DE102017222489A1 - CMC moldings with a new surface, as well as manufacturing processes - Google Patents

Abstract

The invention relates to a shaped body such as a turbine component of a gas turbine and / or a component of an exhaust system, which are at least partially made of CMC, so - ceramic matrix composite - and / or a CMC-metal hybrid and a new, in particular improved in terms of their stability, surface. In particular, the invention relates to the improvement of the adhesion of coatings on a CMC surface and a manufacturing method for improved adhesion of a - for example thermally stable - coating on a CMC surface. The invention provides for the first time a possibility of how the surface of CMC-for example, a roughening-can be rendered mechanically less sensitive, stabilized and / or reinforced. For this purpose, a glass ceramic is incorporated into the surface of the CMC and / or applied thereto. Particularly preferred is the embodiment in which a glass-ceramic slip is sintered together and combined with a CMC green body.

Description

The invention relates to a shaped body such as a turbine component of a gas turbine and / or a component of an exhaust system, which are at least partially made of CMC, so - ceramic matrix composite - and / or a CMC-metal hybrid and a new, in particular improved in terms of their stability, surface. In particular, the invention relates to the improvement of the adhesion of coatings on a CMC surface and a manufacturing method for improved adhesion of a - for example thermally stable - coating on a CMC surface.

So far, for example, moldings such as turbine blades, for example for stationary gas turbines, are made of nickel-based superalloys with additional protective coatings, e.g. TBC coatings used. Although the properties of these materials are constantly evolving, this technique seems to be quite exhausted and little substantial increase is still possible.

In contrast, the technique of CMCs, particularly fiber reinforced CMCs, is an alternative and may be used alone or in combination with superalloys, called CMC metal hybrid moldings, to create novel moldings such as turbine components and / or components in an exhaust line. In combination with alloys, in particular the superalloys mentioned, or other metals is then called a hybrid material of CMC and metal.

Despite the improved properties compared to the pure metals, such as increased oxidation resistance and / or lower density of the CMCs, which allow an increase in the operating temperature and a reduction in the cooling air of the moldings produced therefrom, there are also limiting factors in the CMCs, such as Grain growth within the ceramic matrix.

The CMC material surface therefore does not allow unlimited increases in thermal efficiency. Thus, thermally loadable coatings, in particular so-called TBC (Thermal Barrier Coating) coatings on CMCs are necessary.

The CMCs used are in particular the silicon carbide and / or oxide CMCs, ie CMC materials based on metal carbides and / or metal oxides, since these have increased resistance to, for example, corrosion and / or oxidation.

It is also appropriate, similar to the turbine components mentioned here, for example as moldings, which are made entirely of superalloy, in the CMC superalloy hybrid solutions and / or also in moldings entirely made of CMC, coatings, in particular thermally active barrier materials. Coatings such as the so-called thermal barrier coatings - so-called TBC coatings - apply.

For example, a TBC is applied to a CMC surface via a spray process, for example as an Atmospheric Plasma Spraying APS coating. However, in order for the sprayed and / or plasma-formed coating to adhere well, it is preferable to prepare, for example roughen, the very smooth surface of the CMC or CMC hybrid material. Mechanically sophisticated roughening methods, such as sand blasting or laser irradiation, are also used. However, these can also cause damage to the CMC surface, which then manifests itself, for example, in cracking with the corresponding material disadvantages in the hot gas application. Therefore, according to the prior art, a CMC surface is roughened only slightly or insufficiently before the application of a thermally loadable coating, so that the adhesion of the coating is often insufficient.

Various approaches are known for optimizing the adhesion of the coatings to the CMCs without unduly damaging the CMC surface by roughening. From the DE 102017210819 a molded article is known in which in at least one surface-near layer of a CMC laminate, one or more breaking strength additives such as particles of zirconia -ZrO ₂ -, silica - SiO ₂ -, magnesium dioxide - MgO ₂ -, yttrium-aluminum Garnet -YAG - and / or yttrium oxide Y ₂ O ₃ , alone or in any mixtures, incorporated so that the stability of the CMC surface is improved.

The disadvantage of this can possibly be a certain embrittlement of the CMC surface.

The object of the present invention is therefore to improve the adhesion of a CMC surface with a thermally loadable coating, in particular to achieve an improvement in the stability of a CMC surface over roughening methods such as sandblasting and / or laser treatment.

This object is solved by the subject matter of the present invention as disclosed in the specification and the claims.

Accordingly, the subject matter of the present invention is a shaped body made of a ceramic composite material CMC or of a CMC-metal hybrid material, wherein the CMC surface at least partially comprises glass-ceramic.

• - ersten Verfahrensschritt ein grüner CMC-Formkörper hergestellt wird,
• - in einem zweiten Verfahrensschritt und vor einer Erwärmung und/oder Versinterung des CMC-Formkörpers zur Ausbildung einer Glas-keramischen Oberfläche ein Glaskeramischer Schlicker auf die Oberfläche des grünen CMC-Formkörpers aufgebracht wird und
• - in einem dritten Verfahrensschritt der CMC-Formkörper mit einer Oberfläche aus Glaskeramischem Schlicker zum CMC-Formkörper mit Glaskeramischer Oberfläche oder Glaskeramischen Anteilen an Oberfläche kombiniert gesintert wird.

In addition, the present invention is a process for producing a shaped body of a ceramic matrix composite CMC, wherein in a

• - the first step of the process produces a green CMC molding,
• - In a second step and prior to heating and / or sintering of the CMC molding to form a glass-ceramic surface, a glass ceramic slurry is applied to the surface of the green CMC molding and
• - In a third step, the CMC molded body is sintered combined with a surface of glass ceramic slurry for CMC molding with glass-ceramic surface or glass ceramic portions of surface.

General knowledge of the invention is that a glass-ceramic layer or at least glass-ceramic portions on the surface of a CMC molding there quasi form a protective layer that serves as a thermal and mechanical protective layer and / or forms a surface that further processing, so for example preparation For coating with a Thermal Barrier Coating (TBC) layer, facilitates or only damaging possible.

In particular, by applying a slurry of glass-ceramic material which forms a glass ceramic after sintering, on at least parts of the surface of a unsintered CMC molding, such as a stack of green CMC prepreg layers, an intermediate layer on a molded body of CMC material and or CMC hybrid material produced by heat treatment and / or sintering, whose hardness, thermal and / or mechanical resistance is far better than that of the pure CMC surface and / or roughening before an example following APS process without damage, or with significantly less damage than the pure CMC surface.

For example, it is proposed here to combine the implementation of an APS process for improving the adhesion of TBC layers with a preceding formation of an at least partially glass-ceramic surface which is to be roughened by means of laser or radiation treatment. It is particularly advantageous that neither the ceramic matrix of the CMC, nor the ceramic fibers of the CMC are affected by the combined sintering with the glass-ceramic slip.

• - ersten Verfahrensschritt beispielsweise CMC-Prepreg-Lagen auf eine Stützstruktur abgelegt, dann werden diese noch ungesinterten und/oder grünen CMC-Lagen im
• - zweiten Verfahrensschritt mit glaskeramischem Schlicker oberflächlich versehen, beispielsweise bestrichen, besprüht oder eingetaucht - und im
• - dritten Verfahrensschritt dann kombiniert gesintert und bilden entweder mit oder losgelöst von der Stützstruktur den Formkörper.

For the production in the

• - First step, for example, deposited CMC prepreg layers on a support structure, then these are still unsintered and / or green CMC layers in
• - Second method step provided with glass ceramic slurry surface, for example, coated, sprayed or dipped - and in
• - Third process step then combined sintered and form either with or detached from the support structure, the molding.

A CMC prepreg sheet typically comprises a ceramic matrix, such as a slurry, in which fibers which may be single fiber, braided fiber, fiber fabric and / or fiber composites are embedded. By way of example, these are silicon carbide ceramic-based or so-called oxide-ceramic-based matrix and / or fiber materials.

For example, there is a CMC based on oxide-ceramic-based matrix materials. In it - again, for example - embedded oxide ceramic-based fibers, fiber fabrics and / or fiber composites. Their materials are for example selected from the group of the following materials: doped or undoped aluminum oxide, mullite, yttrium aluminum garnet and / or zirconium oxide-doped aluminum oxide.

All the aforementioned fiber materials may be present in a fiber, a fiber fabric and / or in a fiber composite, as used herein, alone or in any combination, such as alumina-mullite fiber. Likewise, the materials mentioned can serve alone or in any desired combinations for the construction of the matrix.

In the present case, a glass-ceramic material is a mineral material which is processed, for example, as a slip and then sintered, from a molten glass by controlled crystallization. The processing of the preceding slip, a - containing solvent, so for example aqueous - slurry of the mineral material, can be done arbitrarily.

The viscous mass can be applied, for example, at room temperature. Through a temperature treatment to sintering a glass-ceramic state of the material is achieved, which is characterized specifically by its hardness, as of the Glass ceramics is known in daily use. The glassy material is at least partially crystallized after formation, stable and does not melt again. High continuous service temperatures, such as 1200 ° C and more, do not affect the stability of the glass-ceramic material.

As examples of glass ceramic materials, among other many kinds of disilicates are known, for example, the MAS system, MAS ₃ x stands for MgO x Al ₂ O n SiO _2, and the analog with zinc oxide, ZnO _2, constructed in place of the magnesium oxide ZAS and glass ceramics of lithium disilicate and those with phlogopite as base. For example, zirconium (IV) oxide in combination with titanium (IV) oxide is added as an epitaxial nucleating agent.

Advantageously, a mineral material, for example a disilicate, whose thermal expansion coefficient matches that of the carrier substrate, that is, for example, a CMC shaped body and / or CMC laminate layer stack or a CMC metal hybrid material molded body, can also be used as the glass ceramic material , For example, the glass ceramic can be combined stress-free with the CMC ceramic, even at high continuous operating temperatures of over 1200 ° C.

For example, an yttrium-aluminum garnet (YAG) disilicate and / or another yttrium disilicate is suitable as the glass ceramic.

The glass ceramic is preferably, but not exclusively, applied in the form of its slip, that is the pulpy slurry, to the still green, that is unsintered, CMC laminate layer stack. However, the melt of the glass-ceramic material which has not yet been sintered into the glass-ceramic material can also be applied to a CMC surface as a surface and / or intermediate layer.

The glass-ceramic slip is applied to the green CMC molding, for example, by brushing, spraying, ie brushing, wiping, spraying, spraying or other methods.

After sintering, a CMC laminate layer stack is obtained, the surface of which is more temperature-resistant, more robust, for example roughening and / or more corrosion-resistant than the original pure CMC surface by the glass ceramic. Tests have shown that a glass-ceramic CMC surface formed according to the invention is also significantly more resistant to roughening, for example by sandblasting and / or by means of laser treatment, than the unglazed CMC surface.

The glass ceramic surface is preferably combined with the CMC surface if, for example, the glass ceramic is at least partially fused to the CMC surface during the common sintering. At least, after common thermal treatment, there is good adhesion between the CMC surface and the glass-ceramic layer. By way of example, combined sintering can also lead to the formation of ceramic mixed phases and / or covalent chemical bonds between the glass ceramic and the CMC surface. The adhesion of the glass-ceramic layer to the surface of the CMC may be enhanced by forming chemical bonds and / or by forming mixed ceramic phases.

The glass-ceramic surface can also serve, for example, as protection of the CMC laminate layer stack against environmental influences, such as, for example, water vapor corrosion.

A roughened with glass ceramic according to the invention offset surface can be coated with a thermal barrier layer, for example via APS, with a significantly improved adhesion of the thermal barrier layer, especially with respect to the pure non-roughened CMC surface is observed.

According to the invention, the glass-ceramic surface is carried out together with the sintering of the CMC laminate layer stack, so that a good bonding of the glass ceramic to the CMC surfaces is ensured by fusing during sintering.

The invention provides for the first time a possibility of how the surface of CMC-for example, a roughening-can be rendered mechanically less sensitive, stabilized and / or reinforced. For this purpose, a glass ceramic is incorporated into the surface of the CMC and / or applied thereto. Particularly preferred is the embodiment in which a glass-ceramic slip is sintered together and combined with a CMC green body.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102017210819 [0009]

Claims (14)

Shaped body of a ceramic composite material CMC or of a CMC-metal hybrid material, wherein the CMC surface at least partially comprises glass ceramic. Molded body after Claim 1 , which is a turbine component and / or a component of an exhaust line. Shaped body according to one of Claims 1 or 2 , wherein the glass ceramic is at least partially present as a layer on the surface of the shaped body. Shaped body according to one of Claims 1 to 3 , wherein a partial ceramic mixed phase formation and / or a chemical bond between the CMC ceramic matrix, the CMC reinforcing fibers on the one hand and / or the glass ceramic on the other hand present. Shaped body according to one of the preceding claims, wherein a thermally loadable TBC layer is arranged on the surface of the shaped body. Shaped body according to one of the preceding claims, wherein the glass ceramic is chosen so that its thermal expansion coefficient is equalized to the thermal expansion coefficient of the CMC material. Shaped body according to one of the preceding claims, wherein the glass-ceramic comprises a disilicate. Shaped body according to one of the preceding claims, wherein the glass-ceramic comprises a disilicate with an yttrium and / or an yttrium-aluminum garnet. Process for the preparation of a molded body of a ceramic matrix composite CMC, wherein in a - the first step of the process produces a green CMC molding, - In a second step and prior to heating and / or sintering of the CMC molding to form a glass-ceramic surface, a glass ceramic slurry is applied to the surface of the green CMC molding and - In a third step, the CMC molded body is sintered combined with a surface of glass ceramic slurry for CMC molding with glass-ceramic surface or glass ceramic portions of surface. Method according to Claim 9 wherein the green CMC molding is a stack of CMC prepreg laminate sheets. Method according to one of Claims 9 or 10 , wherein in a further method step, the glass-ceramic surface of the molding or the surface comprising at least glass ceramic parts is roughened. Method according to Claim 11 in which the surface is roughened by sandblasting and / or by means of laser treatment. Method according to one of the preceding Claims 9 to 12 in which the surface of the shaped body is coated with a thermal barrier layer - TBC - in a subsequent method step. Method according to one of the preceding Claims 9 to 13 in which the TBC layer is generated by Atmospheric Plasma Spraying - APS.