ES2654858A2 - Method for preparing a flexible metal-ceramic carrier having a nanocrystalline surface layer - Google Patents

Abstract

The invention relates to the field of producing ceramic coatings, having a developed surface, on metal objects having complex shapes, and can be used in applied chemistry for preparing catalyst elements, in mechanical engineering, shipbuilding, the aviation industry, and in preparing objects of space technology when applying protective coatings including anti-corrosion coatings, thermal-barrier coatings, coatings resistant to ice formation, and other coatings. A method for preparing a flexible metal-ceramic carrier having a nanocrystalline surface layer includes the plasma spraying of a special aluminum-based coating onto a metal strip carrier, with the subsequent hydrothermal processing of the flexible semi-finished product. The invention is novel in that the hydrothermal processing, which provides for optimal microstructure, nanostructure and porosity, is carried out in two stages, wherein the first stage of processing is carried out at a pressure of 20-26 atm and temperatures of 200-230 degrees centigrade for 6-12 hours, and the second stage is carried out at a pressure of 4-8 atm and temperatures of 150-170 degrees for 120-160 hours.

Description

METHOD FOR PREPARING A METAL -CERAMIC SUPPORT

FLEXIBLE THAT HAS A NANOCRISTALINE SURFACE LAYER

Technical field

The invention relates to the field of the production of ceramic coatings, which have a developed surface, on metal objects that have complex shapes, and can be used in applied chemistry to prepare catalyst elements, in mechanical engineering, shipbuilding, the aviation industry, and in the preparation of space technology objects

10 when protective coatings, including anti-corrosion coatings, thermal barrier coatings, ice-resistant coatings, and other coatings are applied. Prior art The application of ceramic coatings on a metal support is

15 widely used in industry, allowing to provide reliable protection against various exposure factors to both a natural and artificial environment. For example: document CN101438439, 20 -05-2009, A multi-layer coating, Halvor Larsen Peter; EP2088225 (A1), 12-0-2009,

20 Erosion and corrosion-resistant coating system and process therefor, Pabla Surinder Singh; document CA2664929 (A1), 03 -04-2008, Method and device for depositing a non-metal coatings by means of cold-gas spraying, Luethen Volkmar; document CA2668736, 15-5-2008, A method for the production of thin layers of metal-ceramic composite materials, Clasen Rolf.

25 However, ceramic coatings on a metal substrate have a number of disadvantages that arise from the specific details of their nature. First, it concerns a significant difference in the linear expansion coefficient (LEC) for ceramics and metals (see table 1).

30 Table 1. Linear expansion coefficient for metal and ceramic materials

Type of material

Material Coefficient of thermal expansion at 20 ºC, x 10 -6 / K

Metal

Faith 11.1

Carbon Steel

10.8

Type of material

Material Coefficient of thermal expansion at 20 ºC, x 10 -6 / K

Stainless steel

17.3

Neither

13

To the

2. 3

Ceramics

Glass 8.5

Therefore, when a metal-ceramic composite material is used at elevated or reduced temperatures, which is necessarily associated with the heating and cooling process, thermal stresses appear

5 raised at the border between metal and ceramics, which can lead, in many cases, to structural distortions of both the metal substrate and the ceramic coating and, in some cases, to the destruction of the ceramic layer, appearing as a serious delamination of coating or even exfoliation.

10 The situation becomes even more serious when the coating is used in conditions of thermal shock and thermal cycles with simultaneous exposure to factors such as corrosion or gas erosion.

To compensate for thermal stresses, intermediate layers that are located between the metal substrate and the ceramic lining are often used, thereby providing complete or partial relaxation of

the thermal stresses that arise in the intermediate layer.

Very extreme requirements are imposed on the intermediate layers, in particular, these must provide reliable adhesion to both the substrate metal and the ceramic coating, to provide rapid

20 stress relaxation at its minimum level due to plastic deformation, which is possible only with the maximum plasticity of the intermediate layer material. In addition, the intermediate layer material should see its fragility increased to a minimum during the application of temperature gradients (or the increase in fragility should be released by means of relaxation mechanisms

25 specific only during operation). In addition, based on general provisions, the intermediate layer should have a minimum thickness. All this imposes a range of serious restrictions on the material of

intermediate layer and dramatically limits the range of materials that can be used for these purposes. As an intermediate layer, metals such as aluminum, nickel and copper are often used, which, together with high plasticity, have a

5 Good adhesion to the metal and ceramic substrate, as well as high processability, thereby allowing the use of existing technological processes such as thermal spraying (plasma spraying and flame spraying), magnetron and ion plasma spraying , as well as electrolytic coating methods.

10 When the efficiency of these intermediate layer application methods is estimated from the point of view of adhesion to a metal (steel) substrate, preference can only be given to the magnetron and ion plasma spray methods, which they are preferred over thermal spray methods, the galvanic methods being taken after all

15 others The main advantage of physical deposition methods (magnetron and ion plasma spraying) is the gradual layer-to-layer deposition of metal ions, in which the first layer adheres firmly to the surface layer of substrate and, then, subsequent layers adhere

20 perfectly to the first layer, the second layer, etc. A significant disadvantage of these methods is a very low rate of this growth of the intermediate layers. Therefore, these methods can be applied only to create an intermediate adhesive layer and cannot be used to obtain a layer of a support

25 of catalyst on a metal substrate surface. To obtain a catalytic support layer, other spraying or deposition methods should be used to provide a layer of sufficient thickness that ensures a high degree of surface development. Therefore, for example, technical solutions are known in which

A very thin layer of aluminum is used as the intermediate layer that is deposited by the ion plasma method on the surface of a steel strip. Next, a layer of an aluminum oxide-based catalyst support with alpha modification is applied to its surface by the plasma method.

35 When thermal and galvanic spray methods are used, it is

It is possible to obtain sufficiently thick coatings that can be used as adhesive coatings, as well as forming a catalyst support layer on their surfaces.

A solution is suggested by a series of patents. 5 For example, US Pat. UU. No. 5,362,523 to Gorinin

IV, Farmakovsky BV, Khinsky AP, et al., 1994, describes a method for producing a catalyst strip material that includes a steel substrate, which is first covered with an adhesive sublayer by the plasma spraying method and which is then covered with a coating 10 of multiple catalyst layers by the same method in which the concentration of catalytically active elements gradually increases from 0 at the boundary between the adhesive sublayer and the catalytically active layer to 100 % Over the surface. The increased bond strength between the adhesive layer and the steel substrate is achieved due to the formation of a layer of

15 efficient diffusion in the contact area between the adhesive layer and the substrate. U.S. Patent UU. No. 5,820,940 in the name of Gorinin IV, Farmakovsky BV, Khinsky AP et al., 1998, describes a method for producing an adhesive coating (intermediate layer) on a metal strip support by spraying powder plasma of composite material

20 thermally reactive (such as nickel-aluminum). The method as described provides an intermediate adhesive layer that adheres very closely to the steel strip support, which is demonstrated by the test results. However, the problem of reliable adhesion of the catalytic layer that

25 deposited on the surface of the intermediate layers remains unresolved and the bond strength between these layers, although not mentioned in the patent materials, will obviously be lower than the bond strength between the intermediate layer and the substrate of metal. When catalyst elements made of such a catalyst strip material are used, in

30 extreme conditions, including thermal cycles, intensive gas erosion, etc., a partial delamination of the catalyst layer is possible along with a corresponding decrease in its characteristics.

Attempts to increase the bond strength between the intermediate layer and the catalyst layer through an intermediate thermal processing (US2001014648, Hums E., Khinsky A., 2001), through the use of

various places to introduce the powdered materials into the plasma stream during the spraying process (WO2004079035, Khinsky AP, 2004), through the use of the HVOF method (high velocity oxygen fuel, high speed oxygen fuel) spray

5 composite powder (WO2008063038, Khinsky A. P, Klemkaite K., 2008) results in a certain increase in adhesion strength, although they do not provide a high level of adhesion strength between the intermediate layer and the metal substrate

The use of coatings obtained by thermal spraying

10 of ductile metals and alloys (aluminum, nickel, copper, etc.) provides high adhesion to the sprayed surface due to the high kinetic energy of the particles being sprayed (often, the spraying is carried out at speeds close to, or even higher than, the speed of sound) and the high dynamics of its cooling, which

15 almost always leads to the amorphization (or the transition to the microcrystalline state) of the metal particles being sprayed. However, the compounds that are formed during the instantaneous contact between the molten particles and the metal substrate during the course of the thermal spray process, which are mainly

20 intermetalides of a different composition and stoichiometry that are formed in the contact zone as very thin films, differ considerably in their physical-mechanical characteristics with respect to the usual intermetalides, which are formed during the course of conventional metallurgical processes, including laundry, processing

25 thermal, etc., of special steels and alloys. It is known that conventional intermetalides that are formed under the same conditions are characterized by high hardness and fragility, while non-stoichiometric film intermetalides that are formed during the course of thermal spraying, as practice shows, do not exhibit

30 such properties and, in addition, they provide very good adhesion of the sprayed layer to the substrate. The coatings obtained by the thermal spray method provide another important advantage over the galvanic method and the magnetron and ion plasma spray methods. This advantage

35 lies in the ability to form a surface microstructure during the

thermal spray The typical thickness of such a coating is 10-20 µm.

The structure of the sprayed layer surface can be significantly improved due to the formation of nanostructured "protuberances" in the form of nanocrystals of different configurations

5 (A. V. Lukashin, Создание функциональных нанокомпозитов на основе оксидных матриц с упорядоченной пористой структурой, Автореферат докторской диссертации, 2009, MGU, Moscow).

The creation of nanostructures on the surface of this type increases the activity of catalyst, the resistance to the formation of ice films at 10 temperatures below zero, the optical characteristics of the coatings etc.

Therefore, the use of coatings obtained by thermal spraying (especially plasma spraying) as an intermediate layer, in addition to obtaining high adhesion of the sprayed layer, makes it possible to provide for the formation of its surface developed microstructure.

The application of a catalyst support layer (with or without catalyst as such) on the intermediate layer can be carried out in various ways; however, in any case, the applied layer has to provide the following characteristics: - A sufficiently high free surface with an optimum porosity structure;

20 -High adhesion strength between the catalyst support layer and the intermediate layer; -A sufficiently high level of catalytic properties when interacting with the catalyst as such. Unfortunately, virtually all of the methods

Existing application of a catalytic support cannot provide a high level of catalytic properties and high adhesion to the intermediate coating at the same time. Therefore, choosing the optimal method to form a catalyst support layer on metal substrates is often very difficult.

In addition, the manufacturing process comprising said intermediate phases, that is, the application phase of the intermediate adhesive layer and the subsequent application phase of the catalyst support and possibly also the catalyst application phase, is very complicated. and expensive. Therefore, for example, when a catalyst support that is

35 comprised in an aqueous suspension is applied on a cellular structure

of metal by the method of successive immersion and drying, a very annoying factor that limits the wide applicability of this method lies in the slow drainage of the suspension through the holes during the course of drying and the formation of specific icicles in the part bottom of the

5 cellular structure, which can lead, in some cases, to the complete blockage of its holes.

From this point of view, it seems very advantageous to combine the processes of spraying adhesive coating (intermediate layer) and the subsequent transformation of its surface into a catalyst support. In

The present case, on the other hand, ensures high adhesion of the adhesive coating to the metal substrate which, as mentioned above, is characteristic for the coatings that are applied by the plasma spraying method and, on the other hand, the organic transition of the coating metal to the oxide (or hydroxide) phase.

In general, ductile metals and alloys are used, in particular aluminum, nickel, copper and their alloys as the adhesive coating material as mentioned above. In general, under certain conditions, all of these materials can be transformed from the surface into oxides and hydroxides, which is seen

20 accompanied in some cases by a concomitant development of a porous structure. The latter circumstance is very important for the purpose of forming catalytic coatings.

However, for the metals that have been listed above, which are used to apply an adhesive coating, the formation of porous structure that is required for the catalyst support is observed only in the

aluminum case.

Under certain conditions, aluminum and a series of its alloys can be converted from the surface into aluminum hydroxide. Under ordinary conditions, a surface is formed on the aluminum metal surface

30 thin and very dense oxide film, which is instantly restored after its destruction. This film prevents oxidation of additional aluminum. However, under certain conditions - at a high pressure and temperature in the atmosphere of superheated steam - a gradual transition from aluminum to aluminum hydroxide (boehmite) is observed. As shown

35 in a series of studies, this process is carried out through the

successive hydration of the oxide film that forms on the aluminum metal surface. In a series of articles (Tihov S. F., Fenelonov B. B., et al., Кинетика и катализ, 2000, Vol. 41, No. 6, p. 907-915. Tihov S. F., Zaykovskiy V. I. et al.,

5 Кинетика и катализ, 2000, Vol. 41, No. 6, p. 916-924), it is shown that this process can be used to produce porous cellular ceramic supports based on aluminum oxide.

The articles describe a process for the preparation of a composition of aluminum oxide / metal aluminum metal-porous ceramic

10 when processing aluminum powder briquettes with a sufficiently high porosity (enough for the free circulation of air inside). The processing was carried out in a special autoclave press, which ensures the processing of the briquette in a water vapor atmosphere at a temperature of 150 to 250 ° C and a pressure of 5 to 50 atmospheres.

A patent (RU2256499 (C1) of Pakhomov N. A., Tikhov S. F. et al., 2004) is also known, based on the technology described in the articles.

The present patent suggests a ceramic catalyst for a hydrocarbon dehydrogenation process and a method for the preparation thereof.

The catalyst composition contains chromium oxide and an alkali metal that is applied on a support, which represents a composite material that includes aluminum and aluminum oxide.

The mechanisms as described above in what

25 regarding the transformation of aluminum metal into aluminum hydroxide and its subsequent decomposition to prepare a catalyst support suggest an idea to develop a technology based on these principles for the preparation of a catalyst support after the application of a layer Aluminum adhesive bottom on the surface of a strip holder

30 metal In JP9217178, 19 -08 -1997, Kanbe Yumi, and JP10120499, 12 -05 -1998, Kanbe Yumi, a method for preparing a thin multilayer coating is described. The coating should provide a porous metal oxide structure on which it is deposited

35 the electrically insulating material that fills the pores of the oxide layer of

metal.

According to the patent, during the first phase of the process, a thin and porous metal oxide film is formed on the substrate surface during the course of its hydrothermal processing in salt solutions

5 corresponding.

JP9156.627, 17-06-1997, Nakayama Naomi, discloses a method for preparing a multilayer oxide coating on selected substrate areas, comprising the phases of: forming an oxide coating on the substrate surface, remove the material from

10 mask, then perform the processing in an oxidizing environment to form an oxide coating etc. The final operation is the hydrothermal processing of the coating obtained in aqueous alkaline solutions.

JP3284356, 16-12-1991, Kameyama Hideo, describes a technique for preparing a flat low temperature catalyst element, which includes the following operations. A flat substrate made of an aluminum alloy is annealed at an elevated temperature, preferably in the range of 900-1000 ° C, to form an oxide film based on aluminum oxide on its surface. Next, the substrate undergoes hydrothermal processing in the range of 20 temperatures of 50-350 ° C., And the metal having a catalyst activity is applied on the alumina-based catalyst support that is formed on the substrate surface plane as a result of hydrothermal processing. The catalyst support obtained as a result of hydrothermal processing must be gamma-modified aluminum oxide with a

25 free surface developed. A metal that has a catalyst activity can also be applied in a hydrothermal processing phase. JP2000178792, 27-0-2000, Ishizawa Hitoshi, describes a method for forming a titanium oxide based coating with a raised free surface on a metal substrate. The method includes a phase

30 for preparing the metal substrate surface, an anodizing phase of at least one surface of the substrate to form an anodic oxide film, and an application phase of a suspension based on aqueous solutions of metal salts and alkoxides that They contain dispersed metal oxide particles. After the anodizing phase, a

35 hydrothermal processing.

Document 2004058066, 2004-058066, Wei Zhiqiang, describes a method for forming a thin film metal oxide coating. The method includes the following phases: an application phase of a sol-gel coating comprising at least

5 a metal component on the metal substrate surface, a drying phase of said sol-gel coating, an impregnation phase of the coating obtained in aqueous alkaline solutions containing at least one metal component, a drying phase and a phase of hydrothermal processing.

10 The patents, according to the foregoing, show that great importance, and in some cases a fundamental importance, is given to the method of applying an aluminum coating on the strip support surface. A patent (RU2295588, Hinskogo A. P., March 20, 2007) discloses

15 a process to apply the aluminum powder on a surface. A distinctive feature of the coating as described in this process is its high adhesion to the steel strip that is used as a substrate. A steel strip with a spray coating as a resulting semi-finished product has such a high adhesion strength that it allows to carry out virtually any machining operation, such as cutting, corrugation, drilling, etc. no delamination

or exfoliation of the sprayed layer.

Summary of the invention

Using this process to spray the aluminum layer will create a

25 coating that would combine the functions of an intermediate adhesive layer (on the surface adjacent to the steel strip support) and a catalytic support (on the surface of the coating as such) if it could be converted into a porous oxide-based support aluminum according to the technology as described above.

In addition, the sequence of the application processes of the aluminum coating and its transformation into the catalyst support should be changed. Because it is assumed that the bond strength between the coating and the steel substrate is so high that it will allow the semi-finished product obtained after spraying to be machined, it seems reasonable to include this phase

35 immediately after spraying, and complete the phase of

hydrothermal processing In the present case, taking into account previous patents, the process should include the following successive phases:

1. Apply an adhesive layer of aluminum on the substrate surface of metal strip 5 using the thermal spray method.

2.

Machining (including cutting, corrugation, drilling, etc.) to form the catalytic element in its final form.

3.

Process the resulting catalyst element in a steam atmosphere of

water - air at an elevated pressure and temperature for the partial conversion of the surface portion of the adhesive layer into aluminum hydroxides.

Four.

Thermal decomposition of the hydroxide coating obtained with its transformation into aluminum oxide to form a porous surface structure.

5.

Apply catalysts using the impregnation method.

15 To implement the method as suggested to prepare a catalyst support, work was carried out for phases 1, 2, 3 and 4 of the process, because phase 5 is very trivial and can be carried out without preliminary preparation . Phase 1.

20 Apply an adhesive layer of aluminum on the surface of a metal strip substrate by thermal spraying.

To apply an aluminum layer on the surface of a metal strip substrate, the following materials were used: Cold rolled steel strip made of chrome stainless steel

25 ferritic with a thickness of 40 µm and a width of 100 and 90 mm from Sandvik (Sweden). Table 2 gives data on chemical composition and applicability. Table 2. Characteristics of the Sandvik OS404 cold rolled steel strip

Material

Quality Chemical composition Applicability

Steel strip

OS404 C Cr To the Catalytic units for converters, heat exchangers for high temperatures

cold rolled chrome stainless steel

<0.02 20.0 20.5 5.0 5.5

-

ПА-1 aluminum powder and ПАП-2 aluminum powder (ГОСТ 5494 -95) from Volgograd Aluminum Company (Валком-ПМ).

Basic characteristics of these materials are given in tables 3 and 4. Table 3. Basic characteristics of PA-1 aluminum powder

Quality

Density Chemical composition, %

apparent, g / cm3,

Active aluminum, Residual elements, max. Humidity, max. Specific surface area, m2 / g

min.

min.

Faith Yes Cu

PA-1

0.96 99 0.35 0.4 0.02 0.2 -

Table 4. Basic characteristics of PAP-2 aluminum powder

Parameters

Quality

Coating power in water, cm2 / g, min.

ПАП1 ПАП2

Coating power in water, cm2 / g, min.

7000 10000

008

1.0 -

0056

- 0.3

0045

- 0.5

Flotation,%, min.

80 80

Content in residual elements,% by weight, max.

Faith 0.5 0.5

Yes

0.4 0.4

Cu

0.05 0.05

Mn

0.01 0.01

Humidity, max.

0.2 0.2

To apply the aluminum adhesive layer, the plasma spraying method was used, which is carried out by means of an apparatus

10 specially designed in the air atmosphere using a plasma torch and an original design dispenser (the description of the apparatus and the plasma torch is given in patents RU2295588, WO2008063038, WO2004079035, US2001014648).

The plasma spray modes for aluminum powder and fine powder 15 as well as other process parameters are given in Table 5. Table 5. Basic parameters of the plasma spray process

Operating voltage, V

Operating current, A Device capacity, kVA Distance from plasma torch nozzle, mm Plasma generation gas Powder that is being sprayed Fractional content of the mixture being sprayed

214

150 32.1 98 air Mixture of aluminum powder and fine powder Max. 63 µm

As a result of the tests, a continuous aluminum coating with a thickness of 18-24 µm was obtained. The chemical composition of the sprayed coating is represented by

5 means of the data from an investigation by radiography (Figure 1), which is carried out using the conventional Bragg-Brentane technique by means of a DRON-6 radiography system that is equipped with a secondary graphite monochromator. As a radiation source, Cu Kα radiation (λ = 1.541838 Å) was used.

10 Figure 1 shows an X-ray diffraction pattern of the sprayed aluminum layer.

The adhesion strength between the aluminum coating and the metal substrate was evaluated by means of the results of mechanization of the resulting semi-finished product by a visual inspection for the presence

15 discontinuities in the sprayed coating (delamination, exfoliation, etc.). Corrugation and drilling were chosen as two typical mechanization operations and aggressive enough for continuity assessment. Phase 2.

20 Mechanization (including cutting, corrugation, drilling, etc.) to form the catalytic element in its final form.

This phase has already been partially described in phase 1 (see above), so that an additional description of this phase seems to be superfluous. Phase 3.

5 Process the resulting catalyst element (semi-finished product) in an atmosphere of water vapor - air at an elevated pressure and temperature for the partial conversion of the surface portion of the adhesive layer into aluminum hydroxides.

Hydrothermal processing of semi-finished products from

The support resulting from the spray of plasma and the catalyst elements (cellular structures) prepared from said support was carried out by means of a special apparatus designed and manufactured to solve this problem. The apparatus is an autoclave press (Figure 2), which is designed to operate in the temperature and pressure range (which is

15 shown in table 6) and which includes a reaction chamber that provides a reaction space to receive semi-finished products and catalyst elements (cellular structures) during hydrothermal processing, a gate chamber that provides a pre- placement of catalytic elements for subsequent transport to the chamber of

20 reaction, and a discharge chamber from which the processed catalyst elements are discharged. Table 6. Temperature and operating pressure ranges of the autoclave press

Operating parameters of autoclave press

Temperature range, ºC Pressure range, atm Test duration, h

50 -250

10 -40 Unlimited

The additional equipment of the apparatus includes a device (3) that provides automatic adjustment and maintenance of the main process parameters (temperature, pressure, humidity, flow, etc.). In addition, other elements of the autoclave press, such as: excess valve (1), fixing bolts (2) of the lid, pressure gauge (4), are shown in Figure 2.

30 water vapor exhaust valve (5) and heating element (6). The processing in an autoclave press was carried out in accordance with the

modes given in table 7. Table 7. Basic modes of semi-finished media processing by means of an autoclave press

Operating mode

Temperature, ºC Pressure, atm Duration, h

Mode 1

150 4 6

Mode 2

210 24 6

Mode 3

210 + 150 24 + 2 6 + 120

5 Some studies have shown that hydrothermal processing in all modes (1, 2 and 3) is accompanied by the transition of the surface layer of aluminum coating to aluminum oxide with gamma modification and the development of the surface free of coating and the formation of an optimal porosity structure.

10 The value of the relative free surface that characterizes the development of porosity after hydrothermal processing by means of modes 2 and 3, is in the range of 60 -100 m2 / g, which is a fairly acceptable result. However, if the surface, in general, retains the microstructure

15 morphological of the pulverized layer and, in the superficial layer, the presence of spherical particles of various sizes (from several microns to tens of microns) partially deformed (flattened) and firmly joined together, which is a typical structure of the sprayed layer, a completely different image is observed when processed by mode 3.

In the present case, it was experimentally established that, on the surface of the sprayed layer, an orderly "forest" of needle-shaped nanocrystals with a sufficiently uniform orientation in relation to the substrate is formed. Figure 3 shows, with different magnifications, the surface structure of the sprayed aluminum layer after

25 processing by means of an autoclave press according to mode 3 (see table 7). A similar structure is formed continuously on the surface of the sprayed aluminum layer at the following temperature and pressure ranges (see table 8).

30 Table 8. Parametric intervals to form the coating nanostructure during the processing of a semi-finished product sprayed from a

stage form (mode 3).

Parametric intervals to form the coating nanostructure

Temperature, ºC Pressure, atm Duration, h

Processing Phase 1

200 -230 22-26 6 -8

Processing Phase 2

150 -170 4 -8 120 -140

Regarding the above values, indicate that the procedure phase

5 1 could also be carried out with a duration of between 6-12 hours. In the same way, the procedure phase 2 could also be carried out with a duration of between 120-160 hours. Similarly, the procedure phase 1 could also be carried out with a pressure of 20-26 atmospheres.

10 Figure 3 shows the structure of the surface of the aluminum spray layer after the autoclave press processing in a stepwise manner with the decrease in the processing temperature.

As the investigations of the fine surface structure have shown after hydrothermal processing, the increase in temperature and pressure leads to an increase in the intensity of transformation of the aluminum coating and the process progresses gradually from the coating surface towards its depth In the present case, in the pulverized layer of pure aluminum a gradual layered transformation of metallic aluminum into a corresponding oxide and a formation of

20 specific microstructure. With regard to the specific effect of the nanostructured "forest" of crystals that forms under conditions in a phased manner with the decrease in temperature and pressure in the second phase, this is probably caused by the increase in selectivity of the growth points

25 during the crystallization process of nanocrystals.

Claims (3)

1. A method for preparing a flexible metal-ceramic support having a nanocrystalline surface layer, which comprises spraying 5 plasma of a special aluminum-based coating on a metal strip support with subsequent hydrothermal processing of the flexible semi-finished product, characterized by that hydrothermal processing, which provides for a microstructure, a 10 optimal nanostructure and porosity is carried out in two phases, in which the first phase of the processing is carried out at a pressure of 20-26 atm and temperatures of 200-230 degrees Celsius for 6-12 hours, and the second phase is carried out at a pressure of 4-8 atm and temperatures of 150-170 degrees for 120-160 hours. 2. A method for preparing a flexible metal-ceramic support having a nanocrystalline surface layer according to claim 1 characterized in that the first phase is carried out at a pressure of 22-26 atm and temperatures of 200-230 degrees Celsius during 6 -8 hours 3. A method for preparing a flexible metal-ceramic support having a nanocrystalline surface layer according to claim 1 or 2 referring to a method for preparing a support characterized in that the second phase is carried out at a pressure of 4-8 atm and temperatures of 150 -170 25 degrees for 120-140 hours.