DE1942292B2 - PROCESS FOR DEPOSITING A COATING - Google Patents

Description

The invention relates to a method for depositing a coating from the carbide of one of the Elements from the group of high-temperature-resistant metals and non-metals, in which the Base material heated in a vessel is a gaseous mixture of a hydrocarbon., a Halide of said elements and hydrogen is passed.

The invention thus lies in the general field of deposition from chemical vapors and deals in particular with a method for deposition of carbides on a base material made of iron or on a base material made up of iron alloys,., "". J "" O _r "., J ..... I-. ; "! .., Γι "J., Wi .. Iiuiiv.ii Coit (U-coating to be provided, which is practically resistant to abrasion, deformation, thermal shocks and to the action of most chemicals.

The separation of vapors from chemical substances has already been the subject of numerous research and development work. A summary of the work done so far can be found in "Vapor Deposition" by Carrol F. Powell, Joseph H. O 1 e y, and John M. Blocker, Jr. (John Wiley & Sons, 1966). In particular, there was talk of the deposition of carbides from chemical vapors Substances by reacting a hydrocarbon with a suitable halide Implementation in the heat in an article entitled “Formation of Silicon and Titanium Carbides by Chemical Vapor Deposition "by M. L. Pearse and R.W. Marek reports; this article is in the Journal of the American Ceramics Society, Vol. 51, No. 2, February 1 ^ 8, pp. 84 to 87, released. In U.S. Patents 2,884,894, 2 962 388 and 2 962 399 by Wilhelm R u ρ ρ e r t et al. are still processes for the production of Titanium carbide coatings by converting a titanium halide with a hydrocarbon in a hydrogen atmosphere in the heat.

The prior art known to the applicant includes the following literature references:

1. Powell et al., Vapor Plating, John Wiley and Sons, New York (1966).

2. '. R. Darnell et al., U.S. Patent 3,368,914 (February 13, 1968).

3. R. L. H e s t a η d et al., U.S. Patent 3,367,826 (February 6, 1968).

4. Takahashi, Takehiko et al., Journal Electrochemical Society, 114, No. 12 (Dec. 1967), pp. 1230 to 1235.

5. ME Weech et al., U.S. Patent
3,151,852 (October 6, 1964).

6. J. H. O 1 e y et al., U.S. Patent 3178308 (April 13, 1965).

7. E. N e u e η s c h w a η d e 1 et al., U.S. Patent 3,340,020 (September 5, 1967).

8. M. Turkat, U.S. Patent 3,294,880 (December 27, 1966).

9. Aeiobraze Corporation literature.

10. SJ Sindeband, U.S. Patent
2,685,543 (August 3, 1954).

11. S. J. Sindeband, U.S. Patent

2,685,545 (August 3, 1954).

12. R. L. Samuel et al., U.S. Patent

3,029,162 (April 10, 1962).

13. W. R u ρ ρ e 1 t et al., U.S. Patent
2,962,399 (November 29, 1960).

14. R.W. Marek and M. L. P ehr ce. Electrochemical Technology, Vol. 5, No. 5-6 May-June 1967, pp. 185 to 188.

15. G. A. Seme η ova, A.N. Minkevich, Izvest. VUZ.-Chern. Met. (September 1965), No. S, p. 16S to 170.

16. W. R u ρ ρ ert et al., U.S. Patent
2 962 38S (Nov. 29, 1960).

17. M. L. Pearce and R.W. Marek, Journal of the American Ceramic Society, Vol. 51, No. 2 (February 1968), pp. 84 to 87.

18. WRuppeit et al., U.S. Patent

2 8S4 894 (May 5, 1959).

iy. / Λ. .M u Ii μ ti UUU w. I \ u μ μ t ι ι, zrcti-

Schrift für Elektrochemie, Vol. 57 (1953). No. 7 Pp. 564 to 571.

20. H. Wiegand and W. R up pert. Metal surface. Vol. 14 (1960). No. 8, pp. 229 to 235.

21. A. Munster and K. Sagel. magazine for electrochemistry. Vol. 57 (1953) No. 7 S 571 to 579.

22. G. A. Seme nova. AT. Minkevich. E. V. P a η c henk ο and S. B. M a s 1 e η k ο ν, Metallov edenie i Term. Obra Metallov (November 1965). No. U. S. 37 to 38.

23. Manufacturing Techniques for Application of Erosion Resistant Coatings to Turbine Engine Compressor Components. Interim Engineering Progress Report, April 1968-30. June 1968, MATC Project No. -176-8. Contract No. F 33615-68-C-1487.

24. J. R. Darnell et al., L'SA. patent

3,368,914 (February 13, 1968).

With some of the known methods it is not possible to have fully adherent carbide coatings to achieve a base material. For example, S e m e η ο \ a et al. at. that according to their procedures The coatings obtained generally flake off and adhere poorly. The peeling can be limited Success can be prevented by heating the coated objects for a long time to promote diffusion, but the overall metallurgical properties of the substrate and the practicality and economy of the process are reduced. The application of this process is similar to that of coatings produced by diffusion and ionization were obtained.

Most known processes have in common that they are carried out under conditions which correspond to the thermodynamic equilibrium between the hydrocarbon on the one hand and the hydrogen and the carbon on the other hand, at the temperature used to deposit the coating. If one works with the known methods with low concentrations or partial vapor pressures of hydrocarbon and halide, a volume ratio between hydrocarbon and halide before about 1: 1 applies and at relatively low Tempeiaturen, z. B. works between about 900 and 1200 ⁰ C, so you get very low deposition rates. Furthermore, the prior art shows, in particular
R u ρ ρ ert et al., U.S. Patent 2,962,399 that the presence of carbon in the backing material and the presence of chromium either in or in the vicinity of the liner material gives better results or that these substances are absolutely necessary are, so that top coverings with satisfactory adhesion to the base material and optimal compositions are obtained. When working with a backing material that contains carbon, some of the carbon that enters the caibid composition is supplied by the backing material, and the carbon is made to diffuse through the pre-existing coating ίο as soon as the reaction and deposition take place have taken place. This carbon diffusion leads to the fact that the surface of the base material is depleted of carbon, and it can be llLlltl \ JV.1I t'vKwiiillwii ν «, ^ _Α ίΐ _Ρ . _η _.,.,. ί * ΤΙ. _{Α ι} ~ ΥΪί gVA be obtained with a thickness of several microns, because the reaction does not abläi more smoothly. '<Or even completely stops as soon as the coating is so thick that a carbon diffusion from L'nterlagematerial ago is prevented.

The method of R 11 ρ ρ ert et al is a method for separating vapors from chemical substances, using TiCl ₁ and CH ₄ or a similar hydrocarbon that _{decomposes to the basic compound CH 1} and hydrogen . The concentration of TiCl ₁ is adjusted by flushing a vessel containing TiCl ₁ with a gas at a certain temperature. The TiCl ₁ has a certain vapor pressure at the set temperature.

and the steam is purged into the reaction zone _{along with H 2} or a mixture of H ₂ and CH _1. The deposition temperatures for coating ferrous and non-ferrous surfaces are between about 900 and 1200 ^: C.

R u ρ ρ e r t is very careful about education of elemental carbon and is listed in Table II of U.S. Patent 2,962,388 towards the following maximum permissible CH ^ partial pressures:

temperature

900 ^: C
1000 ^: C
1100 ^: C
1200 -C

PCH,

Volume percentage
CH,

4.72 ■ 10 ²
3.63 · 10 " ²
2:57 · 10- ²
1.51 · ΙΟ " ²

4.5
3.5
2.5
1.5

Expressed mathematically, the ratio between hydrocarbon and hydrogen should not be above 0.047-P ² H ₂ ^{at 900 c} C and not above 0.015 · F ² H ₂ at 1200 ^{: C.} These values are slightly higher than the values calculated in advance from the equilibrium and were determined by R 11 ρ ρ ert et al. regarded as satisfactory; according to the teaching of Rnppert et al. make this bet the giency parameters. R u ρ ρ ert states that "the critical factor is always that at the temperature used to deposit the carbide coating, the hydrocarbon concentration in the gas mixture does not exceed the limit values given above."

Semenova. Minkevich. Panchenko and Maslenkov described in their work in Metallovedenie i Term. Obra Metallov of November 1965, pp. 37 to 38, a process for the deposition of TiC on ferrous substrates. They give the use of TiCI ₁ . H ₂ and C ₆ H ₆ as starting

substances. Your values and working conditions mixture the methane equivalent hydrocarbon refer to a temperature of 1100 ⁰ C. Concentration at least 0.5 percent by volume and that

There are values about the influence of the partial pressure volume ratio of said halide to

of C ₆ H ₆ between 0.5 x 10 ^-2 and 2.5 x 10 ~ ² at equivalent methane hydrocarbon is at least

the growth of the deposition as well as values above 5 6 × 10 ^-6, and in that the on Unterlagcmaterial

the influence of the change in the partial pressure of a temperature of more than 1050 ⁰ C is heated.

TiCl ₄ in the atmosphere from 0.5 · 10 ~ ² to 5.5 · 10 ~ ² In this way it is possible to use documents

specified. The functionally equivalent concentration of high temperature resistant metal and non-metal

des CH ₄ depends on the process conditions. carbides with practically feasible separation img-

Higher hydrocarbons, such as benzene, are difficult io speeds from about 0.15 to 0.94 mm or

It is easier to control than lower hydrocarbons, more to be coated. The coatings can be

such as methane, ethane and propane, as C ₆ H ₆ in a containing documents, ie on documents, consisting

whole range from 0 to a little more than six CH ₄ - made of iron or an iron alloy, to none

Groups can respond effectively. Materials containing higher levels of carbon and iron as well as sub-

Hydrogen can be produced under certain circumstances by punching with a non-metallic surface

The vessel will suffer pyrolysis beforehand or most will. The coating obtained is hard, dense and

"Repel" carbon residues if the pyrolysis is resistant to abrasion and corrosion. It is in

the surface begins. generally not necessary, the supporting material

Semenova et al. indicate the difficulty either before or after the separation of the transfer

towards obtaining coatings that adhere firmly to steel. To subject 20 ges to a heat treatment, but can,

They state that "as a result of the fact that, if necessary, such a heat treatment also occurs

The steel samples sometimes flake off.

Precipitation was observed. Control samples The invention provides a feasible and de-

made of graphite were heated at the same time as the steel. «Significantly improved process for production

The rate of growth of deposit 25 of carbide-containing coatings according to FIG

was calculated over a period of 30 minutes, an advantageous further development of the invention

by increasing the weight of graphite, related to titanium carbide coatings, which are metallurgically related

on the unit area, was determined (AP / Smgl of the support from the base material

mm ² ). The same fixed values are found at R u ρ ρ ert. In the method according to the invention

Positions; He compensates for this effect by measuring the carbide coatings by measuring the gaseous ones

permanent thermal treatment. Components or reactants in a reaction

In general, the known methods have generated tion chamber; if the gaseous constituents

for coating a base material or a part with the heated part or the base in

Chemical contact with the substrate by deposition from vapors, a thermal

Echen substances have clear disadvantages as a result of the mixing and a chemical reduction instead, whereby

long reaction times, the low coating metal or non-metal carbides are generated

velocities, the dependence on the diffusion in a precisely defined, constant relationship

at least one component from which the underlay settles are deposited. It is already known

material and the mandatory presence of upper that TiC by reacting a titanium halide, such as

surface constituents to get the reaction going to 40 TiCl ₄ , with a volatile hydrocarbon such as

set. The known processes are thereby CH ₄ , being formed in a hydrogen atmosphere

limits that, within a reasonable period of time, the following reaction takes place;
only low thickness coatings can be obtained

can; the known processes are also based on CH ₄ 4- TiCl ₄ 2-> xjc 4-HCl

on reaction conditions at equilibrium or 45

near equilibrium. Although, due to the thermodynamics, the

After all, it is the most favorable temperatures, equilibrium constants from the book "Vapor Plating"

by CF. Mitchell et a., 1955, can predict the sides and mole ratios, says the

73 and 74 known, coatings made of carbides highly thermodynamic nothing about the deposition

temperature resistant to produce metals by 50 speeds, the morphology of the deposition,

that the roughness of the surface and the grain size over the highly heated base material

Mixture of a gaseous hydrocarbon, or texture.

a gaseous halide of said metal. The invention is a practical one

and hydrogen is passed. and economical process for the production of

The invention is based on the object of providing a coating of titanium carbide on substrates and for producing hard, dense and opposed uniform titanium carbide bodies with the Carbide properties that are resistant to abrasion and corrosion are available, As already mentioned, in most cases there is no coating on certain supporting materials cugnen, whereby more is required compared to known methods for subsequent heat treatment. Manufacture of carbide coatings relatively quickly 60 In the following, preferred embodiments are now Decision speeds, good adhesive properties of the method according to the invention on hand en on the documentation material and a good reproduction of the drawings described in detail, lucibility is achievable. To solve this problem doing shows

The invention is based on a method for FIG. 1 schematically an example of a Vonich

\ Deposition of a coating from the carbide of a 65 tion for carrying out the method according to

ler elements from the group of high temperature invention,

> Permanent metals and non-metals in accordance with the fig. 2 a curve over the separation

; angs mentioned type and consists in the fact that in the speed of car-

7 ^ 8

; as a function of Abscheidungstem- ner bidüberzügen and cleaners 50, 52 or 54 containing a Trock-

ί temperature, agents and a cleaning agent with their help

i F i g. 3; ine of fig. 2 similar curve, but carbon monoxide and carbon dioxide from the gas

! the deposition occurs on a non-ferrous be absorbed or removed. With these funds

Base material, such as graphite, 5 is, for example, calcium sulfate or

; F i g. 4 shows the curve of sedimentation asbestos coated with sodium hydroxide.

i speed of a carbide coating on a drying and cleaning device 50

i Graphite base as a function of the hydrocarbons - for the hydrogen is the purified hydrogen

I substance concentration (in percent by volume); through a line 56 in two parallel-connected currents

• F i g. 5 shows the curve of the deposition meters 58 and 60, each of which is directed at

! speed as a function of the gas speed input is provided with a control valve 60 or 64

j in the reactor (in cm / min.) with constant deposition. The outlet of the flow meter 58 leads over

j temperature and with constant methane concentration the line 38 into the feed line 36 of the heater 20,

j and making hydrogen as desired and in any

j F i g. 6 shows a schematic representation of some 15 parts with a hydrocarbon such as methane,

j the most important parameter of the invention, namely that can be mixed after the outflow

j the relationship between the hydrocarbons from the container 46 through the drying and Rcini-

: centering (in percent by volume) and the temperature generating device 52 via a line 66 in one

j is directed to flow meter 68 as compared to the same parameters; the gas flow

j State of the art. 20 through the flow meter can be controlled by a

] As already said, valve 70 at the inlet can be controlled according to the procedure, and the output

According to the invention, tightly adhering covers of one step of the flow meter 68 is via a line 40

j Carbide of a highly temperature-resistant metal is connected to the feed line 36 to the heater. That

odci non-metal from the vapor phase to cisenhal inert gas, such as argon, which comes from the container 48,

tigcn, nickel-iron halligcn and non-metallic underflows after drying and cleaning in the

layers are deposited. Drying and cleaning device 54 by the

I To carry out the method according to the invention line 72 in the parallel arranged flow

I tion is a device as shown in FIG. 1 darmesser 74 and 76. The inert gas flow is through the

i is set, used. The device contains a corresponding control valve 78 and 80 regulated. Of the

! Vessel or a reactor 10 with a supply line 12 30 output of the flow meter 74 is via a line

: and a discharge line 14, which connects with a discharge line 16 device 42 with the input line 96 of the heater

■ is connected. A heating element is tied to the reactor 10. The outlets of the hydrogen flow I 18 arranged, the resistance heating element or knife 60 and the argon flow meter 76 wer-I preferably a high-frequency induction heating element is led into a common flushing pipe 82 which is in

■ ment with suitable control devices (not 35 the outlet 14 of the reactor 10, so that the ! shown) for setting the temperature in the system's Rcak fume cupboard with inert gas as required, 'tor can represent. Hydrogen and / or a mixture of the two gases The reactor is preferably made of a material that can be flushed so that the system can be flushed j made, which is resistant to high temperatures and practically possible in the opposite direction.

j table is inert and not heated by induction 40 In the reactor 10 are facilities such. B. a shark

I can be e.g. B. alumina or aluminum oxide. sion 84 and a tripod 86 provided through which the

1 A heater 20, which is preferably made of corrosive part 88, which is to be coated with a layer of carbide.

; is made of resistant steel, is held in the reactor with its outer document file

I end with the feed line 12 of the reactor 10 is consumed. Of course, the bracket 84 is in

bound; Around the heater are devices such as 45 in a manner provided with openings or there are heating coils 22 arranged, with the help of which the interior of thin rods and brackets, which keep the stand 86 the heater at a certain temperature, so that no interruption of the heater Will hold gas flow. A storage container 24, which takes place with heating through the reactor: the stand 86 is provided with pre-devices (not shown), preferably contains a halide of a high-temperature-resistant material made from a material such as alumina.

tails or non-metal that comes with a heating element, the backing material of part 88 is on fol-

which protrudes into the storage container 24, produced in the following way:

Melting temperature can be heated. The part is made of steel, cast iron or the like. Herge

Line 28 of a pump 26 is below the level, so it is degreased and. If necessary, freed from rust of the liquid metal halides in the storage container 24 55 and hammer blow, the rust and arranged, and a discharge line 30 of the pump is oxide layers etched with acid or by a via a flow meter 32 with a line 34 sandblasting or the like Way connected that leads to the heater 20. Become the heater. The part can also be washed in water is provided with a supply line 36, in which, via and by drying, for example in acetone or lines 38, 40 and 42, controllable flows of water 60 in alcohol, are further cleaned to remove material residues, a Remove hydrocarbons such as methane (CH ₄ ) from the surface. The part or an inert gas, such as argon, does not need to be measured individually and does not need to be degassed and it can be put into the reactor 10. The hydrogen, dei hydrocarbons, is placed on the tripod 86 or on a bestoff u.id the Aigon are each held in place from a water-loving other fastening device, a material container 44, a hydrocarbon container 46 65. The valves 78 and 80 are opened, and an argon container 48 from which the control valves 62, 64 and 70 remain closed, individual gases through the corresponding gas dryer and the entire system is flushed with argon. Once and purifier 50, 52 and 54 pour. Each of the dry- the entire system is filled with argon, that will

Valve 80 closed and hydrogen at atmospheric pressure (although higher or lower pressures may be used) is introduced into the system by opening valves 60 and 64 while valve 78 is closed to stop the flow of argon through the system. Once the heater 20 and reactor 10 are filled with flowing hydrogen (at a pressure of just over one atmosphere) the reactor heating element 18 is turned on and the part 88 is rapidly heated to a temperature in excess of 1050 ° C. If the part 88 is made of steel, it is preferably heated to a temperature of about 1100 to 1250 ° C .; If the part 88 is made of graphite, it is heated to a temperature between approximately 1200 and 1600.degree. C., preferably to a temperature in the range from approximately 1275 to 1325.degree. If the part 88 is made of Quaiz, the heating temperature is preferably in the range from 1300 to 1325 ° C.

While the pure hydrogen is still flowing through the heater 20 and the reactor 10 , the liquid halide is fed from the container 24 with the aid of the pump 26 through the flow meter 32 and the feed pipe 34 directly into the heater 20 , in which the liquid halide evaporates immediately and mixes with the pure hydrogen flowing into the reactor through the heater. If the part 88 consists of carbon or a metal, it is very critical in carrying out the method according to the invention that the metal halide is first introduced into the reactor 10 in the correct order before the hydrocarbon is introduced, since on the surface of the part Excess carbon atoms are formed if the hydrocarbon were first introduced into the reactor, which would melt the surface of the part and form a carbon eutectic, or carbon would be absorbed by the metal of the substrate; this would result in melting of the surface of the part and poor adhesion of the carbide coating.

The following is a typical example of the method of the invention for coating a stainless steel part 88 with a dense, coherent, and adherent coating of titanium carbide. After degreasing, washing and drying the part, purging the reactor with purified argon and with purified hydrogen, the part 88 is heated to a temperature of about 1200 to 1250 ° C. in a hydrogen stream. The flow rate of hydrogen depends on the size of the reactor, and in a reactor with a diameter of 50 mm the flow rate of hydrogen is about 13,000 to 14,000 cm ³ / min., Corresponding to a gas speed of 660 to 735 cm / min . Once the part 88 has reached the reaction temperature, liquid titanium tetrachloride (TiCl _4), is introduced into the heater 20, where it immediately vaporizes the heater at a temperature of 350-800 ⁰ C, preferably at a temperature of 600 ⁰ C held will. The _{TiCl 4} vapors enter the reactor 10 in an intimate mixture with the hydrogen and, on approaching the part 88, first convert to a white smoke that quickly turns purple, which is probably due to the heat and through the hydrogen-related reduction of the TiCl ₄ to TiCl _{3 is} caused. At this point the hydrocarbon, preferably methane (CH ₄ ), is added to the gas stream by opening control valve 70; the reaction is carried out for the desired period of time, which depends on the desired thickness of the titanium carbide coating. For example, with a deposition time of 10 minutes under the conditions described above, a firmly adhering titanium carbide coating with a thickness of about 0.075 mm is produced. The coating is metallurgically bonded to the steel and has a micro-thickness of less than 3000 Knoop. whereby values of up to 3800 Knoop can be achieved.

After the part 88 has been treated for a sufficiently long time to achieve the desired coating thickness, the CH ₄ flow is first turned off, then the TiCl ₄ flow, after which the system is flushed with hydrogen. The part 88 is removed from the reactor 10 via a lock (not shown) if the method is carried out with heating of the wall (resistance heating). The coated part 88 can immediately be placed in a cooling lock and quenched with gas therein; however, it can also be removed and cooled in stages so that the desired properties of the base are retained. The choice of procedure depends on the

Material off. If the process is carried out without heating the wall (induction heating), then the part generally in either an argon atmosphere or a hydrogen atmosphere Reactor itself cooled down quickly.

The order in which the gases are introduced into the reactor is, as already said, very critical because one Melting of the surface through the formation of a carbon eutectic or by penetration of carbon into the base metal, if one

it allows excess carbon atoms to form on a part made of steel or a ferrous material in the reactor. All gases are measured against The TiCl ₄ is measured immediately in liquid form into the heater. Direct metering and the use of a heater are features according to the present invention which are not applied to the other known methods. The heater is used to evaporate and mix the other gases. Since the CH ₁

and / or the hydrogen can also be metered directly into the heater and since each gas is regulated individually, the order in which it is added can easily be regulated. By measuring the TiCl ₄ directly into the evaporator as a liquid, one obtains

a high concentration of titanium-containing molecules in the deposition zone; Furthermore, higher deposition rates are thereby possible, which leads to a production process that can be carried out in practice. With the help of the procedure According to the invention, coatings can be applied to any Documents are produced. The method is not limited to reactions with plated surfaces. The surface does not need any components for the TiC coating. So the process is Ren according to the invention is not limited to diffusion processes. In reactions that are restricted by diffusion processes, the TiCl _{4 is} reduced either thermally or chemically, and the titanium atoms combine with that in front of the surface supplied carbon, whereby a very thin TiC layer is formed, which is probably only a few Molecular layers is thick. In order for the thickness of this layer to increase, more carbon has to be added to the upper

"F

diffuse surface to keep up with the new titanium temperatures, and the energetic relationships of the

to implement atoms. That is why these reaction methods are cheaper. If you increase the number of

limited in terms of diffusion time. Carbon atoms on the deposition surface

The diagram of FIG. 2 shows the deposition impingement, so the deposition rate increases.

speed (in microns / min.) as a function of the 5. This can be achieved by having the

Temperature of the part coated in the reactor. The amount of hydrocarbon entering the reactor

Curve was made from the results of a series of or the total flow rate of the gas

Try using titanium carbide coatings that increase after that.

above-described method on corrosion- F i g. 4 shows the influence of the concentration of the resistant steel on graphite and on quartz where hydrocarbons (e.g. CH ₄ ) [in percent by volume] were kept, with hydrogen on the deposition rate of the carbide, in an amount of 95, 2 percent by volume, CH ₄ in one expressed in microns / min. The amount by the curve of 3.2 percent by volume and TiCl ₄ in one of F i g. Results shown in Figure 4 were at an amount of 1.6 percent by volume, corresponding to a constant total gas flow rate
TiCl ₄ / CH ₄ ratio of 0.5 used. The 15 through the reactor of 16,000 cm ³ / min. with a total flow of 4545 cm ³ per minute and a reactor diameter of 75 mm or 353 cm / min., 6.5 cm ² or 716 cm / min. at a constant reaction ^{temperature of 1250 0} C, the curve of F i g. 2 shows that the deposition of a constant TiCl ₄ flow rate of velocities of the composition of 417 cm ³ / min. or 9.18 cm / min, and are independent of a constant base material, which indicates that the deposition time of 30 minutes is obtained, indicates that the method according to the invention was not where the material of the base was graphite. Which is limited by diffusion and that a high methane concentration was, as shown, varied according to the invention by the deposition rate (50 to 100 times higher than 2 percent by volume to more than 20 percent by volume in the known processes). The Kui ve of F i g. 4 clearly shows what is achieved. The curve in FIG. 2 25 that at a certain temperature and a certain temperature the influence of the temperature on the distance TiCl ₄ - and total flow rate and separation rate. The rate of deposition of the TiC increases with the concentration of CH ₄ when graphite is used as the base material. The highest increase occurs between 2 and 3.5 volume percent CH ₄ when steel is used as the base material, with the curve at. With this higher reaction _{- a CH 4} concentration of more than 4 volumetric temperatures - a higher deposition percentage is achieved, which is clearly flattened. This appears to be speeding up, as can be traced back to the illustration of FIG. 3 can be seen. F i g. 3 shows the deposition CH ₄ concentration without a corresponding increase in the speed of TiC on graphite as a function of the TiCl ₄ concentration, the concentration of TiCl _{4 and} the temperature of the base material. is not sufficient for enough titanium atoms with F i g. 3 shows the pronounced effect of the temperature that binds the excess carbon atoms on the rate of deposition.

d. H. at higher temperatures a completely. At different temperatures a whole More pyrolysis of the hydrocarbon takes place, producing 40 series of curves similar to that of FIG. 4, received the number of graze on the surface of the pad. At higher temperatures, the max and with the metal atoms from the metal paint, deposition rates are lower halide reacting carbon atoms increases. Methane concentrations reached as the pyrolysis of the The slopes of the curves in FIGS. 2 and 3 methane and the reaction kinetics at higher tems are not identical. The slope of the curve of 45 temperatures will be cheaper.

F i g. 3 is higher. It appears that the relationships F i g. 5 shows a curve of the deposition rate

are not entirely linear, with a slight increase in speed (in micion / min.) as a function of the gas

occurs at higher temperatures. This is true speed in cm / min. The curve of FIG. 5

apparently to a higher free energy at a higher wuide at a constant deposition temperature

Temperatures, whereby the total 50 of 125O ⁰ C and with a constant methane concentration

reaction is favored. It was also observed tration of 8 percent by volume using a

that a reaction between hydrogen and TiCl ₄ reactor with a diameter of 75 mm

Keep at substrate temperatures in the presence of Grcphite. There have been experiments with graphite as well as with

of more than 900 ° C is possible, with a corrosion-resistant steel as a base material

Diffusion-limited TiC coating forms. It's done 55. Again, were the results obtained

possible that such a deposition of the composition of the base material occurs first

forms, which is independent of the overall thickness of the coating. The curve clearly shows the influence

added, whereby the deposition rate of the gas velocity on the deposition rate

increases. Such a surface reaction will occur at speed. With increasing gas speed it increases

lower temperatures very slowly. However, the rate of deposition is also increased until the

obviously that the temperature is a more pronounced one. Deposition rate remains practically constant

Has an influence on the rate of deposition. or even something decreases. It is believed that the

E; i of the reaction that takes place in the method according to the flattening of the curve to a temperature-reduced

the invention takes place, it is a lowing factor is based on the cool effect of the

Reaction which causes pyrolysis of the hydrocarbon gases flowing past the surface.

substance must occur so that the formation of TiC F i g. 5 also shows that at low gas velocities

is favored. The pyrolysis of the hydrocarbon, which affects the equilibrium conditions

z. B. of methane, is more complete when approaching or corresponding to these conditions, lana-

1 942 ^

13 * 14

equal deposition rates can be obtained, ranging from 0 to about more than six CH ₄ groups

the. can respond effectively. Higher hydrocarbon

The deposition rates for gas can under certain conditions in the reactor

speeds of less than 300, for example, or prematurely pyrolyze most of their coals

up to 350 cm / min, decrease relatively quickly, 5 pieces of fabric "repel" when the pyrolysis is carried out on the upper

as shown in FIG. 5 is shown while the surface of the pad begins.

Divorce speeds in excess of 350 cm / min. F i g. Figure 6 shows the hydrocarbon content in volume remaining fairly constant. With a decreasing gas percentage (CH ₄ ) as a function of the separation speed, the separation conditions approach. The straight line Λ #, the conditions at CH ₄ -Konzentrationer to the equilibrium conditions, which runs from io from 4.5 to 1.5 percent by volume from 900 to 1200 ⁰ C theoretical considerations and on the basis of the Stan- illustrates the conditions according to the des closest to technology liptrpnHpn «-in ^ lit ^ r, n, v ς ^ ηΛ Ηργ -rw-hn.l · A h mnvimaio ru, i ^" _,. "Use of such low gas velocities for the specified temperature range. feels too long deposition times. even if, in contrast to the prior art, the invention, which is in front of a coating with a thickness of only about 0.025 mm, teaches that one wants to be produced at any temperature. These conditions are typical for a minimum _{concentration of CH 1} , but not in the processes according to the prior art. As should be used as a concentration. In the case of an as-by-product of the reaction, gaseous formation of higher concentrations is still obtained, as HCI is generated, it is at a very low gas separation rate. This makes it possible for the HCl concentration to be much more practical and high according to the invention. whereby the kinetics of the deposition becomes more economical. The operating parameters all together and the speed of impact, together with the CH1 concentrations and the reaction set components, on the surface of the part to be overheated lying in the hatched zone where the pulling part is hindered. High HCI concentration F i g. 6. those bounded by the CDBK line im. The ttations on the surface can furthermore lead to a lower operating temperature of 1050 C with a chemical corrosion of the base CH ₄ concentration of not less than 1 Wlum- and the deposition reaction of one vias diffusion percent (point D). Make the upper temperature range dependent on sionsbairieie. Therefore this is around 16 (X) C with a CH ₄ -! - u> ncenti, n> _n principle of the invention that equilibrium is not less than 0.5 percent by volume. Conditions must be avoided and that outside of _{the equilibrium the CH 4} concentration is much lower than the equilibrium, so that high carbide volume percent at lower temperatures. ..H. Deposition rates can be obtained. bc '1050 C and higher than 0.5 percent by volume at the in the F i g. 2 to 5 results shown at higher temperatures, e.g. B. at 1200 C and above, show overall that the Absclieidungsgeschwirdig- In Fig. 6 represents the double hatched / one. the speed limited by the temperature of the support material, 35 by the dashed line FCE i-, ι. The concentration of the hydrocarbon in the gas is preferred. In the case of a low stream, the concentration of the halide in the gas stream, high levels of deposition are maintained and the overall increase in gas velocities means that the time is affected. The increase in Catbid-Ab- which will keep the base on a high temperature separation speed on a base 40 can be kept very short, whereby material. which is achieved when carrying out the method according to a practical, efficient and economical of the invention, ie when working at high temperature processes. The reduction of time periods. If the hydrocarbon concentration is high and if the temperature is high, the ha.'ogenide concentration will also decrease, and if the gas flow is high, the danger that the metallurgical properties of the velocities will be achieved seems to be impaired or changed by the underlying substrate,
Increasing number of the carbon atoms available on the surface of the substrate, if you operate at high temperatures, the available carbon atoms must be the above-mentioned critical order of addition. Precise adjustment of the temperature of the reactants is particularly critical for parts of the substrate, the concentration of halide and based on iron, but under these hydrocarbons and the total gas velocity, a precisely regulated pyrolysis of the carbon is obtained. If you work with high CH ₄ concentrations, hydrogen with the formation of a carbide on the surface, then sufficient TiCl ,, must be achieved for the reaction with the surface of the base material itself and not in the gas phase deposited on the surface of the base. Finds the carbon atoms to be present. It is true that the formation of carbide in a gas phase above the surface does not seem to apply that free or elemental titanium takes place in the material, so one can only obtain a coating which is loosely bound in excess of _{TiCl 4 and has a large surface} - is used, as stated in the literature surface roughness. will. According to the prior art, a TiCl ₁ : CH ₁ -Es can also other hydrocarbons, e.g. B. Ratio of about 1: 1 used. The experimental ethane, propane, benzene, and the like, instead of methane 60 results used using the method according to the invention to obtain these hydrocarbons of the invention show that it is not to be considered functionally equivalent to methane . It is critical if one works with TiCl,: CH ₁ ratios, the hydrocarbon concentration which is functionally equivalent to the concentration of methane above the preferred range of 0.25 to 2.5 ration, although the success is less. if on the procedural conditions. Higher coals are used at ratios of about 6 · 10 ⁵ . Vorvasserstoffe such as benzene are more difficult to-controlling zugsweisc to a TiCl _1: CH.j chen ratio of less than lower hydrocarbons such as methane can be used as \. For economic reasons, vthane and propane, since C ₀ H ₀ in any load, it is preferable, with a low TiCl ₁ : CH.,

Ratio to work because the cost of the TiCl _{1 is} higher than the cost of the other components. If an excessively high TiCl ₄ : CHj ratio is used, a large amount of gaseous HCl can be formed in the reactor, which corrodes the substrate, changes the dimensions or forms depressions on the surface. When using extremely low TiCl ₄ : CH ₄ ratios, on the other hand, a depletion of titanium and excess carbon can occur in the carbide coating. However, with a _{TiCl 4} concentration of only 0.02 percent by volume in methane, satisfactory carbide coatings can still be obtained; this value corresponds to a TiCl ₄ : CH ₄ ratio

«ΛΠ me" 5 · Ifi —4 urar IrIm- Καΐΐιβΐβ4, Jaß w.a «UsIn-.

Working under the conditions according to the invention, the condition of a stoichiometric composition, as recommended by the state of the art, can be disregarded.

The present invention further teaches that gas velocity is a very important process parameter and greatly contributes to increasing deposition rates. There is no reference to this parameter in the known literature. Preferably, a Mn should Gasgescii

speed of more than 100 cm / min.

so that high deposition rates can be obtained.

The high halide concentration throughout

ίο Gas flow is achieved by doing the Introduces halide in liquid form directly into the heater 20, instead of it in gaseous form in the hydrogen om to initiate, as is done according to the state of the art. In the table below, »! some

State of these halides at room temperature and their melting or sublimation temperatures as well the manner of metering the halides into a heater to explain the process indicated according to the invention.

link Condition at
space Enamel
Point Sublimation point Calibration method temperature C. ³ C ZrCl ₄ fixed 331 331 Steam through heated flow meter ZrJ ₄ fixed 431 Steam through heated flow meter ZrJ ₂ fixed 427 liquid above 427 ° C HfCl ₁ fixed 313 Steam through heated flow meter HfJ ₄ fixed 427 Steam through heated flow meter TaCl ₅ fixed 207 liquid between 210 and 234 ° C TaBr ₃ fixed 240 liquid between 240 and 319 ⁰ C NbCl ₅ fixed 212 liquid between 212 and 243 ⁰ C NbBr ₅ fixed 227 liquid between 227 and 272 ⁰ C VCl ₄ fluid -24 Boiling point 164 liquid between -24 and 164 ° C WCl ₄ fixed 327 Boiling point 332 Steam above 332 ° C WCl ₅ fixed 244 liquid between 244 and 276 ° C WCl ₆ fixed 275 liquid between 275 and 337 ° C WBr ₄ fixed 327 steam WF ₆ gas than gas ThJ ₄ fixed 566 liquid between 566 and 837 ° C SiCI ₄ fluid as a liquid SiBr ₄ fluid as a liquid

Using the method according to the invention, carbide coatings have been made on ferrous material, non-ferrous material and non-metallic material. Ferrous material includes, for example, low-carbon steels, alloyed carbon steels, cast steels, corrosion-resistant steels, and tool steels. Non-ferrous materials for the substrates are, for example, tungsten, tungsten carbide, molybdenum and niobium, non-metallic materials are, for example, graphite, aluminum oxide (Al ₂ O ₃ ) and other high-temperature-resistant oxides, boron and borides.

The unusual properties of the parts coated with titanium carbide and other carbides make these parts particularly useful for boats, holders and crucibles in diffusion furnaces for the semiconductor industry. It has been found that the titanium carbide coatings obtained according to the invention are stable in the atmospheres used in these furnaces and that their coefficient of expansion can to a certain extent be matched to that of graphite, so that composite articles made of graphite and titanium carbide do not break when heated or cooled due to the different coefficients of thermal expansion .
Decrease on compressor blades for engines

the titanium carbide coatings reduce erosion and sometimes increase the time to fatigue. The erosion life is sometimes increased by a factor of 10 to 50. One can see the erosion lifespan also by applying a titanium carbide coating to the leading edge of rotor blades from Increase helicopters. The application of the caibid of titanium or any other metal or non-metal as a coating on an iron-based material results in a desirable composite a very hard, abrasion-resistant surface in combination with a relatively ductile base, whereby the original properties of the base are retained and with the desired benefit a coating combined with a hard surface will.

It has been found that thin films of, for example, titanium carbide coatings on ferrous and non-ferrous material, especially on ductile

209532/397

tile documents, have unusual properties, because very thin layers do not show certain properties of the mass, especially brittleness, so much. For example, there is no chipping with loss of large pieces of material; i.e., the coating in a thin layer behaves more like the base and shows the properties of the base.

Carbide coatings on parts of machine tools, such as punches, surface forming tools and punches, have a longer service life than the coatings according to the known processes due to the higher abrasion resistance of the coating produced according to the invention. Others, exposed to wear and tear, WprWeiiijp u / i <»RAikaMon. R / you · «». ·, Τ „^ _α Ioke milling cutters and cutting tools which are provided with the carbide coatings according to the invention have a much longer service life. This is due to the extreme hardness of the coatings and their abrasion resistance.

It has also been found that carbide coatings, in particular titanium carbide coatings, which have been applied to ferrous and non-ferrous materials by the method according to the invention, as friction material and as friction and wear Ii

pad used for aircraft and kiaft vehicle brakes can be. In addition to the desired frictional properties, the composite bodies have excellent properties Heat transfer properties. Furthermore, the carbide coatings can save weight compared to known friction materials be achieved.

As a result of their exceptional wear and tear properties, they have after the process Carbide coatings obtained according to the invention have many dental applications Area, e.g. B. with dental drills and the like. These coated dental drills have a very high life

Other areas of application are in the textile, Leather and synthetic fiber industry, where the coatings according to the invention due to their high wear resistance in operation, e.g. B. used in guides can be.

Composite bodies made from carbide and graphite and from carbide and metal are excellent sealing materials for water pumps, drilling equipment and Sealing parts that are exposed to strong wear and tear and corrosion.

1 sheet of drawings

Claims (13)

Patent claims: 1. Process for the deposition of a coating from the carbide of one of the elements from the group of high-temperature-resistant metals and non-metals, in which over the heated in a vessel Backing material is a gaseous mixture of a hydrocarbon, a halide of the aforesaid Elements and hydrogen is passed, characterized in that in the Mixture of methane equivalent hydrocarbons Stoffknn7Pntriitinn minr1i "ctf> nc f» ^ Vnlnmpmmnf and the volume ratio of said halide to M.'i'nan equivalent hydrocarbon is at least 6 x 10 7 " ^s and that the base material is heated to a temperature of more than 1050 ^{° C.} 2. A method for the deposition of a carbide according to claim 1, characterized in that is deposited as carbide titanium carbide. 3. The method according to claim 1, characterized in that the hydrogen, the halide and the hydrocarbon with a flow rate · όπ more than 100 ccm / min. at is bypassed the document material. 4. The method according to any one of claims 1 to 3, characterized in that daC is used as the base material Iron or an alloy containing iron is used. 5. The method according to one or more of claims 1 to 4, characterized in that the halide is introduced into the vessel prior to the introduction of the hydrocarbon. 6. The method according to any one of claims 1 to 5, characterized in that the vapors one Halide of said element by measuring and evaporating the halide in liquid Form can be obtained in a heater, the output of which is connected to the input of the vessel. 7. The method according to one or more of claims 1 to 6, characterized in that the backing material at more than 1150 ° C and less than 1600 ⁰ C is heated. 8. The method according to any one of claims 1 to 6, characterized in that as a base material an iron alloy heated between 1100 and 1250 ° C is used. 9. The method according to claim 7, characterized in that graphite as the base material used and heated between 1200 and 1600 ° C. 10. The method according to claim 7, characterized in that that quartz heated between 1300 and 1325 ° C is used as a base material. 11. The method according to any one of claims 1 to 10, characterized in that the remainder of the gas mixture hydrogen is used. 12. The method according to any one of claims 1 to 11, characterized in that the hydrocarbon Methane is used. 13. The method according to any one of claims 1 to 12, characterized in that a carbon-containing Pad is used.