AT525599B1 - 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 made from the optionally sintered molding (1) by mechanical post-compacting, carried out as cold compaction, by rolling or compression molding, in which the molding (1) is pressed through or into a die tool (9), at least part of the Molding surface (7) produced.

Description

Description

The invention relates to a method for producing a component from a metal powder and / or ceramic powder, according to which the metal powder and / or ceramic powder is processed by an additive process to form a molded part.

The invention further relates to a component produced by means of an additive method, comprising a metallic component body.

[0003] 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 is computer controlled using CAD data.

[0004] The problem of this method in industrial application is described very well in DE 10 2017 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, since mixed materials are produced with it. The same applies to the impregnation of such components with low-melting metal alloys.

[0005] 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. However, hot isostatic pressing is complex, since the components are pressed in a container that is closed on all sides in order to enable isostatic conditions. In addition, the HIP requires the presence of a closed porosity, which is often not the case with sinter-based processes (and coarser metal powder particles).

DE 10 2018 102 616 A1 discloses a method for producing hard metal bodies, in which a laser-based additive manufacturing method with an energy input by means of a laser at each location of the energy input to realize a temperature of 800° C. to a maximum of <2735° C a hard metal green body is produced 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 90000 Pa and/or gas pressure sintering and pressures up to is subjected to a maximum of 10 MPa up to a compaction of the hard metal body of 98% of the theoretical density.

DE 10 2015 201 873 A1 describes a method for producing a sintered gear wheel according to at least one of the following production methods for forming a noise-reducing agent in the gear wheel: surface rolling and/or surface compression of the toothing to adjust porosity from the point of view of noise reduction, simultaneous arrangement of two or more different powders to be sintered together in a press mold, to form a noise-reducing agent in the gear wheel, an insertion of one or more bodies in and/or on a material to be sintered of the gear wheel to be produced, preferably a strut, a vibration system, a Hollow body or a liquid-filled body.

[0008] DE 10 2021 003 914 A1 discloses a method for producing a component arrangement, comprising the following method steps: providing the base body and a mixture of an iron-based alloy and the reinforcement particles; and producing the composite component in layers on the base body by additive manufacturing. After the additive manufacturing of the composite component, it can be post-compacted using hot isostatic pressing.

US 2018/326493 A1 describes a method for producing an orthopedic implant made of metal, comprising the additive construction of the orthopedic implant and in

in either order, relaxing the orthopedic implant or heating the orthopedic implant and compressing the heated implant with hot isostatic pressure or hot uniaxial pressure and eroding one or more surfaces of the orthopedic implant.

The present invention is based on the object of creating an industrially simpler feasible possibility with which the performance of a component produced 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 formed from the molding by (exclusively) mechanical post-compacting carried out as cold compression by rollers or compression molding, in which the molding is pressed through or into a die tool , At least part of the molding surface is produced. No thermomechanical post-compression is used, as is the case with HIP.

The object of the invention is also achieved in that the component body has, at least in sections, a surface that produces higher density as a subsurface core layer.

The advantage here is that the post-compaction is carried out with a method that can be easily integrated into the process chain for manufacturing the component without major adaptations. There is no need for special containers into which the component must be inserted before compaction is carried out, as is the case with isostatic pressing. Cycle times can thus be shortened and the automation of component manufacture is also possible to a greater extent. In addition, it is possible that only areas of the component surface are compacted, for example by not rolling the entire surface of the component, so that a component with a mix of properties can be manufactured more easily. In addition, the degree of compaction can be controlled more easily, for example by controlling the infeed of the rolling tool, which makes it easier to produce different densities in different components.

It is envisaged that the post-compression is carried out as a cold compression. On the one hand, energy can be saved in this way. On the other hand, if the material is selected accordingly, further hardening of the component can be achieved by increasing the strength of the component material.

As already mentioned, it is possible with the invention to provide a component that has compacted 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. A reduction in tool costs can also be achieved in this way, since they have a longer service life due to less compaction.

Also to extend the service life of the tool can be provided according to another embodiment of the invention that the molding is produced with a maximum density of 80% of the full density. Due to the higher porosity, lower forming forces are required to compact the surface of the component, which means that the tool is also subject to less stress compared to post-compaction of a component that has been manufactured with a density of more than 80% of the full density.

According to another embodiment of the invention it can be provided that the component is sintered after the mechanical post-compacting. A further improvement in the component properties can thus be achieved. The metal-powder contacts produced by compaction form sinter bridges and lead to further hardening and compaction of the mechanically compacted areas. It can also be used to seal the components

be improved by the edge zone compression against liquid ingress.

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 method Powder bed processes, such as selective laser sintering in particular, is. In these additive methods in particular, the mentioned at least partial post-densification of the component surface has proven to be advantageous.

For the same reasons, according to a further embodiment 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, the invention can also be used to use a water-atomized or ground metal powder, which can usually only be used to a limited extent for additive processes due to its morphology and flowability.

According to another embodiment of the invention, it can be provided that the section of the surface with the higher density in comparison 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 the result that the component weight can be reduced or the component can also have a storage capacity for liquid, such as lubricant, for example.

For a better understanding of the invention, this is explained in more detail with reference to the following figures.

In each case, in a simplified, schematic representation:

[0023] FIG. 1 shows the production of a molded part by means of powder bed laser sintering, in particular cold metal fusion; [0024] Fig. 2 shows a first variant of a post-compression of a means of an additional

component manufactured by means of a ditive process;

[0025] FIG. 3 shows a second embodiment variant of a post-compaction of a component produced by means of an additive method;

[0026] FIG. 4 shows a component with surface areas of different densities.

First of all, 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, with the disclosures contained throughout the description being able to be transferred mutatis mutandis 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 are to be transferred to the new position in the event of a change of position.

1 shows a molding 1 during its manufacture by means of an additive process. The molding 1 has a three-dimensional molding body 2 .

The illustrated shape of the molding 1 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 gear wheels, sliding sleeves, clutch bodies, synchronizer rings, connecting rods, bearing caps for a split bearing arrangement, bearing elements, an unbalanced component, torsional vibration dampers, filter structures, etc.

The molded body 2 preferably comprises at least one metallic material and/or ceramic material or consists of it. However, it is also possible to use a different material, such as a polymer plastic, at least partially for the molded body 2 . It is also possible for the molding 1 to consist of or have at least two different metallic materials.

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 metal powders can also be used as an alternative or in addition to this.

The molding 1 is produced by means of 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 variant of the method, a blasting method using electromagnetic radiation or a sinter-based additive method is used as the additive method.

Since these methods are known per se, reference is made (to avoid repetition) to further details on the relevant prior art. 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 is applied. The energy supplied by the laser beam 5 is absorbed by the powder or the binder and leads to locally limited sintering of the powder particles.

In the special case of the use of 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 methods are binder jetting or lithography-based metal manufacturing or generally all additive methods with which metallic green parts can be produced. Purely metallic or metallic/ceramic green bodies produced by bulk sintering processes can be compacted after sintering or debinding 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. In general, rotationally symmetrical components 6 are preferred for the subsequent compaction by means of rollers.

It should be mentioned at this point that the term "recompression" 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. However, a multi-step densification of at least a part or section of the molded surface 7 is possible within the scope of the invention.

When compacting the molding surface 7 by means of rollers, a rolling tool with at least one shaping wheel is used, for example a gear wheel 8, if, as shown in FIG. 2, the toothing of the molding 1 is to be compacted. However, the rolling tool can also have a different geometry, which is correspondingly adapted to the geometry or contour of the molded part 1 or the component 6 .

For the post-compaction of the molding surface 7, the rolling tool is preferably delivered, ie pressed against the molding 1. However, the formed part 1 can also be delivered to the rolling tool.

For the recompression of the molding surface 7, 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 against one another, a greater or lesser degree of post-compaction of the blank surface 7 can be achieved.

The relative movement of the molding 1 and the rolling tool to one another can be uniform, with or without reversing the 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 at the same time or in succession in order to achieve the desired density of the surface 7 of the molded product. 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 smaller outer diameter than the blank 1.

Only for the sake of completeness it should be mentioned that both the molding 1 and the rolling tool for the post-compaction are arranged or clamped accordingly on an axis or shaft.

With this variant embodiment of the post-compaction, 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. If a density gradient develops in the compacted surface layer, this value relates to the maximum density on the surface or the adjoining partial layer of the surface layer, with the maximum density decreasing from the surface of the component 6 towards the interior of the component.

The statements regarding the maximum density can generally apply within the scope of the invention, regardless of the compression method used.

3 shows a variant embodiment of a tool for post-compaction. The compression of the molding surface 7 of the molding 1 is done by compression molding.

The term "compression molding" is understood in the sense of the invention that the molding 1 is pressed through or into a die tool 9 .

The die tool 9 has three compression stages 10 in the illustrated embodiment. A compression stage 10 is characterized in that its inner diameter 11 is smaller than an outer diameter 12 of the molded part 1.

[0051] The molding 1 is inserted into the die by means of an upper punch (not shown).

tool 9 in and pressed through the individual compression stages 10. In this case, the blank 1 can optionally also be supported by a lower punch, not shown in any more detail, so that the blank 1 is therefore arranged between the upper punch and the lower punch.

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, which reduces the porosity of the molding 1 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 molding surface 7 is progressively compressed further and further.

The transitions between the individual compression stages 10 can be designed with sharp edges or chamfered or rounded.

It is also possible that between the individual compression stages 10 a relaxation section with a larger inner diameter than the inner diameter 11 of the preceding compression stage 10 is arranged.

The demoulding of the finished, post-compacted component 6 can be downwards or, as a result of 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 inner diameter 11 is the preferred design.

For the sake of completeness, it should be mentioned that the inner contour of the die tool 9, i.e. the inner cross-sectional shape, is adapted to the outer contour of the molding 1 and the component 6, so that apart from the post-compaction, no further deformation of the molding 1 in the die tool 9 he follows.

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 tool.

A component 6 is thus produced with the method that has a surface which is densified in relation to the density of the molding 1 after its production using the additive method. The entire surface or lateral surface between the axial end faces or the entire toothing of the component 1 can be post-compacted.

According to one embodiment 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. A rolling tool can be used for this purpose, for example, 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 molded product. 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 or no longer have any porosity in at least one section 13 .

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

was, in turn based on the molding 1 after its additive manufacturing.

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 embodiment can also relate to only one or a lower number of compression stages 10 in relation to the total number of compression stages 10 .

It is therefore possible with the method to produce components 6 which have been produced by means of 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 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 left in the form of the molding 1 originally produced.

The post-compression is carried out as a cold compression. This means that no energy is supplied to heat the molded body 1 for the post-compacting. However, the molding 1 can have a temperature deviating from room temperature, which arises due to friction in the process itself.

According to a further embodiment, it can be provided that the molding 1 is deliberately produced with a higher porosity. For this purpose, the molding 1 can be produced with 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.

[0068] Full density is to be understood here as meaning the density of the material with a porosity of zero, ie for example the cast form of the material.

The increased porosity can be obtained by appropriate design of the process parameters, in particular the CAD data.

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.

With the method according to the invention it is possible to produce components 6 similar to components produced by powder metallurgy, but using an additive method.

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 production of the molding 1.

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 shown to scale.

REFERENCE LIST

1 molding 2 molding bodies

3 metal powder

4 platform

5 laser beam

6 component

7 molding surface 8 gear

9 die tool 10 compression stage 11 inner diameter 12 outer diameter 13 section

14 section 15 pore

Claims (9)

patent claims 1. A method for producing a component (6) from a metal powder and/or ceramic powder and optionally further additives, 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 then sintered characterized in that the component (6) is made from the optionally sintered molding (1) by mechanical post-compacting, carried out as cold compaction, by rolling or compression molding, in which the molding (1) is pressed through or into a die tool (9). , at least part of the molding surface (7) is produced. 2. The method according to claim 1, characterized in that differently highly compressed surface areas are produced. 3. The method according to any one of claims 1 or 2, characterized in that the molding (1) is produced with a density of at most 80% of the full density. 4. The method according to any one of claims 1 to 3, characterized in that the component (6) is sintered after the mechanical post-compacting, optionally sintered a second time. 5. The method according to any one of claims 1 to 4, characterized in 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. 6. The method according to claim 5, characterized in that selective laser sintering is used as the blasting method. 7. The method according to any one of claims 1 to 6, characterized in that a sintered steel powder, a metal injection molding powder or a mixture thereof is used as the metal powder. 8. The 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 can be post-compacted by mechanical cold compaction by rolling or compression molding, in which the molded part (1) is or pressed into a die tool (9) has a higher density than a core layer formed below the surface. 9. Component (6) according to claim 8, characterized in that the section of the surface with the higher density in comparison to the core layer is free of open pores (15). 2 sheets of drawings