DE1296069B - High temperature resistant molded body - Google Patents

Description

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The invention relates to high-temperature damage to the protective layer by temperature-turbo-resistant Molded body from a base body to alternating stress, the causes of which sometimes and a coating in which the base body consists of different behaviors of the graphite material Carbon or graphite and finely divided therein a or base body and the material of the protective layer several of the high-melting carbides of Beryl-5 are to be looked for in relation to temperatures. Thin Hums, Bors, Silicon, Titans, Zircon, Vanadins, protective layers are also very sensitive Niobium, tantalum, chromium, molybdenum, tungsten, tho- against mechanical damage, rium, a rare earth element, it is also known that porous graphite forms

is set. body to be vaporized with metal that the

Graphite has good thermal conductivity, 10 pores or the pore walls of the graphite molding have low thermal expansion, high strength, which increases with the temperature rising through the carbide of the vapor-deposited metal, and is filled or covered, so that the whole of the graphite is very resistant to temperature changes . phite bodies penetrate carbide layers. These properties make it an appreciated one, but in no way is the strength compared to the high-temperature material. When used, 15 thermal cycling increases. Although rer temperatures are, however, a neutral atmosphere or the carbide-reducing atmosphere applied to the graphite body is necessary, since graphite from layer with the approximately 500 ° C consisting of the same substance is connected with oxygen or oxygen-containing fillings of the pores, which begins to react with very inhomo gases , so z. B. with air, CO ₂ , the composition of the molded body from Gra water vapor, etc. The speed of the oxyphite on the one hand and carbide on the other hand with their dation - in the technical sense here of different expansion coefficients leads jebrand - increases with increasing temperature - but too rature when exposed to temperature fluctuations. rapid destruction of the molding.

A number of measures are known which, from the present invention, the task is to-

to increase the fire resistance of graphite moldings. 25 reasons for a better gas tightness of the protective layer It is common to use abten and thus reduce their shelf life by reducing burns Means, like phosphoric acid, increase and therefore better arresting phosphates, Boric acid and similar compounds to earth these layers with the base body either on the surface of the graphite base.

applied to the body or in its near-surface 30 This will be impregnated at a high temperature-resistant area. This protection acts moldings of the type mentioned at the beginning only within a certain temperature range, sufficient that according to the invention the base body from above all below 1000 ° C. and there only temporarily. 40 to 99.5 percent by volume of carbon and from 60. For higher temperatures it has partly been made up to 0.5 percent by volume of carbide and according to it, protective layers are made from various substances, ₃₅ powder-metallurgical processes and mainly from carbides and suicides, on which that the - gas-tight - coating from the surface or surfaces of the graphite base body is to be applied carbide components, as they are applied by the base body and thus the destructive effect of the air, or consists of a substance that can be kept away with the graphite. Carbide components of the base body mixed

These layers have already been formed on 40 different crystals.

Applied in a way: by dipping, brushing on, in this way one obtains a chemical affinity

Spraying, melting or impregnating, with the tat between the coating material and the Mate plasma torch or by depositing the connector of the base body and thus the possibility of fertilize from the gas phase. While at the first- formation of chemical compounds from the substances a subsequent insertion of the coating and the base body, If the protective layer needs to be fired, it is not necessary to use a to form the coating

This is the case when the protective layers are applied using a substance or a mixture of substances containing a metal or the plasma torch and when separating the several metals contained in the base body bonds from the gas phase. Carbide component (s) pure or in chemical

The use of protective layers extends 50 mixer compound contains, and if you bring this the area of application of the graphite down to the surface of the base body, about 1500 ° C, but still occur at temperatures above 1200 ° C over -Base of difficulties. _TO form that of one or more carbides

The thermal expansion of the graphite moldings consists of the metals contained in the substance. If the and the applied layers are generally 55 carbide components contained in the base body are identical. To compensate for this, the tables with the material of the coating are allowed, so one layer will only be a few microns thick. It is, however, difficult to anchor the coating with the fine-grained gas-tightness in this small thickness, which is sufficient for the carbide in the base body. In addition, benent is achieved and a solidification and condensation is required of many technical tricks in order to achieve absolute formation of the coating. With this type you can apply homogeneously and without cracks. In the course of anchoring, speak of a dowel-like fastening, in the case of prolonged stress under higher levels of the coating. In addition, there is a temperature, the protective layer long-welding of the carbide particles of the coating is transformed into a carbide or into carbides with a higher level than those of the base body, and this is not just a carbon content. This modification change, often comparable 6 ₅ brittle at the contact surfaces of the base body and connected with changes in the crystal system changed coating, but as a result of solid state diffusion, the physical nature of the layer, it is also within the near-surface regions and leaking. In many cases, the main body also occurs. It is also achieved that

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the thermal expansion coefficients of overstock and 24 percent by volume silicon carbide with a

train and base body are matched to each other. Porosity of 15% is obtained in the following way with a This results in a silicon carbide layer inside and outside that is gas-tight to a high level of temperature change

resistance of the molding. The same applies accordingly: The carbon pipe is in one

same for solid solution forming carbides. 5 vacuum furnace heated to 1500 ° C and then with

The application of the coating can be carried out in the presence of ethyltrichlorosilane (H ₃ CSiCl ₃ ) at 0.1 atmospheres

of the substance in the liquid phase, for example gassed by pressure for 2 hours. During this time,

Dipping, spraying or painting the base body creates a uniform effect on the whole body

happen. If you use volatile compounds green silicon carbide layer from a thickness of

of the metal or metals of the above type, from 200 to 250 microns. It is very dense and tight in

so these connections are anchored by heating the pores of the base body,
sets and the relevant components from the

Deposited gas phase on the base body. Example 3

The fabric for forming the cover is made up of

the metal (s) in the base body. 15 To create a gas-tight protective layer

holding carbide component (components) or a graphite rod (50 x 50 x 1000 mm), which is made of

from the oxide, silicide, nitride or boride of this Me- 70 percent by volume graphite, 25 percent by volume titanium

talls (of these metals), a layer of carbide separates and 5 percent by volume of tungsten carbide consists,

from the selected material on the base material, the following procedure is used:

however, at the high separation temperature, the rod is placed in a 100 mm tube furnace

temperature and also during operation of the mold inner diameter and 3 m length in hydrogen

The body is heated to an intermediate 1350 ° C at higher temperatures. After reaching this temperature

layer, which is made up of the carbide or carbides of the in which is branched off with titanium chloride

selected substance contained metal or the Me- and tungsten chloride saturated propane-hydrogen

talle exists. A base body treated in this way 35 mixture (1: 100) is introduced into the reaction chamber,

then has a coating of carbides and after three hours of mutual fumigation has

In addition, another layer, the so-called a 300 to 400 micron thick gas-tight layer,

Cover layer, made of the metal (s) or consisting of titanium carbide and tungsten carbide,

its oxide, silicide, nitride or boride. divorced.

The compaction and solidification of the coating and 30 Be ^- ςη'el 4

the top layer is then particularly good. "

With particularly high demands on the gas To achieve a well-adhering and gas-tight

tightness of the molded body has proven to be beneficial

proven when the top layer is made of an oxide of the following:

or the metals of the 35 contained in the base body a graphite tube (diameter 20/10 500 mm),

There is a carbide component and an amorphous, glass-containing 10 percent by volume silicon carbide is

like consistency is present. Such moldings are coated with silicon paste and put in argon

are characterized by particularly good oxidation 1450 ° C and then heated with an argon

resistance, because the diffusion of the oxygen thyl chloride gas mixture (50: 1) fumigates for about 1 hour.

through this cover, which acts like a barrier layer, the body is then covered with a gas-tight

layer coated with silicon carbide even at the highest temperatures. Now that will

is practically prevented. Turned off methyl chloride and the argon flow

". . _T by a washing bottle with water at 5 ° C

ö ei game 1 _{leads } md over the} silicon carbide coated

A graphite-zirconium carbide block (100 x 100 x 500mm), 45 bodies passed. After a reaction time of 85 percent by volume graphite 15 percent by volume 10 minutes, the entire body is superficially coated with percent zirconium carbide with a porosity of 20% of a very dense, about 10 micron thick silicon should be coated with a zirconium carbide layer. coated with a layer of dioxide.
For this purpose, the molded body is placed in a tunnel furnace. .

500 ° C and heated in a protective gas container below 50 Example 5

Argon with an arc spray gun or a molded body consisting of 85 percent by volume

Plasma torch evenly coated with zirconium. Carbon, 5 volume percent silicon carbide and To convert the applied zirconium into zirconium 10 percent by volume niobium carbide, argon atomic carbide is used the shaped body is heated to 400 ° C. in a graphite sphere. With a plasma rod heated Oven used, covered with soot 55 burner is niobium silicide powder in a known manner and heated in Co up to 1600 ° C. After reaching this using argon as the carrier gas Temperature is melted into the CO gas methane and on the preheated body in ratio 100: 1 added. Apply a fine layer after an hour. They react perung, all zircon is converted to carbide. Molten particles of niobium silicide at unoriginal Silvery shining coating has after the 60 indirect contact with the surface of the basic tempering assumed a dark gray color. body with the carbon to form It adheres extremely firmly to the base body of niobium carbide and silicon carbide. The following and bursts even with strong temperature changes - - external - particles remain in their original state not off. borrowed composition and form a gas-tight

Example2 ^6s top layer made of niobium silicide.

To the gas tightness of this top layer

A carbon tube (diameter 100/80 x 1000 mm) is further improved by the Plasmamit of the composition 76 percent by volume of the charcoal flame is softened again, so that the

Melting together of the particles forms a pore-free layer on the shaped body.

Example 6

A cylindrical body, diameter 250-300 mm with the composition 60 ^fl / o carbon and 40% NbC is coated with a well-adhering, dense layer of HfC as follows:

Hafnium powder (particle size 40 μ) is applied as an aqueous suspension on the body superficially brushed on and then dried at 110 ° C. Then the body is under argon The surface is briefly heated up to 2000 ° C by a high-frequency furnace. During this temperature treatment the previously applied * 5 hafnium melts and reacts with the Carbon to the HfC. The latter forms with the niobium carbide Mixed crystals of the type NbC · HfC.

Example? ^ao

A tube with a diameter of 70/50 x 2000 mm made of 52% carbon and 48% TiC is fitted with a smooth and gas-tight layer of TiC and titanium coated in the following way:

With a wire flame spray gun, a titanium layer 0.1 mm thick is applied to the pipe surface applied. This porous layer is then melted using an argon arc burner. Included the titanium runs into a pore-free protective layer that reacts with the carbon of the Body consists of a TiC base layer and a titanium top layer.

Claims (2)

Patent claims: 1. High-temperature-resistant molded body made of a base body and a coating in which the main body made of carbon or graphite and finely distributed therein one or more of the high-melting carbides of beryllium, boron, Titans, zircon, vanadins, niobs, tantalum, chromium, molybdenum, tungsten, thorium, one Rare earth element, characterized in that the Base body made of 40 to 99.5 percent by volume carbon and 60 to 0.5 percent by volume There is carbide and is manufactured by powder metallurgical processes and that the - gas-tight - Coating of the carbide component or components, as the base body has, or consists of a substance that has mixed crystals with the carbide components of the base body forms. 2. Shaped body according to claim 1, characterized in that a cover layer is on the coating which is made of the metal (s) of the carbide component contained in the base body (the carbide components) or from the oxide, silicide, nitride or boride of this metal (these metals).