressed into the die tool 9 and through the individual compression stages 10 by means of an upper punch, which is not shown in any more detail. In this case, the molding 1 can optionally also be supported by a lower punch, not shown, so that the molding 1 between

the upper punch and the lower punch is arranged.

After the inner diameter 11 of a compression stage 10 is smaller than the outer diameter 12 of the molding 1, this is compressed when it is pushed through or when it is pressed into the compression stage 10, whereby the porosity of the molding 1 is reduced, as with rolling, and the molding surface 7

is compressed.

Each subsequent compression stage 10 has a smaller inside diameter 11 than the immediately preceding compression stage 10, which means that when the molding 1 is moved through the die tool, the upper

surface 7 is progressively compacted.

The transitions between the individual compression stages 10 can be sharp

tig or chamfered or rounded.

It is also possible that between the individual compression stages 10 an expansion section with a larger inner diameter than the inner diameter

ser 11 of the preceding compression stage 10 is arranged.

The finished post-compacted component 6 can be demolded downwards or inwards.

follow a reversal of movement upwards.

It is possible for the die tool to have only one or two or more than three, for example four, five, six, seven, etc., compression stages 10 . If there is more than one compression stage 10, these can also be divided between several separate die tools 9, so that the molded part 1 has to be transferred from one die tool 9 to a subsequent die tool 9. However, the one-piece design of the die tool 9 with a plurality of compression stages 10 with a decreasing inside diameter 11 is the preferred design.

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For the sake of completeness, it should be mentioned that the inner contour of the die tool 9, ie the inner cross-sectional shape, is adapted to the outer contour of the molded part 1 and the component 6, so that apart from the post-compaction

no further deformation of the molding 1 in the die tool 9 takes place.

With regard to the extent of the post-compaction with the die tool 9, reference is made to the above statements on increasing the density by means of the rolling mill

referenced stuff.

With the method so a component 6 is produced that based on the

Density of the molding 1 after its production with the additive process has a compacted surface. The entire surface or lateral surface between the axial end faces or the entire toothing of the component

1 be compressed.

According to an embodiment variant of the invention, however, it can also be provided that only a region or section of this entire surface or lateral surface between the axial end faces or the entire toothing of the component 1 is post-compacted. For this purpose, for example, a rolling tool can be used, the track of which is narrower than the width of the component 6 in the axial direction. A component 6 can thus be produced, for example, as shown in detail in FIG. 4 . This component 6 has a first section 13 which has been post-compacted and a second section 14 which has the non-compacted surface 7 of the molding. This can be recognized by the fact that there are no longer any pores 15 on the surface of the component 6 in section 13 , but the pores 15 are still formed in section 14 . The component 6 can therefore have different porosities on the surface

have or in at least one section 13 no longer have any porosity.

It is also possible that section 14 was post-compacted, but the compaction was carried out less strongly here, so that pores 15 are still present, but they are smaller than the original pores of molded article 1 or their number was reduced, again based on the molding 1

after its additive manufacturing.

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If the post-compaction is carried out by means of rollers, the compacted section 13 can extend over the entire circumference. However, there is also the possibility of non-compacted or less compacted sections in the die tool 9, which, however, then run in the axial direction (in the pressing direction). For this purpose, longitudinal recesses can be provided in the die tool 9 in the compression stages 10, which do not come into contact with the molding 1 during compression or in which only a lower pressure is exerted on the molding 1, i.e. in the remaining area of the compression stage(s) 10. This version can also be just one or one based on the total number

at compression stages 10 lower number of compression stages 10 concern.

So it is possible with the method to produce components 6, which means a

have been produced using an additive method and which have a uniformly post-compacted surface over the entire surface or lateral surface between axial end faces, or which have sections 13, 14 which have an un-

have different densities.

If necessary, the component 6 can be fully compacted, so that the core layers no longer have any pores 15 either. As an alternative to this, it can be provided that pores 15 are still present in the core layers, as shown in FIG. If required, the core layers can also be in the form of the molding 1 originally produced.

let be.

According to one embodiment variant of the method, the post-compression can be carried out as cold compression. This means that no energy is supplied to heat the molded body 1 for the post-compacting. The Formling

1 can, however, have a temperature that deviates from room temperature

due to friction in the process itself.

In the context of the invention, it is also possible to carry out the post-compression at a higher temperature of the molding 1, for example at a

Temperature between 40 °C and 300 °C, in particular between 40 and 100 °C for

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sinter-based moldings 1 in the green state or at 80-300° C. for metallic moldings 1, for which the molding 1 can be heated or preheated accordingly. Optionally, as an alternative or in addition to this, the post-compression

be heated.

According to a further embodiment variant, it can be provided that the molding 1 is deliberately produced with a higher porosity. For this purpose, the molding 1 can have a density of at most 80%, in particular at most 70%, preferably at most 60%, for example between 40% and 50%, of the full density

of the material are produced.

Full density is the density of the material with a porosity of zero

to understand, for example the cast form of the material.

The increased porosity can be reduced by appropriate design of the process parameters

ter, in particular the CAD data, can be obtained.

According to a further embodiment variant of the method, it can be provided that the component 6 is sintered after the post-compacting (in particular a second piece is sintered). For this purpose, sintering can take place in a furnace, for example a continuous furnace, as is known from powder metallurgy, ie without a laser. The temperature during this sintering is preferably lower than the melting temperature of the material. For example, the temperature can be between 900°C and 1300°C or up to 2000°C in the case of hard metals. In general, the sintering temperature can be between 80% and 90% of the melting temperature of the

material amount.

With the method according to the invention it is possible to produce components 6 similar to components produced by powder metallurgy, but with use

an additive process.

It is also possible with the method not only to carry out a post-compaction of the molding 1, but also to smooth its molding surface 7 or to reduce the roughness in relation to the roughness after the molding 1 has been produced.

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The exemplary embodiments show or describe possible variants, it being noted at this point that combinations of the individual

Variants among themselves are possible.

Finally, for the sake of order, it should be pointed out that, for a better understanding of the structure, elements in the figures are not necessarily to scale.

are represented literally.

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15

Reference List

molding molding body metal powder platform laser beam

Component Molding surface Gear Die tool Compression stage Inner diameter Outer diameter Section

Section

pore

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Claims (10)

patent claims 1. A method for producing a component (6) from a metal powder (3) and/or ceramic powder and optionally further additives, according to which the metal powder (3) and/or ceramic powder is processed into a molded part (1) by means of an additive method, and is preferably then sintered, characterized in that the component (6) from the, optionally sintered, molding (1) by mechanical post-compacting, in particular by rolling or compression molding, at least part of the molding surface (7) herge- is provided. 2. The method according to claim 1, characterized in that the after compacting is carried out as cold compaction. 3. The method according to claim 1 or 2, characterized in that differently highly compressed surface areas can be produced. 4. The method according to any one of claims 1 to 3, characterized in that the molding (1) is produced with a density of at most 80% of the full density becomes. 5. The method according to any one of claims 1 to 4, characterized in that the component (6) is sintered after the mechanical post-compacting, given If necessary, sintered a second time. 6. The method according to any one of claims 1 to 5, characterized in that a blasting method using electromagnetic radiation or a sinter-based additive method or a blast-based powder bed method, such as in particular the cold metal fusion method, is used as an additive method. is set. N2021/29200-AT-00 7. The method according to claim 6, characterized in that as a beam process selective laser sintering is used. 8. The method according to any one of claims 1 to 7, characterized in that a sintered steel powder, a metal injection molding powder or a metal powder mixture thereof is used. 9. Component (6) produced by means of an additive process, comprising a metallic component body, characterized in that the component body has at least sections of a surface that is produced by mechanical post-compression, in particular by rolling or compression molding, higher density than a subsurface core layer. 10. Component (6) according to claim 9, characterized in that the section of the surface with the higher density in comparison to the core layer is free is formed by open pores (15). N2021/29200-AT-00