DE3003186C2 - Use of diffusion welding to join components made of silicon composite materials - Google Patents

Description

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The invention relates to the use of dts diffusion Jchwcißens for the connection of components made of siliuumin " filtered silicon carbide or reaction-bonded silicon carbide

Infiltrated b / w. Reaction-bonded silicon carbide is a ceramic composite made of silicon carbide (SiC) and metallic silicon (Si). The proportion of metallic 5i is up to ω JO volume percent

The dimensions of ceramic components are set by the manufacturing process Grerräeri, so that complex or large parts have to be assembled from several smaller parts. ^6ä If component connections are made in ovens, DE-OS 26 27 993, the dimensions of the workpiece are limited by the oven geometry, which cannot be expanded at will. Technological processes that provide very good material properties, e.g. B. hot pressing are limited to relatively simple shapes. Complicated parts require extensive and costly rework, so that it makes more economic sense. to assemble a complicated component from simple towered components.

The requirements for the connection point are mechanical strength. Pore-free, gas tightness and corrosion resistance, especially oxidation resistance. The total strength of a joined component depends on the weakest point, so that the Connection point should achieve approximately the same strength as the material to be connected.

The strength of ceramics depends heavily on its porosity. so that the junction is possible should be pore-free. In addition to the strength, the gas tightness of the connection point also depends on it Porosity. so that in gas-tight connections extensive freedom from pores must be achieved.

To a joined component the advantages of the material to be able to use it accordingly, it is also necessary that the materia! has the same corrosion resistance as the base material at the joint.

The manufacture of ceramic-ceramic joints poses problems. which are based on specific ceramic properties Ceramics are brittle Material that has practically no plastic deformability even at high temperatures.

As a result, the coefficient of thermal expansion of the connecting material must carefully match that of the ceramic to be connected, otherwise the connection line will be destroyed when the temperature changes will

Ceramic materials often have very high melting points or they decompose before they reach the Melting point such as / B silicon carbide so that a Connection via the melting phase is mostly eliminated.

The ThermosthoLkbcsi.'ndigki ι 'of ceramics is lower than that of metals so that connecting odor nikcn. where M.irke local material · · ™ reinforcements step in, leave.

Ceramic compounds with organic and inorganic Glues only achieve relatively good strength and are not at high temperatures resistant

llochteinpcra'urklcber, iiif ceramic R; isi ·. beh.il th their strength aueh at high temperatures, but are in thermal \ usdehniingskocffizicnten not arbitrarily and independently '.cn iercn to-Fjgenschatten varied and mostly rviros Weger ^one of these properties, they are conditioned from above ovate very applicable

Smelting / welding processes are included due to the resulting thermal loads and the necessary high temperatures from the above-mentioned green not applicable

Various Kera mik metal compounds developed, but mostly the Zje | serve for electrical contacting. Examples are molybdenum / manganese metallization From alumina ceramics, the noble metallization of Zirconium oxide and platinum for oxygen flow probes or the electrical contacting of ceramic capacitor Ren with silver-containing stoving pastes, this process creates a well-adhering, oilable metal layer produced on the ceramic.

One based on this rr.i * .ip. Ceramic-ceramic connection would be produced using a metallic solder, which, however, meets the requirements listed above would have to correspond.

All listed methods are not suitable for high temperature resistance. gas-tight and oxidation-resistant Establish connections between SiC ceramic parts.

The invention is based on the object of a method for joining parts made of silicon carbide to create, whereby the connection is mechanically stable, temperature-resistant to MOOT, gas-tight, temperature change-resistant and resistant to corrosion, especially oxidation should be.

According to the invention, this object is achieved by the ^{] 1} application of diffusion welding to produce gas-tight, mechanically stable up to approx. 1400 C, more resistant to temperature changes and corrosion. in particular oxidation-resistant connections of components made of silicon-infiltrated silicon carbide or reaction-bound silicon carbide dissolved.

From DH-OS 27 35 934 it is known to produce electrically conductive and gas-tight connections of ceramic components by means of diffusion welding, but the materials ² 'mentioned there have a different composition, so that this teaching cannot easily be transferred to SiC ceramic parts . The technique of diffusion welding from Rügen is very general. Welding technology manual. 1974. Page 327 known. ^

In the method according to the invention, the surfaces of the connecting parts are polished, placed one on top of the other and brought under pressure perpendicular to the connecting surface. Dutch use of high temperatures (max. 1300 C) over a longer period of time (max. 5 h) the workpieces are diffusion welded. Silicon carbide oxidizes in air at high temperatures. In this case, the surface forming an SiO> -.. .Not S (, occur only extremely slowly in the diffusion processes, since such diffusion-inhibiting layers make the process unmog- ⁴ⁿ borrowed, it must be run under vacuum or inert gas.

Since this method works without any intermediate layers, the properties of the SiC material are fully retained. However, ⁴ 'a very good surface quality is necessary, which requires a complex machining of the workpieces.

One embodiment of the invention is the use of diffusion welding in the form of a reaction · '" Welding process using an intermediate layer located between the components. The implementation also takes place under pressure at high levels Temperature as described above. The intermediate layer increases the surface roughness of the the end surfaces balanced, so that the surface quality does not have to be as high as with the pure diffusion welding process without an intermediate layer.

Since the intermediate layer can not be made arbitrarily thin, the properties of the ^{h (1} Zwischenschichtmatcrials affect the Cicsamteigcnschaften of the grooved member.

Not every fyletall can be used as an intermediate layer, e.g. titanium, vanadium, iron; cobalt or nickel attack silicon carbide and destroy the ^fc5 material. In addition, the interlayer material must be firm when the temperature is applied. Metallic silicon canvas with or without the addition of boron and aluminum can be used as the intermediate layer. It is also possible to use a mixture of silicon powder and colloidal carbon.

According to the invention, several options can be implemented for applying the intermediate layer:

- The powder of the composition described above is in an organic solvent and slurried an oily substance and applied the suspension with a paint spray process;

- The parts to be connected are in a silicon solution or a silicon solution in which colloidal carbon is slurried, submerged. After drying, the silicon compound thermally decomposed in the absence of oxygen, creating a very finely divided metallic Silicon is formed;

- silicon layers can be vapor deposited;

- Silicon layers can be wound on;

- Silicon layers can be deposited electronically will.

The generation of the necessary for the connection Heat is possible in different ways:

- The connection point is heated inductively with an HF coil, the geometry of which has been selected in this way is that the heat coupling is concentrated on the connection point. Taking advantage Due to their electrical conductivity, the SiC components can act as a susceptor, or it becomes a Graphite susceptor used.

- The connection point is heated by a resistance-heated oven.

- The connection point is heated by hot protective gas.

- The heating is done directly by resistance heating. The tension is applied to the parts to be connected created. The current flow and thus the heating takes place only at the contact points the connecting surfaces instead.

The advantages of the method according to the invention are

- in the ease of implementation

- and in the good properties of the joint.

The process provides mechanically very stable, helium-tight compounds. The maximum appl The working temperature of the joined component is the same wL * that of the base material and is not influenced by the Connection point limited. The connection point shows the same good resistance to temperature changes like the base material. The connection point has the same oxidation behavior as the base material.

Embodiments of the invention are given below explained in more detail with reference to figures. It shows

F i g. 1 a diffusion welding system for joining of components made of silicon-infiltrated Siüciumcar ^ bid or reactive silicon carbide;

F i g. 2 a composite of tubes made of reaction-bound Siüciümca'-bid, and

3 shows a micrograph of a connection point according to the invention.

Fig 1 / eigt a diffusion welding system 2 / ur Production of a connection of two tubes 4 made of reaction-bonded SiIu uimcarbid, which consists of a Cicüst 6, base plate 7. Cover plate 8, a hydraulic cylinder 10 with piston rod II, a quartz tube 12 and an HF heater 14 viewed. The quartz tube surrounds the tubes 4 cylindrically and has the windings of the HF heater 14 on its jacket. Of the Room 16, in which the tubes 4 are on one with the Piston rod II connected punch 17 are located gas-tight and is operated by means of a vacuum pump (not shown) arranged at flange (8) pumped empty.

Fi g. 2 shows a composite of reaction-bound Silicon carbide tubes 4.

3 shows a micrograph of the connection point in different enlargements. The dark phase is Silicon carbide, the light phase silicon. The connection is made over silicon and the seam is completely pore-free.

Example I.

The tube sheets 20, 22 of two tubes 4 (outside diameter 50 mm, inside diameter 40 mm) made of reaction-sintered silicon carbide are ground and lapped. Then they are placed on top of one another and loaded with the help of the punch 17 with an axial pressure of 400 bar. The tube 4 be heated inductively, wherein the Versuchslempcratur! Is 300 ⁰ C and the test data is ν 6 hours. The diffusion welding is carried out at a vacuum of 8.10-'mbaf.

Example 2

Connection of tubes made of reaction-bonded silicon carbide with an external diameter of 42.6 mm and an inner diameter of 29.7 mm.

The pipe surfaces to be connected were ground with diamond grinding tools of grain sizes 65 and 20 μm and lapped with diamond brushes of grain size Ii 15, 7, 3 and I μm. The roughness depth was measured with the Perthomeier R _a = 0.10 μm, R ₁ = 1.32 μm and R ₁ = 0.28 μm.

The tubes were placed on top of one another with the machined end faces and pressed together with an axial pressure of zn 400 bxif. The sample was inductively iruigeneizi And the Versuchstemperaiüf ³ was 1200 C for a test duration of 2 hours, the operation took place under a vacuum of 8 · ⁵ I0'- mbarstatt.

The pipe assembly was mechanically stable and r> helium-tight.

For this purpose 3 sheets of drawings

Claims (11)

Patent claims: 1. Application of the Diffubionsscbciüens for Production of gas-tight up to approx. 1400'C mechanically stable, temperature change resistant and corrosion, in particular oxidation-resistant connections of components made of silicon-infiltrated Silicon carbide or reaction-bonded silicon carbide. 2. Development of the method according to claim 1, characterized in that the diffusion welding in the form of a reaction welding process is carried out using an intermediate layer located between the components. 3. Formation of the method according to claim 2, characterized in that an intermediate layer made of silicon or a metallic alloy containing silicon is used. 4. Formation of the method according to claims 2 and 3, characterized in that a Interlayer made of silicon with additions of boron or aluminum is used. 5. Formation of the method according to claim 2, characterized in that an intermediate layer a mixture of silicon and colloidal carbon is used. 6. Training of the method according to claims 2 to 5, characterized in that the Intermediate layer is sprayed on in powder form. 7 training of the method according to claims 3 and 5, characterized in that the In between, a dissolved silicon compound is applied by thermal decomposition. 8. Training of the method according to claims 2 and 3 thereby, gek-nnzeichnci. that the Interlayer is applied by sputtering q. Training of the method according to the claims Chen 2 and 3. characterized in that the intermediate layer is applied by vapor deposition will. 10. Training of the method according to claims 2 and 3, characterized in that the Interlayer is applied by electrolytic deposition. 11. Training of the method according to claims Chen I to 10. characterized in that the for Connection necessary heat through Sirom passage through the junction, so d'irch Resistance heating is generated. 2 "