RU2624707C1 - Method of producing sealed products from composite materials - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method includes the manufacture of an inner shell of composite material (CM), the formation of a hermetic coating thereon, the manufacture of an outer shell of CM based on the same type of reinforcing fibers as the inner shell CM, and high-modulus high-strength carbon fibers are used. The inner shell is made of carbon-silicon carbide composite material that does not contain free silicon. As a composition, when forming a hermetic coating, a suspension is used which is based on a binder, i.e. a solution of organo-yttrium-oxane-lumoxane siloxane, and a filler, i.e. a mixture of finely divided refractory powders , Y₂O₃, SiO₂ or Al₂O₃, Y₂O₃, HfO₂, SiO₂. The coating is formed by lamination of the suspension interchanging with drying and further heat treatment at 1600°C. The outer shell is produced over the barrier coating formed on top the tight oxide coating. The shell is manufactured in the following sequence: a frame is formed and then impregnated with a coke-forming and/or polycarbosilane binder. Next, a carbon fiber reinforced plastic billet is made, subjected to carbonization and compacted to the maximum possible density by pyrocarbon using the vacuum isothermal method or compacted to intermediate density by pyrocarbon. Nanocarbon is grown in the pores of the material and silicated by the vapour-liquid phase method with the mass transfer of silicon into the pores of the material via the mechanism of capillary condensation of its vapours in the range of 1300-1500°C and the subsequent exposure at a temperature of 1550-1600°C.

EFFECT: providing a possibility of reducing the weight of manufactured products designed to work under excessive pressure at high temperatures and in the presence of an oxidizing environment.

4 cl, 10 ex

Description

The invention relates to methods for the manufacture of sealed products designed to work under excessive pressure at high temperatures and in the presence of an oxidizing environment with unilateral or bilateral access to the product.

A known method of manufacturing a sealed product, including the formation on a carrier basis of the product of a sealed coating [US Pat. RU No. 2471707, 2013].

In accordance with it, as the materials of the carrier base and the hermetic coating, materials are taken whose components are close to each other and the coating has a ctr (coefficient of linear thermal expansion), in particular, low-modulus fibers with a ctl close to a ctr of carbon or carbon-silicon carbide matrix, namely: ~ 4.0 × 10 ^-6 deg ^-1 .

The disadvantage of this method is that it does not exclude the possibility of depressurization of the product under mechanical and / or chemical stress, as well as the relatively low strength of the material of the product, which leads to the need to increase the thickness, and hence its weight, to provide the required strength of the product.

The closest to the claimed technical essence and the achieved effect is a method of manufacturing sealed products from composite material (KM), including the manufacture of an inner shell from KM, the formation on it of a sealed coating compatible in terms of ctr with the material of the inner shell, the manufacture of an outer shell of composite over the coating material based on the same type of reinforcing fibers as the composite material of the inner shell [US Pat. RU No. 2497750, 2013].

In accordance with it, an airtight coating is a pyrocarbon coating, and low-modulus carbon fibers with a clt close to a clt of a carbon and carbon-silicon matrix are used as reinforcing fibers in the manufacture of the inner and outer shells.

The method improves the reliability of the products by protecting the sealed coating from mechanical stress, as well as the effects of chemically aggressive environments.

The disadvantage of this method is that the manufactured products have a relatively large weight due to the low strength of this type of composite materials. In addition, they are not intended for use in an oxidizing environment.

The objective of the invention is to provide the possibility of reducing the weight of manufactured products designed to work under excessive pressure at high temperatures and in the presence of an oxidizing environment, including thin-walled, large-sized and complex ones without performing machining operations.

The problem is solved due to the fact that in the method of manufacturing sealed products from composite material, including the manufacture of an inner shell from KM, the formation on it of a sealed coating compatible in terms of ctr with the material of the inner shell, the manufacture of an outer shell from a composite material on the basis of the same type of reinforcing fibers, as the composite material of the inner shell, in accordance with the claimed technical solution as reinforcing fibers of composite materials The inner and outer sheath series use high-modulus high-strength carbon fibers, in at least one of the reinforcement directions, the inner sheath is made of carbon-carbide-silicon composite material that does not contain free silicon, and a suspension based on a binder - an organo-yttrioxane-aluminum-oxoxane siloxane solution is used as a composition in the formation of a sealed coating - and filler - mixture of Al ₂ O ₃ fine refractory powder, Y ₂ O _3, SiO ₂ or Al ₂ O _3, Y ₂ O _3, HfO _2, SiO _2, Form Coating is carried out by layer-by-layer deposition of a suspension, alternating with drying, and subsequent heat treatment at 1600 ° C, the outer shell is produced by the barrier coating preventing carbon and silicon from accessing it, which is formed over the sealed oxide coating, and it is made (shell manufacturing) in of the following sequence: a framework is formed, it is impregnated with a coke-forming and / or polycarbosilane binder, a carbon-plastic preform is formed, it is carbonized and compacted pyrocarbon vacuum isothermal method to the maximum possible density for this type of material or compacted with pyrocarbon to an intermediate density, nanocarbon is grown in the pores of the material and siliconized by the vapor-liquid phase method by mass transfer of silicon into the pores of the material by the mechanism of capillary condensation of its vapor in the range 1300-1500 ° С followed by exposure at a temperature of 1550-1600 ° C.

The solution to the problem contributes to:

1) the fact that the barrier coating is formed on the basis of a composition of ultrafine powder of the compound thermodynamically compatible with the material of the hermetic coating and a temporary binder by gluing graphite foil on it (on the composition);

2) the fact that the barrier coating is formed on the basis of a composition of ultrafine powder of the compound thermodynamically compatible with the hermetic coating material and the polycarbosilane binder, and the impregnation of the formed outer shell frame with a coke-forming binder is carried out without heat treatment of the polycarbosilane binder;

3) the fact that before forming a sealed oxide coating, the inner shell of UKKM, which does not contain free silicon, is impregnated with a solution of organo-yttriioxanaluminoxane siloxane two to three times, alternating with drying, and then heat treated at 1600 ° C.

The use of high-modulus high-strength carbon fibers as reinforcing fibers creates the prerequisites for obtaining CM with higher strength. In addition, it provides almost the same expansion of the shells when they are heated, which eliminates their cracking.

The manufacture of the inner shell of a carbon-carbide-silicon composite material eliminates the direct contact of the carbon matrix with a sealing oxide coating, thereby eliminating the chemical interaction between them.

The absence of free silicon in this material eliminates the degradation of the sealed oxide coating that occurs during its chemical interaction with silicon.

The use as a composition in the formation of a sealed oxide coating of a suspension based on a binder — a solution of organo-yttrioxanaluminoxoxanesiloxane and a filler — a mixture of finely divided refractory powders Y ₂ O ₃ , Al ₂ O ₃ , SiO ₂ or Y ₂ O ₃ , Al ₂ O ₃ , HfO ₂ , SiO ₂ and the implementation of the formation of the coating by layer-by-layer application of a suspension, alternating with drying and subsequent heat treatment at 1600 ° C, makes it easier to obtain it on large-sized products. In addition, it allows the formation of a sealed oxide coating of complex composition in which SiO _{2 is} chemically bonded to other oxides, i.e. does not have direct contact with SiC, in the presence of which the oxide coating would degrade by the reaction:

SiC + 2SiO ₂ = 3SiO + СО

The implementation (in a preferred embodiment of the method) before forming a sealed oxide coating — two or three-fold impregnation of the inner shell of UKKM, free of free silicon, with a solution of organo-yttrioxanaluminoxoxysiloxane, alternating with drying, followed by heat treatment at 1600 ° C, allows to reduce to some extent the permeability of the material of the inner shell, the consequence of which is to increase the level of tightness of the product as a whole.

The manufacture of the outer shell according to the barrier coating formed over the sealed oxide coating, which prevents the access of carbon and silicon to the oxide coating, eliminates the degradation of the properties of the oxide coating both during the manufacturing of the outer shell and during the operation of the product.

The manufacture of an outer shell on a barrier coating formed over a sealed coating based on a composition of ultrafine powder of a compound thermodynamically compatible with an oxide coating and a temporary binder on which (a composition) is glued graphite foil (in one of the preferred embodiments of the method) eliminates the chemical interaction between barrier coating material (based on a composition of ultrafine powder) and a sealed oxide coating material, and it also allows (due to the presence of a layer of graphite foil in the barrier coating) to exclude the access of the coke-forming binder and carbon-containing gas to the oxide coating (and thereby exclude direct contact of the oxide coating with carbon), as well as to prevent silicon from accessing it.

The manufacture (in another preferred embodiment of the method) of the outer shell on a barrier coating formed over an airtight oxide coating based on a composition of an ultrafine powder of a compound thermodynamically compatible with the oxide coating and a polycarbosiloxane binder eliminates the chemical interaction between the components of the barrier coating material with the oxide coating material, and in conjunction with the impregnation of the outer shell frame with a coke-forming binder without conducting the heat treatment and carbonization polikarbosiloksanovogo binder avoids access coke-forming binder for the oxide coating (and thereby prevent direct contact of the material with carbon oxide coating).

In addition, in conjunction with the operations of compaction of the material with pyrocarbon and the formation of nanocarbon (carried out before the siliconizing operation) in its pores, this helps to prevent silicon from accessing it (oxide coating) at the stage of siliconizing the material.

The implementation of the operation of manufacturing the outer shell in the sequence: forming a framework, impregnating it with a coke-forming binder, carbonizing and sealing with pyrocarbon by a vacuum isothermal method to the maximum possible density for this type of material, works to create conditions that exclude direct contact of carbon (which is part of the outer shell material) with sealed oxide coating material, and also allows you to limit the temperature effect on the material of the barrier coating (when SRI the operation temperature does not exceed 950-980 ° C).

In addition, the manufacture of the outer shell using the operation of molding a plastic workpiece allows the manufacture of thin-walled complex products, including large ones, without the need for a machining operation.

To a greater degree, the conditions under consideration are created in the case when, at the stage of the frame impregnation, instead of the coke-forming binder - or along with it - a polycarbosilane binder is used, during the pyrolysis of which silicon carbide is formed, which shields carbon (which is part of the outer shell material) from direct contact with oxide coating material.

The implementation of the operation of manufacturing the outer shell in a slightly different sequence (the second version of the shell manufacturing), namely in the sequence: forming a framework, impregnating it with a coke-forming and / or polycarbosilane binder, carbonization, densification with pyrocarbon to an intermediate density, growing nanocarbon material in the pores and silicification, allows get a shell of carbon-carbide-silicon material with a low content of free silicon (due to the small pore size of the material after growing nanocarbon in them and as a result, a small amount included in each individual pore silicon carbon sufficient only for carbonization), providing the possibility of the product in an oxidizing environment.

The above sequence of operations in the manufacture of the outer shell from UKKM in conjunction with the silicification of the workpiece by the vapor-liquid method during mass transfer of silicon into the pores of the material by the mechanism of capillary condensation of its vapor in the range of 1300-1500 ° C with subsequent exposure at a temperature of 1550-1600 ° C allows on the one hand, introducing silicon into arbitrarily small pores, including nanoscale ones, and then converting it to silicon carbide, on the other hand, creates some difficulties in terms of vapor access or Moisture build up of silicon vapor on the way to the barrier coating and further - to the oxide coating, as well as reduce thermal and chemical effect on them of silicon, if any, would be possible.

This creates the conditions for eliminating the degradation of the properties of the oxide coating.

In the new set of essential features, the object of the invention has a new property: the ability to impart tightness to products made of composite materials based on high-modulus high-strength carbon fibers and carbon and / or carbon-silicon carbide matrix, as well as the ability to shape the product at the stage of molding a plastic blank and thereby eliminate the need for machining products.

Thanks to the new property, the task is solved, namely: it is possible to reduce the weight of manufactured products designed to work under excessive pressure at high temperatures and in the presence of an oxidizing environment, including thin-walled, large-sized and complex ones, without performing a machining operation.

The method is as follows:

An inner shell is made of composite material (KM); moreover, it is made of carbon-carbide-silicon composite material (UKKM) that does not contain free silicon. In its manufacture, high-modulus high-strength carbon fibers are used as reinforcing fibers.

Then, on top of the inner shell, a hermetic coating is formed according to the CTE with the material of the inner shell, and a suspension based on a binder — a solution of organo-yttrium oxoaluminoxoxysiloxane and a filler — a mixture of finely divided refractory powders Y ₂ O ₃ , Al ₂ O ₃ , SiO, is used as a composition when forming a sealed coating ₂ or Y ₂ O ₃ , Al ₂ O ₃ , HfO ₂ , SiO ₂ . The coating is formed by layer-by-layer deposition of a suspension, alternating with drying, and subsequent heat treatment at 1600 ° C, resulting in a sealed oxide coating.

Then, a barrier coating is formed over the sealed oxide coating to prevent carbon and silicon from accessing the sealed coating. In one of the preferred embodiments of the method, a barrier coating is formed on the basis of a composition of ultrafine powder of the compound thermodynamically compatible with the material of the hermetic coating and a temporary binder by gluing graphite foil on it (on the composition).

In another preferred embodiment of the method, a barrier coating is formed on the basis of a composition of an ultrafine powder of a compound thermodynamically compatible with a sealed oxide coating material and a polycarbosilane binder.

Then, on top of the barrier coating, an outer shell is made of a composite material based on the same type of reinforcing fibers as the composite material of the inner shell, i.e. based on high modulus high strength carbon fibers. The manufacture of the outer shell is carried out in the following sequence: they form a framework, impregnate it with a coke-forming and / or polycarbosilane binder, form a carbon-plastic preform, carbonize it and compact it with pyrocarbon using a vacuum isothermal method to the maximum possible density for this type of material or compact it with pyrocarbon to an intermediate density, grow it the pores of the material are carbon nanocarbon and are silicified by the vapor-liquid phase method during mass transfer of silicon to the pores of the material by mechanical prism of capillary condensation of vapor in the range of 1300-1500 ° C, followed by aging at a temperature of 1550-1600 ° C.

In one of the preferred embodiments of the method (in the case where the barrier coating is formed on the basis of an ultrafine powder of a compound thermodynamically compatible with the material of the hermetic oxide coating and a polycarbosilane binder) in the manufacture of the outer shell, the formed outer shell frame is impregnated with a coke-forming binder without carbonization and heat treating the polycarbosilane binder in the barrier coating.

The following are examples of specific implementation of the method. In all examples, the manufactured product was a pipe ∅30 × ∅50 × h 400 mm.

Example 1

One of the known methods produced an inner shell of ∅30 × ∅50 × h 400 mm from UKKM on the basis of a fabric-stitched framework of high-modulus carbon fibers UKN-5000 and a carbon-silicon matrix that does not contain free silicon (for this, the UKKM was heated and holding at 1800-1850 ° C in vacuum, which allowed to drive free silicon from it). Then, a sealed oxide coating of the composition Y ₂ O ₃ × AlO ₃ × SiO _{2 was} formed over the inner shell from UKKM. For its formation, a suspension was used based on a binder — a toluene solution of organo-yttrium oxanaluminoxoxysiloxane — and a filler — a mixture of refractory powders Y ₂ O ₃ , Al ₂ O ₃ , SiO _2.

The ratio of the components of the suspension was chosen so that the coating material had a close ctr to the materials of the inner and outer shell (an increase in the SiO ₂ content in the composition led to a decrease in the ctl of the coating material).

The coating was formed by layer-by-layer application of a suspension, alternating with drying in a humid atmosphere. In a particular case, three coating layers were formed. Then, the coating was heat treated (for sintering) at a temperature of 1600 ° C. As a result, a coating of the above composition with a thickness of 0.6-0.9 mm was obtained. Then, a barrier coating was formed over the sealed oxide coating. The barrier coating was formed on the basis of ultrafine powder of silicon carbide (with a particle size of not more than 5 μm) and a temporary binder, which was used as a 4% solution of polyvinyl alcohol in water (silicon carbide, at least up to a temperature of 1500 ° C, is thermodynamically compatible with the material oxide coating). After drying, the coatings were pasted onto it (onto the same composition) graphite foil with a density of ~ 1.1 g / cm ³ and a thickness of ~ 0.2 mm.

Then, on top of the barrier coating, an outer casing was made of UUKM based on high-modulus high-strength carbon fibers of the UKN-5000 brand. Its manufacture was carried out as follows. First, a framework of a fabric-piercing structure of the indicated fibers was formed over the barrier coating. Then the frame was impregnated with a coke-forming binder, which was used as a solution of liquid bakelite in isopropyl alcohol. After this, the carbon fiber blank was formed.

The carbon fiber preform was carbonized at 850 ° C in nitrogen. Then, the carbonized carbon fiber preform was sealed with pyrocarbon by the isothermal vacuum method at technological parameters that provided the CCM of the maximum possible density for this type of material. As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 25 atm.

Example 2

The product was manufactured analogously to example 1 with the significant difference that the barrier coating was formed using a polycarbosilane binder as a binder in the composition. At the same time, the casing of the outer shell was impregnated with a coke-forming binder without heat treatment at 1300 ° C of the polycarbosilane binder, which is part of the barrier coating. As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness established that the product is tight under pressure up to 30 atm.

Example 3

The product was manufactured analogously to example 1, with the significant difference that when forming the oxide coating, Y ₂ O ₃ , Al ₂ O ₃ , HfO ₂ , SiO _{2 were} used as refractory powders of the suspension. As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 36 atm.

Example 4

The product was manufactured analogously to example 2, with the significant difference that the outer shell was made of UKKM. For this, a carbonized carbon fiber preform was sealed with pyrocarbon to an intermediate density. Then, nanocarbon was grown in the pores of the material. The resulting preform was siliconized by the vapor-liquid phase method during mass transfer of silicon into the pores of the material by the mechanism of capillary condensation of its vapor in the range 1300-1500 ° C, followed by exposure at 1550-1600 ° C. As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 42 atm.

Example 5

The product was manufactured analogously to example 4, with the significant difference that in the manufacture of the outer shell, the frame was impregnated with a polycarbosilane binder. As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 48 atm.

Example 6

The product was made analogously to example 4 with the significant difference that in the manufacture of the outer shell, the carbonized carbon fiber preform was impregnated with a polycarbosilane binder before being sealed with pyrocarbon and heat treated at 1300 ° C. As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 51 atm.

Example 7

The product was manufactured analogously to example 1 with the significant difference that before forming a sealed oxide coating, the inner shell of UKKM, free of free silicon, was impregnated three times with toluene solution of organo-yttrioxane aluminoxane siloxane, alternating with drying in a heat cabinet with a humidity of 90%, after which it was heat treated at 1600 ° C . As a result of the study of the product material (from its stock) by optical and X-ray phase methods, no changes in the structure and composition of the sealed oxide coating were detected. Tests for tightness found that the product is tight under pressure up to 63 atm.

Example 8

The product was manufactured analogously to example 4 with the significant difference that the frame of the inner and outer shell was formed on a circular loom machine with a reinforcement scheme:

- based on and in dressing, the low-modulus carbon thread of the Ural-N brand (less durable than the high-modulus thread of UKN-5000)

- for weft - high-modulus carbon thread UKN-5000.

As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 58 atm.

Example 9

The product was manufactured analogously to example 1 with the significant difference that in the composition for forming a barrier coating, zirconium diboride in the form of an ultrafine powder was used as a compound thermodynamically compatible with the material of the hermetic coating.

As a result of studying the material of the product (from its stock) by optical and x-ray phase methods, changes in the structure and composition of the oxide coating were not detected. Tests for tightness found that the product is tight under pressure up to 20 bar.

Example 10

The product was manufactured analogously to example 4 with the significant difference that when siliconizing the workpiece, isothermal exposure (after the mass transfer of silicon to the pores of the material in the range 1300-1500 ° C was performed at 1600-1700 ° C. As a result of the study of the material of the product (from its stock) optical X-ray diffraction methods revealed a change in the structure and composition of the oxide coating, namely: silicides of the corresponding metals formed in its composition, and the coating itself has cracks. e sealed pressurized to 1 atm.

Thus, the possibility of manufacturing sealed products from KM, reinforced with high-modulus, high-strength carbon fibers, using the inventive method is proved.

Claims (4)

1. A method of manufacturing a sealed product made of composite material, including the manufacture of an inner shell of a composite material, the formation of a sealed coating compatible with the coefficient of linear thermal expansion with the material of the inner shell, the manufacture of an outer shell of a composite material based on the same type of reinforcing fibers on top of the coating as the composite material of the inner shell, characterized in that as the reinforcing fibers of the composite materials the inner and outer shells use high-modulus high-strength carbon fibers (in at least one of the directions of reinforcement), the inner shell is made of carbon-carbide-silicon composite material that does not contain free silicon, and a suspension based on a binder - an organo-yttrioxane-aluminum-oxoxane siloxane solution is used as a composition - and filler - a mixture of finely divided refractory powders Al ₂ O ₃ , Y ₂ O ₃ , SiO ₂ or Al ₂ O ₃ , Y ₂ O ₃ , HfO ₂ , SiO ₂ , formation the coatings are carried out by layer-by-layer deposition of a suspension alternating with drying and subsequent heat treatment at 1600 ° C, the outer shell is produced by the barrier coating formed over the sealed oxide coating that prevents carbon and silicon from accessing it, and the shell is fabricated in the following sequence: form the frame impregnated with a coke-forming and / or polycarbosilane binder, forming a carbon-plastic preform, subjecting it to carbonization and pyro-carbon compaction by vacuum isothermal method to the maximum possible density for a given type of material or compacted with pyrocarbon to an intermediate density, nanocarbon is grown in the pores of the material and siliconized by the vapor-liquid phase method by mass transfer of silicon into the pores of the material by the capillary condensation mechanism of its vapor in the range of 1300-1500 ° С with subsequent exposure at a temperature of 1550-1600 ° C. 2. The method according to claim 1, characterized in that the barrier coating is formed on the basis of a composition of ultrafine powder compounds, thermodynamically compatible with the material of the sealed oxide coating, and a temporary binder, gluing graphite foil to it. 3. The method according to claim 1, characterized in that the barrier coating is formed on the basis of a composition of ultrafine powder of the compound thermodynamically compatible with the material of the hermetic oxide coating and a polycarbosilane binder, and the formed outer shell frame is impregnated with a coke-forming binder without heat treatment of the polycarbosilane binder . 4. The method according to claim 1, characterized in that before forming a sealed oxide coating, the inner shell of a carbon-carbide-silicon composite material that does not contain free silicon is impregnated with a solution of organo-yttrioxane aluminoxane siloxane two to three times, alternating with drying, and then heat treated at 1600 ° C.