DE1902819B2 - METHOD OF COATING BODIES MADE OF CARBON OR GRAPHITE - Google Patents

Description

in the atmosphere after relatively long deposition 45 In a preferred embodiment of the invention

Times of unevenly thick layers are deposited using the method according to the invention, a powder mixture

will. from 4 to 55 percent by weight, preferably 10 to

It is also known to use 45 percent by weight of metal layers, the metals titanium, molybdenum, Melting of metal powder on the to be coated Iridium, Ruthenium, individually or in groups, 0.7 tend to bring up bodies. Here too, up to 12 percent by weight, preferably 1.5 to 10 percent by weight, must be high Temperatures are applied, still weight percent, the chlorides of the aluminum, Zirßen when heating intricately shaped koniums, zinc, titanium, manganese, iron and 33 bis Share difficulties, especially when the 95.3 weight percent, preferably 45 to 88.5 parts by weight have different cross-sections. weight percent, oxides and / or nitrides and / or

It is also known to use carbon or gra- 55 carbides of silicon, magnesium, calcium, aluminum

Phite body uses a silicon carbide layer thereby on miniums, titanium, zirconium, hafnium

spend that in a mixture of silicon and the heat treatment at one temperature

carbide, titanium carbide, zirconium carbide, hafnium between 700 and 1200 ⁰ C, preferably 800 and

carbide and tantalum carbide and silicon metal or HOO ⁰ C carried out.

Silicon dioxide powder embedded and there on a 60 It has proven to be particularly useful

very high temperature in the range between 1500 the body to be coated after the coating

and heated to 2200 ° C. A disadvantage of this conversion treatment in a carbon or nitrogen

Driving is in particular the need for the short-term and / or oxygen-containing atmosphere

use of very high temperatures. to be heated to 500 to 1000 ° C, whereby the metal

Furthermore, there are processes for coating 65 lische surface in a metal compound with

in particular, consisting of iron or steel, carbon, nitrogen and / or oxygen

pern with diffusible metals such. B. silicon, is leading. If necessary, the coating

Titanium, zirconium, vanadium, niobium, tantalum, chromium, treatment can be repeated one to three times.

3 4

The invention is based on the knowledge that all open pores close to the edge up to a depth

when heating powder mixtures according to which about 3.5 mm are completely covered with niobium.

Invention of intermediately formed volatile metal The plates have an uptake of niobium

halides not only appear on the surface of carbon - 7.6 ± 1 percent by weight.

material or graphite bodies with the deposition of 5 For use in chlor-alkali electrolysis

Metals are thermally decomposed, but to some extent the plates are then still with an approx

penetrate into the pore system of this body and 0.5 μm thick activation layer made of ruthenium

Metal is deposited on the pore walls - provided as follows:

The metal phase extending into the pores is The already metallized plates become one-sided

works without alloying with the base body io with a thin coat of 0.5 weight percent

a firm anchoring of the superficially deposited- Ru + 2.5 weight percent ZnCl ₂ + 97 weight-

those layers of metal. percent SiO ₂ , suspended in Zapon varnish, provided,

The advantages of the invention exist in particular then up to 110 ⁰ C in the heating cabinet.

in that firmly adhering layers of silicon and / dries and finally in stacks in a ceramic

or transition metals from IV. to VHI. Group xs mixed bonded silicon carbide container with SiO ₂

of the periodic table of uniform thickness poured under and in a vacuum at 10 Torr up to

Heated at relatively low temperatures and a small 800 ° C for 1 hour. Following this procedure are

Apparatus expenditure on carbon or graphite the graphite plates with an approximately 20 μm thick

body can be applied. Niobium base layer and an approximately 0.5 μm thick

To further explain the invention, 20 Ru top layers can be provided very evenly,

the embodiments described below. .

to serve. Example J

Titanium silicide coating of graphite electrodes

Example 1 for steelmaking

Zirconium coating of graphite _{tubes a5} The coating of graphite electrodes with

for reactor purposes 500 φ 2100 mm takes place in such a way that the shape

For coating the inside of graphite tube bodies in steel containers with a bed of

50/40 φ 1500 mm these are mixed with a mixture of 10 weight percent Ti, 20 weight percent Si, 2.5 Ge

of 20 percent by weight zirconium (<100 μΐη), percent by weight Na ₃ AlF ₆ , 2.5 percent by weight ZnCl ₂ ,

2.5 percent by weight ZrCl ₄ , 77.5 percent by weight 30 65 percent by weight Al ₂ O ₃ in a layer thickness of

ZrO ₂ (<40 to 150 μτη) filled, then both 50 mm poured. The ones packed on bogies

on both sides with caps and then in a container with a thickness of about 150 mm

a steel vat packed with coke. Covered in coke soot and then inside

closing the tub is in a ⁰ to 1000 C for 8 hours up to HOO ⁰ C in a tunnel furnace

standing argon protective gas furnace inserted and heated 35. The bodies treated in this way point to the

Maintained at temperature for 4 hours. After that, the plating has a layer thickness of 30 μm, with

Tubes on the inside over the entire length with about 5 mm of the near-surface pores completely

a very even zirconium layer one lined with titanium silicide.

Thickness of 15 to 20 μm coated. The layer is _R,. . .

up to a depth of 2mm in the wall of the 40 example 4

Pipes anchored. Titanium coating of graphite rods

. . The rods are in a cylindrical graphite

For example, 2 containers with a distance of 10 to 15 mm

Niobium coating of graphite anodes of a mixture of 30 percent by weight titanium (20 to

for the chlor-alkali electrolysis _4S 100 μπι), 30 percent by weight Al ₂ O ₃ , 60 to 150 μΐη,

For the all-round coating of graphite plates 40 percent by weight SiC, 60 to 150 μΐη poured 10 · 250 · 50 mm, these are placed in a brick-built and then in a bogie bogie container preheated to 400 ° C vertically with a vacuum furnace. The furnace is then evacuated from 10 mm in a mixture of 50 weight to 80 to 90 Torr and heated to 1000 ° C on percent Nb (20 to 100 μm), 7.5 weight percent 50. As soon as the temperature and the vacuum er-ZnCl ₂ + 42.5 percent by weight SiC (40 to 150 μm) is sufficient, _{TiCl 4 is} packed into the furnace via a valve. The bogie is then blown into the room for 2 hours, the pressure being kept between 140 and 160 Torr when the oven has already been preheated to 500 ° C. After this treatment and then under argon in 5 hours up to 850 ° C., the furnace is cooled and heated under argon. After a dwell time of 6.5 hours, the rods have a very smooth α-titanium layer with a thickness of 55 mm after the reaction plating. At this temperature the furnace is switched off and the material is cooled down in it. After unpacking 40 ± 10 μπι on. The titanium deposition is sufficient as a result of the plating mixture, the plates have one of the previous evacuations to a depth on all sides niobium coating, the walls from 20 to 25 mm.

Claims (3)

1 2 Molybdenum and tungsten become known, according to patent claims: which the body to be coated in a metal or metal compounds, halogens and given 1. Method for applying a layer of packing containing refractory inert substances, silicon and / or transition metals of the range to 5 are heated. According to U.S. Patent 1,893,782 Vm. Group of the periodic table on the body it is known, for example, to cast iron workpieces in a powder pack made of carbon or graphite, characterized by 5% ferrosilicate, 3% ferric chloride and 92% quartz, that the sand to be coated is kept at 650 to 950 ° C Body to be heated in 0.5 to 50 ^e / o of the amount to be applied, whereby firmly adhering Le metal, 40 to 98% inert substance with a melting alloy layer on the base metal is formed by diffusion above 1500 ° C and 2 to 8 ° / o fleeting the. In carbon and graphite, the powder mixture containing diffusion metal halides is embedded in the proposed speed of metals and then extremely small in an inert atmospheric temperature range, and the sphere or in a vacuum to a temperature formation of between 800 and 1200 ° C for the adhesion of the coating layers be heated. 15 essential alloys are not known 2. The method according to claim 1, characterized in that the invention is based on the object of providing carbon marks, that powder in grain sizes of material or graphite body is used while avoiding the 20 to 150 to. Disadvantages of the above known methods 3. The method according to claim 1 and 2, characterized with firmly adhering and dimensionally accurate metal layers ? V characterized in that provided as 20 in the powder mixture. Metal halide zinc chloride is used. The object is achieved according to the invention by that the body to be coated in a 0.5 to 50% of the metal to be applied, 40 to 98% inert substance with a melting point above 1500 ° C and 25 containing 2 to 8% volatile metal halides Powder mixture embedded and then in The present invention relates to a method in an inert atmosphere or in a vacuum to a temperature for applying a layer of silicon and / or heated between 800 and 1200 ° C.
Transition metals of the IV. To VIII. Group of According to a preferred embodiment of the procedural periodic table on bodies made of carbon or rene according to the invention, the powder is used in grain graphite, sizes from 20 to 150 .mu.m. As a metal Coating bodies of carbon halide in the powder mixture is preferred or graphite with, for example, silicon or super-zinc chloride is used. transition metals from IV. to VI. Group of the period - As metal halides are used in the powder system, z. B. titanium is known. For example, there is a mixture of chlorides and / or iodides of sodium, wise the coating of graphite with titanium so far potassium, aluminum, zinc, lead, cadmium, tin, usually through thermal decomposition of titanium-cerium, titanium, zirconium, chromium, manganese, iron, an iodide or by reducing titanium chloride with one or more. As chlorides and / or iodides Hydrogen gas at high temperatures. The gas can be used in particular double salts, reaction or pyrolysis has the well-known disadvantage pyrolytic process that they are with considerable- preferably oxides, nitrides or carbides of the elements Lich equipment expenditure is connected, that silicon, magnesium, calcium, aluminum, titanium, Relatively high temperatures are used zirconium, hafnium, individually or in groups and that it turns due to differences in concentration.