CA1053547A - Process for coating inorganic substrates with carbides, nitrides and/or carbonitrides - Google Patents

Abstract

PROCESS FOR COATING INORGANIC
SUBSTRATES

ABSTRACT OF THE DISCLOSURE

A process for coating inorganic substrates, especially metallic or metalloid substrates, sintered metal carbides and carbon materials, with carbides, nitrides and/or carbonitrides, using certain triazines and pyrimidines as sources of carbon and nitrogen, is described. High deposition rates and smooth coatings of good to very good adhesion are achievable by this process.

Description

The present invention relates to a process for coating inorganic subs~rates with carbides, nitrides or carbonitrides or mixtures thereof.
It has been found that inorganic substrates can be coated in a simple manner with carbides, nitrides or carbonitrides or mix-tures thereof, of iron, boron or silicon or of the transition metals of sub-groups 4 - 6 of the periodic table by direct thermal reaction of iron, boron, silicon or transition metals of sub-groups 4 - 6 of the periodic table or derivatives thereof with substances which act as sources of carbon and nitrogen, by using, as sources of carbon and nitrogen, at least one compound of the formula I

, .
Xl ~ N ~ x3 Y ~N (I) wherein Y represents =N-, =CH- or =C-halogen, one of Xl, X2 and X3 represents hydrogen, halogen, alkyl, phenyl, -CN, _~ ~ 1 or -~ -N ~ 3 and the other two independently of one another represent halogen, -CN, -NH2, -N ~ 1 or -~ -N ~ 3 , Rl, R3 and R4 independently of one another denote hydrogen, alkyl, halogeno-alkyl, cyanoalkyl, aminoalkyl, alkylaminoalkyl or alkenyl, R2 denotes alkyl, halogenoalkyl, cyanoalkyl, aminoalkyl, alkylamino-

- 2 -~: - -: :
- ~ : ~ :
::: . . .
,: : : ,: :

la~3s47 alkyl or alkellyl and ~5 denotes hydrogen or alkyl, and alkyl groups contain 1-4 carbon atoms, the alkyl parts in substituted alkyl groups contain 2-4 carbon atorns each and alkenyl groups contain 3 or 4 carbon atoms each.
Compared to known methods, the process according to the invention is distinguished, above all, by its simplicity and economy, in that the elements car~on and nitrogen required to form the carbides, nitrides and/or carbonitrides, and optionally other elements which influence the course of the reaction, such as hydrogen and/or halogen, can be fed to the reaction zone in a simple manner and in the desired ratios.
Furthermore high deposition rates and smooth coatings of goo~ to very good adhesion can be achieved in accordance with the process of the invention, regardless of the type ~f substrate and even at reaction temperatures below approx.
900C. A further advantage is that the process can in general be carried out at normal pressure or slightly reauced or slightly elevated pressure (approx. 700-800 mm Hg) -which in many cases permits simplification of the apparatuses required to carry out the reaction.
The compounds of the formula I provide carbon and nitrogen, and where rele~ant hydrogen and/or halogen, in a reactive state, under the reaction conditions.
Alkyl or alkenyl groups represented by Xl, X2 or X~
or Rl, R2, R3, R4 or R5, can be straight-chain or branched.
Halogen denotes fluorine, bromine or iodine, but especially chlorine.
Examples of alkyl groups Xl, X2 or X3 according to the .
, . ~- . . ,: :.

-.-. . . . . . . ...

definition are the methyl, ethyl, n-propyl, isopropyl, n butyl, sec,-bu~yl and -tert.-butyl group, The following are examples of / Rl 15 / R~
radicals -N \ or -N -N \ represented by Xl, X2 or X3:

. /C~3 CH3, ~ CT.2''H3, -~7l~CH , ~H2Cl?c~l3' . C~

-N~l CH2C~12CH2CH3, In~;l -CH3, N\ ~ N(C~12v~l3j2, CH3 ~H3 . 3 ~ 3 /~H : .
N~ . , ~ 3 , ~ ~CH2C~2Br,--~C~2C~I2C~I2c~r, . C~12C}I:~i, C~
'H

', ' ' ' 1'~2CH2C~`r , ~CH3 ~N~l-cH2cH2cH2h~H2~ -lY~ ' ~2~ 2 C~I2(~13, , : ' `.. --N~C:H2CH2N~ , , --N~C~I2CH=CH2, 2 2~ ~I2~ -N~ -~CH~, -NH--NI~CH CH CH

~: - 4 -.. . ~ : , .. . . . . .

.. . . . .. .
. . , i .. . . . . .

14~5;~547

3~ 2~ I; C~ 3 N ~ n~ N - N}~2 ~ . . NE~H--C~2C~'52C'~J, Cil3 ' C~ C
C~21~2C~
f-~Cr~2~}12ilH2 ~ --~r~I~ ~C~I2CEI2~12NE~CH3 and CH~

C~ H2.

Preferred compounds of the formula I are those wherein ~: Y represents =N- or =C-halogen, one of Xl, X2 and X3 represents 2 < R or -N - N / and the other t~o independently of one another represent halogen, -N < or R5 R3 . 2 -N-N ~ R ' wherein Rl, R3, R4 and R5 lndependently of one another . denote 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.
'J.' Particularly preferred compounds are those of the form-:- ula I wherein Y represents =N-, one of Xl, X2 and X3 represents -N'" Rl or -N - N ~ R3 and the other two independently of one another represent chlorine, -N or -N - N~~~ 3, and those of the formula I ~herein Y represents -N- and Xl, X2 and X3 independently of one another repr.esent -N or -N-NH2, and : - 5 -.~ , .

~ , . , ~ ~ - . . ., -.. - .. : : ~ . ... . . . . - - -1(~53547 Rl and R5 denote hydrogen or alkyl ~ith 1-4 carbon atoms, R2 denotes alkyl with 1-4 carbon atoms or alkenyl with 3 or 4 carbon atoms and R3 and R4 denote alkyl with 1-4 carbon atoms.
The compounds of the formula I are known or can be manufactured in a kno~ manner. The following may be mentioned as specific compounds of -the formula I: 2,4J5,6-tetra-chloropyrimidine, 2,4,6-tribromopyrimidine or 2,4,6-trichloro-pyrimidine, 2,4-dichloropyrimidine, 2,4-dichloro-6-methyl-pyrimidine, 2,4-dichloro-6-isopropyl-pyrimidine or 2,4-d-ch'oro-6-phenylpyrimidine, 2,4-dib~omo-6-cyano~yrimidlne, 2-chloro-4-n-butyl-6-methylam-ino-pyrimidine, 2-chloro-4,6-diethylamino-pyrimidine,~2-chloro-4,6-b s-(dimethylamino)-pyrimidine, 2,4,6 tris-methylamino-pyrimidine, 2,6-bis-(dimethylamino)-5-cyano-pyrimidine, 2-propyl-4,6-di-isopropylamino-pyrimidine, 2-chloro-

4,6-bis-(~-cyanoethylarnino)-pyrimidine, 2-chloro-4,6-bis-(~-bromoethylamino)-pyrimidine, 2,4-dichloro-6-(~-dimethylamino-ethylamino)-pyrimidine, 2-chloro-4,6-diallylamino-pyrimidine, 2-chloro-4,6-dihydrazino-pyrimidine, 2-bromo-4-ethyl-6-ethyl-hydrazino-pyrimidine, 2,4,6-trichloro-s-triazine or 2,4,6-tri-bromo-s-triazine, 2,4-dichloro-6-n-butyl-s-triazine, 2,4-, .
dichloro-6-phenyl-s-triazine, 2-chloro-4,6-diethylamino-s-triazine, 2,4-dichloro-6-methylamino-s-triazine, 2~4-dichloro-6-diethylamlno-s-triazine and 2,4-dichloro-6-diisopropylamino-s-; triazine, 2-chloro-4,6-dimethylamino-s-triazine, 2-chloro-4,6-. di-n-butylamino-s-triazine, 2-chloro-4,6-bis-(diethylamino)-s-triazine and 2-chloro-4,6-bis-(diisopropylarnino)-s-triazine, ~^ 2,6-dichloro-4-(~-cyanoethylamino)-s triazine, 2-chloro-4-iso-., , . . :

-; . .

~053547 propylamino-6-allylamino-s-triazine, 2,4-diamino-6-methallyl-amlno-s-triazine, 2,4~diamino-6-cyano-s-triazine, 2-chloro-4,6 bis-(~-bromoethylamino)-s-triazine, 2,4-dichloro-6-ethylamino-methylamino-s-triazine, 2-dipropylamino-4,6-dihydrazino-s-triazine, 2,4-diisopropylamino-6-methylhydrazino-s-triazine, 2,4-bis-(dimethylaJnino)-6-[N,N-bis-(aminoethyl)]-hydrazino-s-triazine, 2,4,6-tris-(diethylamino)-s-triazlne, 2,4-bis-(di-e~hylamino)-6-dimethylamino-s-triazine, 2,4-bis-(diethylamino)-6-isopropylamino-s-triazine, 2,4-bis-(dimethylamino)-6-n-butyl-amino-s-*riazine and 2,4-bis-(dimethylamino)-6-(1-methylhydraz-ino)-s-triazine.
Examples of transition metals of sub-groups 4-6 o~ the periodic table which can be used in the process according to the lnvention are titanium, zirconium; hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten and uranium.
Preferred elements are iron, uranium, tantalum, vanadium and tungsten, but especially boron, silicon and titanium.
The iron, boron and silicon ar,d the transition metals of sub-groups 4-6 of the periodic table can be employed in any desired form, for example in the ~orm of the elements.
Ho~lever, they are conveniently used in the form of deriva~ives, especially in the case of the transition metals according to -the definition. Examples of suitable derivatives are hydrides, carbonyls, carbonyl-hydrides, organometallic com-pounds and halides, such as silicon hydride (SiH4), titanium hydride (TiH2), zirconium hydride (ZrH2), boranes, chromium hexacarbonyl, molybdenum hexacarbonyl and tungsten hexa-carbonyl, iron pentacarbonyl [Fe(CO)5~, FeH2(CO)4, tetra-, .. ,, ~ . ................... . .
, . . , . . -, ethylti~anium, tetrame-thyl~i.l.me and tetraethylsilane, methyl-dic~orosilane, trichlorosilane, methyl-trichlorosilane, ethyl-trichlorosllane, trime-thylchlorosilane, boron trichloride, silicon te-trachloride, titanium dibromide, titanium trichloride, titanium tetrachloride and-titanium tetrabromide, zirconium tetrachloride, vanadium trichloride and vanadium tetrachloride, niobium pen-tachlori.de, tantalum pentachloride, chromium tri~
chloride, tungsten hexachloride and tungsten hexafluoride, iron-II chloride and iron-III chloride, uranium tetrachloride an~ uranium hexafluoride.
The halides, especially the chlorides, above all those o~ boron, silicon and the transition metals, are preferred.
Boron trichloride, silicon tetrachloride and titanium tetra-chloride are very particularly preferred.
Depending on the end use and/or the type of compound of the formula I it can be desirable to carry out the reaction in the presence of further additives, such as hydro-gen, hydrogen chloride, atomic or molecular nitrogen or other compounds which act as sources of 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 reactio~ more towards the nitrides or the carbides. Examples of such additional compounds which ac-t as sources of nitrogen and/or carb~n under the reaction conditions are methane, ethane, n-butane, N-methylamine, N,N-diethylamine, ethylene diamine, benzene and ammonia, The coating, according to the inven-tion, of inorganic -, , ~, ~ . ~ .
,. .: , ~ , . :

sub~trates l~i.`t~! carbides, nitrid~, and/or carbonitrides can be carrie~ out, ~ithin the scope of the definitio~, in accordance with any desire~ methods which are in themselves known.
One of the most important processes is the chemical deposition from the gas phase, also referred to as the CVD
process (chemical vapour deposition), The reaction in the gas phase can be carried out with application o~ heat or radiant energy In this process, the iron, boron and sili-con or the transition metals, and the compound of the formula I are usually employed in the form of gaseous compounds.
The reaction tempera-tures are in general between about 500 and 1,800C, preferably between 800 and 1,500C.
Hydrogen is preferably 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 z~ne.
According to another method7 the substrates to be coated can also be covered with mixtures of materials, for example powder mixtures, or be mixed, and optionally compacted with materials which contain all or - preferably -some of the starting materials required to form the carbides, nitrides or carbonitridesO Thereafter, the whole is heated, preferably to temperatures of between 500 and 1,200~C, the heating being carried out, in accordance with the composition OI the mixture of materials, in the presence of the starting materials which are as yet lacking in the ,, _ 9 . . ~ .
' .

,... . . . - : , ., ., ~ . ,, - : . . .

mixtur~ ol mateIials, that is to say in the presence of a gaseous compoulld of the forrnula I or i.n the presence of suitabln de~i~ratives, in the gaseous state, of i~on, boron or silicon or of a transition metal - The coating of -the subs-trates with carbides, nitrides and/or carbonitrides can also be carried out by reaction of the starting materials in a plasma, for example by so-called ; plasma spraying. The plasma can be produced in ~ny desired manner, for ex~mple by means of an electric arc, glow dis-charge or corona discharge The plasma gases used are pre-ferably argon or hydrogen. Coa-tings according to the defi-nition can furthermore be produced in accordance with the ~lame spraying process 5 wherein hydrogen/oxygen or ace-tylene/

oxygen flames are generally used.
A further method is to impregnate the substrate ~hich is to be coated ~ith a solution or suspension o~ a suitable derivative o~ iron, boron or silicon or of a transition metal and subsequently to react the impregnated material, at elevated temperatures, with a compound of the formula I .
The process according to the invention is preferably carried out in accordance with the CVD technique.
Inorganic substrates which can be coated with the aid of the process according to the invention are above all metallic and metalloid substrates, sintered metal carbides and carbon materials of any desired type, which can also con-tain incompletely pyrolysed constituents, such as glassy (amorphous) carbon, partially graphitised carbon and graphite.
The process according to the invention is also suitable for coating ceramic substrates, glasses, oxides, nitrides and - 10 ~
:.;

Y

~- - . .
- ~ . . ~ -1 0 ~ 3 5 4 7 carbides.
E~amples of metallic subs-trates are ferrous metals, such as steel and cast iron, -titani~lmS and high-melting metals, such as tungsten, molybdenum, niobium, vanadi.um and tantalum. Examples of sui-table metalloids are boron and silicon, whilst suitable sintered metal carbides, that is to say sintered materials consisting of carbides of the transi-tion metals of sub-groups 4-6 of the periodic table and cobalt as the binder,are above all alloys of tungsten car-bide/cobalt, tungsten carbide/tantalu~ carbide/cobalt, tungsten carbide/titaniurn carbide/cobalt, tungsten carbide/
vanadium carbide/cobalt, tungsten carbid~/titanium carbide/
tantalum carbide/cobalt, tungsten carbide/tantalum carbide/
niobium carbide/cobalt and tungsten carbide/titanium carbide/
tantalum carbide/niobium carbide/cobalt, Examples of suit-able ceramic substrates and oxides are porcelain, chamotte and clay materials, or aluminiurn oxide, SiO2 and zirconium dioxide; Examples of nitrides and carbides are Si3N4, SiC
and chromium carbides~ ;
If carbon materials are used as substrates, a con-siderable improvement in the oxidation resistance and corrosion resistance of the carbon materials can in some cases be achieved by coating the materials in accordance with the invention.
The substrates can consist wholly or partially of one or more of the materials mentioned and can be in any desired form, for example in the form of powders, foils, fibres, filaments, shaped articles or components of very diverse . .

, , - , . . .. . . ..
- . , .; .. - . ~ ~ . -~ , ,.. , ,, ~. .. .. ....

.

ty~cs .
Dependillg on the choice of the s-tarting materials and addi-tives, the reaction temperatures and/or the substrates, carbides, nitrides, carboni-trides or mix-tures thereof are formed in accordance with the process of the inven-tion;
The principal fields in which the process according to the invention is applied are: the surface irnprovement or surface hardening of metals and sintered metal carbides to increase the wear resis-tance and corrosion resistance, for example in the case of tool steel, cast iron, titanium, metal subs-trates containing titanium, shee-t tantalum, sheet vanadium and sheet iron and sintered metal carbides of the abovementioned type, such as WC-Co alloys, for example for use in lathe tools, press tools, punches, cutting tools and drawing dies, engine components, precision components for watches and textile machinery, rocket jets, corrosion-resistant apparatuses for the chemical industry, and the like;
the coating of carbon electrodes and graphite electrodes, of carbon fibres, including so-called "chopped fibres", to pro-t~ct the fibres, to improve the adhesion and wettability by the metal matrix and to prevent undesired reactions between the carbon fibres and the metal matrix, of carbon-carbon composites, above all for turbine construction; of graphite seals and the like; the coating of ceramic materials or glasses, for example ceramic supports for catalysts and filter glasses, and, finally, the coating OI` boron, silicon and tungsten fibres or filaments to achieve better wettability by the me-tal matrix, and to protect the fibres.

. ., ~, - - . - .
- -.
., .. ,,................... - ::. .. . ..

.. . . . . .
- . :
.. . , . -- ~05~S47 Example 1 The ex~)eLilnen~s are c~rried out in a vertical CVD
reactor of ~yrex glass (Pyrex" is a trade mark) which is closed at the top and bo~tom by means of a flan~e lid. The reaction gases are passed i~ltO the reactor through a sprayhead, to ~Leve a unifonll stream of gas. The temperature on the sub-strate i~ measured by means of a pyrometer. The compounds of the formula I are v~porised ln a vaporiser device inside or out~ide the reactor Th~ sub~trate can be heated by res1stance heating, inductive heating or high frequency heating or in a reactor externally hea-ted by mean~ of a ~urnace.
A wire of carbon-rich ~teel (piano wire) of diameter 0.6 mm i8 heated to 950C by resistance heating in an argon atmo~phere ln an apparatus o~ e type described above. At ~-this temperature, a.gas mix-ture consi8ting of 97% by volume of hydrogen, 1% by ~olume o~ titanium tetrachloride and 2% by volume of cyanuric chlor~de is passed over the substrate for 2 hour8~ the total ga8 flow being 0.202 li~re/minute [1/min,3 and th~ internal pressure in the reactor being 720 mm Hg.
A$ter thl~ perlod~ a grey, hard layer has ~ormed on the ~ub-strate~ The layer thicknes8 i8 120-140 ~m; Vickers micro-hardnes~ HVo 05 = 3,700 kg/mm2.
Examples 2-6 Wire9 of steel (analy9is: 1% by weight C, 0.1% by weight Sil 0.25% b~ weight Mn, 0.1% by weight V), molybdenum, tung8ten and niobium are coated analogously to the procedure de~cribed in Example 1. The reaction conditions and results are 8ummari~ed in Table I which follows.

. . .
~ ~ - 13-~., .. , , .. , . ~ , . . . . .
. :, ~ . .-, :; ~ . ..... :' - ~ - : -: : ' ., , :

as3s47 - - o -- o - o -;~ ;~
u~ l l u~ o o o o o I a, c~l u~ o ~ ~-- u~ c~ Lr~ o Lr~ c~
h ~ ~O C~ O O O O~ O O O O
O hO C~J O ~ O C\J O t~ O
~ ~ ~ ~ ~ ~Ij ~j ~;

h,~ .~ _ __ +~ ~ O ~ O 0 ~D
~ ~ J J ~ L~ _ J
O
P~ h a,a) ~ ., h ~ ~ h h h ~ ~.0 .- ~ ~-- +' ~
~) ~ r~~1~ ~ ~ ~n ~D ~LO
u~ O a) ~ a) h~ a~ ~ ~ a) ~ r` , ~, .Q rl a) O h ~ O a)r I h Oa) ~ h O a~ O O o ~ c~ ~ ~a ~ ~ ~-~ ~ ~ &
_ .
~I h 0 O J ~ `J ;~
E~ C
__ O - ~ ~.
~ ~\J t) C) r-l O ~ ~ h ~ ~ C` ~J t~l ~I C~l O O J ~ h C~ - - - -r~ O ~ ~ C~ 1~ 1 U ~5 ~1 ~1 t~ cn o~ o~
. rl ~ O

h 0,~
o a) ~ o o o o o 0 ~ ~ ~OC`J C~l C`JC~
P~
~' ~ .
~bO
~o~ O O O O O
~q C~l C\J ~I ~ C~l :, a)~ C~
. _ _ ___ q1 ~ o o o o o ~ ~ C~ U~ In LO ~ ~
~ E-l~ _ __ cr~ a~ ~

H _ ____ _ ~ ~ -X ~ ~ ~ ~ U~
~i ~ ~ Q~ æ ~ ~_ .
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.. :

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.. . . .,. . -lV53S47 Exa A steel wire of diameter 0.78 mm (analysis: 1% by weight C, 0.1% by weight Si, 0.25% by weight Mn, 0.1% by weight V) is coated analogously to Example l at 95~C/72~ mm Hg and a gas flow of 1.03 l/min. The gas mixture used contains 97%
by volur.le of hydrogen, 1% by volume of titanlum tetrachloride and 2% by volume o~ 2-chloro-4,6-bis-(diethylamino)-s_triazine.
After 120 minutes, a layer 20 ~m thick is obtained; Vickers micro-hardness HVo 05 = 2,270 kg/mm ~

~ Further steel wires are coated analogously -to the description in Example 7. The reaction conditions and results are summarlsed ir Table II wAich follows:

~' .
. .
, .
., .
_ 15 --~f ~, .. . .
,, ~ ... . .. .

: ~ - - , . , -: , . . .

lC~53547 _ o CO o u~ N ZiO
I a) N lf~ LS~ N 11~ 1 0 5~ ~ 00 00 O 00 U'~

5 . ~ ~i . o . o . . ~) ~-) h ~ O Lr~ O C`J O O ~N O
_ ~ _ ~ l . _ _ a~
C
h.~ ~ rl ~ 1~ O O
~1 1~ ~
_ ~n ~
O Q~ ~ C) ~ Q) ,~ _~
h ~ h f:~ ~ ~ S~ ,_ P~ ~ . ~ ~: ~ h h h 01:) ~ 00 ,n 0~ ,n ,~
- I ~ I ~ I ~ X
u~ o a) ~ a) . ~ a) . ~ sd ,Q ~1 a) O a~ a) O a~ ~) O ~ ~1 ~ O +~ h ~ h ~ h P~
. u~ o ~ o u~ ~o u~ _ ~ a ~ ~ ~ .
+O ~ i O C~ O
E~ ~CH ~ ~ ~ ~ .~ U
_ _ 4~ ~ ~
~ ~ tU ~
. o o ~ o ~1 ;- - - o a ~ ~ C~ C~ ~
U~ Q ~ C~ ~ ~ rl 1 0 ~ ~ .. .- . .. t~
u~ H ~3R r-l H r-l t~l ~ _ I O
.~ .,1.~ ~ H ~::
~ O~ C~OJ C~~l C~Ol t~
t~ ~1 ~_1 ~1 ~ ~0 ,, ~ ~ u h ~ 'H ~:;
. ~ ~ ~ O ~ ~ ~

C-- L-- O O

~' _ I nl t~
V $ g O :1 o O ~ O ~
~1 ~ .
, ~ ~ O ~ ~

.

- .~ .~ . . . - , .
-. . ~ ~ ~ . , 1(3S3~7 Exa~ple 11 A sintered metal carbide rod (containing 92% by weight -~
of tungsten carbide, 2% by weight of titanium carbide and 6% by weight of cobalt) of 1 mm diameter is coated, in the manner de-scribed in the preceding examples, for 120 minutes at 950C and 720 mm Hg. The gas mixture used contains 97% by volume of hydrogen, 1% by volume of titanium tetrachloride and 2% by volume of 2-chloro-4,6-bis-(diethylamino)-s-triazine. The total gas flow is 1.03 l/min. A grey-yellow, very well-adhering layer, which shows no cracks or pores, is obtained. Layer thickness approx.
22 ~m; Vickers micro-hardness HVo 05 = 2>600 - 3,000 kg/mm2, as compared to a micro-hardness of the uncoated substrate of HVo 05 = 1,800 - 2,000 kg/mm .
Example 12 - A tungsten wire of diameter 0.5 mm is coated, analogo-usly to the procedure described in Example 1, at 950C and 720 , mm Hg. The gas mixture used contains 1% by volume of titanium tetrachloride, 2% by volume of 2,4,5,6-tetrachloropyrimidine and 97% by volume of hydrogen. The total gas flow is 1.03 l/min.
2Q After a reaction time of two hours, a layer which is approx.
70 ~m thick and has a Vickers micro-hardness of HVo 05 = 2,150 kg/mm is obtained.
Example 13 :
Nioblum wire coated with Al?O3 in accordance with the CyD process ~diameter 0.7 mm; thickness of the layer of ceramic coating 3 ~m) is coated, in the manner described in the preceding examples, for 120 minutes at 950C and 720 mm Hg.

~' .
.~ - - .

.

. .
.

- ,.

105~5~7 The ~as rni.xiure u-.e(l contains 97~0 by volume o~ hydrogen, 1% by volume o~ titani~ tetrachloride, 20,' by volume of 2,4-dichloro-

6-diethylamino-s-triazi.ne; total gas 10w 1.03 l/min. A well-adhering grey layer is obtai.ned; laycr thickness 20 ~m;.
Vi.ckers micro-hardness HVo 015 = 2,720 kg/mm2; composition of the layer, as determined by X-ray methods: TiCo 55No ~5.
Example 14 A steel wirc coated with chromium carbide (diameter 0.78 mm; thickness of the layer of ceramic coating 6 ~m) is coated,analogously to Exam~le 13,with a gas mixture consisting of 97% by volume of hydrogen, 1~' by volume of titanium tetra-chloride and 2/~ by volume of 2,4,6-tris--(diethylamino)--s~
triazine. A well-adhering grey-brown layer which is 30 ~m thick and has a Vickers micro-hardness HVo o5 = 2,580 kg/mm2 is obtained.
Examples 15 32 Table III which follows describes further substrates which were Goated in a CVD reactor in the manner indicated above:
' ~ 18 -. . ...
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A graphite rod of diameter 2 n~ is heated to 950C by resistance heating in an argon atmosphere in an apparatus of the type clescribed in Example 1. At this temperature, a gas mixture corsisting o~ 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 being 1.03 l/min. and the in-ternal pressure in the reactor being 720 mm Hg; After this period, a matt grey, uniform, crack-free and non-porous layer has formed on the graphite rod. The layer, ~hich adheres very firmly, is 190 ~m thick and has a Vickers micro-hardness HVo 05 = 4,330-4,5~0 kg/mm2.
Example 34 A graphite rod of 2 mm diameter is coated analogously to Example 33, under the following reaction conditions:
temperature 950C; pressure 720 mm Hg; reaction time 2 hours; gas mixture: 97% by volume of hydrogen, 1% by volume of titanium tetrachloride, 2% by volume of 2-chloro-4,6-bis-(diethylamino)-s-triazine; total gas flow: 1 03 l/min.
A graphite rod coated with a grey, hard layer is obtained; layer thickness45 ~m; layer micro-hardness H~o 05 =
3,000-3,430 kg/mm2 Example 35 Example 34 is repeated, but at a temperature of 1,100C/
720 mm Hg and with a reaction time of 110 minutes A grey layer, 200-250 ~m thick, having a micro-hardness HVo-05 =
2,580-3,180 kg~mm2 is obtained on the graphite rod.

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Examples ~ 4-4 Table lV which follows describes further carbon materials which were coated in the abovementioned manner in a CVD reactor~ The coatings obtained in accordance ~ith these examples have good adhesion and are free from pores and cracks.

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10'~35~7 Exam~le 45 The cxperirnent is carried out in a plasma reactor using a plasma torch of conven-tional construction rModel PJ 139 II of Messrs Arcos, Brussels; torch ra-t.i.ng: 7.8 kw (30 V, 260 A)~, The reactor is locat~d in a water-cooled reaction chamber of stainless steel, sealed from the outside atmosphere. The plasma is produced by a ~C ~ec-bic arc formed between the tung- -sten 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 gases. The recction gases are intrc~ced into the plasMa beam with the aid of a carrier gas, through lateral bores in the outlet jet of the copper anode. The con centration of the reac-tion gases in the stream of carrier gas is ad~usted by means of the~nostatically controllable vaporiser devices and flow regulators. The substrate, which ~der certain circumstances can be water-cooled, is at a distance of 1-5 cm in front of the outlet orifice of the plasma beam in the copper anode.
At the beginning of the experiment, ~he reaction chamber is evacuated, flushed ar.d filled with argon. The plasma gas (argon, 90 mols/hour) is then introduced and the plasma fl~ne is lit. A graphite substrate is located at a aist~nce of 2 cm from the outlet orifice of the plasma bearn and the reaction gases and the carrier gas are introduced into the plasma beam as follows: titaniwn tetrachloride: 0.02 mol/hour; carrier gas (hydrogen) for TiCl4: l mol/hour; 2,4,6--tris-(diethyl-amino)-s-triazine: 0.001 mol/hour. The temperature of the plasma flame is above 3,000C; -the temperature of the substrate ... .- .. . - -- ,.... . . .
: - . . .

, . . . .

surface i.s ap~rox. 2,500C. After a reaction time of 6 rninutes the plasma torch is switched off and the coated sub-stra-te is cooled in the gas-filled reaction chamber. A
homogeneous, light grey layer having a metallic gloss is obtained; thickness 4 ~I.m; composition as determined by X-ray diffraction: TiC (lattice constant a = 4.33 Example 46 An aluminium oxide subs-trate is treated analogously to the method described in ~xample 45. The temperature o~
the substrate surface during coating is approx. 1,900C.
A hard, relatively porous layer is obtained, which is built up of several zones of different colour. The outermost, grey layer has a lattice constan-t a = 4.25 ~.

....... .

Claims (6)

WHAT WE CLAIM IS:

1. A process for coating inorganic substrates with carbides, nitrides or carbonitrides or mixtures thereof of iron, boron or silicon or of the transition metals of sub-groups 4-6 of the periodic table by direct thermal reaction of iron, boron, silicon or transition metals of sub-groups 4-6 of the periodic table, or derivatives thereof, with substances which act as sources of carbon and nitrogen, characterised in that at least one compound of the formula I

(I) wherein Y represents =N-, =CH- or =-halogen, one of X1, X2 and X3 represents hydrogen, halogen, alkyl, phenyl, -CN, or and the other two independently of one another represent halogen, -CN, -NE2, or R1, R3 and R4 independently of one another denote hydrogen, alkyl, halogenoalkyl, cyanoalkyl, aminoalkyl, alkylamlnoalkyl or alkenyl, R2 denotes alkyl, halogenoa]kyl, cyanoalkyl, amino-alkyl, alkylaminoalkyl or alkenyl and R5 denotes hydrogen or alkyl, and alkyl groups contain 1-4 carbon atoms, the alkyl parts in substituted alkyl groups contain 2-4 carbon atoms each and alkenyl groups contain 3 or 4 carbon atoms each, is used as a source of carbon and nitrogen.

2. A process according to Claim 1, characterised in that compounds of the formula I, wherein Y represents =N- or =?-halogen, one of X1, X2 and X3 represents halogen, -CN, -NH2, or and the other two independently of one another represent halogen, or , wherein R1, R3, R4 and R5 independently of one another denote 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, are used.

3. A process according to Claim 1, characterised in that compounds of the formula I, wherein Y represents =N-, one of X1, X2 and X3 represents or and the other two independently of one another represent chlorine, or , or compounds of the formula I wherein Y represents =N- and X1, X2 independently of one another represent or , and R1 and R5 denote hydrogen or alkyl with 1-4 carbon atoms, R2 denotes alkyl with 1-4 carbon atoms or alkenyl with 3 or 4 carbon atoms and R3 and R4 denote alkyl with 1-4 carbon atoms, are used.

4. A process according to Claim 1, characterised in that metallic or metalloid substrates are used.

5. A process according to Claim 1, characterised in that sintered metal carbide substrates are used.

6. A process according to Claim 1, characterised in that carbon materials are used as substrates.