Method for treating the surface of components produced by 3D printing, and corresponding component

Abstract

The invention relates to a method for treating the surface of components produced by means of 3D printing. The method comprises the steps of (i) providing a component, in particular produced by 3D printing, made of a base material having an untreated surface, (ii) immersing the component in a suspension, wherein the suspension contains more than 40% by mass of a solid similar in type to a base material of the component, and (iii) pulling the component out of the suspension, wherein a component surface having a roughness lower than that of the untreated surface is produced. The invention also relates to a correspondingly produced or treated component.

Description

[0001] 2024PF00573 - Foreign version

[0002] 1

[0003] Description

[0004] Methods for treating the surface of components manufactured via 3D printing, and corresponding components

[0005] The present invention relates to a method for treating or smoothing the surface of components manufactured by means of 3D printing or additive manufacturing, in particular via so-called "binder jetting", as well as a correspondingly manufacturable or treated component.

[0006] The component in question is preferably a core or a component used in casting or investment casting. Such components are particularly intended as tools for the downstream (casting) production of turbine components, such as components used in the hot gas path of a gas turbine. These latter components often require fluid cooling during operation and therefore frequently exhibit delicate features and complex internal cooling channels.

[0007] Alternatively or additionally, the final component may be a component for use in the automotive or aviation sector.

[0008] The design and material properties of high-performance machine components are subject to continuous development in order to increase or expand the functionality and / or application areas of the respective components. In the case of heat engines, especially gas turbines, development often aims for ever higher operating temperatures. To meet the challenges of changing industrial requirements, for example, development strives in particular for increased strength, as well as increased (thermomechanical) load-bearing capacity and service life of such components. 2024PF00573 - Foreign version

[0009] 2

[0010] Due to technological advancements, generative or additive manufacturing is becoming increasingly interesting for the series production of the aforementioned components, such as turbine blades or burner components.

[0011] Additive manufacturing (AM), also commonly referred to as 3D printing, includes, for example, powder bed fusion and / or binder jetting techniques, or free-jet binder application. AM is further characterized by an advantageously short chain of process steps, according to which the manufacturing of the component can largely be based on a corresponding CAD file and the selection of appropriate manufacturing instructions.

[0012] Furthermore, manufacturing costs and setup and lead times can be advantageously reduced. Components manufactured using conventional methods, such as injection molding, lag significantly behind additive manufacturing, for example, in terms of their design freedom, as well as in terms of the required lead time and the associated high costs and manufacturing effort.

[0013] Ceramic casting cores are integral components in the production of highly efficient investment castings, such as gas turbine blades, and determine their internal structure and thus their cooling efficiency. With increasing geometric complexity, which can include undercuts and multi-walled designs, the currently used conventional methods for manufacturing injection molding cores are reaching their limits. Here, 3D printing of ceramic or oxide casting cores offers the advantage that there are no geometric restrictions in the production of components.

[0014] However, printed cores exhibit higher porosity. The layered structure inherent in the process results in a 2024PF00573 - foreign version.

[0015] 3. Rougher surface compared to conventionally manufactured cores.

[0016] Up to now, casting cores have been produced primarily using injection molding techniques, which are limited in terms of shaping freedom and inherently inferior to additive techniques.

[0017] It is therefore an object of the present invention to provide means by which the production of high-quality components or casting cores can be significantly improved. Consequently, the solution according to the invention also enables the improved, faster, simpler and more cost-effective production of the aforementioned high-performance components, without being dependent on the limitations of conventional techniques.

[0018] This problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims.

[0019] One aspect of the present invention relates to a method for treating, in particular smoothing, the surface of components produced by 3D printing, in particular additive free steel binder deposition.

[0020] The process encompasses the provision of a component, particularly one manufactured by 3D printing, from a base material with an untreated surface. This surface is specifically intended to be a surface achieved directly through the manufacturing process ("as-manufactured").

[0021] As indicated above, the provision or initial production of the component is preferably carried out via 3D printing or additive manufacturing processes, in particular “binder jetting”, layer by layer from the base material.

[0022] The process further comprises immersing the component in a suspension, in particular a water-based suspension, wherein the suspension preferably contains more than 40% or 50% mass fractions of a solid similar to a base material of the component.

[0023] The term "similar" in this context means that the material of the solid and that of the base material are preferably substantially the same, similar, or identical. If, for example, the base material of the component is a ceramic material, the solid of the suspension should preferably also be a ceramic, and in particular, the same ceramic.

[0024] The term "suspension" is intended to refer in particular to a heterogeneous mixture of substances consisting of a liquid or soft mass and solids dissolved therein.

[0025] The process further includes extracting or removing the component from the suspension, resulting in a component surface with reduced roughness compared to the untreated surface, i.e., possibly after a subsequent sintering or drying process.

[0026] In one embodiment, the method is a dip coating or part thereof, which is preferably carried out such that the untreated surface is coated with a layer thickness of at most 0.2 mm. Subsequently, sintering, drying, or baking of the coated component may be advantageously offered to finalize the application.

[0027] According to one embodiment, the present method can include surface infiltration, whereby unevenness of the untreated surface of the component is leveled, filled or smoothed.

[0028] The advantages of a smoother or less rough surface achieved through infiltration include, in the present context, the avoidance of stress concentrations at notches, which can provoke crack centers or increase the risk of crack formation during the casting process of (gas turbine) components, thus significantly impairing the service life of the components.

[0029] Since the surface of the tool component ultimately mirrors the surface of the component to be produced by casting, the surface smoothed according to the invention advantageously enables the reduction of (cooling air) pressure losses and thus significantly more efficient operation. Advantageously, the present invention allows precisely the degree of surface roughness to be provided for the component, which no longer results in any significant pressure loss, but advantageously influences or optimizes heat transfer via cooling.

[0030] In one embodiment, the base material is or comprises a ceramic or an oxide, for example silicon carbide, aluminum oxide and / or silicon dioxide. However, the present method can, in principle, be applied equally to a wide variety of materials, including (other) metallic, oxide-based or ceramic materials.

[0031] The suspension in question is particularly water-based and, according to one embodiment, contains up to 65% by mass of the solid component. In a more specific embodiment, the suspension can, for example, contain only up to 60%, up to 55%, or up to 50% by mass of the solid component.

[0032] In one embodiment, the base material and the solid component of the suspension are of the same type, or identical, and / or have the same or substantially the same stoichiometry or percentage distribution. The use of the same or identical raw materials for the base material and the suspension solid advantageously prevents undesirable reactions. 2024PF00573 - Foreign Version

[0033] Component with the (printed) core can be avoided. In other words, a particularly robust process can be provided, the advantages of which according to the invention become all the more apparent the more similar the materials or material classes in question are.

[0034] In one embodiment, the solid component of the suspension consists of a powder with an average powder particle size between 5 pm and 15 pm. In particular, the proportion of the so-called "d90" percentile of the powder fraction can be less than 10 pm; this means that 90% of the particle diameters in the corresponding sample are smaller than 10 pm. This embodiment advantageously results in a powder fraction for the suspension that is, on average, significantly smaller than that of a powdered starting material used for the (additive) production or provision of the component. This, in turn, enables or facilitates infiltration and surface smoothing through the solid morphology used in the suspension.

[0035] In a further embodiment, the suspension also contains additives – for example, in quantities of less than 5% by mass – such as defoamers, which can be mixed into the suspension. These additives particularly advantageously adjust the viscosity and / or surface tension of the suspension. It is evident that the layer thickness, and thus the quality of the resulting surface, can be controlled by adjusting the water or solids content of the suspension, and optionally by adjusting the withdrawal rate.

[0036] In a further embodiment, the design of the component includes channels and / or through-holes, or has, for example, pores according to a (complex) and predetermined geometry, which, after the component is withdrawn from the suspension, are expediently filled with a 2024PF00573 - Foreign version

[0037] 7

[0038] Air jets can be used to blow out the suspension or to remove it again.

[0039] Another aspect of the present invention relates to a component whose untreated surface is or has been treated or smoothed according to the described method, wherein the component is preferably homogeneous and made from a single base material. The base material in question is therefore the base material of the component, which is the same as or identical to the solid used for the suspension.

[0040] The component is further advantageously characterized by the surface obtained through the process, which, compared to the untreated surface, exhibits improved properties in terms of flow resistance (with respect to the volume flow during cooling) and heat transfer coefficient. In other words, the resulting component surface, with otherwise identical geometry, is optimized with respect to flow resistance or pressure loss, while advantageously increasing heat transfer.

[0041] According to the invention, improved surface properties can be provided for the tool, which can be transferred to the target component via a subsequent process; thus, the advantages of the invention are consequently manifested in the final component.

[0042] In one embodiment, the component surface, preferably in its final, sintered state, has a maximum roughness depth of 10 µm or a mean roughness value of less than 10 µm. These roughness values ​​appear advantageous, particularly for optimizing the heat transfer of the cast workpiece. 2024PF00573 - Foreign version

[0043] 8

[0044] The features, characteristics and / or advantages that relate to the process in this case obviously also directly affect the component, and vice versa.

[0045] The expression “and / or” or “or” used here, when used in a series of two or more elements, means that each of the listed elements can be used alone, or any combination of two or more of the listed elements can be used.

[0046] Further details of the invention are described below with reference to the figures.

[0047] Figure 1 shows, by means of a schematic flowchart, process steps according to the invention, and further details of the present invention are also illustrated by way of example.

[0048] In the examples and figures, identical or equivalent elements may each be designated with the same reference symbols. The depicted elements and their relative sizes are generally not to be considered to scale; rather, individual elements may be exaggeratedly thick or large for clarity and / or better understanding.

[0049] Figure 1 shows on the left a schematic flowchart indicating process steps according to the invention. The process relates to the treatment of the surface 11 for components 10 produced by 3D printing, comprising providing (i) a component 10, in particular produced by 3D printing, from a base material with an untreated surface 11.

[0050] The process further comprises immersion (ii) of component 10 in a suspension 5, wherein the suspension 5 2024PF00573 foreign version contains more than 40% mass fractions of a solid similar to a base material of component 10.

[0051] Furthermore, the method according to the invention includes extracting (iii) the component from the suspension 5, resulting in a component surface 12 with a reduced roughness compared to the untreated surface 11.

[0052] The provision or production according to step a) is particularly preferably carried out by an additive manufacturing process, in particular so-called "binder jetting" by means of free-jet binder application, as shown in Figure 1 above right. The basic principle of "binder jetting" is shown there by means of a pictogram-like sectional view. Specifically, a corresponding system or a corresponding 3D printer comprises a print head or nozzle 1, which makes it possible to provide a binder 4 selectively and layer by layer in a build chamber to define the component geometry. Furthermore, a powder or powder bed 2 is provided or arranged on a platform 3. After each layer, the build platform 3 is preferably lowered by an amount corresponding to the layer thickness (compare downward-pointing arrow in Figure 1).

[0053] The geometry of the component is typically defined by a CAD file (Computer-Aided Design). After such a file is imported into the machine, the process first requires dividing the component geometry into individual layers. In this way, a component is additively built up layer by layer.

[0054] Component 10 preferably represents a casting core or a corresponding casting tool.

[0055] Furthermore, the powder 2 or starting material for the component can be a ceramic or oxide material, 2024PF00573 - Foreign version

[0056] 10 especially silicon carbide, aluminium oxide or silicon dioxide .

[0057] The powder in question preferably corresponds approximately or completely to the solid component of the suspension and / or has the same stoichiometry.

[0058] The immersion of component 10 into the suspension 5 according to process step ii) is also shown schematically further to the right in Figure 1. This process step can, for example, represent a dip coating and / or surface infiltration.

[0059] For example, compared to the starting material 2 from which component 10 is produced or provided, a solid component of the suspension 5 preferably consists of a powder with an average powder particle size between only 5 pm and 15 pm. This means the powder fraction is preferably smaller, so that irregularities of the (untreated) surface 11 produced directly by the additive manufacturing process can be compensated for. A key parameter can be the withdrawal rate of the component from the suspension 5, which should be selected accordingly for an optimal coating result.

[0060] Suspension 5 may also contain additives, for example in amounts of less than 5 mass percent, in order to adjust, in particular, the viscosity and / or surface tension of Suspension 5.

[0061] In the middle illustration, corresponding to process step iii), it can be seen that the design of component 10 includes channels and / or through-holes 13, which can be cleared, for example, with an air jet, after component 10 has been withdrawn from the suspension 5. 2024PF00573 - Foreign version

[0062] 11

[0063] After the component 10 is extracted from the suspension 5, it comprises a surface modification with an advantageously smoothed surface 12. The figure indicates that a measured mean roughness Ra after extraction from the suspension 5 can be approximately 15 pm, in particular 15.43 pm, and a corresponding spatial depth Rz can be approximately 30 pm, in particular 31.30 pm.

[0064] The surface thus obtained may then need to be dried or "baked" by means of a sintering process (see optional process step b)) to achieve the final surface quality. Accordingly, the surface 12 shown further down in the figure exhibits both a measured mean roughness and a depth of space of less than 10 pm. As indicated, the mean roughness value can be, in particular, 5.29 pm and the depth of space, in particular, 6.08 pm.

[0065] Only then can the casting process for the turbine blade (see step c at the bottom of Figure 1) commence. Without smoothing, the layer-by-layer additive manufacturing process can result in a wavy surface on component 10, which cannot be easily corrected or smoothed in the final design of the component.

[0066] With the surface smoothing according to the invention, or by the infiltration according to the invention, “valleys” in the waviness of the surface can be advantageously filled and the surface of component 10 can thus be provided with an advantageous roughness or surface structure.

[0067] Compared to the untreated surface 11, the smoothed surface 12 exhibits improved properties, for example with regard to flow resistance and heat transfer coefficient, which are required for the cast components. 2024PF00573 - Foreign version

[0068] 12

[0069] Component 10 may be a cast component or a casting tool, in particular a casting core for the manufacture of turbine components or parts for turbomachinery. Such machine components may include, for example, rotor or guide rollers, ring segments, combustion chamber or burner parts, heat shields, nozzles, seals, filters, resonators, vortex generators, or similar designs.

[0070] Alternatively, the present invention can be described in other words as enabling the successful and applicable smoothing of the surface for all possible geometries. This is achieved by the described infiltration through immersion of component 10 in the suspension 5.

[0071] This is preferably a water-based suspension which can be supplemented with up to 65% by mass of the appropriate solids.

[0072] To avoid unwanted reactions with the printed core, the solids in the suspension preferably consist of the same raw materials and are present in the same percentage distribution as those used for the printed core. However, their particle size distribution is preferably significantly finer, with a percentile value “d90” of less than 10 pm.

[0073] The applied layer thickness should not exceed 0.2 mm. This can be significantly determined and adjusted by the choice of the suspension composition and the withdrawal rate of the core from the suspension 5.

Claims

2024PF00573 - Foreign version 13 Patent claims 1. Method for treating the surface (11) of components (10) produced by 3D printing, comprising the following steps: - (i) Providing a component (10), in particular produced by 3D printing, made from a base material with an untreated surface (11), wherein the base material is a ceramic or an oxide, in particular silicon carbide, aluminium oxide and / or silicon dioxide, - (ii) Immersion of the component (10) in a suspension (5) wherein the suspension (5) contains more than 40% by mass of a solid similar to a base material of the component (10), - (iii) Extracting the component from the suspension (5) , resulting in a component surface (12) with a reduced roughness compared to the untreated surface (11 .

2. Method according to claim 1, wherein the component (10) is manufactured layer by layer from the base material via 3D printing, in particular so-called “binder jetting”.

3. Method according to claim 1 or 2, wherein the component (10) relates to a casting core or a component used in the casting process.

4. Method according to any of the preceding claims, wherein the suspension is water-based and contains up to 65% by mass of the solid component (10).

5. Method according to any of the preceding claims, wherein the base material and the solid of the suspension are the same and have the same stoichiometry.

6. A method according to any one of the preceding claims, wherein the method is a dip coating method, such that 2024PF00573 - Foreign version 14 is carried out by coating the untreated surface (11) with a layer thickness of no more than 0.2 mm.

7. Method according to one of the preceding claims, comprising a surface infiltration, wherein unevenness of the untreated surface (11) of the component (10) is leveled.

8. Method according to any of the preceding claims, wherein the solid of the suspension (5) consists of a powder (1) with an average powder particle size between 5 pm and 15 pm.

9. A method according to any of the preceding claims, wherein the suspension (5) further contains additives in amounts of less than 5% by mass, in particular to adjust the viscosity and / or surface tension of the suspension (5).

10. Method according to one of the preceding claims, wherein the component (11) has channels and / or through-holes (13) which are blown clear with an air jet after the component (10) has been withdrawn from the suspension (5).

11. Component (10) whose surface has been treated according to the method of any one of claims 1 to 10, wherein the component (10) is made from a single base material, and wherein the component surface (12) has improved properties compared to the untreated surface (11) in terms of flow resistance and heat transfer coefficient.

12. Component (10) according to claim 11, wherein the component surface (12) has a mean roughness value of less than 10 pm.

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