JP2006327888A - Brazed structure of ceramic and metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brazed structure of a ceramic and a metal in which the residual stress of a joint part after brazing in brazing joint of the ceramic and the metal is remarkably reduced without inhibiting the reactivity of the ceramic surface with a brazing filler metal and the thickness of the joint part is thin and which is excellent in manufacturing stability and gas leakage resistance and strong in repeated thermal shock. <P>SOLUTION: At least one kind of an additional element selected from a group comprising Ni, Si, Fe, Cr, Co, Mn, Ag, Au, Pd, In and Sn is added in a brazed joint layer in the brazed structure of the ceramic and metal. A peak position of the content of the additional element is controlled to be near to the metal side from the center of the joint layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brazing technique of ceramics and metal, and more particularly to a brazing structure in which a thin plate made of a ceramic material and a thin plate made of a metal material are joined through a thin brazing joining layer.

  Conventionally, when joining ceramics and metal, a method of performing brazing after metallizing (metal coating) an active metal (for example, Mn-Mo, Ti, Zr, Al, Hf, etc.) on the ceramic-side joint, There is a method of directly brazing using a brazing material containing an active metal such as Ti or Al. The active metal segregates at the ceramic side interface in the brazing material joining layer and joins by promoting the reaction between the ceramic and the brazing material. However, since ceramics and metals generally have different coefficients of thermal expansion, thermal stress is generated during the cooling process in which the brazing material solidifies, and cracks and the like are generated near the bonding interface on the ceramic side. It is difficult to obtain a bond with good thermal conductivity.

As a method of reducing the residual stress of the ceramic-metal joint, for example, a stress relaxation material at the brazed joint between the ceramic and the metal, a metal that is softer and more deformable than the metal to be joined (for example, Pure Cu, pure Ni, etc.), alloys, or metals or alloys having an expansion coefficient located between ceramics and metals are also brazed.
In addition, it is disclosed that 5 to 20% by volume of ceramic fine powder such as alumina is contained in a bonding layer made of an Ag—Cu-based metal brazing containing an active metal (for example, see Patent Document 1). This is to obtain a joined body by brazing ceramics and metal with improved thermal shock resistance by blending ceramic fine powder, introducing minute defects in the joint, and releasing residual stress.
JP-A-5-163078

However, in the case where the stress relaxation material is sandwiched between the ceramic and metal joints described above, the stress after brazing is reduced, but not a little, so when the structure is used in a temperature range of 300 ° C. or higher, When used in an environment in which a thermal cycle is loaded, cracks occur in the ceramics and the brazing layer due to differences in the expansion coefficient of the joints, and there are problems with reliability, life, and the like regarding the airtightness of the brazed parts. In particular, brazing using a stress relieving material has a problem in that it is difficult to manufacture a structure having a thin joint portion because the size of the joint structure, that is, the thickness of the joint portion is limited.
In addition, when ceramic fine powder is blended in the brazed joint, the active metal element tends to segregate at the interface between the ceramic fine powder and the brazing material because the specific surface area of the ceramic fine powder is large and the reactivity is high. There is a problem in that the bonding reaction at the interface between the ceramic material to be bonded and the brazing material is hindered, resulting in variations in bonding characteristics such as bonding strength and gas sealability of the bonded portion.

  The present invention has been made in order to solve the above-mentioned problems in brazing and bonding of ceramics and metals, and the object of the present invention is to provide a bonding structure of ceramics and metals in the ceramic surface. The residual stress of the joint after brazing can be greatly reduced without impairing the brazing material reactivity, the thickness of the joint is thin, excellent in manufacturing stability and gas leak resistance, and repeated thermal shock It is to provide a brazing structure made of ceramic and metal that is resistant to damage.

  In order to solve the above-mentioned problems, the inventors of the present invention have made various studies on the joint between the ceramic thin plate and the metal thin plate, focusing not only on the vicinity of the ceramic side interface in the bonding layer but also on the element distribution in the vicinity of the metal side interface. As a result of layering, various stress-relieving elements are concentrated in the vicinity of the metal-side interface, and the peak of the composition ratio (magnitude of composition ratio) is changed. The present invention has been completed.

  The present invention is based on the above knowledge, and in the ceramic and metal brazing structure of the present invention, the brazing joint layer has Ni, Si, Fe, Cr, Co, Mn, Ag, Au, Pd, In. And Sn, preferably at least one selected from the group consisting of Ni, Si, Mn, Ag, Au, Pd, In and Sn, more preferably selected from the group consisting of Ni, Si, Mn, In and Sn An additive element is contained, and the peak position of the content of such an additive element is on the metal side with respect to the center of the bonding layer.

  According to the present invention, the brazing filler metal constituting the brazing joint layer includes one or more additive elements selected from the above metal group, and such additive elements become granular and the metal side of the joining layer Dispersed in the vicinity of the interface, or the additive elements are distributed in layers in the vicinity of the interface on the metal side, becoming an alloy phase with a low thermal expansion coefficient or an alloy phase with a brazing filler metal component or a base metal component. Since these function as a stress relaxation phase, it is possible to prevent the occurrence of cracks in the bonding layer, which is excellent in gas leakage resistance even when the thickness is thin, and ceramics having a bonding layer that is resistant to repeated thermal shocks. A metal brazing structure can be obtained.

  The ceramic and metal brazing structure of the present invention will be described in detail below together with the production method. In the present specification, “%” means mass percentage unless otherwise specified.

  In the brazing structure of ceramics and metal according to the present invention, the materials to be joined made of these ceramics and metals are joined via a brazing joint layer, and the joint layer is Ni, Si, Fe, Cr, Co, Mn. , Ag, Au, Pd, In, and Sn, or any combination thereof, and the additive element content peak is located closer to the metal side than the center of the brazing joint layer. However, from the viewpoint of thermal shock resistance, the additive element is preferably at least one selected from the group consisting of Ni, Si, Mn, Ag, Au, Pd, In, and Sn. It is desirable to use at least one selected from the group consisting of Ni, Si, Mn, In and Sn.

  That is, in the present invention, the various additive elements described above have an action of promoting the diffusion of the component elements in the brazing joining layer in the metal that is the material to be joined (base material). As a result, in the joining layer, The main component of the brazing filler metal, including the component elements and additive elements, reacts metallurgically to form a low thermal expansion alloy phase and a stress relaxation alloy phase (alloy phase that is easily deformed and relaxes stress by strain deformation). By doing so, there are elements that exhibit a stress relaxation effect and elements that form a low thermal expansion alloy phase and a stress relaxation alloy phase suitable for stress relaxation, and most of the additive elements have both functions.

  In addition to the fact that the formation of these alloy phases directly contributes to stress relaxation, as a stress relaxation mechanism, these alloy phases are layered (cladding structure type) or granular in the bonding layer as an indirect factor. It exists as a phase (particle-dispersed type), and it is considered that the stress relaxation effect is produced at the interface between the alloy phase and the brazing metal phase, and the stress of the entire brazed joint layer is relaxed.

Here, Fe, Ni, Cr, Co and the like have an effect of promoting stress relaxation and are elements included in the additive element, but are also elemental elements of the base metal, and in a general brazing method, These component elements may diffuse into the brazing material layer. However, since the diffusion amount of the component elements of the base metal is generally determined by the brazing temperature and its holding time, the amount and distribution of these alloy phases are controlled by the brazing conditions (temperature, holding time). This means that the manufacturing process takes a long time, and there is a limit in terms of productivity (yield and mass productivity) in manufacturing the bonded structure.
That is, in the present invention, the low thermal expansion alloy phase suitable for thermal stress relaxation can be obtained by adding the additive element directly into the brazing material or brazing the ceramic surface or metal surface in a film-formed state. (E.g., Fe-Ni-Cr-Si alloy, Fe-Ni-Cr-Mn-Si alloy) or stress relaxation alloy phase (e.g., Cr-Fe- (Si) alloy, Ag-In-Sn-Fe alloy, Cu -In-Sn-Fe alloy, Cu-In-Sn-Ni alloy, etc.) are easily controlled and the stress relaxation action is more effectively exhibited.

  The distribution of Ag and Cu, which are the main components of the brazing filler metal, in the bonding layer is as follows: Cu alloy (an alloy containing an element that exhibits a stress relaxation effect, an active metal) / Ag alloy / Cu alloy (metal) Side diffusion elements, including elements that exhibit a stress relaxation effect) / base metal, that is, a Cu alloy / Ag alloy / Cu alloy, etc. clad structure, each of the Cu alloys exhibiting a base element (stress relaxation effect) In other words, a structure having a gradient structure and a solid structure is desirable. Note that the Cu alloy on the ceramic side or metal side as the base material and the Ag alloy in the center may be dispersed in a granular form instead of a complete layer.

As a method of brazing by controlling the composition ratio of the additive element in the brazing joint layer, a foil, a wire, a powder, or a paste brazing material in which the element is added to the brazing material can be used.
For example, a brazing filler metal that includes an active metal such as Ti and is laminated or laminated with a brazing filler metal foil that has a bonding reaction on the ceramic surface and a brazing filler metal foil that contains the above-described additive elements that exert a stress relaxation effect on the metal interface side. A foil can be used.

Also, after metallizing by reacting a Ti-containing active metal brazing material on the ceramic surface, a bonding layer is formed from a brazing material or a base metal containing Ag, Au, and Pd, which are elements that exert a stress relaxation effect on the metal interface side. Mn, Si, In, Sn, Ni, Fe, Cr, which are elements that promote diffusion into the brazing material layer to form a stress relaxation phase on the metal side or promote the formation of a low expansion alloy layer. It can also be made to braze using a brazing material containing Co.
Further, by using a PVD method such as a plating method or a vapor deposition method on the metal surface, the additive element having a stress relaxation effect can be formed into a film and then brazed by a known active metal brazing method. The active metal and the additive element can be formed on the ceramic surface and the metal surface, respectively, and a brazing material component can be formed and brazed together.

  As the brazing material used in the present invention, silver brazing, gold brazing, palladium brazing, nickel brazing, titanium brazing and the like can be used. In addition, for the purpose of increasing the reactivity with ceramics, it is possible to add an active metal such as Ti, Zr, Hf, Al or the like in advance to the brazing material or braze in a state of being laminated on the ceramic side. .

  When a brazing material containing Cu as a component is used, the general Cu content is in the range of 0.05 to 50%, preferably about 20 to 35%. Furthermore, 0.1-15% of Ti, Al, etc. may be included for the purpose of increasing the reactivity with ceramics.

On the other hand, when using an Ag—Cu brazing filler metal as the brazing filler metal, at least one element selected from the group consisting of Ni, Si, Mn, In and Sn is added as an additive element having a stress relaxation effect to the entire layer. Composition ratios of Ni: 0.1-80%, Si: 0.1-20%, Mn: 0.1-40%, In: 0.1-30%, Sn: 0.1-30% By forming the bonding layer contained therein, a bonding layer having excellent thermal shock resistance and gas sealing properties can be obtained.
Further, at this time, from the viewpoint of joining stainless steel or Ni-based alloy, it is necessary to use Ni as an essential component as an additive element and to use Ni and one or more of other elements in combination. Joining ceramics with a heat-resistant Ni-based alloy such as steel or Inconel is desirable because heat resistance and heat shock resistance are improved.

  In addition, when the addition amount of the above elements is 0.1% or less, the stress relaxation function cannot be exhibited, and when the addition amount exceeds the upper limit value of each element, the stress relaxation ability is practically reduced. At the same time, a large amount of intermetallic compounds and alloys of these additive elements and metal elements are formed inside the bonding layer after brazing, and the bonding layer tends to become brittle, leading to a decrease in strength of the structure (joined body). . Further, when these compounds are formed in a large amount, voids, shrinkage cavities, and cracks (small cracks) are likely to occur in the brazing joint layer, and there is a tendency for leakage resistance to be problematic.

  In addition, when a brazing material containing Ni as a main component is used, at least one element selected from the group consisting of Fe, Cr, Si, Mn and Co as an additive element having a stress relaxation effect is Fe: 0.1-20%, Cr: 0.1-20%, Si: 0.1-5%, Mn: 0.1-10%, Co: contained within the range of 0.1-10% By forming a layer, when joining a Ni-based alloy such as stainless steel or Inconel with ceramics, heat resistance can be improved by suppressing oxidative degradation of the joining layer.

  The base metal used in the brazing structure of the present invention is preferably a metal containing one of Fe (iron) and Ni (nickel) as a main component. Considering the application, a structural material made of stainless steel (SUS430, SUS304, SUS316L, etc.), heat resistant steel (SUH330, SUH446, etc.), superalloy (Incoloy, Inconel, etc.), etc. can be used.

  On the other hand, as the base ceramic, stabilized zirconia added with yttria, scandium oxide, samarium oxide, neodymium oxide, gadolinium oxide, calcium oxide, etc., and oxide ceramics mainly composed of ceria, magnesia, bismuth oxide, and alumina. Further, carbide ceramics mainly composed of silicon carbide, titanium carbide, tungsten carbide, nitride ceramics such as aluminum nitride, silicon nitride, and the like can be used.

In the ceramic and metal brazing structure of the present invention, it is preferable that the total thickness of the bonded portion obtained by adding up the thicknesses of the ceramic, the brazed bonding layer, and the metal is 3 mm or less. If the thickness is greater than 3 mm, microcracks are likely to occur between the ceramic and the bonding layer due to the thermal stress during cooling after brazing, and the production yield of structures with good gas leakage and thermal conductivity is reduced. This is not preferable because of the possibility.
Further, the thickness of the base metal is preferably 2 mm or less, and if it is thicker than this, the elongation of the metal is large, the ceramic is easily broken, and the structure with good gas leakage and thermal conductivity is also obtained. This is not preferable because the manufacturing yield tends to decrease.
The thicknesses of the ceramic, brazing joint layer and metal are 0.05 to 1 mm for ceramics and metal as the base material to be joined, and 0 for the brazing joint layer in consideration of uses as described later. More desirably, the thickness is about 0.001 to 0.3 mm.

  Applications of the ceramic and metal brazing structure of the present invention include, for example, a junction between an ion conductive ceramic in a solid oxide fuel cell, an oxygen sensor, a NOx sensor, etc. and a metal member holding the carbon, It can be applied to joints with insulating ceramics in power extraction terminal parts such as molten salt type, polymer electrolyte fuel cells, sodium sulfur batteries and lithium batteries, and joints of insulating layers in large current inverters.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

(Experiment 1)
As shown in FIG. 1, as a base material to be joined, a disk shape having a thickness of 0.1 mm and a diameter of 30 mm is formed. From YSZ (yttria stabilized zirconia), 92% Al ₂ O ₃ , SiC, Si ₃ N ₄ Four types of ceramic thin plates 2 and a donut shape having a thickness of 0.1 mm, an outer diameter of 60 mm, and an inner diameter of 26 mm, ferritic stainless steel SUS430 (Fe-16% Cr), Kovar alloy (Fe-29% Ni-17) % Co), an iron-nickel alloy (Fe-42% Ni), and three kinds of metal thin plates 3 are used, and the above-mentioned position is directly above the hole portion (diameter 26 mm) of the metal 3 according to the method and conditions described later. Ceramics 2 (diameter 30 mm) was brazed through the additive element layer 4 and the brazing material 5 serving as a brazing joint layer, and the influence of various additive elements on the brazing joint was investigated.

<Brazing joining method>
As brazing conditions, Ar gas is allowed to flow as a carrier gas in a vacuum of about 5 × 10 ⁻¹ Torr, and a load of about 3 × 10 ⁻³ kgf / mm ² is applied from the vertical direction of the brazing portion. After preheating at a temperature below the solidus of the brazing material, brazing was performed at a temperature above the liquidus of the brazing material. The heating rate and cooling rate were 10 ° C./min.

Regarding the addition of various additive elements having a stress relaxation effect, brazing materials used in advance by additive elements (Ni, Fe, Ag, Pd, In, Sn) in the brazing portion on the metal side in each combination of the materials to be joined After forming a layer 4 rich in additive elements by coating a layer whose thickness is controlled to a predetermined content, brazing is performed with a brazing material 5 inserted between the layer 2 and the ceramic 2. It was.
Further, addition of Ti, Mn, and Co was performed by inserting a pure metal 4 in the form of powder or foil between the brazing material 5 and the thin metal plate 3. The brazing material 5 used for brazing includes six types of silver-copper brazing, Ni-based brazing, palladium brazing, gold brazing, Cu brazing and Ti-based brazing materials containing active metal Ti, and a foil having a thickness of 0.05 mm. Alternatively, an alloy powder having a particle size of 100 μm or less was used. The powdery material was mixed with a special binder to form a paste-like brazing material. Moreover, it brazed without adding these elements as a comparison material.

<Joint evaluation method>
About each joined body after brazing, after performing a He leak test | inspection using a well-known gas leak detector, the cross-sectional structure | tissue of the junction part was observed and the distribution state of the stress relaxation element was investigated. In addition, as a heat cycle test, an air atmosphere electric furnace was used, and each joined body was subjected to a heat load 10 times in a temperature range from room temperature to about 300 ° C., and then the He leak test was performed again. These results are shown in Table 1 together with the combination of the base material to be joined, the brazing material and the additive elements.
In addition, as a criterion for determining the He leak test, “◎” indicates that the result is 1.0 × 10 ¹⁰ Pa · m ³ / sec or less, and “1.0” indicates that the result is 1.0 × 10 ⁵ Pa · m ³ / sec or less. “○” and “X” indicates those that cannot be joined at the ○ level. In addition, although it was generally good, it was evaluated as “Δ” if the reproducibility was slightly inferior because it could be joined or not at the level “◯”.

As is clear from the results in Table 1, in the joined body of the comparative example in which brazing was performed without adding an additive element, stable leakage resistance was not obtained, but various additions having a stress relaxation effect were obtained. It was confirmed that by adding the element to the metal side, good results can be obtained in the leak inspection after brazing and after the thermal cycle test. It was also confirmed that leakage resistance was improved by performing diffusion treatment at 500 ° C. for 1 hour after brazing.
In addition, the distribution state of the additive element from the ceramic side or central part to the metal side interface in the bonding layer differs depending on the type of metal used, the main component element of the brazing filler metal, and the combination of additive elements (increase → decrease → In either case, the content peak of these additive elements is located on the metal side of the center of the brazing joint layer, and the low thermal expansion alloy phase and stress relaxation alloy phase containing these additive elements It is formed in a layered shape or a granular shape, and an equivalent stress relaxation effect is obtained.

FIG. 2 shows, as a representative example of the above example, Example 1 (ZrO ₂ (YSZ) and SUS430 using Ag-26% Cu-2% Ti brazing filler metal and 5% Ni-2.5% as an additive element. The element composition analysis result of the junction layer cross section in (Mn addition) is shown.
As shown in FIG. 2, the composition ratio is such that Ag—Cu, which is the main component of the brazing material, is separated into two phases (Ag alloy, Cu alloy) and the additive elements Ni, Mn are dissolved in the Cu alloy. It is confirmed that there is an increase → decrease → increase distribution from the ceramic side to the metal side interface in the brazing joint layer, and it is confirmed that the peak of these contents is located on the metal side from the center position of the joint layer Is done. Further, Ni is concentrated on the metal side interface, and the addition of Ni element promotes diffusion of Cr and Fe, which are component elements of the base metal, into the bonding layer (formation of Ni—Fe—Cr alloy). It is considered effective.

That is, as a structure of the brazing joint layer, a Cu alloy (an element exhibiting a stress relaxation effect, an alloy containing an active metal) / Ag alloy / Cu alloy (a diffusion element on the metal side, an element exhibiting a stress relaxation effect) from the ceramic side In the layer structure close to the clad material that becomes the base metal, the base element (including the element that exerts the stress relaxation effect) is dissolved in the Cu alloy, resulting in a graded layer structure. Thus, a residual stress after brazing is reduced, and a brazed structure having excellent gas leak resistance and strong against repeated thermal shocks can be obtained.
Note that the Cu alloy on the ceramic side and the metal side in the bonding layer is not completely layered, and the same effect can be obtained even if the layer is partially interrupted or dispersed throughout the bonding layer. (For example, Example 6).

(Experiment 2)
As a base material to be joined, ZrO ₂ (YSZ) having a disk shape with a diameter of 30 mm and four types of thickness (0.1 mm, 1.0 mm, 1.5 mm, 2.0 mm) as in the above example. And a donut shape (outer diameter: 60 mm, inner diameter: 26 mm) similar to the above embodiment, and five thicknesses (0.1 mm, 0.5 mm, 1.5 mm, 2.0 mm) , 2.5 mm), a ferritic stainless steel (SUS430), a metal plate 3 made of Kovar alloy and an iron-nickel alloy (Fe-42% Ni), and the thickness of the ceramic plate and the metal plate affecting the brazing property We investigated the influence of the above. The brazing material used was Ag-26% Cu-2% Ti, and Ni and Mn were added as additive elements.
In addition, brazing is performed at a rate of 10 ° C./min after preheating at a temperature below the solidus line of the brazing material while maintaining the temperature at a rate of 10 ° C./min, and holding for about 20 min at a temperature above the liquidus line. It was cooled with. The addition method and the evaluation method of the obtained joined body are the same as those in Example 1. The results are summarized in Table 2.

  As is apparent from the results shown in Table 2, the thickness of the joint in the ceramic-metal brazing structure (the thickness of the entire structure after joining) is preferably 3 mm or less, and more than 3 mm. It is not preferable because the manufacturing yield of a bonded body having good gas leakage and thermal conductivity tends to be reduced due to thermal stress during brazing cooling. Further, the thickness of the metal plate is preferably 2 mm or less, and if it is thicker than 2 mm, the production yield of the joined body having good gas leakage and thermal conductivity is likely to be lowered, which is not preferable.

It is sectional drawing which shows an example of the brazing joining structure of the ceramics and metal of this invention. It is a graph which shows an example of distribution of the component element in the brazing joining layer in the brazing joining structure of the ceramics and metal of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brazing joint structure of ceramics and metal 2 Ceramics 3 Metal 5 Brazing material

Claims (10)

  In a brazing structure in which ceramics and metal are bonded via a brazing bonding layer, the bonding layer is selected from the group consisting of Ni, Si, Fe, Cr, Co, Mn, Ag, Au, Pd, In, and Sn. A brazing structure of ceramics and metal comprising at least one additional element, wherein a peak position of the content of the additional element is on the metal side with respect to the center of the bonding layer.   In a brazing structure in which ceramics and metal are bonded via a brazing bonding layer, the bonding layer is at least one additive selected from the group consisting of Ni, Si, Mn, Ag, Au, Pd, In, and Sn A brazing structure of ceramics and metal comprising an element, wherein the peak position of the content of the additive element is on the metal side of the center of the bonding layer.   In a brazing structure in which ceramics and metal are bonded via a brazing bonding layer, the bonding layer includes at least one additional element selected from the group consisting of Ni, Si, Mn, In, and Sn, and the addition A brazing structure of ceramics and metal, wherein the peak position of the element content is on the metal side with respect to the center of the bonding layer.   The brazing structure of ceramics and metal according to any one of claims 1 to 3, wherein the brazing joint layer is formed using a brazing material containing Cu.   4. The ceramic-metal brazing structure according to claim 3, wherein the brazing joint layer is formed using an Ag-Cu brazing material.   The ceramic and metal brazing structure according to claim 5, wherein the additive element is at least one element selected from the group consisting of Ni and Si, Mn, In, and Sn.   The brazing joint layer is formed using a brazing material containing Ni as a main component, and the additive element is at least one element selected from the group consisting of Fe, Cr, Si, Mn and Co. The brazed structure of ceramics and metal according to claim 1 characterized by the above-mentioned.   The ceramic-metal brazing structure according to any one of claims 1 to 7, wherein the metal is a metal containing Fe or Ni as a main component.   The brazed structure of ceramics and metal according to any one of claims 1 to 8, characterized in that the thickness of the entire joint portion made of ceramics, brazing joint layer and metal is 3 mm or less.   The thickness of the said metal is 2 mm or less, The brazing structure of ceramics and a metal as described in any one of Claims 1-9 characterized by the above-mentioned.

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