RU2490238C1 - Method of manufacturing products from composite materials and device for its realisation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of products from composite materials (CM) with metal and carbide-metal matrixes, as well as from cermets. Blank from porous heat-resistant material is obtained, placed together with crucibles with metal in closed converter volume, heated, kept for definite time and cooled in vacuum in metal vapour. At the stage of blank heating and/or cooling crucibles with metal are heated to higher temperature than blank temperature; with blank being kept at the temperature which does not exceed the temperature of metal re-evaporation from material pores. Device for metalising contains heater or system of heaters, located around external converter, internal converter of closed volume with placed inside it metalised products and crucibles with metal, flow-type reactor, heat insulation from porous carbon-graphite materials and pneumo-gas-vacuum system. External and internal converters are made by height from several parts and are placed coaxially to each other with clearance, external converter being provided with sockets for connection of inter-converter clearance with pneumo-gas-vacuum system. Said device additionally contains bottom heater, or heaters located around external converter in lower part have higher temperature zone, located opposite lower parts of external and internal converter, where crucibles with metal are located.

EFFECT: increased degree and uniformity of metalising, as well as increased degree of reproducibility of results of product metalising, including those with large dimensions, without essential degradation of properties of soaked porous material.

4 cl, 1 tbl, 1 dwg

Description

The invention relates to the production of products from KM with metal and carbide-metal matrices, as well as from cermets.

A known method of manufacturing KM, including cermets, including the preparation of a mixture of heat-resistant material and metal, followed by pressing and sintering or hot pressing [L.I. Tuchinsky “Composite materials obtained by the impregnation method” M.: Metallurgy. 1986. p. 74, 174, 175].

The specified method due to the complex hardware design is applicable only to obtain small parts.

A known method of manufacturing KM, including the manufacture of a workpiece from a porous heat-resistant material and its impregnation with a molten metal [L.I. Tuchinsky. "Composite materials obtained by impregnation." M .: Metallurgy. 1986, p. 74, 100, 184, 198]. The method requires less complex hardware design and allows the manufacture of larger parts.

However, due to the need to heat the molten metal to a temperature above its melting point, which is made to give it a low viscosity, partial degradation of the porous material often occurs, despite its heat resistance. In particular, this may be due to the fact that due to the high temperature of the metal melt, a chemical interaction occurs between it and the heat-resistant material, as a result of which the strength characteristics of the material are reduced. Another disadvantage of the method in some cases is the need for impregnation with a molten metal under pressure [see, in particular, article V.A. Gulevsky et al. “Investigation of the properties of copper alloys intended for the impregnation of porous graphite frames with the aim of creating metal-carbon composites for functional purposes” in the journal Perspective Materials, 2011, No. 2, pp. 60-64].

The closest in technical essence and the achieved effect to the claimed is a method of manufacturing products from KM, including the manufacture of a workpiece from a porous heat-resistant material and its metallization by placing the workpiece and crucibles with metal in a closed volume of retort, heating, holding for 1 ... 3 hours and cooling in vacuum in metal vapor. Silicon [RF Patent No. 1834839, class. C01B 31/02, 1993].

It is known that metal vapors are formed at a temperature below its melting point [S. Deshman. Scientific foundations of vacuum technology. M.: Mir, 1964]. Thus, there is a fundamental possibility of metallization at relatively low temperatures and without the use of pressure impregnation devices. In this case, the method of manufacturing products, including large ones, is simplified while completely eliminating the possibility of degradation of the strength properties of the workpiece material, or at least with a significant reduction in the negative effect of the metal on the material.

However, in this method, metallization (in the specific case, silicification) is performed at temperatures significantly higher than the melting temperature of the metal, and the need for this is explained by the desire to increase the concentration of metal vapor, which, as you know, increases with increasing temperature. Therefore, when metallizing using this method, the degradation of the properties of the material to be metallized is not ruled out, which ultimately leads to CM with a low level of physical and mechanical properties.

It should also be noted that this method only relates to the manufacture of products from carbon-carbide-silicon material using a siliconization process. The method does not involve the use of other metalating agents. In addition, this method considers the diffusion mechanism of metal delivery into the pores of the material a, and, as you know, its speed is very low, which leads to a low degree of metallization. Moreover, in addition to a low degree of metallization, uneven metallization is observed, as well as poor reproducibility of the metallization results from process to process.

The objective of the invention is to increase the degree and uniformity of plating, as well as increasing the reproducibility of the results of plating products, including large ones, from process to process without significant degradation of the properties of the impregnated porous material.

This problem is solved due to the fact that in the method of manufacturing products from KM, including the manufacture of a workpiece from porous heat-resistant material, its volume metallization by placing the workpiece and crucibles with metal in a closed volume of a retort, heating, holding and cooling in vacuum in metal vapor, in in accordance with the claimed technical solution, the crucibles with the metal at the stage of heating and / or cooling the workpiece is heated to a higher temperature than the temperature of the workpiece; while the exposure of the workpiece is carried out at a temperature not exceeding the temperature of evaporation of the metal from the pores of the material.

The implementation at the stage of heating and / or cooling (raising and / or lowering the temperature) of the billet heating the crucibles to a higher temperature than the temperature of the metallized billet, provides the possibility of the occurrence of a supersaturated state of metal vapor in the vicinity of the billet, which leads to their condensation directly in the pores of the material and / or on the surface of the part.

The implementation of the exposure of the workpiece at a temperature not exceeding the temperature of re-evaporation (sweating) of the metal from the pores, provides the most rapid completion of the process of filling pores with metal condensate; moreover, either complete completion, or - to the extent that it is completely completed at the cooling stage. At the same time, time is not wasted for metallization, as if re-evaporation of the metal took place. In addition, the metallization process is carried out at a lower temperature, which means that the molten metal has a less negative effect on the degradation of the properties of the metallized material.

The workpiece is cooled in metal vapor, depending on whether it is carried out when the crucibles with metal are heated to a higher temperature than the metal to be coated, or in the absence of such heating, leads to different degrees of condensation of the metal vapor, and also to the completion of the metallization process as a whole.

In the new set of essential features, the object of the invention has a new property: the ability to mass transfer metal into the pores of the material by the diffusion-condensation mechanism, the speed of which is significantly higher than by the diffusion mechanism; moreover, the mass transfer rate of the metal into the pores of the material can be quite high even at a temperature on the workpiece less than or equal to the melting temperature of the metal, which completely eliminates the degradation of the workpiece material or at least substantially reduces it.

The new property allows to increase the degree and uniformity of metallization, as well as to increase the reproducibility of the results of metallization of products (including large-sized ones) from process to process and to obtain CM with sufficiently high strength characteristics.

The method is as follows.

One of the known methods of making a workpiece from a porous heat-resistant material. Then the workpiece, together with crucibles filled with pieces of metal, is placed in a closed volume of the retort. After that, the billet and crucibles with metal are heated in metal vapor, and then - also in metal vapor - cooled. Moreover, at the stage of heating and / or cooling the billet, the crucibles with the metal are heated to a higher temperature than the temperature of the billet. If the heating of crucibles with metal to a higher temperature than the metallized workpiece is carried out at the stage of temperature rise, then in the vicinity of the workpiece a supersaturated state of the metal vapor occurs, which leads to their partial condensation. Moreover, depending on the temperature of the metal vapor and the temperature of the workpiece, the metal vapor condenses on the surface of the workpiece and / or in the volume of the material of the workpiece.

If metal vapors condense on the surface, then under the action of capillary forces, the vapor condensate of the metal impregnates the workpiece.

During capillary condensation of metal vapors, their condensation proceeds directly in the pores of the workpiece material. Then produce exposure at a temperature not higher than the temperature of re-evaporation of the metal. This eliminates the sweating of the metal from the pores of the workpiece material and thereby does not waste time on the metallization process, and also reduces the temperature of the metal on the workpiece material.

If the heating of crucibles with metal to a higher temperature than the temperature of the workpiece is also carried out at the stage of cooling the workpiece (with decreasing temperature), then a supersaturated state also arises in the vicinity of the workpiece. And in size it is much larger than at the stage of heating the workpiece. And if at the stage of heating and aging the full filling of open pores has not yet occurred, then it ends at this stage. After cooling the preform and crucibles to room temperature, the preform is removed from the retort.

The following are examples of specific implementation of the method.

Example 1

UT-900 brand carbon fabric was formed on a forming mandrel by winding a skeleton (a blank of porous heat-resistant material - --160 × h300 × δ8 mm). The frame and crucible with pieces of aluminum were placed in a retort; moreover, the crucible was placed at the bottom of the retort, and above it a frame. The retort was covered with a lid, giving it a closed volume. Then the retort was installed in a ⌀220 mm heater, which had a higher temperature zone in the lower part than in the section opposite the aluminized billet (frame). Then the heater was covered with a lid. After that, the assembly was mounted in a vacuum installation. Next, the framework was heated to a temperature of 700 ° C at a pressure in the reactor of 12 mm Hg. in aluminum vapor that has already formed when the crucible reaches a temperature of ~ 600 ° C.

At a temperature of 700 ... 740 ° C, re-evaporation of aluminum from the pores does not yet take place on the frame. At the same time, during heating produced at a speed of 150 ° C / h, a temperature was set on a crucible with aluminum that was 100 ... 120 ° C higher than the temperature of the frame. Then, a three-hour isothermal exposure was performed at 700 ... 740 ° C on an aluminized frame. At the same time, a temperature of 760 ... 800 ° C was set on the crucible with molten aluminum.

During the heating period and at isothermal exposure at 700 ... 740 ° C, in the vicinity of the aluminized frame, a supersaturated state of aluminum vapor appeared, as a result of which they condensed directly in the frame pores.

Then the workpiece was cooled. During the cooling of the billet to 600 ° C, a temperature 30 ... 40 ° C higher was set on the crucible with aluminum. Thus, cooling was carried out in aluminum vapor and was also accompanied by their condensation.

After cooling to 70 ° C, the preform was removed from the retort and removed from the forming mandrel. Then the workpiece was machined.

The resulting CM, which is called carbon aluminum, had a density of 2.24 g / cm ³ , which indicates a high degree of metallization of the porous preform.

As a result of repeated re-manufacturing of such blanks, it was found that the spread in the density of the material is within 12%, which indicates a fairly high degree of reproducibility of the metallization results of the claimed method.

As a result of microstructural and X-ray diffraction studies, the absence of chemical interaction between carbon fibers and aluminum was established, which indicates the absence of degradation of the carcass material.

Example 2

A blank was made of carbonized carbon fiber ×180 × h300 × δ5 mm, density 1.16 g / cm ³ . Moreover, for impregnation with a phenol-formaldehyde binder, the same framework was used as in Example 1.

The billets were aluminized according to the same regime as in Example 1. As a result, a component from KM (carbon aluminum) with a density of 2.05 g / cm ^{3 was} obtained. As a result of repeated repetition of the manufacturing process of the part in accordance with the technological parameters of this example, it was found that the spread in material density is within 15%.

Example 3

A blank was made by partially sealing the frame with pyrocarbon using a vacuum isothermal method. After compaction with pyrocarbon of the same framework as in example 1, the porous material had a density of 0.83 g / cm ³ .

The billets were aluminized according to the same mode as in Example 1. As a result, a part from CM (carbon aluminum) with a density of 2.18 g / cm ^{3 was} obtained. The density spread in a batch of 10 pieces of parts manufactured in accordance with the technological parameters of this example was 8.6%.

Example 4

Made the same preform as in example 3, with a density of 0.87 g / cm ³ . The workpiece was processed in copper vapor. For this, the preform was heated to a temperature of 1180 ° C at a pressure in the reactor of 27 mm Hg. at a rate of -150 ° C / hour. Then kept for 5 hours at 1180 ... 1220 ° C. At the same time, at the stage of heating and holding, the temperature on the crucible with copper was 60 ... 90 ° C, respectively, 40 ... 60 ° C higher than on the workpiece.

During heating and isothermal aging at 1180 ... 1220 ° C in the vicinity of the workpiece, supersaturation of copper vapors occurred, as a result of which they condensed directly in the pores of the material. Then, the workpiece was cooled in copper vapor, as a result of which copper vapor also condensed.

After cooling the preform to 70 ° C, it was removed from the retort and machined.

The resulting CM had a density of 2.64 g / cm ³ .

As a result of repeated fabrication of the part in accordance with the technological parameters of this example, it was found that the spread in the density of the material is within 11%.

Example 5

A Japanese «Nikalon’ brand of silicon carbide fibers was used to form a frame ⌀160 × h300 × δ8 mm on a forming mandrel.

Along with the frame, a crucible filled with pieces of silicon was installed in the cage.

Then, the framework was heated in silicon vapors to a temperature of 1400 ° C at a reactor pressure of 27 mm Hg. with a heating rate of 180 ° C / hour. After that, a 5-hour exposure was performed at 1400 ... 1450 ° C.

During heating and isothermal aging on a crucible with silicon, the temperature was set to 100 ... 120 ° C and 60 ... 90 ° C, respectively, than on the frame. Then the workpiece was cooled. During the cooling of the preform to 1100 ° C, the temperature was set to 20 ... 30 ° C higher on the crucible with silicon. At all stages (heating, isothermal holding, cooling), in the vicinity of the siliconized preform, a supersaturated state of silicon vapors appeared, which led to their condensation in the pores of the preform material.

As a result, a blank of KM with a density of 2.46 g / cm ^{3 was} obtained.

As a result of a 5-fold repetition of the workpiece manufacturing process in accordance with the technological parameters of this example, it was found that the density spread is 18%.

Example 6

As the porous preform used the same frame as in example 5.

Alumination of the frame was carried out in accordance with the technological parameters of example 1.

The result was a workpiece with a density of 2.93 g / cm ³ . As a result of a 4-fold repetition of the manufacturing process of the workpiece in accordance with the technological parameters of this example, it was found that the density spread is 14%.

The remaining examples, including those described above, are summarized in the table, where examples 1 ... 10, 13, 15 correspond to the claimed method, and examples 11, 12, 14 correspond to the prototype method.

As can be seen from the table, the manufacture of products in accordance with the proposed method in comparison with the prototype allows you to:

1) to carry out the metallization process at lower temperatures on the workpieces;

2) to obtain more reproducible results with a higher strength of the composite material.

A device is known for metallizing products by the vapor-liquid-phase method containing heaters located around a closed volume retort made of several parts for placing crucibles with carbide-forming metal and metal products in it, a water-cooled flow-type reactor, thermal insulation from porous carbon-graphite materials and a pneumatic-gas-vacuum system (US Pat. RU No. 1834839 C. C01B 31/02, 1993).

The disadvantage of this device is the low degree and uniformity of metallization, as well as poor reproducibility of the results from process to process. Another disadvantage of the device is the lack of reliability of its operation due to the compaction of the porous material of thermal insulation with condensate of metal vapors that escape through the joints of the retort into the reactor space, due to which the heat-insulating properties of the material are lost.

The closest to the proposed technical essence and the achieved effect is a metallization device containing a heater or a system of heaters located around the outer retort, an internal retort for volume metallization with metallized products and crucibles with metal placed inside it, a flow-type reactor, thermal insulation made of porous carbon-graphite pneumatic-gas-vacuum system materials; while the outer and inner retorts are made of several parts in height and are located coaxially to each other with a gap, and the outer retort is equipped with nozzles for connecting the inter-clearance gap to the pneumatic-gas-vacuum system (Pat. RU for utility model No. 110089, 2011 )

Such a design of the device allows to increase the reliability of its operation by eliminating the access of metal vapor to porous carbon-graphite materials of thermal insulation.

However, a low degree and uniformity of metallization, as well as poor reproducibility of the results from the process to the process carried out in this device, is maintained. The reason for this is the departure of the metal vapor at the joints between the parts of the inner retort, which leads to a decrease in their pressure (concentration) in the vicinity of the metallized products.

The objective of the invention is to increase the degree and uniformity of metallization, as well as increasing the reproducibility of the results of metallization from process to process, carried out in this device.

This problem is solved due to the fact that the metallization device containing a heater or a system of heaters located around the outer retort, an internal retort of a closed volume with metal parts and crucibles placed inside it, a flow type reactor, thermal insulation from porous carbon-graphite materials and pneumatic gas-vacuum system, in which the outer and inner retorts are made of several parts in height and are located coaxially to each other with a gap, and the outer retort is equipped with a pat cutting to connect the inter-clearance gap with the pneumatic-gas-vacuum system, this device in accordance with the proposed technical solution further comprises a bottom heater or heaters located around the outer retort and have a higher-temperature zone in the lower part opposite the lower parts of the outer and inner retorts, and crucibles with metal are consolidated at the bottom of the inner retort.

In a preferred embodiment of the device, it contains a bottom heater and also has higher temperature zones in the lower part of the heaters located around the outer retort.

In another preferred embodiment of the device, the bottom heater is equipped with an autonomous power source.

The additional presence in the bottom heater device or the presence in the lower part of the heaters around the outer retort of a higher temperature zone opposite the lower parts of the outer and inner retort, when the crucibles are consolidated with metal in the lower part of the retort, allows crucibles with metal to be heated to a higher temperature than temperature of metal products.

If the opportunity is realized, then in the vicinity of the metal products (even with permeable joints between the parts of the inner retort) at the stages of heating, isothermal holding and cooling, a supersaturated state of the metal vapor occurs, which will result in their condensation on the surface and / or in the pores of the material of the products.

Providing the bottom heater with an autonomous power source allows you to adjust the power supplied to the heater, turn it on and off when necessary, i.e. create one or another temperature difference between metal vapors and metal products.

So, if at the cooling stage the crucibles are not heated to a higher temperature than the temperature of the metal products, then in their vicinity there will not be an excessively supersaturated state of the metal vapor, which will result in the exclusion of growths on the metal products, which are frozen drops or condensate deposits metal vapor.

In the new set of essential features, the object of the invention has a new property: the ability to effectively influence the mass transfer of metal to metallized products at any stage of this process.

The new property allows to increase the degree and uniformity of metallization, as well as reproducibility of the results from the process to the process carried out in this device.

The technical nature of the proposed technical solution is illustrated by the drawing, which shows a General view of the device.

The inventive device for metallizing products contains heaters 1, an external retort 2, consisting of parts 2a, 2b, 2c, 2g, an internal retort 3, consisting of parts 3a, 3b, 3c, 3g, a flow type reactor 4, thermal insulation from porous carbon-graphite materials 5 and a pneumatic-gas-vacuum system (with a designation on the drawing of gas supply and vacuuming places).

The inner retort 3 has a closed volume and is located with a gap 6 coaxially to the outer retort 2. In the inner retort 3, metalizable articles 7 and crucibles with metal 8 are placed. The outer retort 2 is equipped with nozzles 9a and 9b for connecting the between-clearance gap 6 with a pneumatic-gas-vacuum system .

The device further comprises a bottom heater 10 or heaters 1 located around the outer retort and in the lower part have a higher temperature zone 1b opposite the lower parts of the outer and inner retorts 2g and 3g, and crucibles with metal 8 are consolidated in the lower part of the inner retort 3g.

In one preferred embodiment of the device, it comprises a bottom heater 10 and also has higher temperature zones 1b in the lower part of the heaters 1 located around the outer retort 2.

In another preferred embodiment, the bottom heater 10 of the inventive device is equipped with an autonomous power source.

The device operates as follows.

When power is supplied to the heaters 1, the retorts 2 and 3, and then the metal products 7 and the crucibles with metal 8 are heated. As soon as the temperature on the crucibles with metal 8 reaches its evaporation temperature, the metal evaporates.

The evaporation of the metal contributes to the vacuum of the reactor 4. It also protects the product from oxidation. When the reactor 4 is evacuated, the internal cavities of the retorts 2 and 3 are evacuated through the joints between their parts 2a-2g, 3a, 3g and the inter-clearance gap 6.

Metal vapors diffusely fill the closed volume of the inner retort 3 and through the joints between its parts 3a-3g go into the inter-clearance gap 6. Due to the presence of the outer retort 2, as well as the supply of inert gas to the inter-clearance gap 6, they are entrained in the vacuum system, which prevents them exit into the reactor volume 2.

Due to the release of metal vapor into the inter-clearance gap 6, even a saturated state of metal vapor cannot occur in the vicinity of the metal products, unless appropriate measures are taken. So, when carrying out high-speed heating from 1200 to 1500-1600 ° C in the vicinity of the metal products located in the center of the inner retort 3, a supersaturated state of the metal vapor can form due to the lag of the product temperature from the temperature of the metal vapor evaporating from the inner surface of the retort 3, where their presence is due to their condensation at the stage of intermediate or final cooling (this is one of the appropriate measures).

In this case, one does not have to rely on obtaining consistently good metallization results.

If there is a bottom heater 10 in the device or in the lower part of the heaters located around the outer retort of the higher temperature zone 16 (in comparison with zones 1a) and the crucibles are consolidated with metal 8, the latter are heated to a higher temperature than the metalized products 7. Due to the resulting difference temperature, in spite of the outflow of metal vapor into the permeable joints of the retort 3, in the vicinity of the metal products there is a supersaturated state of the metal vapor, which causes them to condense on the surface and / or pores of material products.

If there is a bottom heater in the device and at the same time there are heaters in the lower part of the heaters located around the outer retort 16, it is easier to create a higher temperature difference between the metal vapor and the metal products and thereby more effectively prevent the negative effect of the outflow of metal vapor into the permeable joints of the retort 3.

When the bottom heater 10 is supplied with an autonomous power source, it becomes possible to regulate the power supplied to the heater, turn it on and off when it is necessary from the point of view of expediency of the process of condensation of metal vapor in a given temperature range, at one or another stage of the metallization process.

All this makes it possible to significantly increase the likelihood of achieving a high degree and uniformity of metallization, as well as obtaining reproducible results from the process to the process when metallizing in the inventive device.

Claims (4)

1. A method of manufacturing products from composite materials, including the manufacture of a workpiece from a porous heat-resistant material and its bulk metallization by placing the workpiece and crucibles with metal in a closed volume of retort, heating, holding in vacuum and cooling in metal vapor, characterized in that at the stage of heating , and / or isothermal aging, and / or cooling, the crucibles with the metal are heated to a higher temperature than the temperature of the workpiece, while the workpiece is aged at a temperature not exceeding eraturu reispareniya metal from the pores of the material. 2. A device for volume metallization, containing heaters located around the outer retort, an inner retort of a closed volume with metal parts and crucibles placed inside it, a flow-type reactor, thermal insulation from porous carbon-graphite materials and a pneumatic-gas-vacuum system, and in which the outer and the inner retorts are made of several parts with a height and are located coaxially to each other with a gap, and the outer retort is equipped with nozzles for connecting the inter-clearance gap to the air Mo-gas-vacuum system, characterized in that it further comprises a bottom heater, or heaters located around the outer retort have in the lower part a higher temperature zone opposite the lower parts of the outer and inner retorts, and the crucibles are consolidated in the lower part of the inner retort. 3. The device according to claim 2, characterized in that it contains a bottom heater, and also has a higher temperature zone in the lower part of the heaters located around the outer retort. 4. The device according to claim 2, characterized in that the bottom heater is equipped with an autonomous power source.

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