WO2018138210A1

WO2018138210A1 - Method for producing high temperature-resistant objects with improved thermomechanical properties

Info

Publication number: WO2018138210A1
Application number: PCT/EP2018/051864
Authority: WO
Inventors: Christos Aneziris; Patrick Gehre; Andreas HERDERING
Original assignee: Technische Universität Bergakademie Freiberg
Priority date: 2017-01-25
Filing date: 2018-01-25
Publication date: 2018-08-02
Also published as: DE112018000221B4; DE112018000221A5

Abstract

The invention relates to a method for producing high temperature-resistant objects, having the following steps: a) producing a temporary molded body from salt and/or sugar using generative manufacturing processes, b) applying a layer of high temperature-resistant materials onto the temporary molded body using thermal coating methods, and c) removing the temporary molded body, wherein the coating of high temperature-resistant materials is applied onto the temporary molded body such that the materials form the high temperature-resistant object after the temporary molded body is removed in step c).

Description

Process for the production of high-temperature resistant products with improved thermomechanical properties

The invention relates to a process for the production of high-temperature resistant products with improved thermomechanical properties. High-temperature-resistant products are used in various industries, such as in the foundry industry, in the glass industry or in energy technology. High-temperature resistant products are, for example, metallurgical vessels for melting or pouring metal or glass melts, such as crucibles, spout components. But also products such as filters for molten metal filtration or catalyst carriers in the chemical industry.

High temperature products are used at temperatures above 600 ° C. High temperature solid products are used, for example, as spout components in metallurgy, as core shells in metal foundries, as ceramic or metalloceramic filters for molten metal filtration, as heat shields for power engineering, as inlays in slide plates, as molds in the glass industry, as complex components e.g. Catalyst carriers in the chemical industry, used as mixing components in the homogenization of metal melts or as complex components in the automotive industry. High-temperature-resistant products are produced from non-metallic ceramic materials or high-melting metallic materials. The high-temperature-resistant products are generally produced by customary coarse or fine-grained processes, for example powder metallurgy or ceramic production processes via casting or press molding or via the melt. However, these methods can not produce complex geometries. Furthermore, in most of these processes, water must be added to the raw material.

Complex component geometries can today be produced with the help of regenerative manufacturing processes of additive manufacturing using the example of ceramic or metallic products. The example of the ceramic products is u.a. the SD laser printing technology is a promising method and the example of the metallic products u.a. the electron melting of high resolution of great interest.

US 3 090 094 A1 (Schwartzwalder method) discloses a method for producing an open-cell, porous ceramic body, comprising the steps of: immersing an open-celled element of a polyurethane sponge material in a suspension containing a ceramic coating material around the cell-defining walls of the element to coat; Removal of the excess suspension from the element, and firing of the element to remove the sponge material and a cured structure of a to produce porous ceramic. A disadvantage of this method is that the polyurethane sponge material must be burned out, which can cause cracks in the applied ceramic coating. Another disadvantage is the low achievable form fidelity of the ceramic body.

The combination of a lost core in combination with flame spraying is already disclosed in DE 102009006778 B4 or in EP 0807479 A1. However, in both cases no water-soluble sugar or salt cores are disclosed. In DE 102009006778 B4 carbon-based cores and paper-based cores are presented or in EP 0807479 A1 cores on a separate plastic basis, e.g. Polyamide described.

DE 102009006778 B4 discloses a process for producing a flame or plasma sprayed thermoshock and corrosion resistant ceramic layer based on A 03-TiO 2 -ZrO 2. In this case, an insert piece for flame or plasma spraying is produced from AI2O3, fully stabilized ZrCk and TiO2 powder. On a substrate or a lost nucleus, e.g. carbon-based or paper-based is applied by flame or plasma spraying the sintered insert workpiece a layer. The thermal shock resistant layers have excellent thermomechanical properties. These properties are based on lamellar microstructures with corresponding in situ generated crack networks. In the flame-sprayed layers, a primary crack pattern is formed, while a secondary crack pattern during thermal shock loading is formed in the use of the refractory product.

EP 0807479 A1 discloses a method for producing a light metal casting, in particular a cylinder block for internal combustion engines with a coating of a wear and / or corrosion resistant material. The coating is formed prior to casting by thermal spraying of the material onto a lost core of the casting, the lost core consisting of a foamed styrene polymer.

DE 197 16 524 C1 discloses a method for producing a body with at least one cavity, in which a body is produced with a water-soluble core of an aluminum or magnesium alloy, which is subsequently dissolved out. The water-soluble core has a porosity of at least 1% by volume. Such cores are used for producing a combustion chamber wall of an engine, wherein the water-soluble aluminum alloy is introduced by flame spraying between the ribs of an inner wall to form cores, which are subsequently dissolved out. The outer wall is applied to the fins and the cores by thermal spraying and the cores are subsequently dissolved out to expose the cooling channels of the combustion chamber wall. DE 691 25 064 T2 discloses a method of molding a product using a mold core. The mold core comprises an inert particulate material, wherein the inert particulate material is bound by a binder and the binder contains a water-soluble carbohydrate. The binder comprises a silicate salt, preferably a sodium silicate. The water-soluble carbohydrate is selected from saccharides and starches. Saccharides are here dextrose and molasses and starch is a corn starch. The inert particulate material is selected from the group: sand, metal scrap, plastic polymers, glass, alumina, clays or mixtures thereof. The mixed core material is introduced into a core container and cured by heat, preferably microwave radiation, in the core container. Such cores are used in molds in which metal or plastic materials are injected in the liquid state to form the final product.

DE 29 17 208 A1 discloses a casting core for producing difficult to access cavities in castings made of aluminum and a method for producing the casting core. The casting core consists of a base substance and a hardened organic binder, wherein the binder is sugar or a sugar derivative. The basic substance is a water-soluble salt, quartz sand, metal granules or a mixture thereof. The basic substance is mixed with the binder in aqueous or organic solution, pressed into molds and baked at elevated temperature.

DE 103 12 782 A1 discloses water-soluble salt cores for foundry purposes, which are produced under pressure and subsequent sintering, these containing a porosity-generating additive, such as sugar. Further, the document discloses a method for producing the salt cores by mixing water-soluble salts with sugar, pressing this mixture in a mold, and sintering the pressed salt core.

DD 151 047 A discloses protective layers on water-soluble cores for the production of cooling cavities, in particular in liquid-pressed pistons, which are thermally resistant and able to absorb the pressures occurring during liquid-pressing. The water-soluble cores are coated with a metallic or non-metallic material as a protective layer. The protective layer is 0.5 to 10 mm thick.

Gehre et al 2017 discloses carbon-bonded ceramic Ab03-C foam filters of pore class 10 ppi, which were subsequently coated with a cold coating of Al2O3 or a flame-sprayed coating of Al2O3. The Ab03-C foam filter with a flame-sprayed AbO3 coating shows a clear reaction with the molten steel and the inclusions dissolved therein compared to the uncoated A Os-C foam filter and the Ab03-C foam filter with cold AbO3 coating. DE 10 2014 008 0892 A1 discloses a method for improving the thermal shock resistance of refractory products, wherein a thermal spray coating is applied to the refractory products whose thermal expansion coefficient is higher by 1 to 20% compared to the refractory product. For producing the thermal spray coating, Al 2 O 3 and / or MgO and / or ΤΊΟ 2 and / or ZrO 2 and / or CaO and / or SiO 2 are used.

The object of the invention is to provide an improved process for the production of high-temperature resistant products, which are easier to produce and have improved thermal shock resistance.

According to the invention the object is achieved by a method for the production of high-temperature-resistant products with the steps:

a) producing a temporary shaped body from salt and / or sugar by means of generative production methods,

b) applying a coating of high-temperature-resistant materials to the temporary shaped body by means of thermal coating methods,

c) removing the temporary molded body.

wherein the coating of high-temperature-resistant materials is applied to the temporary molded body so that it forms the high temperature resistant product after removal of the temporary molded body in step c)

Advantageously, high-temperature-resistant products with improved thermal shock resistance can be produced by the method according to the invention. Furthermore, the inventive method allows the saving of process steps and process costs and the production of high temperature resistant products with improved tolerance and dimensional accuracy.

With the method according to the invention can high temperature resistant products such as spout components in metallurgy, core shells in metal foundries, ceramic or metalloceramic filter for molten metal filtration, heat shields for power engineering, inlays in slide plates, forms in the glass industry, complex components such. Catalyst carriers in the chemical industry, mixing components in the homogenization of metal melts or complex components in the automotive industry are produced.

Such high-temperature resistant products have a porosity of 5 to 90 vol .-%, wherein high-temperature-resistant products with a porosity of <45 vol .-%, also referred to as dense high temperature resistant products, for example, used as spout components in metallurgy or as a delivery. High-temperature resistant products with a porosity of> 45% by volume, also referred to as porous high-temperature-resistant products, For example, they are used as filters for molten metal filtration or as catalyst supports.

Advantageously, in step b) applied by thermal coating coating of high temperature resistant materials subject to any shrinkage, as in conventional coarse or fine powder metallurgy or ceramic processes, so that a better dimensional accuracy of the high temperature resistant products can be achieved.

Further advantageous is achieved by the lamellar structure of the applied by thermal coating coating of high temperature resistant materials better thermal shock resistance than conventional coarse or fine powder metallurgy or ceramic processes.

A temporary molding of salt and / or sugar in the context of the invention is a molding, hereinafter also referred to as the core, which is used for the production of the high-temperature resistant product and removed after application coating of high-temperature resistant materials.

The temporary molded body may have a cellular or a compact structure.

Cellular temporary shaped bodies, also referred to as porous cores, have a porosity of> 45% by volume.

In the cellular temporary shaped bodies, there are combined a solid and a gaseous phase, wherein the gaseous phase is embedded within cells or pores of the cellular shaped body in the solid phase.

Advantageously, a temporary molded body with a cellular structure open-celled, also referred to as open-pored.

The pores or cells may be interconnected, also referred to as open-celled, or isolated from each other, also referred to as closed-cell, present in the cellular shaped body.

Open-cell in the sense of the invention means that the pores of the cellular shaped body are interconnected by webs and accessible from the outside. Examples of open-cell cellular, temporary shaped bodies are foam structures, honeycomb structures or complex 3-dimensional structures.

By means of open-pore cellular temporary moldings, it is preferable to produce porous high-temperature-resistant products, such as, for example, filters for molten metal filtration, which have a porosity of> 45% by volume.

Closed-cell in the sense of the invention means that the individual pores of the cellular shaped body are separated from each other by cell walls. Compact temporary shaped bodies, also referred to as dense cores, have a porosity of less than 45% by volume.

By means of compact temporary moldings, dense, high-temperature-resistant products, such as crucibles or pouring nozzles for metallurgy, which have a porosity of <45% by volume, are preferably produced.

The temporary shaped body is manufactured by means of generative manufacturing processes so that it forms the mold for the high-temperature-resistant product produced by thermal coating and subsequent removal of the temporary shaped body.

The coating of high-temperature-resistant materials is applied by thermal coating method to the temporary shaped body that this forms after removal of the temporary molded body in step c) the high temperature resistant product. By means of thermal coating processes, the temporary shaped body is purposefully coated in such a way that the coating gives the high-temperature-resistant product in terms of thickness, structure and dimension.

In a compact temporary molded body, the coating of high temperature resistant materials in step b) is applied to the compact temporary molded body so that the coating follows the contours of the compact temporary molded body. Advantageously, with the method according to the invention, near net shape high temperature products can be produced. This eliminates subsequent steps, such as sintering and the associated shrinkage, which occurs in conventional powder metallurgy or ceramic manufacturing process.

On an open-cell cellular temporary shaped body, the coating in step b) is applied such that the coating is present on the webs of the open-cell cellular FK. Porous high-temperature-resistant products whose pore structure and size almost correspond to the pore structure of the open-cell cellular temporary shaped body can advantageously be produced by the method according to the invention since subsequent steps such as sintering and the associated shrinkage are eliminated.

In one embodiment, the temporary shaped bodies consist of salt and / or sugar, salt and / or sugar being present as fine and / or coarse solid grains.

Sugars are, chemically speaking, water-soluble carbohydrates. They include monosaccharides such as glucose or fructose, also referred to as fructose, oligosaccharides such as maltose, lactose and sucrose, also referred to as sugar or cane sugar or beet sugar, a disaccharide of glucose and fructose. Salts are chemical compounds made up of positively charged ions, also cations, and negatively charged ions, also anions. The salts may be water-soluble or water-insoluble, preferably the salts are water-soluble.

Coarse solid grains in the sense of the invention means that the particle sizes of the individual salt and / or sugar particles are in the range from 40 μm to 500 μm, preferably in the range from 40 μm to 200 μm.

Fine solid grains in the sense of the invention means that the particle sizes of the individual salt and / or sugar particles are smaller than 40 μm.

In one embodiment, the porous or dense cores consist of fine and / or coarse solid grains of water-soluble carbohydrates.

In one embodiment, the porous or dense cores of fine and / or coarse solid grains consist of monosaccharides or oligosaccharides or mixtures thereof.

In one embodiment, the porous or dense cores consist of fine and / or coarse solid granules of glucose or fructose or maltose or lactose or sucrose or mixtures thereof.

In one embodiment, the porous or dense cores consist of fine and / or coarse solid granules of water-soluble salt or common salt.

In one embodiment, the porous or dense cores of fine and / or coarse solid grains consist of mixtures of water-soluble carbohydrates with water-soluble salt or common salt.

Generative manufacturing processes according to the invention are methods for the rapid and cost-effective production of models, moldings, samples, prototypes, tools and end products. The production takes place in layers, additive, of materials which are present for example as a liquid, gel, paste, powder or as a band, wire or sheet-like material, which are solidified by means of chemical and / or physical processes. By means of generative manufacturing processes, it is also possible to produce complex shaped bodies which can not be produced using conventional production methods or only with considerable effort.

The generative manufacturing processes include, for example, 3D printing processes, melt-coating processes (also known as fused filament fabrication) or electron beam melting.

The temporary shaped body of salt and / or sugar is preferably produced by means of an SD printing process. In the context of the invention, 3D printing processes are understood to be processes in which a shaped body is built up in layers from superimposed cross sections. Advantageously, complex shaped bodies can also be generated by means of 3D printing processes.

In one embodiment, the temporary shaped body is produced by means of a powder-based SD printing method, an extrusion-based 3D printing method or a suspension-based 3D printing method, preferably a powder-based SD printing method.

Powder-based 3D printing processes work with powder beds, the so-called powder bed, which are consolidated in layers in accordance with the shaped body to be produced locally with the aid of a binder or by the action of energy.

Powder-based 3D printing processes, which achieve solidification of the powder bed with the aid of binders, include binder jetting, 3D powder printing.

Powder-based 3D printing processes, which achieve solidification of the powder bed by the action of energy, are, for example, selective laser sintering (also referred to as SLS), which generates 3D laser sintering technology by partial heating by means of a laser individual layers.

Suspension-based 3D printing processes include stereolithography (also referred to as SLA), liquid composite molding (also referred to as LCM), layer-slurry deposition, lithography-based processes, 3D screen printing.

Extrusion-based 3D printing processes include, for example, melt-coating processes such as Fused Filament Fabrication (FFF) or Fused Deposition Modeling (FDM).

In one embodiment, the cores may be fabricated using additive manufacturing techniques based on powder-based or suspension-based methods, preferably by SD laser sintering, selective laser sintering, 3D powder printing, gas assisted powder deposition, 3D screen printing, lithography based processes, SD thermoplastic printing or coating Slicker deposition can be generated.

In one embodiment, the porous or dense water-soluble cores, consisting of fine or coarse solid grains based on water-soluble carbohydrates or based on salt, sodium chloride or mixtures thereof by means of additive manufacturing processes based on powder-based or suspension-based methods preferably by means of 3D laser sintering technology, Selective laser sintering , 3 D powder pressure, gas assisted powder deposition, 3D screen printing, lithography based process, 3D Thermoplastic printing process or layer slurry deposition. Depending on the used generative manufacturing process for the preparation of the temporary shaped body of salt and / or sugar different grains of salt and / or sugar are used.

Fine solid grains of sugar and / or salt are used, for example, for extrusion-based 3D printing processes.

Coarse solid grains of sugar and / or salt are used, for example, for laser sintering processes.

In one embodiment, the porous or dense water-soluble cores consisting of fine or coarse solid grains based on water-soluble carbohydrates or based on salt, sodium chloride or mixtures thereof by means of the press molding, the plastic molding preferably by means of extrusion molding or casting on aqueous or not produced aqueous base and optionally post-treated mechanically and / or thermally.

In one embodiment, the water-soluble cores are produced by uniaxial pressing, extrusion, injection molding or slip casting with special dispersing media. In the case of conventional manufacturing processes of the sugar cores or the salt cores, these can be mechanically removed, e.g. be reworked by drilling, milling.

In one embodiment, the porous water-soluble cores are based on water-soluble carbohydrates or based on salt, sodium chloride or mixtures thereof via direct foaming of an aqueous slurry consisting of dissolved carbohydrates with or without dissolved salt and its stabilization with the aid of further additives containing the Surface tension of the bubbles change, generated.

In one embodiment, the porous water-soluble cores are based on water-soluble carbohydrates or on the basis of salt, for example sodium chloride; or mixtures thereof can be generated by direct foaming of an aqueous slip consisting of dissolved carbohydrates with or without dissolved salt and stabilization thereof by means of further additives which change the surface tension of the bubbles.

Additives which change the surface tension of the bubbles are, for example, alcohol alkoxylates, acrylate copolymers, polyether siloxanes, silicone surfactants.

High-temperature-resistant materials in the context of the invention are materials which can be used permanently at temperatures of more than 600 ° C. and have sufficient mechanical properties over a long period of use. High-temperature resistant materials according to the invention are ceramic or metallic materials or combinations thereof. Thermal coating method according to the invention means thermal spraying. According to DIN EN 657, thermal spraying involves processes in which spray additives inside or outside of sprayers are fused, melted or melted onto a surface. The spray additives represent the coating material. The coating is preferably applied from high-temperature-resistant materials by means of flame or plasma spraying.

Coatings applied by means of thermal coating processes have a lamellar layer structure, the coating consisting of several superimposed layers of the coating material.

In one embodiment, the coating of high-temperature-resistant materials applied in step b) by means of thermal coating processes comprises at least one layer of high-temperature-resistant materials.

In one embodiment, in step b), the coating of high-temperature-resistant materials is applied to at least one side of the temporary molded body by means of thermal coating methods.

In one embodiment, in step b), the coating of high-temperature-resistant materials is applied to at least one side of the compact temporary molded body by means of thermal coating methods.

In one embodiment, in step b) the coating of high-temperature-resistant materials is applied on all sides to the temporary molded body by means of thermal coating methods.

In one embodiment, in step b) the coating of high-temperature-resistant materials is applied on all sides to the open-cell cellular temporary shaped body by means of thermal coating methods.

In one embodiment, in step b), the coating of high-temperature-resistant materials is applied by means of computer-controlled thermal coating methods.

In one embodiment, in step b) the coating of high-temperature-resistant materials is applied on all sides with robot support and / or rotation of the temporary shaped body.

An apparatus for applying a coating of high temperature resistant materials to an open-cell cellular temporary shaped body on all sides comprises a thermal coating apparatus, a robotic arm, a computer controller, an apparatus for rotating the open cell cellular temporary shaped body. In order to form the high-temperature resistant product, the temporary shaped body is removed in step c).

The removal of the temporary shaped body takes place by dissolving the temporary shaped body. The dissolution of the temporary shaped body is preferably carried out by means of a solvent. Preferably, the solvent used is water.

In one embodiment, the temporary molding is removed by immersing the coated temporary molding in water.

In one embodiment, the temporary shaped article is dissolved by spraying the coated temporary shaped article with water.

Immediately after the removal of the water-soluble cores, the high-temperature-resistant products according to the invention can be dried and used directly. Advantageously, the method according to the invention takes into account not only economic and qualitative aspects but also ecological aspects. The inventive method allows the saving of process steps, so eliminates the known from the Schwartzwalder method burning out of the temporary shaped body.

Furthermore, the material of the temporary shaped body can be recovered after the dissolution of the temporary shaped body in water, so that advantageous material is saved.

The exposed, flame or plasma sprayed ceramic, metal or metalloceramic high temperature resistant products have excellent thermal shock properties.

In order to combine the advantages of additive manufacturing with respect to the generation of complex geometries with the excellent micro-structures from the flame spraying or from the plasma spraying process, porous or dense lost, water-soluble cores consisting of fine or coarse solid grains are generated, which are thermally coated and subsequently be removed with the help of water.

In one embodiment, porous or dense ceramic, metallic or metalloceramic high temperature products are made by combination of a thermal coating process such as flame spraying or plasma spraying of ceramics, metals or mixtures of metals and ceramics on porous or dense sugar-based or salt-based cores or mixtures thereof, wherein the porous or dense cores consist of fine or coarse solid grains which are water-soluble and are subsequently removed with the aid of water as the solvent. Surprisingly, not only does the melting point of the salt, eg of sodium chloride, also designated as common salt of about 801 ° C. for a flame or plasma sprayed product suffice Technology, but also that of sugar, in a temperature range of 150 ° C to 180 ° C.

In one embodiment, coarse or fine crystalline sugars are converted via SD laser sintering printer technology into complex porous or dense cores, which are then thermally coated by flame spraying.

In one embodiment, dense or porous ceramic or metallic or metalloceramic materials are prepared by thermally coating porous or dense water-soluble cores consisting of fine or coarse solid grains by flame spraying or plasma spraying, and then removing the cores in a water bath.

In one embodiment, an intermediate layer of ceramic materials, of carbon or of salt is applied to the temporary shaped body before step b) by means of a cold coating method.

Ceramic materials include oxide or non-oxide ceramic materials. In one embodiment, an intermediate layer of non-oxide ceramic materials is applied. Non-oxide materials include boron nitride and silicon nitride.

In one embodiment, an intermediate layer of salt is applied to the temporary shaped body.

Cold coating processes in the context of the invention are coating processes in which the material of the intermediate layer is present at a temperature of less than or equal to 50 ° C. and applied to the temporary shaped body. Cold coating methods are, for example, spray methods, dipping methods, impregnation methods or deposition methods.

Preferably, the intermediate layer is applied by spraying or dipping.

In one embodiment, the intermediate layer is applied to a temporary shaped body of sugar and / or salt, preferably a temporary shaped body of sugar.

Advantageously, the intermediate layer serves for the thermal stabilization of the temporary shaped body for the subsequent thermal coating.

In one embodiment, the intermediate layer applied before step b) is a temporary intermediate layer. Temporary intermediate layer according to the invention means that the intermediate layer is removed in a subsequent process step, preferably the temporary intermediate layer is removed in step c).

In one embodiment, the intermediate layer remains at least partially preserved after removal of the temporary shaped article in step c). In one embodiment, the intermediate layer is applied to the temporary shaped body with a layer thickness of 1 μm to 500 μm.

In one embodiment, the sugar cores are coated prior to thermal coating with a boron nitride or silicon nitride slurry in the cold state at room temperature by means of spraying or impregnation.

In one embodiment, an intermediate layer of carbon is deposited on the temporary shaped body after step a) and before step b).

The carbon can be advantageously adjusted based on the combustion of acetylene at the beginning of the flame spraying process.

In one embodiment, carbon deposits are generated based on the combustion of acetylene on a water-soluble substrate.

In one embodiment, before the flame spraying or plasma spraying, the water-soluble cores are coated at room temperature with a boron nitride or silicon nitride-based impregnating or spraying film.

In one embodiment, the coating of high-temperature-resistant materials having a layer thickness of 3 μm to 20 mm is applied in step b), preferably with a layer thickness of 40 μm to 10 mm.

In one embodiment, in step b), the coating of high-temperature-resistant materials having a locally varying layer thickness is applied to the temporary shaped body.

Advantageously, a local reinforcement of the high temperature resistant product can be achieved thereby. A local reinforcement of the high temperature resistant product is used, for example, in crucibles to locally increase the mechanical stability of the high temperature resistant product.

In one embodiment, the temporary shaped body has a porosity of 5 to 97% by volume.

Temporary moldings with a porosity of <45% by volume are preferably used for the production of compact high-temperature-resistant products, such as, for example, spout components, such as spout nozzles or also crucibles for melting metals.

Temporary shaped articles with a porosity of> 45% by volume are preferably used for the production of porous high-temperature-resistant products, such as filters for molten metal filtration. In one embodiment, the high temperature resistant product after step c) is thermally treated at a temperature of 50 to 2000 ° C.

Advantageously, the thermal after-treatment of the high-temperature-resistant product increases the strength of the high-temperature-resistant products, reduces the porosity and / or achieves a phase transformation of the applied high-temperature-resistant materials.

In one embodiment, the high temperature resistant product after step c) is thermally treated at a temperature of at most 150 ° C. Advantageously, the drying of the high-temperature-resistant product is achieved after the release of the temporary molded body.

In one embodiment, the high temperature resistant product after step c) is thermally treated at a temperature of 600 ° C to 1000 ° C. Advantageously, this increases the strength of the high temperature resistant product, reduces porosity, and achieves phase transformation within the high temperature resistant materials.

In one embodiment, after removal of the cores, the dense or porous ceramic or metallic or metalloceramic products are optionally thermally post-treated at a temperature of between 50 to 2000 ° C.

Advantageously, the applied by thermal coating method coating with ceramic materials, metallic materials or mixtures thereof.

In one embodiment, metallic materials applied in step b) are selected from:

1 . metallic materials with a melting temperature of more than 1000 ° C,

2. intermetallic phases with a melting temperature of more than 1000 ° C or

3. refractory metals

4. or mixtures thereof.

Metallic materials with a melting point greater than 1000 ° C are Cu, Fe, Si, Ni, Ti or mixtures thereof.

Intermetallic phases are known to the expert homogeneous mixtures of two or more metals, such as high temperature materials such as NiAl, TiCr2, TaFeAl or high-temperature lightweight materials such as Ti3AI, TiAl or the sigma phase FeCr. The intermetallic phases are chemically resistant and have a high melting point.

Refractory metals in the context of the invention are refractory, base metals of the 4th, 5th, 6th or 7th subgroup of the periodic table with a melting point greater than 1600 ° C. or mixtures of these metals. Base metals of the 4th subgroup are, for example, Ti, Zr, Hf. Base metals of the 5th subgroup are, for example, V, Nb or Ta. Common metals of the 6th subgroup are, for example, Cr, Mo or W. Unwanted metals of the 7th subgroup are, for example Mn, Tc or Re.

In one embodiment, grains used in flame spraying or plasma spraying are ceramic or metallic or intermetallic phases or mixtures thereof.

In one embodiment, ceramic materials applied in step b) are selected from oxidic ceramic, non-oxidic ceramic materials or combinations thereof.

In one embodiment, the oxide ceramic materials are selected from: calcium oxide, magnesium oxide, dolomite, chromium oxide, aluminum oxide, mullite, zirconium mullite, zirconium dioxide, magnesium aluminate spinel, bauxite, yttrium oxide, titanium dioxide, lanthana, lanthanum chromium or mixtures thereof.

Calcium oxide, magnesium oxide, dolomite, chromium oxide, aluminum oxide, mullite, zirconium matte, zirconium dioxide, magnesium aluminate spinel, bauxite, yttrium oxide, titanium dioxide, lanthanum oxide, lanthanum chromium or combinations or mixtures thereof are used as oxidic grains in flame spraying or plasma spraying.

In one embodiment, oxidic grains used in flame spraying or plasma spraying are ceria oxide, magnesium oxide, dolomite, chromium oxide, aluminum oxide, mullite, zirconium mullite, zirconium dioxide, magnesium aluminate spinel, bauxite, yttrium oxide, titanium dioxide, lanthanum oxide, lanthanum chromium or combinations or mixtures.

In addition, the oxide, the carbides or the nitrides of the refractory metals can serve as oxidic or non-oxidic ceramic materials.

In one embodiment, the non-oxide ceramic materials are selected from silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum nitride and carbon or mixtures thereof.

The non-oxidic grains may be silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum nitride and carbon, or combinations or mixtures thereof.

In one embodiment, silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum nitride and carbon or combinations or mixtures of these are used as non-oxidic grains in flame spraying or plasma spraying.

In an embodiment, the metallic materials having a melting temperature greater than 1000 ° C are selected from: Cu, Fe, Si, Ni, Ti, or mixtures thereof.

As metals for the thermal spraying with a melting point above 1000 ° C serve Cu, Fe, Si, Ni, Ti or mixtures thereof. In one embodiment, the refractory metals are selected from Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re or mixtures thereof.

In addition, for thermal spraying, refractory metals are preferably Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re or mixtures thereof.

In one embodiment, the metal grains used in flame spraying or plasma spraying are Cu, Fe, Si, Ni, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re or mixtures thereof.

In one embodiment, the intermetallic phases having a melting temperature greater than 1000 ° C are selected from: NiAl, TiCr2, TaFeAI, T13AI, TiAl, FeCr, or mixtures thereof.

Instead of metals having a melting point greater than 1000 ° C, intermetallic phases such as e.g. NiAl, TiCr2, TaFeAI, TI3AI, TiAl, FeCr or mixtures thereof.

In one embodiment, the grain sizes used in flame spraying or plasma spraying are intermetallic phases NiAl, TiCr, TaFeAl, TbAl, TiAl, FeCr or mixtures thereof.

The process of the present invention can advantageously produce high temperature products such as spouts for metallurgy, core shells for metal foundries, ceramic or metallo-ceramic filters for molten metal filtration, heat shields for power engineering, slide plate inlays, molds for the glass industry, complex components e.g. Catalyst supports for the chemical industry, mixing components for homogenizing molten metal or complex components for the automotive industry are produced.

Preferably, crucibles for the melting of metals from ceramic materials, such as Al 2 O 3, mullite, ZrO 2 or aluminum titanate, which have a better thermal shock resistance, can be produced by the method according to the invention.

Foam filters for molten metal filtration of ceramic materials, such as Al 2 O 3, for example, which have better thermal shock resistance and dimensional stability than ceramic foam filters produced by the Schwartzwalder process, can preferably be produced by the process according to the invention.

The high-temperature-resistant products produced by the process according to the invention have a lamellar structure of the applied coating of high-temperature-resistant materials, so that advantageously the thermal shock resistance of the high-temperature resistant products is improved.

In one embodiment, the high temperature resistant products made by the process of the invention have a porosity of from 5% to 90% by volume. High-temperature-resistant products having a porosity of> 45% by volume, prepared by the process according to the invention, are used, for example, as filters for molten metal filtration.

High-temperature-resistant products having a porosity of <45% by volume, produced by the process according to the invention, are preferably used, for example, as spout components or crucibles in metallurgy.

In one embodiment, a plurality of high temperature resistant products will be joined together by thermal coating.

In particular, porous high-temperature-resistant products having complex structures and large dimensions can be produced by joining together a plurality of high-temperature-resistant products produced by the method according to the invention by means of thermal coating methods.

Advantageously, it is achieved that the coating of high-temperature-resistant materials is applied on all sides on the open-cell cellular shaped body used for the production of porous high-temperature resistant products.

Advantageously, thereby porous high-temperature resistant products can be produced with enlarged dimensions.

For the realization of the invention, it is also expedient to combine the above-described embodiments and features of the claims.

embodiments

The invention will be explained in more detail with reference to some embodiments and associated figures. The embodiments are intended to describe the invention without limiting it.

Fig. 1 shows a cross-sectional view of a coated compact temporary shaped body for producing a high-temperature resistant nozzle for metallurgy.

Fig. 2 shows a cellular temporary molded body used to make a ceramic filter for molten metal filtration.

Fig. 3 shows a cross-sectional view of a coated compact temporary molded article for producing a crucible for melting metals. Example 1 Hollow body of a spout nozzle for metallurgy

Fig. 1 shows the cross-sectional view of a coated compact temporary shaped body of sugar 1 for producing a high-temperature resistant pouring spout for metallurgy. With the aid of a 3D printing process, the so-called laser sintering technology (laser sintering), a water-soluble, wedge-shaped sugar core is produced as a compact, temporary shaped body 1 of a pouring nozzle. In each case, a powder bed of 90 wt .-% maltose and 10 wt .-% impurities with particle sizes in the range of 40 to 60 μηη is used.

The powder bed of maltose is solidified by energy input by a laser, with a sintering temperature of 120 ° C with a 14 W C02 laser with a focus diameter of 100 μηη and 50% power throttling is achieved. Subsequently, the next layer of a powder bed of maltose is applied and solidified by the entry of laser energy. The maltose sugar kernel 1 produced in this way has a height of 100 mm, an outer diameter of 20 mm at the inlet and 10 mm at the outlet. The nuclear production took about 4 hours.

From 85 wt.% Of alumina powder having a particle size between 0.05 and 150 μηη, 10 wt.% MgO partially stabilized zirconia powder with a particle size between 0.05 and 40 μηη and 5 wt.% Titandioxidpulver with a particle size between 0.05 and 20 μηη were homogeneously mixed with the addition of dispersants and processed from the mixture, a vapourous mass. From this mass rods were produced by extrusion. These bars were fired white at 1200 ° C. The rods produced in this way are used as high-temperature-resistant material for coating the compact temporary molded body by means of flame spraying. The burned rods were introduced to a flame spray gun. By means of flame spraying a coating 2 with a thickness of about 5 mm was applied to the surface of the wedge-shaped granular sugar core 1. Table 1 shows the parameters of flame spraying.

Table 1 . Parameters during flame spraying

Flow rate of oxygen, m ³ / h 2.0

Oxygen pressure, bar 5.5

Flow rate of acetylene, m ³ / h 0.9

Acetylene pressure, bar 1, 1

Flow rate of air, m ³ / h 38.0 Air pressure, bar 5.5

Distance flame spray gun to the temporary 100

Shaped body, mm

Feed rate of spray material, mm / min 50

After the flame spraying process, the maltose sugar core 1 was dissolved in the water by dipping the coated sugar core 1 in water. The exposed spout nozzle has the dimensions: height of 120 mm, inner diameter at the inlet 20 mm and at the outlet 10 mm and a wall thickness of about 5 mm.

could be molten with steel melt directly after a thermal heat treatment, such as drying at 150 ° C for 24 hours in a special steel casting simulator. Without preheating, the spout nozzle survived the steel gating and steel casting phase of about 100 kg of steel in about 10 minutes.

Example 2 ceramic filter for molten metal filtration

Fig. 2 shows a cellular temporary molded body 3 used for producing a ceramic filter for molten metal filtration. Using the direct laser sintering technology, a cellular temporary shaped body of salt 3 was produced. For this purpose, layer by layer of common salt, consisting of 90 wt .-% sodium chloride and 10 wt .-% impurities with particle sizes in the range of 40 to 80 μηη applied as a powder bed and solidified in layers by means of energy input by a laser. By means of a 1000 W C02 laser with a focus diameter of 100 μηη a sintering temperature of 780 ° C was achieved.

The cellular temporary shaped body 3 thus produced has an open-cell spongy structure of the pore class 10 ppi with a porosity of 95% by volume and has the dimensions 50 × 50 × 25 mm ³ .

The coating of the open-cell cellular temporary shaped body 3 takes place by means of flame spraying, wherein an acetylene-oxygen mixture is used as the fuel gas. By means of flame spraying, a coating consisting of 99.7% by weight of Al 2 O 3 and 0.3% by weight of other oxides as impurities having a layer thickness of 500 μm is applied on all sides, rotating the open-cell cellular temporary shaped body 3. Table 2 gives the parameters of flame spraying: Table 2: Parameters for flame spraying

After the flame spraying process, the open cell cellular temporary shaped body is removed. For this purpose, the coated temporary molded body is immersed in a water bath

The ceramic filter obtained after removal of the temporary molded body was dried at 150 ° C for 24 hours. The ceramic filter produced in this way shows improved form retention compared with a ceramic Ab03 foam filter produced by the Schwartzwalder process.

Example 3 Ceramic crucible for molten metals

Fig. 3 shows a cross-sectional view of a coated compact temporary molded article 1 for producing a crucible for melting metals. The compact temporary shaped body 1 was produced by means of an extrusion-based 3 D printing process. For this purpose, a mixture of 70 wt .-% sodium chloride, 4 wt .-% sucrose with particle sizes less than 40 μηη was homogeneously dispersed with the addition of 24 wt .-% ethanol as a solvent and 2 wt .-% organic additives. The mass thus produced was heated in an extruder and the temporary molded body 1 was produced in layers therefrom.

The thus produced compact temporary molded body 1 has the dimensions: height 140 mm and outer diameter of 120 mm and a wall thickness of 5 mm and has a porosity of 25 vol .-%.

On the inside of the compact temporary shaped body, an intermediate layer of salt is applied by dipping the temporary shaped body in a dispersed salt solution. The intermediate layer has a layer thickness of 500 μm.

The coating of the compact temporary molded body 1 by means of flame spraying, wherein an acetylene-oxygen mixture is used as the fuel gas. By means of flame spraying is on one side of the temporary molded body 1, a coating consisting of 99.7 wt .-% Al2O3 and 0.3 wt .-% of other oxides applied as impurities with a layer thickness of 10 mm. Table 3 gives the parameters of flame spraying:

Table 3

On the temporary shaped body 1, an increased layer thickness of the Al 2 O 3 coating was locally applied in order to achieve a local reinforcement of the high-temperature-resistant crucible. In the area of the metal level in the later use of the crucible, the coating is applied by means of flame spraying with a layer thickness of 15 mm.

After the flame spraying process, the compact temporary shaped body is removed. For this purpose, the coated temporary molded body is immersed in a water bath. The exposed crucible has a filling volume of 250 ml with the dimensions height 140 mm, outside diameter 1 10 mm and a wall thickness of 10 mm.

The ceramic crucible obtained after removal of the temporary molded body was dried at 150 ° C for 24 hours.

Cited non-patent literature

Gehre et al 2017: See P, Schmidt A, Dudzig S, et al. Interaction of slip and flame spray coated carbon bonded alumina filters with steel melts. J Am Ceram Soc. 2018; 00: 1-12. https://doi.org/10.1 1 1 1 /iace.15431

reference numeral

1 Compact temporary molded body

2 coating of high temperature resistant materials

3 Porous temporary shaped body

Claims

claims

1 . Process for the preparation of high temperature products comprising the steps of:

b) applying a coating of high-temperature-resistant materials to the temporary shaped body by means of thermal coating processes, c) removing the temporary shaped body,

wherein the coating of high-temperature-resistant materials is applied to the temporary molded body so that it forms the high temperature resistant product after removal of the temporary molded body in step c).

2. The method according to claim 1, characterized in that on the temporary molded body before step b) an intermediate layer of ceramic materials, of carbon and / or salt is applied by means of a cold coating process.

3. The method according to claim 1 or 2, characterized in that the applied in step b) coating of high temperature resistant materials with a layer thickness of 3 μηη is applied to 20 mm.

4. The method according to any one of claims 1 to 3, characterized in that the temporary shaped body has a porosity of 5 to 97 vol .-%.

5. The method according to claim 1 to 4, characterized in that the high temperature resistant product after step c) is thermally treated at a temperature of 50 to 2000 ° C.

6. The method according to any one of claims 1 to 5, characterized in that are applied as high-temperature resistant materials ceramic materials, metallic materials or mixtures thereof.

7. The method according to claim 6, characterized in that the metallic materials selected from metallic materials having a melting temperature of more than 1000 ° C, intermetallic phases having a melting temperature of more than 1000 ° C, refractory metals or mixtures thereof are applied to the temporary molding.

8. The method according to claim 6, characterized in that the ceramic materials selected from oxidic ceramic, non-oxidic ceramic materials or combinations thereof are applied to the temporary molded body.

9. The method according to claim 8, characterized in that the oxidic ceramic materials are selected from: calcium oxide, magnesium oxide, dolomite, chromium oxide, aluminum oxide, mullite, zirconium mullite, zirconium dioxide, magnesium aluminate spinel, bauxite, yttrium oxide, titanium dioxide, lanthanum oxide, lanthanum chromium or mixtures from that.

10. The method according to claim 8, characterized in that the non-oxidic ceramic materials are selected from: silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum nitride and carbon or mixtures thereof.

1 1. A method according to claim 7, characterized in that the metallic materials having a melting temperature of more than 1000 ° C are selected from: Cu, Fe, Si, Ni, Ti or mixtures thereof.

12. The method according to claim 7, characterized in that the refractory metals are selected from Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re or mixtures thereof.

13. The method according to claim 7, characterized in that the intermetallic phases having a melting temperature of more than 1000 ° C are selected from: NiAl, TiCfe, TaFeAl, ΤΊ3ΑΙ, TiAl, FeCr or mixtures thereof.

14. The method according to any one of claims 1 to 13, characterized in that a plurality of high temperature resistant products are joined together by means of thermal coating.

15. High-temperature resistant product, produced by a process according to one of claims 1 to 13, characterized in that the high-temperature-resistant product has a porosity of 5 vol .-% to 90 vol .-%.