CH593133A5 - Hard coating of carbides or (carbo)nitrides - applied by direct thermal reaction of iron, boron, silicon, etc., with di- or triazine cpd. - Google Patents

Abstract

Inorg. substrates are provided with a coating layer of carbides-, nitrides and or carbonitrides of Fe-, B-, Si or gp. 4-6 transition metals, by direct thermal reaction of Fe, B, Si or gp. 4-6 transition metals, opt. with other additives with a C- and N- providing cpd. of formula (in which Y is =N-, =CH- or =C-halogen; one of X1, X2 and X3 = H, halogen, alkyl, -CN, -NR1R2 or -N(R5)-N(R3)(R4) and the other two = (independently) -CN, -NH2, -NR1R2 or -N(R5)-N(R3)(R4); R1, R3 and R4 = (independently) H, (halo)alkyl, cyanoalkyl (alkyl)aminoalkyl or alkenyl; R2=(halo)alkyl, cyanoalkyl, (alkyl)aminoalkyl or alkenylf and R5 = H or alkyl; the alkyl gps. 1-4C, the alkyl part of substd. alkyl gps. has 2-4C and the alkylene gps. have 3 or 4 C). The coatings are applied at relatively moderate temps. (e.g. ca 900 degrees C) and slightly reduced pressures and at high rates of growth to give adherent, smooth coatings.

Description

  

  
 



   The present invention relates to a method for coating carbon materials with carbides, nitrides and / or carbonitrides.



   It has been found that carbon materials with carbides, nitrides and / or carbonitrides of iron, boron, silicon or one of the transition metals of subgroups 4-6 of the periodic system can be obtained in a simple manner by direct thermal action of iron, boron, silicon or one of the transition metals of subgroups 4-6 of the Periodic Table in elemental form or as a compound and in the presence of a substance that provides carbon and nitrogen on the material to be coated, optionally in the presence of further additives, by using at least one compound of the carbon and nitrogen suppliers Formula I.
EMI1.1
 used where
Y = N-, = CH- or = C-halogen, one of X1, X2 and X3 hydrogen, halogen, alkyl,

   Phenyl,
EMI1.2


<tb> <SEP> / R1
<tb> -CN, -Ns <SEP> or
<tb> <SEP> R2 <SEP> R4
<tb> and the other two independently halogen,
EMI1.3


<tb> <SEP> R1 <SEP> R3
<tb> -CN, -NH2, -Ns <SEP> or-NH-Ns
<tb> <SEP> R2 <SEP> R4
<tb> represent, R1, R3 and R4 independently of one another hydrogen, alkyl, haloalkyl, cyanoalkyl, aminoalkyl, alkylaminoalkyl or alkenyl and R2 denote alkyl, haloalkyl, cyanoalkyl, aminoalkyl, alkylaminoalkyl or alkenyl, where alkyl radicals 1-4, the alkyl parts in substituted Alkyl radicals each have 2-4 and alkenyl radicals each have 3 or 4 carbon atoms.



   Compared to known methods, the method according to the invention is characterized above all by its simplicity and economic efficiency, in that the elements required for the formation of the carbides, nitrides and / or carbonitrides are carbon and nitrogen and, if appropriate, other elements that influence the course of the reaction, such as hydrogen and / or halogen can be fed to the reaction zone in the desired proportions in a simple manner.



  In addition, the process according to the invention enables high growth rates and excellent adherence, smooth coatings to be achieved, with a considerable improvement in the oxidation resistance of the carbon materials being achieved in some cases. Another advantage is that it is generally possible to work at normal pressure or slightly under or overpressure (approx. 700-800 Torr), which in many cases enables the equipment required to carry out the reaction to be simplified.



   Under the reaction conditions, the compounds of the formula I give off carbon and nitrogen and, if appropriate, hydrogen and / or halogen in a reactive state.



   Alkyl or alkenyl radicals represented by X1, X2, X3 or R1, R2, R3 or R4 can be straight-chain or branched. Halogen means fluorine or bromine, but especially chlorine.



   Examples of alkyl radicals X1, X2 or X3 according to the definition are the methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl radical. As a residue represented by X1, X2 or X3
EMI1.4


<tb> <SEP> zR1 <SEP> R3
<tb> or <SEP> -NH-N = <SEP> come
<tb> <SEP> R2 <SEP> R4
For example, <tb> consider the following:

  :
EMI1.5
  
EMI2.1

Preferred compounds of the formula I are those in which Y = N- or = C-halogen, one of X1, X2 and X3
EMI2.2


<tb> <SEP> R1
<tb> Halogen, <SEP> -NH2, <SEP> -NX <SEP> or <SEP> -NH-N <SEP> and <SEP> the <SEP> both
<tb> <SEP> R2 <SEP> R4 <SEP> oR1
<tb> other <SEP> independent <SEP> from each other <SEP> halogen, <SEP> -Ns <SEP> or
<tb> <SEP>, R3 <SEP> R2
<tb> -NH-N <SEP> - <SEP> represent, <SEP> whereby <SEP> R1, <SEP> R3 <SEP> and <SEP> R4 <SEP> are independent
<tb> <SEP> oR4
<tb> of one another denotes hydrogen or alkyl with 1-4 carbon atoms and R2 denotes alkyl with 1-4 carbon atoms or alkenyl with 3 or 4 carbon atoms.



   Particularly preferred are compounds of the formula I in which Y = N- or = C-CI and X1, X2 and X3 independently of one another are chlorine or
EMI2.3


<tb> <SEP>, R1
<tb> -N <SEP> represent,
<tb> <SEP> oR2
<tb> where R1 is hydrogen or alkyl with 1-4 carbon atoms and R2 is alkyl with 1-4 carbon atoms or alkenyl with 3 or 4 carbon atoms.



   The compounds of the formula I are known or can be prepared in a known manner. Specific compounds of the formula I include: 2,4,5,6-tetrachloropyrimidine, 2,4,6-tribromo- or trichloropyrimidine, 2,4-dichloropyrimidine, 2,4-dichloro-6-methyl-, -6- isopropyl- or -6-phenylpyrimidine, 2,4-dibromo-6-cyanopyrimidine, 2-chloro-4-n-butyl-6-methylamino-pyrimidine, 2-chloro-4,6-di-ethylamino-pyrimidine, 2-chlorine -4,6-bis (dimethylamino) -pyrimidine, 2,4,6-tris-methylamino-pyrimidine, 2-propyl-4,6-di-isopropylamino-pyrimidine, 2-chloro-4,6-bis (see p -cyanäthylamino) pyrimidine, 2-chloro-4,6-bis (ss-bromo ethylamino) pyrimidine, 2,4-dichloro-6- (ss-dimethylamino ethylamino) pyrimidine, 2-chloro-4, 6-di-allylamino-pyrimidine, 2-chloro-4,

   6-di-hydrazino-pyrimidine, 2-bromo-4-ethyl-6-ethylhydrazino-pyrimidine, 2,4,6-trichloro- or tribromo-s-triazine, 2,4-dichloro-6-n-butyl s-triazine, 2,4-dichloro-6-phenyl-s-triazine, 2-chloro-4,6-di-ethylamino-s-triazine, 2,4-dichloro-6-methylamino-, -6-diethylamino- and -6-di-isopropylamino-striazine, 2-chloro-4,6-dimethylamino-s-triazine, 2-chloro-4,6-din-butylamino-s-triazine, 2-chloro-4,6- bis (diethylamino) - and - (di-isopropylamino) -s-triazine, 2,6-dichloro-4- (ss-cyanoäthylamino) -s-triazine, 2-chloro-4-isopropylamino-6-allylamino-striazine, 2,4-diamino-6-methallylamino-s-triazine, 2,4-diamino6-cyano-s-triazine, 2-chloro-4,6-bis (ss-bromoethylamino) -triazine, 2,4-dichloro 6-ethylamino-methylamino-s-triazine, 2 dipropylamino-4,6-di-hydrazino-s-triazine, 2,4-di-isopropylamino-6-methylhydrazino-s-triazine,

   2,4-bis- (dimethylamino) -6- [N, N-bis- (aminoethyl) j-hydrnzino-s-tnazine, 2,4,6 tris- (diethylamino) -s-triazine, 2, 4-bis (diethylamino) -6-dimethylamino-s-triazine, 2,4-bis (diethylamino) -64sopropylamino-s-triazine, 2,4-bis (dimethylamino) -6-n-butylamino- striazine.



   As transition metals of subgroups 4-6 of the periodic system, for example titanium, vanadium, niobium, tantalum, molybdenum, chromium, tungsten, zirconium and uranium come into consideration in the process according to the invention. Preferred elements are iron, uranium, tantalum, vanadium and tungsten, but in particular boron, silicon and titanium.



   The iron, boron, silicon and the transition metals of subgroups 4-6 of the Periodic Table can be used in any form, e.g. B. can be used in elementary form. However, they are expediently used in the form of compounds, especially the transition metals as defined. Suitable compounds are e.g. B.

  Hydrides, carbonyls, carbonyl hydrides, organometallic compounds and halides, such as silicon hydride (SiH4), titanium hydride (TiH2), zirconium hydride (ZrH2), boranes; Chromium, molybdenum and tungsten hexacarbonyl, iron pentacarbonyl [Fe (CO) S], FeH2 (CO) 4; Tetraethyltitanium, tetramethyl and tetraethylsilane, methyl dichlorosilane, trichlorosilane, methyl trichlorosilane, ethyl trichlorosilane, trimethylchlorosilane; Boron trichloride, silicon tetrachloride, titanium dibromide, titanium trichloride, titanium tetrachloride and tetrabromide, zirconium tetrachloride, vanadium trichloride and tetrachloride, niobium pentachloride, tantalum pentachloride, chromium trichloride, tungsten hexachloride and uranium hexachloride, iron hexachloride and uranium hexafluoride, iron hexachloride and uranium hexafluoride, iron hexachloride and uranium hexachloride, iron hexachloride and uranium hexachloride.



   The halides, especially the chlorides, especially those of boron, silicon and transition metals are preferred. Boron trichloride, silicon tetrachloride and titanium tetrachloride are very particularly preferred.



   Depending on the intended use and / or nature of the compound of the formula I, it may be desirable to carry out the reaction in the presence of further additives, such as hydrogen, hydrogen chloride, atomic or molecular nitrogen or other compounds which release nitrogen and / or carbon under the reaction conditions. These substances or compounds can contribute to the formation of the carbides, nitrides or carbonitrides or shift the equilibrium of the formation reaction more towards the nitrides or the carbides. Such additional, under the reaction conditions nitrogen and / or carbon donating compounds are z. B. methane, ethane, n-butane, N-methylamine, N, N-diethylamine, ethylenediamine, benzene and ammonia.



   The inventive coating of the carbon materials with carbides, nitrides and / or carbonitrides can be carried out within the scope of the definition by any method known per se.



   One of the most important processes is chemical deposition from the gas phase, also known as CVD (Chemical Vapor Deposition). The reaction in the gas phase can be carried out with the supply of heat or radiation energy. In this process, iron, boron, silicon or the transition metals and the compound of the formula I are usually used in the form of gaseous compounds. The reaction temperatures are generally between about 600 and 1500 C, preferably between 800 and 12000 C.



   If necessary, hydrogen is used as the reducing agent. In certain cases it can also be advantageous to use a carrier gas such as argon to transport the starting materials into the reaction zone.



   According to another method, the carbon materials to be coated can also be used in mixtures of substances, e.g. B.



  Powder mixtures, enveloped or mixed with substances and optionally pressed, which contain all or - preferably - some of the starting materials required for the formation of the carbides, nitrides or carbonitrides.



  The whole is then preferably heated to temperatures between 500 and 1200 C, depending on the composition of the substance mixture in the presence of the starting materials still missing from the substance mixture, i.e. H. in the presence of a gaseous compound of the formula I or in the presence of suitable compounds of iron, boron, silicon or a transition metal in the gaseous state.



   The coating of the carbon materials with carbides, nitrides and / or carbonitrides can also be achieved by reacting the starting materials in a plasma, e.g. B. by so-called plasma spraying. The plasma can be generated in any way, for example by means of an arc, glow discharge or corona discharge. Argon or hydrogen are expediently used as plasma gases. In general, the temperature of the plasma is above 2000 C.



   Coatings according to the definition can also be produced by the flame spraying process, with hydrogen / oxygen or acetylene / oxygen flames generally being used.



   Another method consists in impregnating the substrate to be coated with a solution or suspension of a suitable compound of iron, boron, silicon or a transition metal and then reacting the impregnated material with a compound of the formula I at elevated temperatures.



   The method according to the invention is preferably carried out according to the plasma, flame spray or CVD technique.



   With the aid of the method according to the invention, carbon materials of any type, such as glassy (amorphous) carbon, partially graphitized carbon and graphite, can be coated. The substrates can consist entirely or partially of carbon and be in any form, for example as powder, fibers, threads, foils, moldings or components of various types.



   The main areas of application are the coating of carbon and graphite electrodes; of carbon fibers, including so-called chopped fibers as fiber protection and to improve adhesion and wettability through the metal matrix; of carbon-carbon composites, especially for turbine construction; Graphite seals, etc.



   Depending on the choice of starting materials, additives and reaction temperatures, carbides, nitrides, carbonitrides or mixtures thereof are formed in the process according to the invention.



   example 1
The tests are carried out in a vertical reactor made of Pyrex glass, which is closed at the top and bottom with a flange. The reaction gases are introduced into the reactor through a shower in order to achieve a uniform gas flow. The temperature of the substrate is measured with a pyrometer. The compounds of the formula I are evaporated in an evaporator device inside or outside the reactor. The substrate can be heated by resistance heating, inductively or in a reactor heated from the outside with an oven.



   In an apparatus of the type described above, a graphite rod with a diameter of 2 mm is heated to 950 ° C. in an argon atmosphere by resistance heating.



  At this temperature, a gas mixture consisting of 97% by volume of hydrogen, 1% by volume of titanium tetrachloride and 2% by volume of cyanuric chloride is passed over the graphite rod for 2 hours, the total gas flow rate being 1.04 liters / minute [l / min.] and the internal pressure in the reactor is 720 torr.



  After this time, a gray, hard layer of titanium carbonitride has formed on the graphite rod. The very firmly adhering layer has a thickness of 40 u and a micro Vickers hardness of HVo, os = 3300-3700 kg / mm2.



   Example 2
A graphite rod with a diameter of 2 mm is coated analogously to Example 1 under the following reaction conditions: temperature: 950 ° C.; pressure 720 Torr; reaction time: 2 hours; gas mixture: 97% by volume of hydrogen, 1% by volume of titanium tetrachloride, 2% by volume. % 2-chloro-4,6-bis (diethylamino) triazine; total gas flow: 1.03 l / min.

 

   A graphite rod coated with gray titanium carbonitride is obtained; Layer thickness 35, u; Micro hardness of the layer of HVoos = 3300-3710 kg / mm2.



   Example 3
Example 2 is repeated, but at a temperature of 1100 C / 720 torr and with a reaction time of 110 minutes. A gray titanium carbonitride layer with a layer thickness of 200-250 u and a microhardness of HVoos = 2580-3180 kg / mm2 is obtained on the graphite rod.



   Examples 4-12
The following table describes other carbon materials which have been coated in a CVD reactor in the manner indicated above. The coatings obtained according to these examples have good adhesive strength and are free from pores and cracks.



     table
Example reactor heating temperature pressure reaction gas mixture total gas product no. C torr duration (in vol.%) Flow substrate / color layer thickness m / out micro hardness kg / mmê minutes l / min. (in% by weight) see layer 4 resistance 850 720 120 97% H2 1% TiCl4 2% 1.03 graphite electrode 30-40 m HV0.05 = approx. 4200-4380 heating cyanuric chloride # 6.2 mm silver-gray glossy 5 do. 950 720 120 89% H2 1% TiCl4 10% 2.4-1.03 graphite rod 55 m HV0.05 = approx. 3580 dichloro-6- (diisopropylamino) - # 2 mm gray s-triazine 6 do. 950 720 120 97% H2 1% TiCl4 2% 2,4-Di- 1,03 do. 50 m HV0.05 = 3100 chloro-6- (diisopropylamino) s-triazine 7 do. 950 720 120 97% H2 1% TiCl4 2% 2-Di- 1.03 do. approx. 20 m HV0.05 = 2450-3090 methylamino-4,6-bis- (diethylamino) -s-triazine 8 do.

   950 720 120 92% H2 1% TiCl4 7% 2-di- graphite rod 40 m HV0.05 = 3070-3860 methylamino-4,6-bis- (di- # 2 mm gray ethylamino) -s-triazine 9 from the outside with 800 100 300 95.5% H2 1.5% TiCl4 3% 1.03 graphite rod 15 m HV0.05 = 1500 furnace heated 2,4-dichloro-6- (diallylamino) - # 2 mm matt gray, good adhesion, s-triazine non-porous 10 do. 800 20 240 93.5% H2 1.5% TiCl4 5% 0.4 C / C composite 8 m HV0.015 = approx. 2400 2,4-dichloro-6- (diallylamino) - light gray good adhesion, s- triazine pore-free 11 do. 800 20 240 do. 0.4 glassy carbon 10 m HV0.015 = approx. 2000 light gray, good adhesion, pore-free 12 do. 800 20 240 do. 0.4 carbon fiber approx. 5 m HV0.015 = 2300-3000 light gray, good adhesion, pore-free
Example 13
The experiment is carried out in a plasma reactor with a plasma torch of conventional design [model PJ 139 H from

  Arcos, Brussels; Burner output: 7.8 kw (30 V, 260 A) j performed. The reactor is arranged in a water-cooled reaction chamber made of stainless steel, which is sealed off from the outside atmosphere. The plasma is generated by a direct current arc arranged between the tungsten cathode and the copper anode of the plasma torch. The cathode and anode are also water-cooled.



  Argon or hydrogen can be used as plasma.



  The reaction gases are introduced into the plasma jet with the aid of a carrier gas through lateral bores in the outlet nozzle of the copper anode. The concentration of the reaction gases in the carrier gas flow is set with the aid of thermostatically adjustable evaporator devices and flow regulators. The substrate, which may be water-cooled under certain circumstances, is located at a distance of 1-5 cm in front of the exit opening of the plasma jet in the copper anode.



   At the beginning of the experiment, the reaction chamber is evacuated, flushed and filled with argon. Then the plasma gas (argon, 90 mol / hour) is introduced and the plasma flame is ignited. A graphite substrate is placed at a distance of 2 cm in front of the exit opening of the plasma jet, and the reaction gases and the carrier gas are introduced into the plasma jet as follows:
Titanium tetrachloride: 0.02 mol / hour, carrier gas (hydrogen) for trick: 1 mol / hour, 2,4,6-tris (diethylamino) -s-triazine: 0.001 mol / hour.

 

   The temperature of the plasma flame is above 3000C C; the temperature of the substrate surface is approx. 2500 C.



  After a reaction time of 6 minutes, the plasma torch is switched off and the coated substrate is cooled in the gas-filled reaction chamber. A homogeneous, shiny metallic, light gray layer is obtained; Thickness 4 µm; Composition determined by X-ray diffraction: TiC (lattice constant a = 4.33).

 

Claims (1)

PATENT CLAIM Process for coating carbon materials with carbides, nitrides and / or carbonitrides of iron, boron, silicon or one of the transition metals of subgroups 4-6 of the periodic system by direct thermal action of iron, boron, silicon or one of the transition metals of subgroups 4-6 of the Periodic Table in elemental form or as a compound and in the presence of a substance which supplies carbon and nitrogen on the material to be coated, characterized in that at least one compound of the formula I EMI5.1 used where Y = N-, = CH- or = C-halogen, one of X1, X2 and X3 hydrogen, halogen, alkyl, phenyl, EMI5.2 <tb> <SEP>, R1 <SEP> oR3 <tb> -CN, <SEP> -N- <SEP> or <SEP> -NH-N, <tb> <SEP> R2 <SEP> R4 <tb> and the other two independently halogen, EMI5.3 <tb> <SEP>, R1 <SEP> R3 <tb> -CN, -NH2, -NX <SEP> or -NH-N <tb> <SEP> R2 <SEP> R4 <tb> represent, R1, R3 and R4 independently of one another hydrogen, alkyl, haloalkyl, cyanoalkyl, aminoalkyl, alkylaminoalkyl or alkenyl and R2 denote alkyl, haloalkyl, cyanoalkyl, aminoalkyl, alkylaminoalkyl or alkenyl, where alkyl radicals 1-4, the alkyl parts in substituted Alkyl radicals each have 2-4 and alkenyl radicals each have 3 or 4 carbon atoms. SUBCLAIMS 1. The method according to claim, characterized in that a compound of the formula I is used in which Y = N- or = C-halogen, one of X1, X2 and X3 EMI5.4 <tb> <SEP> R, <SEP> wR3 <tb> Halogen, <SEP> -NH2, <SEP> -N <SEP> or-NH- <SEP> and <SEP> die <tb> <SEP> sR2 <SEP> R4 <SEP> R <tb> both <SEP> other <SEP> independent <SEP> of each other <SEP> halogen, <SEP> -N <tb> <SEP>, R3 <SEP> R2 <tb> or <SEP> -NH-N <SEP> represent, <SEP> whereby <SEP> Ri, <SEP> R3 <SEP> and <SEP> R4 <SEP> are independent <tb> <SEP> NR4 <tb> of one another denotes hydrogen or alkyl with 1-4 carbon atoms and R2 denotes alkyl with 1-4 carbon atoms or alkenyl with 3 or 4 carbon atoms. 2. The method according to claim, characterized in that a compound of the formula I is used in which Y = N- or = C-Cl and X1, X2 and X3 independently of one another chlorine or EMI5.5 <tb> -N <SEP> represent, <tb> <SEP> sR2 <tb> where Rf is hydrogen or alkyl with 1-4 carbon atoms and R2 is alkyl with 1-4 carbon atoms or alkenyl with 3 or 4 carbon atoms.