WO2023155951A1

WO2023155951A1 - Method for producing a sintered component and sinter support for arranging a component blank within a sintering unit

Info

Publication number: WO2023155951A1
Application number: PCT/DE2023/100084
Authority: WO
Inventors: Heiko Blunk; Arthur Seibel
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.
Priority date: 2022-02-16
Filing date: 2023-02-02
Publication date: 2023-08-24
Also published as: DE102022103671A1

Abstract

The invention relates to a method for producing a sintered component (34'), comprising the steps of: positioning a component blank (30-40) in a positioning section (4) of a sinter support (1), and sintering the component blank (30-40) positioned in such a way, wherein the sinter support (1) within the positioning section (4) has a structured surface (6) which is designed in such a way that a coefficient of friction between the component blank (30-40) and the sinter support (1) is reduced in order to reduce a deformation of the component blank (30-40).

Description

Method for producing a sintered component and sinter base for arranging a component blank within a sintering unit

The invention relates to a method for producing a sintered component, a sintering base for arranging a component blank within a sintering unit, a sintering unit and a method for producing a sintering base.

Methods for producing sintered components are known in principle. A sintered component is produced by sintering a component blank. The component blank can be provided using different methods, for example using a metal binder jetting method, an injection molding method, in particular an MIM method, or an extrusion method. A so-called green part produced in this way generally has a high porosity. Furthermore, such a green part has a higher volume compared to the final component. After the green part has been produced, the binder can be removed before the sintering process, resulting in a so-called brown part. The brown part is then sintered. during the During sintering, the component blank generally shrinks by around 10-20%.

Since the component blanks are usually arranged on a polished sinter base during sintering, the shrinkage causes a relative movement between the component blank and the sinter base. This relative movement is influenced by a frictional force between the sinter base and the component blank. In particular, this frictional force counteracts the movement brought about by the shrinkage, so that a generally undesirable deformation of the component results.

Sintered components therefore usually always show a deformation that can only partially be taken into account when designing the component. In the case of high-precision components in particular, this deformation requires post-processing of the sintered component. In addition, the degree of freedom in the design of the components is restricted, since certain geometries are deformed to such an extent during sintering that they cannot be produced under economic conditions.

One approach to reducing such deformations is to adapt and simplify the component design so that, for example, a closed contact surface with the sinter base is provided. At the same time, however, this means that the components are heavier and may need to be made of more material. Typically, such a departure from the ideal design also results in reduced device performance.

Another approach to reducing deformations during sintering is to use a sintering base that shrinks with it. Such a sinter base is to be understood as an additional element that is made from the same material and using the same process as the component blank. It can thus be ensured that the sintering-inherent causal relationships of the shrinking sintering base and the component are comparable. For example, such a sintering base can be designed as a plate that corresponds in its base to the base of the component and between the actual sintering base and the component is placed. However, such an additional sinter base that shrinks with it requires the use of additional material and an additional tool may be required.

An alternative approach to reducing deformations during sintering is to use spherical granules that are placed between the sinter base and the component blanks. The resulting rolling friction between the component and the sinter base takes into account the shrinkage effects during sintering. One disadvantage of using spherical granules is that they are not suitable for every component. For example, the granules can lead to imprints on the component. In addition, not all geometries of components are suitable for such a granulate, for example if it does not have a flat support.

There is a demand in the industry for sintered components with high tolerance requirements that require no or reduced post-processing. Furthermore, it is a requirement from industry to produce sintered components whose scrap rate is low.

DE 10 2013 004 807 A1, DE 69 703 750 T2, DE 42 06 007 A1 and CN 205673589 U disclose sintering bases and methods for producing sintered components.

It is therefore an object of the invention to provide a method for producing a sintered component, a sintering base for arranging a component blank within a sintering unit, a sintering unit and a method for producing a sintering base that reduce or eliminate one or more of the disadvantages mentioned. In particular, it is an object of the invention to provide a solution that enables the production of sintered components with little or no deformation during sintering.

This object is achieved with a method and a sintering base according to the features of the independent patent claims. Further advantageous refinements of these aspects are described in the respective dependent patent claims specified. The features listed individually in the patent claims and the description can be combined with one another in any technologically meaningful way, with further embodiment variants of the invention being shown.

According to a first aspect, the object is achieved by a method for producing a sintered component, comprising the steps: positioning a component blank in a positioning section of a sintering base and sintering the component blank positioned in this way, the sintering base having a structured surface within the positioning section that is configured in this way is that a coefficient of friction between the component blank and the sinter base is reduced to reduce deformation of the component blank.

The invention is based on the finding that the generally polished surfaces of sintered bases do not allow optimal production of sintered components. In particular, it was found that a structured surface leads to improved component quality. The invention is also based on the knowledge that the coefficient of friction between the component blank and the sintering base can be reduced by the sintering base having a structured surface in a section in which the component blank is placed. A coefficient of friction reduced by means of the structured surface is to be understood in particular as meaning that the coefficient of friction is reduced in comparison to a polished surface. Due to the reduced coefficient of friction, the frictional forces between the shrinking component blank and the sinter base are reduced, so that the deformation of the finished component is reduced or eliminated.

The method is designed to produce a sintered component, in particular to sinter a component blank. The method includes, among other things, the step: positioning the component blank in the positioning section of the sintering base. Two or more component blanks are preferably arranged in the positioning section. In normal operation, the sintering base preferably has a horizontal bearing surface on a surface within which the positioning section is provided. The positioning section can be formed by a section of the supporting surface and/or the surface of the sintering base. Alternatively, the positioning section can be formed on the entire bearing surface and/or the surface. The positioning can be or include, for example, arranging and/or placing the component blank on the sintering base.

In a further step, the component blank positioned in this way is sintered. During sintering, the component blanks are generally heated to a temperature close to the melting point of the material of the component blank in a short time in order to compact the particles of the component blank by capillary forces. The reduction in surface free energy typically changes the geometry of the sintered component through non-compacting and consolidating mechanisms.

The sintering can include, among other things, arranging the sintering base with the component blank within a sintering unit, for example a sintering furnace. Alternatively, the component blank can be arranged on the sintering base inside the sintering unit.

The sinter base has the structured surface within the positioning section. The structured surface is designed in such a way that the coefficient of friction between the component blank and the sinter base is reduced in order to reduce deformation of the component blank. A structured surface is to be understood in particular as a non-polished or non-smooth surface. In particular, it can be preferred that the structured surface is formed in a defined manner. Furthermore, the structured surface can have uniform and/or non-uniform structures, for example microstructures.

In a preferred embodiment, a lubricant is applied between the component blank and the sinter base. With such a lubricant, the coefficient of friction between the component blank and the sinter base can be further reduced. The lubricant can be liquid and/or solid. For example, the lubricant may be or include carbon and/or a molybdenum substance. In a further preferred embodiment of the method, it is provided that the component blank is arranged directly on the sinter base. This means in particular that no intermediate layer or the like is arranged between the component blank and the sintering base. In particular, there are either no further elements and/or the lubricant between the component blank and the sintering base. Furthermore, in this variant of the method there are no sinter beads between the component blank and the sinter base.

It is further preferred that the method includes the step: producing the component blank. For example, the component blank can be produced using a metal binder jetting process, a metal or powder injection molding process, or a fused filament fabrication process. Furthermore, it is preferred that the method comprises the step: providing the sintering base comprising a base body, which is formed with a sinter-resistant material, and the positioning section provided on the base body, the base body having the structured surface within the positioning section.

Furthermore, it is preferred that the method includes the step: arranging the sintering base in a sintering unit, for example a sintering furnace. Provision can be made for the component blank to be positioned on the sintering base within the sintering unit. In addition, the method can include the step of removing the sintering base from the sintering unit after the component blank has been sintered within the sintering unit.

According to a further aspect, the object mentioned at the outset is achieved by a sintering base for arranging a component blank within a sintering unit, comprising a base body which is formed with a sinter-resistant material, a positioning section provided on the base body, the base body having a structured surface within the positioning section , which is formed in such a way that a coefficient of friction between the component blank and the sinter base is reduced in order to reduce deformation of the component blank.

The sinter-resistant material of the base body is designed to be particularly resistant to high temperatures. It is preferred that the sinter-resistant Material is not reactive with the material of the component blank, in particular non-reactive with ceramic materials and / or metal materials formed. The sinter-resistant material is particularly temperature-resistant up to preferably at least 250°C, 500°C or 1000°C. The sinter-resistant material is in particular a high-temperature material, for example a high-temperature alloy and/or a ceramic.

The positioning section is provided in particular on a surface of the base body, which preferably has a surface orthogonal in normal operation, which is aligned essentially vertically upwards. The positioning section is designed for arranging at least one component blank, in particular two or more component blanks. It may be preferable that the base body has two or more positioning sections. For example, two sections of the base body can have a structured surface, which accordingly form two positioning sections.

In a preferred embodiment variant of the sintering base, it is provided that the structured surface is formed with the sinter-resistant material of the base body. In particular, the structured surface is not formed with a further material in this embodiment variant. Such a sinter base is comparatively easy to produce and robust.

In a further preferred embodiment of the sintering base, it is provided that a coating of the base body forms the structured surface. For example, a surface of the sinter base can be provided with the coating and this coating can be structured. The coating can be, for example, a ceramic spray, a nitrided layer or a polytetrafluoroethylene layer.

In a preferred development of the sintering base, it is provided that the structured surface is formed in a defined manner. A structured surface formed in a defined manner is to be understood in particular to mean that it is formed, in particular was produced, according to a predefined structural specification. In particular, a structured surface is not to be understood as meaning any generally existing porosity or roughness of a surface unless this is explicitly intended to form the structured surface to reduce the coefficient of friction.

The structured surface formed in a defined manner can be formed regularly or irregularly.

In a further preferred embodiment of the sintering base, it is provided that the structured surface has a large number of microstructures. The microstructures can have grooves, bores and/or cylindrical structures, for example.

In particular, the microstructures can be in the form of depressions and/or elevations or can include them. The microstructures designed as elevations can be produced, for example, using a build-up method. For example, the structured surface can have a large number of cylindrical microstructures that are arranged next to one another. Alternatively, a large number of cylindrical bores can be provided, which form the structured surface.

In a further preferred embodiment variant of the sintering base, it is provided that the microstructures have a cylindrical, honeycomb, conical, pyramidal, semi-ellipsoidal, semi-spherical and/or polygonal geometry. Furthermore, the microstructures can have triangular and/or quadrangular geometries. The geometries described above can in particular be cross sections. In particular, these cross sections can be formed orthogonally to a vertical and/or a horizontal line.

A further preferred development of the sintering base is characterized in that the microstructures are designed in the form of grooves, which preferably extend in at least two groove directions aligned at an angle to one another. In normal operation, the directions of the grooves are in particular aligned essentially horizontally.

Another preferred embodiment of the sinter base is characterized in that the microstructures have a structure depth of less than 200 Micrometers, in particular less than 100 micrometers. The structural depth is aligned essentially orthogonally to a surface of the base body, in particular orthogonally to the structured surface of the base body. In addition, it is preferred that the structural depth is between 100 nanometers and 200 micrometers, in particular between 500 nanometers and 200 micrometers, preferably 100 micrometers.

A further preferred development of the sinter base is characterized in that the microstructures have an aspect ratio of greater than 1. The inventors have found that, in particular, an aspect ratio of greater than 1 leads to a particularly advantageous reduction in the coefficient of friction between component blanks and the sinter base. An aspect ratio is generally to be understood as a ratio of a depth of an indentation and a width of the indentation. If the width of the indentation cannot be clearly determined, for example because the indentation tapers conically, the width of the indentation can also be an average width of the indentation.

According to a further aspect, the object mentioned at the outset is achieved by a sintering unit for sintering component blanks, comprising a sintering base according to one of the embodiment variants described above.

According to a further aspect, the object mentioned at the outset is achieved by a method for producing a sinter base, in particular a sinter base according to one of the embodiment variants described above, comprising the steps: providing a base body formed with a sinter-resistant material, preferably with a surface that can be structured, and structuring a or the surface of the base body, so that a structured surface is formed in a positioning section. It is preferred that the structured surface is formed with elevations and/or depressions.

In a preferred embodiment variant of the method, it is provided that a laser structuring method is used for the structuring. In addition, it can be preferred that an etching method, a coating or a profiled rolling is used for the structuring. Alternatively you can further shaping and/or removing and/or applying methods for producing the structured surface can be used.

For further advantages, design variants and design details of the individual aspects and their possible developments, reference is also made to the description given for the further aspects, the corresponding features and developments.

Preferred exemplary embodiments are explained by way of example with reference to the accompanying figures. Show it:

Figure 1: a schematic, three-dimensional view of an exemplary

Embodiment of a sinter base;

FIG. 2 shows a schematic, three-dimensional view of a further exemplary embodiment of a sintering base with component blanks;

FIG. 3: a schematic, two-dimensional sectional view of an exemplary embodiment of a sinter base;

FIG. 4: a schematic, two-dimensional sectional view of a further exemplary embodiment of a sinter base;

FIG. 5: schematic, two-dimensional views of a component blank and a component sintered from the component blank;

Figure 6: a schematic, three-dimensional view of an exemplary

embodiment of a sintering unit;

FIG. 7 shows a schematic view of an exemplary embodiment of a method for producing a sintered component; and

FIG. 8: a schematic view of an exemplary embodiment of a method for producing a sinter base.

In the figures, identical or essentially functionally identical or similar elements are denoted by the same reference symbols. FIG. 1 shows a sinter base 1 for the arrangement of component blanks 30-40 shown in FIG. The sintering base 1 extends in horizontal directions B1, B2 and in the vertical direction T. The sintering base 1 comprises a base body 2 which is made of a sinter-resistant material, for example ceramic. A positioning section 4 is provided on the base body 2 . In the present case, the positioning section 4 is surrounded by the dashed line. The base body surface 8 of the base body 2 is structured within the positioning section 4 , so that a structured surface 6 is formed within the positioning section 4 . The structured surface 6 is designed in such a way that a coefficient of friction between a component blank 30-40 and the sintering base 1 is reduced in order to reduce or avoid deformation of the component blank 30-40 during sintering.

A modified sintering base 1 is shown in FIG. 2, the base body 2 having a coating 10 which is surrounded by the continuous line. The coating 10 can also be provided on the entire base body surface 8 or on all base body surfaces of the base body. In the present case, the coating 10 is structured so that the structured surface 6 is formed. The component blanks 30-40 are indicated here for clarification. In the present case, the geometry of the component blanks 30-40 is shown as cylindrical, although no restriction to such a geometry is intended. The component blanks 30-40 can have any desired geometry.

The structured surface 6 has, in particular, depressions and/or elevations in the depth direction T. The elevations and/or depressions have extensions orthogonal to the depth direction T in the directions B1 and B2. It is preferred that an extension in the depth direction T is greater than in the directions B1 and B2, so that an aspect ratio of greater than 1 is established.

FIG. 3 shows a sectional drawing of an exemplary embodiment of a structured surface 6. In the present case, the structured surface 6 is formed by depressions 16 between elevations 12, 14. Such a Structured surface 6 reduces the coefficient of friction between the sintering base 1 and a component blank 30-40 arranged on the sintering base 1 .

A further exemplary embodiment of a structured surface 6 is shown in FIG. For example, the elevations 18, 20 can be produced by a build-up manufacturing process. In addition, the elevations 18, 20 can be formed by a coating and the depression 22 by a machining process.

FIG. 5 shows in panel A the effect of a conventional sintering process without the process and the sintering base which are the subject of the present disclosure. The sintering of the component blank 34 leads to a visible deformation, so that the sintered component 34' produced in this way has a change in geometry. Deformation occurs in particular as a result of the coefficient of friction between the component blank 34 and the sinter base and the resulting frictional forces.

In figure B the use of a sinter support 1 and a method according to the disclosure is shown. The volume of the component blank 34 is inherently reduced towards the sintered component 34 ″. Due to the optimized sinter base, however, a deformation of the sintered 34" component is not recognizable.

FIG. 6 shows a sintering unit 42 for sintering component blanks 30-40. The sintering unit 42 can be a sintering furnace, for example. The sintering unit 42 includes a sintering base 1, as shown in FIGS. 1 and 2, for example.

FIG. 7 shows a method for producing a sintered component. In step 100, a component blank 30-40 is produced, for example using a powder injection molding process. In step 102, a sintering base 1 is provided, comprising the base body 2 formed with a sinter-resistant material and the positioning section 4 provided on the base body 2, wherein the Base body 2 has the structured surface 6 within the positioning section 4 . In step 104, a component blank 30-40 is positioned in the positioning section 4 of the sinter base 1, i.e. on the surface 6 of the base body 2.

Further, in step 106, the sintering base 1 is placed in the sintering unit 42. FIG. The order of steps 104 and 106 can also be reversed. In step 108, the component blank 30-40 is sintered, in particular subjected to a high temperature. After the component blank 30-40 has been sintered in step 108 and the sintered component 34'' has been produced, the sinter base 1 is removed from the sintering unit 42 in step 110.

FIG. 8 shows a method for producing a sinter base 1 . In step 200, a base body 2 formed with a sinter-resistant material and having a surface that can be structured is provided. In step 202 the surface is structured so that a structured surface 6 is formed in the positioning section 4 . The basic body 2 can be provided by manufacturing.

The previously described method for producing a sintered component 34'' and the sintered base 1 described have the advantage that the coefficient of friction and thus the frictional forces between the sintered base 1 and a component blank 30-40 arranged on the sintered base 1 are reduced.

This reduced coefficient of friction or the reduced frictional forces lead to reduced deformation of the component blank 30-40 and thus of the sintered component 34”. As a result, the sintered component 34'' has improved shape and dimensional accuracy. Therefore, less post-processing of the component 34″ is required or the component 34″ is suitable for the application without the scrap rate reducing the economic efficiency of the component 34″. REFERENCE MARKS

1 sinter pad

2 basic bodies

4 positioning section 6 textured surface

8 body surface

10 coating

12 elevation

14 Elevation 16 Deepening

18 survey

20 elevation

22 deepening

30-40 component blank 34', 34" sintered component

42 sintering unit

Claims

CLAIMS Method of manufacturing a sintered component (34'), comprising the steps of:

Positioning a component blank (30-40) in a positioning section (4) of a sintering base (1), and sintering the component blank (30-40) positioned in this way,

- wherein the sintering base (1) has a structured surface (6) within the positioning section (4), which is designed in such a way that a coefficient of friction between the component blank (30-40) and the sintering base (1) is reduced in order to prevent deformation of the To reduce component blank (30-40). Method according to Claim 1, in which a lubricant is applied between the component blank and the sintering base (1). Method according to one of the preceding claims, in which the component blank is arranged directly on the sinter base (1). Sintering base (1) for arranging a component blank (30-40) within a sintering unit, comprising a base body (2) which is made of a sinter-resistant material, a positioning section (4) provided on the base body (2),

- wherein the base body (2) has a structured surface (6) within the positioning section (4), which is designed in such a way that a coefficient of friction between the component blank and the sintering base (1) is reduced in order to prevent deformation of the component blank (30-40 ) to decrease. Sinter base (1) according to the preceding claim, wherein the structured surface (6) is formed with the sinter-resistant material of the base body (2).

6. sinter base (1) according to the preceding claim, wherein a coating of the base body (2) forms the structured surface (6).

7. sinter base (1) according to any one of the preceding claims, wherein the structured surface (6) is formed defined.

8. sinter base (1) according to any one of the preceding claims, wherein the structured surface (6) has a plurality of microstructures.

9. Sinter base (1) according to one of the preceding claims, wherein the microstructures are designed as depressions (16, 22) and/or as elevations (12, 14, 18, 20).

10. Sinter base (1) according to one of the preceding claims, wherein the microstructures have a cylindrical, honeycomb, conical, pyramidal, semi-ellipsoidal, semi-spherical and/or polygonal geometry.

11. Sinter base (1) according to any one of the preceding claims, wherein the microstructures are formed in grooves.

12. Sinter base (1) according to one of the preceding claims, wherein the microstructures have a structure depth of less than 200 μm.

13. Sinter base (1) according to one of the preceding claims, wherein the microstructures have an aspect ratio of greater than 1.

14. sintering unit (42) for sintering component blanks (30-40), comprising a sintering base (1) according to any one of the preceding claims. Method for producing a sinter base (1), in particular a sinter base (1) according to one of the preceding claims 1-13, comprising the steps:

Providing a base body (2) formed with a sinter-resistant material, and

Structuring a surface of the base body, so that a structured surface (6) is formed in a positioning section (4). Method according to the preceding claim, wherein a laser structuring method is used for the structuring.