Carbide in iron- and nickel-based materials

Abstract

The invention relates to a composite material that consists of an iron- or nickel-basic alloy with integrated carbide and / or boride particles. The proportion of carbide and / or boride particles is more than 1 vol.-% and / or less than 35 vol.-%.

Description

[0001] Description

[0002] Carbides in iron and nickel-based materials

[0003] The invention relates to a composite material made of an iron-based or nickel-based alloy with integrated carbide and / or bond particles.

[0004] Components made of composite materials with enclosed hard materials such as carbides or bonds can be produced by casting into a mold or by sintering a compact.

[0005] Iron-based alloys are materials whose main component is iron and which usually contain the chemical element carbon. Iron-based alloys in the form of steel or cast iron form the basis of today's widely used technical alloys.

[0006] Nickel-based alloys are materials whose main component is nickel and which are usually produced by melting with at least one other chemical element. These alloys exhibit good corrosion and / or high-temperature resistance.

[0007] Metallic carbide compounds are formed by elements from transition groups 4 to 6. Typical examples are titanium, tantalum, and tungsten. They generally do not have a precisely defined stoichiometry. Rather, the carbon atoms are embedded in the tetrahedral interstices or, depending on their size relative to the metal, in the octahedral interstices of the metal lattice, forming interstitial compounds. These substances are characterized by high mechanical and thermal stability and high melting points of over 3000 °C and are used as hard materials and ceramics in chemical equipment and plant engineering, for coating grinding tools, and for the production of hard metal inserts for cutting tools.

[0008] Most bonds involve metals, many of which exhibit ceramic properties and are thus classified as non-oxide ceramics. The use of borides is generally limited to specialized applications. Due to their hardness and chemical and thermal resistance, borides are materials for the most demanding applications and are used, for example, in high-temperature furnaces, turbine blades, and rocket nozzles. Perhaps the most important boride is titanium boride (TiB2), which is characterized by its high hardness, high melting point of over 3200 °C, and electrical conductivity, making it suitable for applications under correspondingly extreme conditions.

[0009] DE 60 2005 004 301 T2 discloses a material suitable for the production of parts or coatings for applications subject to high wear and intensive friction, wherein the material comprises prefabricated hard material particles made of carbides which are applied by means of flame spraying or plasma powder welding and which are embedded in a matrix made of a relatively soft base material, wherein the carbide particles are prefabricated spherical particles with a hardness in the range between 1000 and 2000 HV / 10 and wherein the base material is a nickel-based alloy which additionally contains C, Cr, Mo, Fe, Si, B and Cu in the following ranges (in wt%): C 0.005 - 1.0; Cr 10.0 - 26.0; Mo 8.0 - 22.0; Fe 0.1 - 10.0; Si 3.0 - 9.0; B 1.0 - 5.0; Cu 0.1 - 5.0.

[0010] Chilled cast iron is metastable cast iron with a high carbide content. Metastable solidification leads to the formation of ledeburite, which is particularly hard and wear-resistant. DE 195 12 044 A1 describes a corrosion- and wear-resistant chilled cast iron with the following composition in weight percent: Cr = 36-46, Ni = 5-12, Mo = 2-6, Cu < 3, N < 0.2, Si < 1.5, Mn < 1.5, C = 1.4-1.9, the remainder Fe and melting-related impurities; the following composition in volume percent: austenite 20-40, ferrite 20-40, carbides 20-40, with the carbides having a net-like structure.

[0011] Hard metals are metal matrix composites in which hard materials, present as small particles, are held together by a metal matrix and can be produced by sintering a compact. The materials are first prepared in a defined particle size distribution, mixed according to a recipe, and pressed with a binder into a green compact. Subsequently, fine-grained ceramic and / or metallic materials are usually heated under elevated pressure, but the temperatures remain below the melting point of the main components, so that the shape of the component is retained. This typically results in shrinkage because the particles of the starting material become denser and pore spaces are filled.

[0012] DE 10 2016 207 028 A1 discloses a hard metal comprising a phase of hard material grains and a phase of a heterogeneously distributed binder metal, wherein the hard material grains have an average grain size in the range from 1 nm to 1000 nm, preferably 50 nm to 500 nm, and the heterogeneously distributed binder metal is present in the hard metal in the form of binder islands which have an average size of 0.1 pm to 10.0 pm, preferably 0.2 pm to 5.0 pm, and an average distance between the binder islands of 1.0 pm to 7.0 pm, preferably 2.0 pm to 5.0 pm, and particularly preferably from 1.0 pm to 4.0 pm.

[0013] With both known processes, the shaping of composite components with embedded hard materials, and especially the finishing of the surfaces, is severely limited due to the properties of the hard materials. Furthermore, it is difficult to specifically influence the toughness, brittleness, hardness, and chemical and mechanical resistance of the composite component.

[0014] One problem with the listed and known materials is that only carbides or borides can be precipitated from a casting. Thus, the material can only contain carbides that were previously introduced into the casting mass. If one wishes to introduce additional or different carbides or borides into the material to create a material for special applications, complex coating processes for a surface layer or the creation of a sintered material, with all their associated advantages and disadvantages, are required. However, bonding the carbides or borides is usually problematic due to their lack of chemical similarity.

[0015] The object of the invention is to provide a composite material made of an iron-based or nickel-based alloy into which carbides or borides can be specifically incorporated in the form of particles. The carbides or borides should exhibit good bonding to the iron-based or nickel-based alloy. Furthermore, the composite material should exhibit improved tensile strength and optimized hardness without exhibiting particularly brittle properties. The composite material should be able to be constructed into a component without any limiting boundary conditions. The composite material should be simple and cost-effective to produce.

[0016] This object is achieved according to the invention by a composite material made of an iron-based or nickel-based alloy according to the features of claim 1. Preferred variants can be found in the independent main claims, the subclaims, the description, and the drawings.

[0017] According to the invention, the proportion of carbide and / or boride particles is more than 1 vol.% and / or less than 35 vol.%. In an advantageous variant of the invention, the proportion of carbide and / or boride particles is more than 2 vol.%, preferably more than 5 vol.%, in particular more than 8 vol.% and / or less than 30 vol.%, preferably less than 25 vol.%, in particular less than 20 vol.%.

[0018] The composite material has a well-defined proportion of carbide and / or bond particles, so that an improvement in the mechanical-technological properties can be achieved without the composite material exhibiting adverse brittleness.

[0019] Carbide particles used include, for example, particles made of tungsten carbide and / or titanium carbide.

[0020] For example, the composite material has a bonding zone between the iron-based or nickel-based alloy and the carbide and / or bond particles.

[0021] In an advantageous variant of the invention, the carbide and / or bond particles are embedded in the iron-based or nickel-based alloy.

[0022] The carbide and / or boride particles are preferably bonded firmly into or to the metallic matrix of the iron-based or nickel-based alloy by the special additive manufacturing process, in particular the powder bed process or laser powder deposition welding. This is evident, for example, in fracture patterns, especially in tensile test specimens, where a fracture through the carbide or boride particle is evident. The melting or melting zone around each carbide or boride particle firmly bonds the particles into the metallic matrix.

[0023] For example, thanks to the special additive manufacturing process, the composite material exhibits a material bond between the iron- or nickel-based alloy and the carbide and / or bond particles. This material bond significantly increases the strength of the composite material. The alloy powder particles are melted and fused during the additive manufacturing process of the composite material, allowing diffusion processes, for example, to occur in the liquid phase. Optionally, tungsten or titanium can diffuse into the metallic matrix and contribute to the strengthening of the bonding zone.

[0024] The carbide and / or boride particles within the composite material, for example, significantly improve the wear behavior of the composite material. The blasting wear when the composite is damaged by a 30 g / L quartz sand suspension with a quartz sand particle size of 100 pm, a beam speed of 20 m / s, and a beam angle of 45° is 0.71 mm. 3 / kJ. In comparison to an Alloy718 without carbide or boride particles, the jet wear is 2.18 mm 3 / kJ.

[0025] The elastic strain and the RPO,2 yield strength of the composite material are significantly improved, for example, by the incorporation of tungsten carbide particles and the uniform arrangement of the tungsten carbide particles in the metallic matrix. The RPO,2 yield strength is 933 MPa for the tensile bar made of Alloy 718 with a 12% tungsten carbide content, significantly improved compared to the RPO,2 yield strength of 636 MPa for the tensile bar made of Alloy 718. The tensile strength of Alloy 718 was improved from 965 MPa to 1288 MPa by incorporating the 12% tungsten carbide content. The plastic strain in the form of elongation at break was reduced from 31.6% to 5.2%.The incorporation of the tungsten carbide particles into the metallic matrix of Alloy718 moderately increases the brittleness, but the special bonding as well as the uniform arrangement in the structure leads to a brittleness that is significantly lower than would be expected from such a proportion of tungsten carbide particles.

[0026] Ideally, the composite material based on an iron- or nickel-based alloy is mechanically and technologically enhanced by the carbides and / or borides. For example, the composite material exhibits optimized elastic strain while reducing plastic strain, without exhibiting the plastic strain behavior of a ceramic.

[0027] For example, the carbide and / or bond particles have a round and / or angular shape. Regardless of the particle shape, the particles are excellently integrated into the metallic matrix.

[0028] In a preferred variant of the invention, the composite material has a plurality of layers with a layer thickness, wherein the size of at least 80% of the carbide and / or bond particles is less than a factor of 1.5 larger or less than a factor of 1.5 smaller than the layer thickness.

[0029] The composite material is preferably produced in layers using powder bed deposition or laser cladding, whereby the layer thicknesses are determined depending on the particle size of the powder mixture. For example, the particle sizes of the alloy powder are comparable to the particle sizes of the carbides or borides, allowing the creation of a uniform layer with a precise layer thickness and a favorable component surface.

[0030] For example, the size of more than 80% of the iron-based or nickel-based alloy particles is more than 5 pm, preferably more than 10 pm, in particular more than 15 pm, and / or less than 50 pm, preferably less than 45 pm, in particular less than 40 pm.

[0031] Optionally, the size of more than 80% of the carbide or bond particles is more than 5 pm, preferably more than 10 pm, in particular more than 15 pm, and / or less than 50 pm, preferably less than 45 pm, in particular less than 40 pm.

[0032] In a conventional process for producing a composite material with carbides or borides, carbides or borides are usually formed from the melt, particularly from carbon or boron dissolved in the melt matrix, with one or more elements from the melt. These elements can enter the melt, for example, through the addition of scrap, recycled material, or other impurities. As a result, the formation of carbides, especially mixed carbides, from the melt cannot be precisely controlled. Thus, when producing a composite material from the melt, mixed carbides are usually formed, which are referred to as "impure" in the sense of a defined, mechanical-technological creation of a composite material.

[0033] Due to its special manufacturing process, the composite material according to the invention contains less than 0.5 vol.% or no mixed carbides, and thus exclusively "pure" carbides and a quantity of monocarbide adjusted by targeted addition. The targeted embedding and uniform arrangement of defined carbides creates a composite material with improved mechanical and technological properties.

[0034] In a particularly preferred variant of the invention, the composite material comprises exclusively monocarbides or monoborides. These are precisely the carbides and / or borides that were previously mixed with the alloy particles of the metallic matrix and then generated into a composite material using a powder bed process. The special production of the composite material ensures the defined and targeted incorporation of the carbides and / or borides into the composite material, thus achieving the desired mechanical and technological properties.

[0035] Optionally, the embedded carbide and / or bond particles exhibit a homogeneous arrangement in the metallic matrix of the iron-based alloy and / or the nickel-based alloy. This corresponds to an arrangement that cannot be achieved by producing a chilled or sintered casting.

[0036] Homogeneity refers to the uniformity of a property across the entire extent of a system or the similarity of elements within a system. Ideally, the arrangement of the embedded carbide and / or bond particles is uniform and / or consistent and / or uniform and / or similar and / or homogeneous within the metallic matrix.

[0037] Such an arrangement or distribution of the embedded carbide and / or bond particles in the metallic matrix cannot be generated from the melt, especially through supersaturation of the metallic matrix. Furthermore, this homogeneous arrangement of the carbide and / or bond particles in the metallic matrix cannot be achieved through precipitation at grain boundaries.

[0038] According to the invention, the composite material for producing a component is produced using an additive or generative manufacturing process. For this purpose, a powder mixture of alloy and carbide or boride powder is created. The powder mixture is applied to a substrate and, by selectively exposing a layered powder mixture to radiation, melted and solidified into a composite material. Using a three-dimensional data set, a complete component, preferably a flow-guiding component, such as a pump impeller, can thus be formed from the composite material according to the invention.

[0039] For example, the composite material is produced using the powder bed process.

[0040] In the powder bed process or selective laser melting, the powder mixture of the composite material is applied in a thin layer to the build platform using a coater. The layers are gradually melted into the powder bed by precisely controlling the laser beam according to the layer contour of a component. Upon re-solidification, they fuse with the underlying and neighboring structures. The build platform is then lowered slightly, and a new layer is applied.

[0041] A composite material is created using an additive manufacturing process from a powder mixture of alloy and carbide or boride powder. The layered buildup is computer-controlled from a powder mixture according to specified dimensions and shapes. Physical or chemical hardening or melting processes take place during the buildup.

[0042] In selective laser melting, the composite material with the required component dimensions is produced using a process in which a layer of a powder mixture of particles from a powder mixture is first applied to a substrate. The powdered composite material is then completely melted locally at the desired locations using radiation, and after solidification, a solid layer of material forms. The substrate is then lowered by the amount of one layer's thickness, and more powder is applied. This cycle is repeated until all layers have been produced and the finished composite material or composite component has been created.

[0043] A laser beam, for example, can be used as the radiation source, which generates the composite material from the individual powder mixture layers. The data for guiding the laser beam is generated using software based on a 3D CAD model. As an alternative to selective laser melting, an electron beam (EBN) can also be used.

[0044] In a particularly advantageous variant of the invention, a composite material is produced from a mixture of powdered particles by successively melting and solidifying layers using radiation. Different properties of the composite material can also be generated by varying the radiation. By specifically controlling the local heat input, the material properties are modified during the construction of the composite material. This makes it possible to create zones and structures with different material states and thus different properties within a single area of ​​the composite material.

[0045] For example, using the powder bed process, a composite material can be produced that contains only monocarbides or monoborides. This is not the case with the production of a composite material from the melt, as this automatically produces mixed carbides. The special properties of the composite material are primarily based on the uniform arrangement of the monocarbides in the composite material and the good bonding of the monocarbides or monoborides in the alloy matrix.

[0046] Ideally, the carbides or borides are uniformly distributed in the metallic alloy matrix of the composite through selective laser melting. This leads to a significant increase in the wear resistance and strength of the composite.

[0047] In principle, a component made of the composite material can be produced by selective laser melting, with regions melted with different mixtures of the powdered particles. For example, the proportion of tungsten and / or titanium carbide can be adjusted to the load situation of composite components. This can preferably be achieved with a higher carbide content and / or varied radiation energy.

[0048] In a variant of the invention, for example, damaged components can be repaired using a powder mixture of composite material according to the invention and the use of selective laser melting and can be permanently adapted to the existing load situation by means of a modified proportion of carbides or borides.

[0049] Optionally, the composite material is produced using a laser cladding process.

[0050] For example, the composite material is produced by directing radiation from an energy source, preferably a directed laser beam, to melt and / or melt a surface, and then introducing a powdered material mixture into the melt of the composite body via a powder dispensing device with at least one powder channel. Ideally, the process for producing a composite material is carried out as laser metal deposition welding (also referred to as laser metal deposition (LMD), direct metal deposition (DMD), or direct energy deposition (DED)).

[0051] Preferably, a molten pool is created on the surface of a composite material using a laser, or a base material forming the surface is heated. The molten pool can also generally be referred to as the process zone, which contains the heated or molten material of the body. The molten pool can, for example, be several hundred micrometers thick. The powder mixture of the composite material is automatically introduced using a powder dispensing device, usually in the form of a nozzle. Welded beads or flat material layers are created, which form the body of the composite material.

[0052] Laser cladding enables, for example, the application of three-dimensional structures to existing or new, possibly even uneven, body surfaces.

[0053] Complex body geometries can be created generatively and changes in powder compositions can be easily adapted.

[0054] Laser cladding typically uses a material deposition unit with a laser unit that directs the laser beam onto a body, while the powder dispensing device delivers powder to the body in a directed manner.

[0055] The powder dispensing device is typically designed to dispense the material powder toward the workpiece or body via a nozzle or multiple powder dispensing units, which can be configured, for example, as powder outlet openings. This results in one or more powder jets. These powder jets are centered in a material focus zone.

[0056] The powder dispensing units have multiple powder channels. The number of powder channels corresponds to the number of powder dispensing units. For example, seven powder dispensing units provide seven powder channels. The powder distribution unit can thus provide homogeneous or heterogeneous material flows of iron-based alloy powder and / or nickel-based alloy powder and / or carbide or boride powder in varying proportions. Furthermore, different powdery components of carbide or boride powder can also be mixed together in one layer of the composite material.

[0057] According to the invention, an additively manufactured composite material is used to improve the mechanical-technological material properties, in particular the yield strength R P o,2 and wear resistance.

[0058] Further features and advantages of the invention will become apparent from the description of embodiments with reference to the drawings and from the drawings themselves.

[0059] It shows:

[0060] Fig. 1 a microscopic magnification 1600x of a microstructure image of the composite material made of Alloy718 with 12% tungsten carbide,

[0061] Fig. 2 a microscopic magnification 1000 times of a microstructure image of the composite material made of Alloy718 with 12% titanium carbide,

[0062] Fig. 3 a stress-strain diagram.

[0063] Fig. 1 shows a microscopic image of the composite treated with V2A pickling at 1600x magnification. The metallic matrix is ​​based on Alloy 718, 2.4668, with a tungsten carbide content of 12%. The metallic matrix exhibits a well-fused, coherent structure, while the tungsten carbide particles are embedded in the metallic matrix in a nearly round or circular shape.

[0064] The average size of the tungsten carbide particles is 10–40 pm. The tungsten carbide particles are evenly distributed and exhibit a homogeneous arrangement. At a 12% tungsten carbide content, the average number of particles per mm is 2 200 - 250.

[0065] The tungsten carbide particle shown in Fig. 1 exhibits a melting zone arranged in the form of a light gray stripe around the round tungsten carbide particle. This melting zone is formed during the formation of the composite material in the powder bed process, with tungsten also diffusing into the iron-based alloy matrix in detectable amounts. This melting zone demonstrates excellent bonding of the tungsten carbide particles in and to the iron-based alloy matrix.

[0066] Fig. 2 shows a microscopic image of the composite treated with V2A pickling at 1000x magnification. The metallic matrix is ​​based on Alloy 718, 2.4668, with a titanium carbide content of 12%. The metallic matrix exhibits a well-fused, coherent structure, while the titanium carbide particles are embedded in the metallic matrix in a angular and angular manner.

[0067] The average side length of the titanium carbide particles is 10–30 pm. The titanium carbide particles are evenly distributed and exhibit a homogeneous arrangement. At a titanium carbide content of 12%, the average number of particles per mm is 2 150 - 250.

[0068] A thin melting zone can be seen around the individual titanium carbide particles, which ensures good bonding of the titanium carbide particles in and to the metallic matrix of the Alloy718.

[0069] Fig. 3 shows a stress-strain diagram in which the stress-strain curve during a tensile test according to DIN EN ISO 6892-2 is plotted for a test bar made of Alloy718 and for a test bar made of Alloy718 with 12% tungsten carbide.

[0070] The elastic strain and the RPO,2 yield strength are significantly improved by the incorporation of the tungsten carbide particles as well as by the uniform arrangement of the tungsten carbide particles in the metallic matrix. The RPO,2 yield strength is 933 MPa for the tensile bar made of Alloy 718 with 12% tungsten carbide content and is significantly increased compared to the RPO,2 yield strength for the tensile bar made of Alloy 718 with

[0071] 636 MPa. The tensile strength was improved from 965 MPa to 1288 MPa by incorporating the tungsten carbide component. The plastic strain in the form of elongation at break was reduced from 31.6% to 5.2%. The incorporation of the tungsten carbide particles into the metallic matrix of Alloy 718 moderately increases brittleness; however, the special bonding and the uniform arrangement in the microstructure lead to a brittleness that is significantly lower than would be expected from the proportion of tungsten carbide particles.

Claims

Patent claims Carbides in iron and nickel-based materials 1. Composite material made of an iron-based or nickel-based alloy with integrated carbide and / or bond particles, characterized in that the proportion of carbide and / or bond particles is more than 1 vol.% and / or less than 35 vol.%.

2. Composite material according to claim 1, characterized in that the proportion of carbide and / or bond particles is more than 2 vol.%, preferably more than 5 vol.%, in particular more than 8 vol.%, and / or less than 30 vol.%, preferably less than 25 vol.%, in particular less than 20 vol.%.

3. Composite material according to claim 1 or 2, characterized in that the composite material has a bonding zone between the iron-based or nickel-based alloy and the carbide and / or bond particles.

4. Composite material according to one of claims 1 to 3, characterized in that the composite material has a material connection between the iron-based or nickel-based alloy and the carbide and / or bond particles.

5. Composite material according to one of claims 1 to 4, characterized in that the composite material comprises a plurality of layers with a layer thickness wherein the size of at least 80% of the carbide and / or bond particles is less than a factor of 1.5 larger and / or less than a factor of 1.5 smaller than the layer thickness.

6. Composite material according to one of claims 1 to 5, characterized in that the size of more than 80% of the iron-based or nickel-based alloy particles is more than 5 pm, preferably more than 10 pm, in particular more than 15 pm, and / or less than 50 pm, preferably less than 45 pm, in particular less than 40 pm.

7. Composite material according to one of claims 1 to 6, characterized in that the carbide and / or bond particles are embedded in the iron-based or nickel-based alloy.

8. Composite material according to one of claims 1 to 7, characterized in that the carbide and / or bond particles in the iron-based or nickel-based alloy have a homogeneous arrangement.

9. Composite material according to one of claims 1 to 8, characterized in that the composite material does not contain mixed carbides.

10. Process for the additive manufacturing of a composite material for a component, comprising the following steps: - Production of a powder mixture of alloy and carbide powder and / or boride powder - Selective exposure of radiation to a layered powder mixture - Manufacturing a component from a composite material 11. A method according to claim 10, characterized in that the composite material is produced using a powder bed process.

12. The method according to claim 10, characterized in that the composite material is produced by laser deposition welding.

13. Use of an additively manufactured composite material according to one of claims 1 to 9 for improving the mechanical-technological material properties.

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