WO2013045306A1

WO2013045306A1 - Laser soldering of silicon carbide-based materials for the production of ceramic parts

Info

Publication number: WO2013045306A1
Application number: PCT/EP2012/068295
Authority: WO
Inventors: Andreas Kienzle; Tanja Damjanovic; Albin Von Ganski; Blasius Hell
Original assignee: Sgl Carbon Se
Priority date: 2011-09-30
Filing date: 2012-09-18
Publication date: 2013-04-04
Also published as: DE102011083865A1

Abstract

Disclosed is a method for producing a part from ceramic workpieces, comprising the steps of: a) placing plate-shaped ceramic materials in defined positions in one or more crucibles or in defined positions on one or more frames, the edges being placed side by side in such a way that a defined gap is created between the plates; b) covering the entire area of the gap with a solder and then drying the solder; d) reactive soldering using a defined beam diameter, both the gap and the region of the edges of the plate-shaped ceramic materials being evenly covered.

Description

Laser beam Necessity of silicon carbide based materials for the production of ceramic components

The invention relates to a method for laser beam soldering for the production of ceramic components.

The technical field of the invention can be referred to as reactive soldering, that is to say that temperatures of more than 1200 ° C. are used, which makes it possible to use the composite produced where the

Temperatures, for example, exceed 900 ° C and go up to 1600 ° C or even beyond.

Due to the high temperatures - for example, around 1000 ° C - which may be exposed to ceramics such as SiSiC, the production of ceramic components by adhesion with organic products is excluded.

The state of the art is to process SiSiC ceramics by means of laser cutting. Thermal ablation with laser beams is defined as separation of material particles by heat processes, whereby heat is converted by energy conversion during the heat treatment

Occurrence of a laser beam on the workpiece arises. With lasers, a treatment is possible regardless of the material hardness, with no wear on the material. The focus of laser applications in the machining of

Ceramics is in the separating processing of plate-shaped or thin-walled curved workpieces. In addition to this separating processing, the

Laser treatment the possibility of material removal from the surface without complete cutting of the workpiece.

Since silicon carbide does not form its own melting phase, the classic

Bonding techniques that work with or without welding consumables (TIG, electron or laser welding) and imply a partial melting of the parts to be joined, not usable for the removal of critical defects of silicon carbide based materials because a ceramic substrate or part can not be melted can and in particular the SiC decomposes before melting. Therefore, a cohesive joining method as in the oxide ceramics, in which the parts to be joined are locally melted in the seam area, not possible.

As a result, solid-phase diffusion bonding, sintered bonding, and reactive soldering are currently the most common techniques for refractory bonding of ceramics.

Diffusion bonding in the solid phase as well as the sintered joining technique have the disadvantage of being problematic in terms of their performance.

In contrast, the LSI process (Liquid Silicon Infiltration) is characterized by short process times and low production costs.

When realizing a connection between ceramics particularly important to limit the residual stresses that occur during cooling due to

develop different coefficients of thermal expansion of the parts to be joined, if they are of different types, but also between the ceramic and the solder, if the two ceramics are of the same kind. For this reason, the thermal expansion coefficient of the solder must be very close to that of

Corresponding ceramic parts correspond.

It is therefore the task of finding a new method for cohesive soldering of ceramic components. A mechanically strong,

Corrosion and high temperature resistant compound of similar or identical material from the solder to the surrounding structure are guaranteed with localized energy input.

This object is achieved by a method for producing a component from ceramic workpieces with the following steps: a) placing plate-shaped ceramic materials in defined positions in one or more crucibles or in defined positions on one or more racks, the edges are placed against each other so that a defined gap

(Length, width, depth) between the plates,

b) Full-surface coating of the gap with a solder and then

drying,

d) reactive soldering with a defined beam diameter, wherein both the gap and the region of the edges of the plate-shaped ceramic materials are uniformly covered with solder.

The reactive soldering takes place cohesively with supply of silicon carbide powder or a mixture of Si, C and SiC powder. In order that the coefficient of thermal expansion of the solder is almost equal but slightly higher than that of the silicon carbide, the

Silicon content should not exceed the value of 97%, expressed as atomic percentage. A method using solders whose atomic percentages are within the above-mentioned range is easy to apply because these compositions have very good wetting and adhesion properties to SiC. The solder composition itself is not expensive, because it contains no expensive elements. The soldering is preferably carried out with the laser in the free atmosphere or, if necessary, in a protective gas atmosphere.

Preferably, the plate-shaped workpieces have a thickness of 3 to 15 mm.

The surface of the crucible facing the plates is preferred before

Laying the plate-shaped ceramic materials coated with a BN suspension.

Preferably, the crucible or frame (s) are made of graphite.

The gap between the plates preferably has a distance of 0.1 mm to 1 mm.

Preferably, a continuous or a pulsed laser for reactive soldering or a combination of the two laser modes is used. It is preferable that a CO ₂ laser or a Nd: YAG laser or a combination of the two laser sources is used for reactive soldering.

Preferably, the soldering with a laser in the free atmosphere or in

Protective gas atmosphere carried out.

The laser used is preferably a short-pulse laser with a pulse time of less than 10 ps and a focus diameter of 20 μm.

Preferably, the defined beam diameter is 1 to 10 mm.

Preferably, no pretreatment of the ceramic material, except for mechanical preparation of the joining surfaces, such as degreasing or

Dusting the ceramic material.

The solder composition used is preferably a compound or elements such as SiC and / or Si and / or C contained in the ceramic base material.

The solder composition preferably consists of SiC and / or C and / or Si in an amount of from 5 to 95% by weight of SiC and / or C and / or Si, based on the weight of the solder composition, and is in a form consisting of a powder, grains, pieces, particles, a fabric, a nonwoven, a felt or a

Foam can exist.

Preferably, a powder of a solder composition is formed, this powder is treated with an organic binder in suspension or pasty form and the sections or edges of the molded body to be soldered are coated with the resulting suspension.

The powder of the solder composition is preferably processed into compacts and locally melted by the action of lasers on the parts to be soldered. In reactive soldering, preference is given to using nitrogen or compressed air as purge gas or inert gas such as argon or helium as protective gas.

Preferably, in reactive soldering, a temperature of at least 1200 ° C is achieved by the laser light at the plate edges and in the gap.

Preferably, the soldered parts are detachable again.

Particularly preferably, the plates are firmly bonded by reactive soldering with a SiSiC layer.

It is preferred that the silicon carbide-based materials are selected from unpressurised silicon carbide ("PLS-SiC"), silicon-infiltrated silicon carbide

Silicon carbide ("SiSiC" or "RBSC"); porous recrystallized silicon carbide ("RSiC"), graphite silicon ("C-SiC"), which consists of graphite and is coated with a layer of SiC; the SiC / SiC composites, for example with fibers or whiskers; the C / SiC composite materials, for example with fibers or whiskers of carbon and with a SiC matrix; the SiC monocrystals; SiC composites with another ceramic, such as SiC / Si3N and SiC / TiN composites.

Preferably, the silicon carbide-based materials have one

Silicon carbide content greater than or equal to 80 wt .-% to.

The silicon carbide-based materials are preferred for the production of ceramic moldings for the automotive industry, the construction of air and

Spacecraft and used for furnace construction.

example 1

Preparation of the mixture of the solder

In an Eirich intensive mixer 400 g of Si powder (average particle size 100 μιτι) 300 g SiC powder of grain size F 360 (particle size d50: 22.8 ± 1, 0 μηη), 200 g of powder the granulation F 600 (particle size d50: 9.3 ± 1, 0 μηη) and 240 g powder of grain size F 1200 (particle size d50: 3.0 ± 0.5 μηη), and 50 g of a graphite powder of average grain size 30 μηη given and homogenizing the mixture at a swirling speed of 200 rpm for 5 minutes and then at 1200 rpm with the addition of 300 ml of ethanol and 10 ml of paraffin oil. The thereby forming plastic ethanol wet mass is transferred to a container with a lid.

Example 2

Connection of the ceramic workpieces

The prepared and degreased plate-shaped ceramic workpieces of a thickness of 15 mm are placed in a crucible made of graphite. The surface of the crucible facing the plates was previously coated with BN suspension to prevent subsequent sticking by molten silicon. The cleaned edges are put together so that there is a gap of 1 mm between the plates. In this gap is now the produced solder

Filled in layers. It is important to ensure that no air bubbles are included. The gap is covered by approx. 1 mm and then dried at RT in air. By means of a CO ₂ laser of wavelength 10.6 μιτι is under a protective gas atmosphere and a maximum power of 700 W is aligned with a beam diameter of 3 mm so that it covers both the gap and the region of the edges of the plates evenly with one millimeter. The laser light reaches a temperature> 1420 ° C in the plate edges and in the gap and it comes to the melting of the silicon, the simultaneous onset of reaction of silicon with carbon in an exothermic reaction to form SiC. Due to the additional heat which is formed by the reaction, heating also takes place in the depth of the gap and the plate edges. This reactive soldering makes the plates SiSiC

Layer firmly connected.

Claims

claims

1 . Method for producing a component from ceramic workpieces with the steps:

a) placing plate-shaped ceramic materials in defined positions in one or more crucibles or in defined positions on one or more racks,

the edges are laid together so that a defined gap is created between the plates,

b) full-surface coating of the gap with a solder and subsequent drying,

d) reactive soldering with a defined beam diameter, wherein both the gap and the region of the edges of the plate-shaped ceramic materials is uniformly painted over.

2. A method for producing a component from ceramic workpieces according to claim 1, characterized in that the plate-shaped workpieces have a thickness of 3 to 15 mm.

3. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the surface of the crucible, which faces the plates, is coated before depositing the plate-shaped ceramic materials with a BN suspension.

4. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the one or more crucibles or the frame (s) are made of graphite.

5. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the gap between the plates has a distance of 0.1 mm to 1 mm.

6. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that a continuous or a pulsed laser or a combination of the two laser modes is used.

7. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that a CO ₂ laser or a Nd: YAG laser is used for reactive soldering.

8. The method according to one or more of the preceding claims, characterized in that a short-pulse laser with a pulse time less than 10 ps and a focus diameter of 20 μιτι is used as the laser.

9. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the defined beam diameter is 1 to 10 mm.

10. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that no pretreatment to mechanical

Preparation of the joining surfaces or degreasing or dedusting of the ceramic material takes place.

1 1. Method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that a solder composition with additives contained in the ceramic base material SiC and / or Si and / or C is used.

12. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the solder composition of SiC and / or C and / or Si in an amount of 5 to 95 wt .-% SiC and / or C. and / or Si, based on the weight of the solder composition and in a form which may consist of a powder of different particle sizes, fabrics or a foam.

13. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that a powder of a defined solder composition is formed, this powder with an organic binder in

Suspension or pasty form is prepared and the sections or edges of the molded body to be soldered are coated with the resulting suspension.

14. The method according to one or more of the preceding claims, characterized in that the powder of a solder composition is processed into compacts and locally melted by the action of lasers on the parts to be soldered.

15. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the reactive soldering as purge gas nitrogen or compressed air or inert gas as a noble gas is used.

16. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the reactive soldering a temperature of at least 1200 ° C is achieved by the laser light at the plate edges and in the gap.

17. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the soldered parts are releasable again.

18. A method for producing a component from ceramic workpieces according to one or more of the preceding claims, characterized in that the plates are fixedly connected by the reactive soldering with a SiSiC layer.

19. A method of manufacturing a component according to one or more of the preceding claims, characterized in that the silicon carbide-based materials are selected from unpressurised silicon carbide ("PLS-SiC"); silicon-infiltrated silicon carbide ("SiSiC" or "RBSC") porous recrystallized silicon carbide ("RSiC"); Graphite silicon ("C-SiC") made of graphite and coated with a layer of SiC; the SiC / SiC composites, for example with fibers or whiskers; the C / SiC composites, for example with fibers or Carbon and SiC whiskers, the SiC single crystals, the SiC composites with another ceramic, for example SiC / Si3N and SiC / TiN composites.

20. A method for producing a component according to one or more of the preceding claims, characterized in that the silicon carbide-based materials have a silicon carbide content greater than or equal to 80 wt .-%.

21. Use of silicon carbide based materials treated according to

Claim 1 for the production of ceramic moldings for the

Automotive engineering, the construction of aircraft and spacecraft as well as for furnace construction.