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AU686320B2 - Soldering of high-temperature joints in solid-electroltye high-temperature fuel cells - Google Patents
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AU686320B2 - Soldering of high-temperature joints in solid-electroltye high-temperature fuel cells - Google Patents

Soldering of high-temperature joints in solid-electroltye high-temperature fuel cells Download PDF

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Publication number
AU686320B2
AU686320B2 AU16306/95A AU1630695A AU686320B2 AU 686320 B2 AU686320 B2 AU 686320B2 AU 16306/95 A AU16306/95 A AU 16306/95A AU 1630695 A AU1630695 A AU 1630695A AU 686320 B2 AU686320 B2 AU 686320B2
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Australia
Prior art keywords
chromium
temperature
high temperature
weight
hard solder
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Ceased
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AU16306/95A
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AU1630695A (en
Inventor
Johann Eiter
Thomas Huber
Wolfgang Dr Kock
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Plansee SE
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Plansee SE
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Publication of AU686320B2 publication Critical patent/AU686320B2/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Description

OF HIGHEPE2wFruRE IOImTrs (0 5OLIO ELECTRLLYTE HIGH- TEMPErr-mee~. FuEL CELLS The invention relates to a hard solder for high-temperature soldering operations for joining high temperature-resistant materials, especially chromium and alloys based on chromium.
Known solders for the hard soldering of such materials are hard solders such as zirconium, titanium, vanadium, or hard solders based on nickel, with up to about 20% by weight chromium content, and up to about 4% by weight boron and/or silicon content, which are used especially for soldering chromium or alloys based on chromium. In addition to boron and/or silicon, the last-mentioned solders may contain low contents of molybdenum and/or iron as well.
Said solders based on nickel are manufactured from powders, using a special melt-metallurgical process (melt spinning) for producing such solders in the form of amorphous foils, such solders being referred to as "rapidly solidified filler metals". The boron and/or silicon components in the solders .serve the purpose of lowering the melting point, on the one hand, and of enhancing the wettability of the solder on the other hand.
-1- It is a drawback in connection with the above process that in the soldering process, the boron and/or silicon components cause the formation of intermetallic phases with undesirable hardness values or insufficient strength to some extent. Furthermore, because of their low chromium content, the known solders have a melting point of about 1200°C at the most, which is often inadequate in many application cases.
SChemical Abstract 103-11394c describes the use of an Ni-Cr-alloy with up to 44% by weight chromium component for melting down porcelain in dental prosthetics. Chemical Abstract 108-60867w describes the use of an Ni-Cr-alloy with up to 50% by weight chromium component for objects Sthat are exposed to corrosive stress. The use of such alloys as solder material for high-temperature soldered joints is not disclosed in said two earlier publications.
Chemical Abstracts 119-165908, 114-231119j, 112-1,22117v and 120-251017b describe solder alloys based on Ni-Cr, with a maxium chromium content of 30% by weight. Such solder alloys, however, are only insufficiently suitable for high-temperature soldered joints of objects consisting of chromium, or of alloys based on chromium.
-2- 3 Therefore, the problem of the present invention is to make available a process for soldering high-temperature soldered joints, in solid-electrolyte hightemperature fuel cells with a hard solder which, during the soldering process, does not cause any formation of embrittling intermetallic phases, and which permits the soldered materials to be exposed to operational temperatures of at least up to 13000C.
Accordingly to the invention, this is accomplished in that the hard solder consists of 40% to 70% by weight chromium, up to 2% by weight of one or several metals selected from the group of vanadium, niobium, tantalum, titanium, zirconium and hafnium, up to 2% by weight of one or several metals and/or their oxides selected from the group of rare earths and yttrium, as well as nickel as the balance.
It comes as a complete surprise that the solder employed according to the invention excellently wets the materials to be joined even without any boron and/or silicon components, and exhibits a well-controllable flow of the solder, which prevents the solder from exiting from the soldered gap, and consequently avoids reworking of the parts joined by soldering. The solder is particularly suitable for joining chromium or chromium-containing materials. However, other o: high-temperature-resistant °o «o materials, and particularly high-melting metals such as tungsten or molybdenum, graphite, and also ceramic materials such as SiC, TiC, TiB 2 and the like are highly suitable as well for being joined by soldering with application.of the solder according to the invention.
In addition to said properties, the solder according to the invention exhibits high ductility, good thermal and good electrical conductivity, as well as excellent resistance to corrosion.
By using one or several of the metals selected from the group of vanadium, niobium, tantalum, titanium, zirconium and hafnium in amounts of up to 2% by weight, the ductility of the solder can be enhanced further without any notable negative influence on the other good properties.
An improvement of the solder with respect to its resistance to corrosion caused by hot gases is achieved by adding rare earths, yttrium and/or their oxides in amounts of up to 2% by weight.
A solder with 50% by weight chromium, the balance nickel has been found to be particularly advantageous.
-4- ILi cp~ Preferably, the solder is used in the form of thin foils with a sheet thickness between 50 and 200 pm..
Advantageously, the foils are manufactured by powdermetallurgical processes. In a particularly preferred process, a compact is produced by mixing, pressing and sintering of the powdery starting materials. Subsequently, the compact is encased airtight and the encased compact is hot-rolled to a sheet thickness of approximately 2 mm. Following removal of the encasing material, the sheet is cold-rolled to the Sdesired sheet thickness. In addition to the sheet form, the solder according to the invention can be manufactured in the S form of wire as well. The solder according to the invention has been successfully used especially for soldering parts in solid electrolyte, high-temperature fuel cells (SOFC fuel cells).
SWith such fuel cells, a ceramic solid electrolyte based on Zr02 is used, which is connected to metallic electrodes on both sides, whereby oxygen is supplied on one electrode and the fuel on the other. In addition to hydrogen, hydrocarbons are suitable fuels for SOFC fuel cells as well.
In the manufacture of SOFC fuel cell'modules, several seriesconnected fuel cells which are arranged one flat on top of the other can be interconnected by way of so-called bipolar plates, whereby the bipolar plate electrically conductively connects the cathode of the one cell to the anode of the adjacent cell.
Alloys based on chromium are used as the preferred materials for the bipolar plates, but also for other components of the high-temperature fuel cells. The individual parts of such fuel cells are advantageously joined with each other by soldering, whereby the solder is expected to meet a great number of different requirements. For example, the solder has to exhibit good thermal conductivity and good electrical conductivity; the coefficient of thermal expansion has to be as close as possible to the one of the ceramic electrolyte and of the metallic parts; and most of all, it has to be resistant to corrosion vis-a-vis the hot gases such as air and hydrogen, as well as hydrocarbons.
The solder according to the invention satisfies each one of said properties in an excellent way, so that it is especially suitable for said special case of application.
The invention is explained in greater detail in the following on the basis of examples.
-6- EXAMPLE 1: For the manufacture of a bipolar plate for a high-temperature fuel cell, several sheets with the dimensions of 200 x 200 mm and a sheet thickness of 2 mm and consisting of a chromium alloy with 5% by weight iron and 1% by weight yttrium oxide were joined flat with each other, using the solder according to the invention. For this purpose, the sheets were cleaned in the ultrasound bath. Thereafter, the soldering structure was arranged, using three sheets arranged one on top of the other and with solder foils consisting of 50% by weight nickel and 50% by weight chromium and with a layer thickness of 0.075 mm arranged between each two sheets. The soldering structure was loaded with weights, about 20 to 40 g/cm 2 and charged in a soldering furnace. Soldering was carried out in a hydrogen atmosphere. The soldering furnace was heated within 2 hours and 30 minutes from room temperature to 1350 0 C, and maintained at the latter temperature for 5 minutes. Subsequently, cooling to room temperature took place within 3 hours. A nondestructive testing of the soldered composite showed a flawless condition of the soldered joint between the individual sheets. No solder material had exited from the soldering gaps, so that no reworking of the bipolar plate was required. A bipolar plate so produced was installed in an SOFC-fuel cell and tested. After the fuel cell had operated about 1000 hours, no cracks of any -7type or negative effects of corroding influences were found on the bipolar plate.
EXAMPLE 2: For the manufacture of a solder foil with the composition by weight chromium, the balance nickel, 5 kg chromium powder with an average grain size of 30 pm, and 5' kg nickel powder with an average grain size of 3 pm was mixed together.
Subsequently, the powder mixture was compressed with a 2 pressing pressure of 3 t/cm to obtain a compact with the dimensions 25 x 170 x 400 mm. The compact was sintered for 6 hours at a temperature of 1200°C and subsequently encased airtight by welding in a steel jacket with a wall thickness of 2 mm, following evacuation of said jacket. The encased sintered compact was hot-rolled to a thickness of 2 mm at a temperature of 1200 0 C. Following chemical removal of the steel jacket, the sheet was ground and cold-rolled to a foil thickness of 50 pm.

Claims (5)

1. A process for joining high temperature-resistant parts in solid-electrolyte high-temperature fuel cells, which construction parts are made of chromium and alloys based on chromium, comprising the steps of: applying a hard solder between the high temperature-resistant parts, the hard solder consisting essentially of: 40% to 70% by weight chromium; up to 2% by weight of at least one of the metals selected from the group consisting of vanadium, niobium, tantalum, titanium, zirconium and hafnium; up to 2% by weight of at least one of the metals or their oxides selected from the group consisting of rare earths and yttrium; and the balance being nickel; heating the hard solder and high temperature-resistant parts; and cooling the hard solder and high temperature-resistant parts to create a high-temperature soldered joint connecting the high temperature- resistant parts.
2. Process for joining high temperature-resistant parts according to claim 1, characterised in that the hard solder consists of 50% by weight chromium, the balance nickel.
3. Process for joining high temperature-resistant parts according to claim 1 and 2, characterized in that the hard solder is present as a ductile foil.
4. Process for joining high temperature-resistant parts according to claim 3, characterised in that the hard solder used is manufactured by the following process steps: manufacture of a compact by mixing, pressing and sintering of the powdery starting materials; L s airtight encasing of the compact; hot-rolling of the encased compact to a sheet thickness of about 1 to 3mm; removal of the encasing material; and cold rolling of the sheet to the desired foil thickness. DATED this 7th day of October, 1997 PLANSEE AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS 4TH FLOOR, "DURACK CENTRE" 263 ADELAIDE TERRACE PERTH W.A. 6000 AUSTRALIA f** 1 '=111 ABSTRACT The invention relates to a hard solder for high-temperature soldered joints for joining high temperature-resistant materials, especially chromium and alloys based on chromium. The hard solder consists of 40% to 70% by weight chromium, up to 2% by weight of one or several of the metals selected from the group of vanadium, niobium, tantalum, titanium, zirconium and hafnium, up to 2% by weight of one or several of the metals or their oxides selected from the group of rare earths and ego**** yttrium, as well as nickel as the balance. The solder according to the invention is particularly suitable for joining by soldering parts in solid-electrolyte, high-temperature fuel cells.
5 -11- L
AU16306/95A 1994-04-13 1995-04-03 Soldering of high-temperature joints in solid-electroltye high-temperature fuel cells Ceased AU686320B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT75994 1994-04-13
AT759/94 1994-04-13

Publications (2)

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AU1630695A AU1630695A (en) 1995-10-26
AU686320B2 true AU686320B2 (en) 1998-02-05

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017093700A1 (en) * 2015-12-04 2017-06-08 Commissariat à l'Energie Atomique et aux Energies Alternatives Method for assembling a first metal part and a second metal or ceramic part by brazing, brazing composition

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB487263A (en) * 1937-02-12 1938-06-17 Patent Treuhand Ges Fure Elek Improvements in solders for uniting the metallic parts of vacuum devices
US3787202A (en) * 1970-11-18 1974-01-22 Cyclops Corp High temperature chromium-nickel alloy
JPH03199337A (en) * 1989-12-27 1991-08-30 Tosoh Corp High-temperature corrosion resistant material and production thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB487263A (en) * 1937-02-12 1938-06-17 Patent Treuhand Ges Fure Elek Improvements in solders for uniting the metallic parts of vacuum devices
US3787202A (en) * 1970-11-18 1974-01-22 Cyclops Corp High temperature chromium-nickel alloy
JPH03199337A (en) * 1989-12-27 1991-08-30 Tosoh Corp High-temperature corrosion resistant material and production thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017093700A1 (en) * 2015-12-04 2017-06-08 Commissariat à l'Energie Atomique et aux Energies Alternatives Method for assembling a first metal part and a second metal or ceramic part by brazing, brazing composition

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