FR3044570A1 - METHOD FOR ASSEMBLING A FIRST METAL PIECE AND A SECOND PART OF METAL OR CERAMIC BY BRAZING, BRAZING COMPOSITION - Google Patents

Abstract

A method of assembling a first part and a second part by brazing, the face to be assembled of the first part being made of a first metal and the face to be assembled of the second part being made of a second metal or ceramic, the method comprising the following successive steps: - contacting the faces to be joined with a solder composition, said solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98 y ranging from 0.01 to 1 Wherein z = 0 to 0.25 and such that x + y + z = 100% - melts the braze composition by heating it to a brazing temperature above the melting temperature of the CrxNiyTiz alloy to form a solder joint.

Description

A method of assembling a first piece of metal and a second piece of metal or ceramic by soldering, solder composition.

TECHNICAL FIELD OF THE INVENTION The invention relates to a method of assembling a first piece of metal and a second piece of metal or ceramic by soldering, and a solder composition. State of the art

In many industrial processes and devices, it is necessary to be able to obtain reliable and accurate temperature values at high temperatures. For example, thermal sensors in motors must withstand frequent high temperature air stresses. The metal / metal or metal / ceramic joints of these devices must be hermetic.

To ensure good mechanical strength and good sealing at the assembly, only processes using a liquid phase, such as brazing, can be envisaged. Brazing consists of melting a brazing alloy, called solder, or alloy filler, capable of wetting and spreading on the interfaces of the parts to be assembled and to solidify after cooling.

After cooling, the solidified solder ensures the cohesion of the assembly.

However, most of the present solders are not sufficiently resistant to the oxidation and / or temperatures of the targeted applications, or they are based on relatively expensive compounds, such as palladium, which does not make them applicable for applications. in large scale.

US Patent 6863995 discloses, for example, solder compositions for joining metal parts. The parts are made of nickel-chromium alloy and are intended to form stator vanes. The brazing temperature is less than 998 ° C. This type of solder is resistant to oxidation and corrosion.

However, these solders are relatively expensive because they contain gold and the operating temperatures (below 1000 ° C) are too low for the targeted applications (1100 ° C under air).

CN1027797 discloses solder compositions for joining a ceramic part to another ceramic or metal part. These solders include copper, a rare earth element and, inter alia, an antioxidant element. The solder joint is carried out at 880 ° C under vacuum at 1.10'5 Torr. The solder joint has improved air oxidation resistance at 600 ° C.

The application temperatures are also too low for the targeted applications. In addition, this type of alloy is not suitable for industrial application because it requires the use of rare earths.

WO 99/61195 discloses a braze composition based on a CrNiWPdSiBCo alloy for joining Fe-Cr-Al based alloys. This alloy forms, during the formation of the solder joint, an intermetallic compound AlPd resistant to oxidation at high temperature. A low concentration of boron and silicon avoids embrittlement of the joint. The melting temperature of this alloy is between 1050 ° C and 1180 ° C.

US Patent 3662455 discloses a NiTiNb alloy for joining ceramic or ceramic and metal parts. The solder joint is made at a temperature of 1190 ° C-1220 ° C under vacuum or under an inert atmosphere. The set is resistant to hot alkali metal fumes such as cesium or rubidium.

However, elements such as niobium and palladium are rare elements and the use of brazing with such elements is difficult to apply on a large scale.

US Pat. No. 4,596,354 discloses the brazing of ceramic and / or metal parts with an alloy AINi resistant to oxidation. The brazing process is carried out in a non-oxidizing atmosphere at a temperature ranging from 1450 ° C to 1550 ° C. These temperatures are, however, very high and require a high energy input to make the solder joint. In addition, at such temperatures, during cooling, the risk of failure due to thermomechanical stresses increases considerably.

OBJECT OF THE INVENTION The object of the invention is to overcome the disadvantages of the prior art and, in particular, to propose a brazing process that is applicable on a large scale and that makes it possible to obtain resistance to oxidation at high temperature. and, more particularly, at temperatures of the order of 1100 ° C. or even up to 1400 ° C.

This object is achieved by a method of assembling a first part and a second part by soldering, the face to be assembled of the first part being made of a first metal and the face to be assembled of the second part being in a second part. metal or ceramic, the method comprising the following successive steps: - bringing the faces to be joined into contact with a solder composition, said solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98 up to from 0.01 to 1/3 z ranging from 0 to 0.25 and such that x + y + z = 100% - melting the braze composition by heating it to a brazing temperature above the melting temperature of CrxNiyTiz alloy to form a solder joint.

This object is also achieved by a solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98 y ranging from 0.01 to 1/3 z ranging from 0 to 0.25 and such that x + y + z = 100%.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given by way of nonlimiting example and represented in the accompanying drawings, in which: FIG. , schematically, the triangle of composition of the solder alloy whose vertices are delimited by the points:

Cr 2,98Ni 0, o 1 Ti 5, o 1, Cro, 5 Ni 10, 25 Ti, 25 and Cr 2/3 Ni 1/3; FIG. 2 schematically represents, in section, a step in the method of assembling an Al 2 O 3 part with two pieces of Haynes® alloy, according to the invention, - Figure 3 shows a photograph of the device of Figure 2 after the brazing process.

Description of a preferred embodiment of the invention

The assembly method makes it possible to assemble by brazing a first piece and a second piece.

The face to be assembled of the first piece is made of a first metal and the face to be assembled of the second piece is made of a second metal or ceramic.

Ceramic means ceramic oxides, non-oxide ceramics but also composite ceramics. The ceramic is preferably an oxide ceramic. It is preferentially a zirconia or alumina. Preferably, the first and / or second metal is an alloy of nickel or iron.

The first and / or second metal is a Ni-Cr-W-Mo alloy, for example Haynes® 230 (Ni62-Cr22-Wi4-M02).

The first and / or second metal is a Ni-Cr-Al-Fe alloy, for example Haynes® 214 (Ni-Cr16-Al45-Fe3).

The faces to be assembled can be in the same material or in two different materials.

Advantageously, when the parts are made of the same material, the thermal coefficient differential between the two parts to be assembled is very low, or even zero.

The solder assembly method comprises the following successive steps: bringing the faces to be joined into contact with a solder composition, said solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98 up to from 0.01 to 1/3 z ranging from 0 to 0.25 and such that x + y + z = 100% - melting the braze composition by heating it to a brazing temperature above the melting temperature of CrxNiyTiz alloy to form a solder joint.

By 1/3 we mean the exact fraction of the rounding 0.33. The solder alloy, also called brazing alloy, is of the CrxNiyTiz type. The alloy may include impurities, but their amount is negligible compared to other constituents.

Advantageously, the alloy consists of chromium, titanium and nickel, or chromium and nickel only if z = 0.

This type of alloy melts and wets ceramics, and, more particularly, oxide ceramics via the formation of interface sub-oxides (titanium and chromium oxides), obtained thanks to the presence of titanium and / or of chromium contained in the solder composition. This type of solder also wets all metals and, in particular, metals based on iron, nickel, chromium, titanium, aluminum, molybdenum, tungsten, zirconium, copper. The alloy of the solder composition is advantageously defined by a composition triangle whose vertices are delimited by the points (FIG. 1) Cr 0.98 Ni, o Ti 10, o 1 · Cro, 5 Ni 10, 25 Ti 10, and Cr 2/3 Ni / 3.

A solder joint obtained with such an alloy will be more resistant to oxidation. The alloy is, preferably, an alloy Cr0.6475Ni0.2775Ti075

According to a first embodiment, the solder composition comprises, in the initial state, nickel particles, titanium particles and chromium particles.

The particles are obtained by mixing powders of nickel, titanium and chromium.

The particles advantageously have a diameter of 1μηη and ΙΟΟμιτι.

The solder composition comprising particles with such diameter ranges is advantageously homogeneous.

According to another embodiment, the solder composition comprises particles of a CrxNiyTiz alloy.

The particles are then obtained by finely grinding a solid piece of a CrxNiyTiz alloy.

The solid piece of CrxNiyTiz alloy is, for example, obtained by melting a mixture of pure elements. This elaboration is done by introducing into a crucible the different elements. The crucible is placed in an oven and heated under a neutral gas or secondary vacuum. The temperature depends on the composition of the alloy and is chosen so as to be able to melt the constituents of the alloy and obtain a homogeneous alloy.

The neutral gas is, for example, argon or nitrogen.

According to another embodiment, the pure elements can also be placed in a cold crucible. This avoids the risk of pollution by interaction crucible / elements. The elements are thus melted by inductive heating, advantageously under argon or secondary vacuum so as to melt the various components.

After melting and cooling of the various elements, an ingot is obtained. This ingot is then ground to obtain a powder.

Preferably, it is ground in a ball mill to obtain a powder whose particles have a diameter of between 1 pm and 100 pm.

The solder composition may be in the form of a particle powder. According to another embodiment, the solder composition comprises, in addition to these particles, a binder, a liquid organic cement or a gel, both viscous and sticky in order to obtain a solder composition in the form of a dough.

The particles are suspended in the binder.

Advantageously, the binder decomposes between 100 ° C. and 300 ° C. without leaving any traces.

It may be, for example, a Nicrobraz® brand organic cement or a gel.

The solder composition and the binder form a solder paste.

The paste is, advantageously, easily handled and can be easily arranged on the parts to be assembled.

According to another alternative, the solder composition is in the form of a sheet or strip, in the form of a CrxNiyTiz alloy wire. It can also be in the form of a wire of the CrxNiyTiz alloy.

Before bringing the faces to be joined into contact with the solder composition, the faces of the parts to be brazed are advantageously degreased, cleaned in a solvent and in an ultrasonic bath. The solvent is, for example, acetone or alcohol. The pieces are then dried.

Then, to bring the faces of the parts to be assembled into contact with the solder composition, several configurations can be envisaged.

The brazing can be performed in sandwich configuration or in capillary configuration.

In sandwich configuration, the solder composition is spread on one or both of the solder faces and the solder faces are brought into contact. In this case, the solder composition is directly placed between the parts to be assembled.

The heat treatment, carried out above the melting point of the solder composition, melts the latter which fills the joint.

In capillary configuration, the parts are brought into contact without having put a solder composition between them. The solder composition is then deposited near the seal in contact with the two parts to be assembled to allow its infiltration into the joint after its fusion.

A first piece 1 and a second piece 2, for example, are arranged offset with respect to each other, as shown in FIG. 2. The offset between them is at least a few μηη, for example of 10μιτι 200μιτι so as to create a surface capable of receiving the solder composition near the seal formed by the faces to be assembled. The solder composition 3 may be disposed in the form of a solder bead, at the edge of the seal, in contact with the faces to be joined.

The heat treatment, performed above the melting point of the solder composition, melts the solder composition leading to infiltration of the solder composition into the seal by capillarity. After cooling, the solder joint is formed.

By contact between the solder and the faces of the parts to be joined, it is meant that the solder is, for example, disposed between the two faces of the parts to be assembled, and in contact with them, and / or in contact with the edges of the faces, at least one edge of the joint.

Preferably, the parts to be brazed are arranged in the brazing furnace. The oven is brought to the brazing temperature, to allow the assembly of parts.

Preferably, the brazing temperature used in the process for assembling the different parts is between 1200 ° C. and 1500 ° C., and preferably between 1200 ° C. and 1400 ° C.

Advantageously, the brazing temperature is 20 ° C to 50 ° C higher than the melting temperature of the solder composition, and preferably 30 ° C higher than the melting temperature.

The melting temperature of the solder composition is between 1150 ° C and 1450 ° C.

Advantageously, with such brazing temperatures, the alloys wet well the faces to be assembled. During the cooling of the alloy, it adheres well to said faces, which allows to secure the parts together.

Brazing is, according to a first embodiment, carried out under secondary vacuum. By secondary vacuum means a pressure less than 10'3mbar, for example from 1.10'3 mbar to 1.10'7 mbar.

The brazing can also be carried out under an inert atmosphere, that is to say under an atmosphere of neutral gas, such as an atmosphere of argon, helium or dinitrogen.

Preferably, the neutral gas is argon.

Brazing is, for example, performed in a controlled atmosphere brazing furnace such as a resistive furnace.

Part of the brazing cycle can be performed under secondary vacuum and the other part of the brazing cycle under an inert atmosphere.

The brazing temperature is kept constant between 1 minutes and 60 minutes, and preferably between 5 minutes and 30 minutes depending on the dimensions of the parts to be assembled. This is the soldering bearing.

The brazing stage makes it possible to obtain a good wetting and a good spreading of the brazing alloy on the interfaces to be assembled.

After cooling, the alloy solidifies and the parts are securely and mechanically assembled.

The brazing temperature can be obtained by observing a rise in temperature. The temperature rise ramp is between 1 ° C / min and 20 ° C / min depending on the size of the parts, to have sufficient thermal homogeneity.

Preferably, the process comprises during the rise in temperature up to the brazing temperature, the passage through a first temperature step. This first temperature step is performed at a temperature between the evaporation temperature of the binder and the soldering temperature. The rise in temperature to the first stage makes it possible to evaporate the binder. After evaporation, the binder does not leave a residue. At the end of the brazing heat cycle, during the cooling phase, the solder solidifies and the assembly is effective.

An isothermal bearing can be realized, during cooling, to relax the mechanical stresses between the assembled parts.

Once the solder joint is formed, it is resistant to an oxidation treatment under air up to the re-melting temperature of the joint.

More particularly, the solder joint is resistant to oxidation from 20 ° C to 1400 ° C, depending on the initial composition.

The solder joint is resistant to oxidation up to 50 ° C below the melting temperature of the solder composition.

Four different solders were made by mixing powders formed of the various constituents. The following four solders were produced: - solder 1: Ti0.oi-Nio.29-Cr0.7 - solder 2: Tio.o75_Nio.2775_Cro.6475 - solder 3: Tio.i-Ni0.5-Cr0.4 - solder 4: Ti0.572-Nio.o28-Cr0.4

Ceramic / metal bonds brazed with these solder compositions were then tested in an air oxidation oven. The oxidation tests are carried out in a tubular oven made of alumina in air at 1100 ° C. for 100 hours and then the solder joints are cooled to ambient temperature. By ambient temperature is meant a temperature of the order of 20-25 ° C.

The following table gives the characteristics of the solder joints obtained:

Solder joints obtained with solder Nos. 3 and 4 which do not meet the alloy definition of the solder composition are less resistant to oxidation than the solder joints obtained with solder Nos. 1 and 2 .

Solder # 2 was used to solder a piece of alumina with two pieces of Haynes® alloy. The parts were assembled according to the diagram of FIG. 2: the first part 1 is the alumina part, the second 2 and third parts are made of Haynes® 230 alloy (Ni62-Cr22-Wi4-Mo2).

The method was also used to assemble a piece of alumina 1 with two pieces 2, 2 'Haynes® alloy 214 (Ni-Cr16-Al45-Fe3), arranged in the same configuration. Two cords 3, 3 'were arranged at the contacts between the face to be assembled of the first part 1 and the faces to be assembled of the second and third parts 2, 2' respectively.

Figure 2 is a sectional view of metal passages in the center of the ceramic.

It is possible to arrange the solder differently, for example by passing it around the metal passages.

Figure 3 shows a photograph of the device before the soldering process.

The solder melted and allowed the establishment of a hermetic seal at 2.10'9 atm.cm3 / s. The seal is resistant to repeated thermal shock from 220 ° C / min to 1100 ° C in air. The assembly was aged 100h at 1100 ° C without

observes catastrophic oxidation leading to a loss of hermeticity. The invention also relates to a solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98, y ranging from 0.01 to 1/3 z ranging from 0 to 0.25 and such that x + y + z = 100% The alloy of the solder composition is defined by a composition triangle whose vertices are delimited by the points: Cr 0.98 Ni, o Ti 10, o 1, Cr 0.5 Ni 0.25 Ti, 25 and Cr 2/3 Ni / 3.

Preferably, the alloy is Ti0.075Ni0.2775 ^ 0.6475 ·

The composition comprises particles CrxNiyTiz alloy having a diameter between 1μιτι and ΙΟΟμιτι and a binder.

The solders obtained with these compositions are active solders resistant to oxidation at high temperature. These compositions can be used to make hermetic metal / metal or metal / ceramic junctions resistant to solicitations under air and at high temperature. They can, for example, be used to assemble thermal probes for motors.

These brazing compositions can be used on a large scale because they are devoid of rare and expensive elements such as rare earths or gold for example.

Claims (19)

claims 1. A method of assembling a first part and a second part by brazing, the face to be assembled of the first part being made of a first metal and the face to be assembled of the second part being made of a second metal or ceramic the process comprising the following successive steps: bringing the faces to be joined into contact with a solder composition, said solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98 y ranging from 0.01 at 1/3 z ranging from 0 to 0.25 and such that x + y + z = 100% - melting the solder composition by heating it to a brazing temperature above the melting temperature of the CrxNiyTiz alloy to form a solder joint. 2. Method according to claim 1, characterized in that the brazing temperature is between 1200 ° C and 1400 ° C. 3. Method according to one of claims 1 and 2, characterized in that the brazing is carried out under secondary vacuum. 4. Method according to one of claims 1 and 2, characterized in that the brazing is carried out under an inert atmosphere, such as an argon, helium or dinitrogen atmosphere. 5. Method according to any one of claims 1 to 4, characterized in that the first and / or second metal is an alloy of nickel or iron. 6. Method according to claim 5, characterized in that the first and / or second metal is a Ni-Cr-W-Mo alloy. 7. Process according to claim 5, characterized in that the first and / or second metal is a Ni-Cr-Al-Fe alloy. 8. Method according to any one of claims 1 to 7, characterized in that the ceramic is a zirconia or alumina. 9. Process according to any one of claims 1 to 8, characterized in that the solder composition comprises nickel particles, titanium particles and chromium particles. 10. Process according to any one of claims 1 to 8, characterized in that the solder composition comprises CrxNiyTiz alloy particles. 11. Method according to the preceding claim, characterized in that the particles of CrxNiyTiz alloy are obtained by grinding a solid part of a CrxNiyTiz alloy. 12. Method according to one of claims 9 to 11, characterized in that the solder composition further comprises a binder so as to form a solder paste. 13. Method according to one of claims 9 to 12, characterized in that the particles have a diameter of 1μιτι and ΙΟΟμιτι. 14. A method according to any one of claims 1 to 13, characterized in that the alloy of the solder composition is defined by a composition triangle whose vertices are delimited by the points: Cr0.98Nio, oiTio, oi, CrO, 5Ni, 25Ti, 25 and Cr2 / 3Ni-1/3. 15. Process according to any one of claims 1 to 14, characterized in that the solder composition is an alloy Cr0.6475NiO, 2775TiO, o75 · 16. Solder composition comprising a CrxNiyTiz alloy, with: x ranging from 0.5 to 0.98, y ranging from 0.01 to 1/3 z ranging from 0 to 0.25 and such that x + y + z = 100% 17. Composition according to claim 16, characterized in that the alloy is defined by a composition triangle whose vertices are delimited by the points: Cro, 98Ni0, oiTiO, oi> Cro.sNiO ^ sTiOs and Cr2 / 3Ni -i / 3. 18. Composition according to one of claims 16 and 17, characterized in that the alloy is Tio, o75Ni0,2775Cr0,6475 · 19. Composition according to any one of claims 16 to 18, characterized in that it comprises CrxNiyTiz alloy particles having a diameter between 1 .mu.m and 100 .mu.m and a binder.