CA1306100C - Process for joining molded silicon nitride parts - Google Patents
Process for joining molded silicon nitride partsInfo
- Publication number
- CA1306100C CA1306100C CA000552831A CA552831A CA1306100C CA 1306100 C CA1306100 C CA 1306100C CA 000552831 A CA000552831 A CA 000552831A CA 552831 A CA552831 A CA 552831A CA 1306100 C CA1306100 C CA 1306100C
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- Prior art keywords
- silicon nitride
- nitrogen
- layer
- silicon
- nitride layer
- Prior art date
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- Expired - Lifetime
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Abstract
ABSTRACT OF THE DISCLOSURE.
For joining shaped bodies of silicon nitride together, silicon nitride surfaces to be joined are first polished and then put into an apparatus for applying sputtered layers where they are first cleaned by ion bombardment in argon, followed immediately by sputtering with silicon in a nitrogen atmosphere such that a layer is deposited having a nitrogen content exceeding the Si3N4 stoichiometric ratio. This readily provides a layer of the composition Si3N5.5. A complementary nitrogen deficient layer is also provided in the joint before hot pressing,either in the form of a silicon layer that goes between the nitrogen-rich silicon nitride layers or in the form of a nitrogen-deficient silicon nitride layer sputtered onto a polished silicon nitride surface at relatively low nitrogen pressure. The parts are isostatically hot pressed together at 1500 to 1750°C in a nitrogen atmosphere. The layers which are usually thinner than 1 µm interact,with the disappearance of excess nitrogen and silicon, so that once the joint is produced all traces of jointure tend to disappear. The presence of a small amount of Y2O3 at the joint has a favorable effect.
For joining shaped bodies of silicon nitride together, silicon nitride surfaces to be joined are first polished and then put into an apparatus for applying sputtered layers where they are first cleaned by ion bombardment in argon, followed immediately by sputtering with silicon in a nitrogen atmosphere such that a layer is deposited having a nitrogen content exceeding the Si3N4 stoichiometric ratio. This readily provides a layer of the composition Si3N5.5. A complementary nitrogen deficient layer is also provided in the joint before hot pressing,either in the form of a silicon layer that goes between the nitrogen-rich silicon nitride layers or in the form of a nitrogen-deficient silicon nitride layer sputtered onto a polished silicon nitride surface at relatively low nitrogen pressure. The parts are isostatically hot pressed together at 1500 to 1750°C in a nitrogen atmosphere. The layers which are usually thinner than 1 µm interact,with the disappearance of excess nitrogen and silicon, so that once the joint is produced all traces of jointure tend to disappear. The presence of a small amount of Y2O3 at the joint has a favorable effect.
Description
d'fS ~ c~
~IL3~61!DO r IN THE UNITED STATES PATENT AND TRADEMA~K OF~IC~
"PROCESS FOR JOINING MOLDED SILICON NITRIDE~ =
PA~TS"
:, ' The invention concerns a process for Joining toge~her ; by isostatic hot pressing molded parts having a silicon nitride surface at least in the region of the ~oi~t, in which process polished surfaces to be ~oined, with or without an interposed silicon layer, are bonded together at pressures of at least 10 MPa and temperatures above 1300 C.
Various processes are known for joining Si3N4 ceramic parts. These can in a general ~ay be subdivided into two groups of processes which respectively operate with and without addition of other (foreign) matter.
In the first group is a joining process in which the bonding of molded parts made o isostatically hot pressed silicon r~itride (HPSN) or reaction bonded Si3N4 tRBSN) is intended to be obtained by nitriding an interposed silicon lS disk. According to another process, the bond between ~PSN or ~3~0~ ~
RBSN ceramics is produced by hot press~ng(H~ or lsostatic hot pressing (HIP) with an interpos~d layer of Si3~4 powder or an interposed RBSN disk. After isostatic hot pressing, bending s~rength values up to 276 MPa at room ~emperature are obtained.
In the second group, there are processes using intermediate layers of individual metals, alloys9 oxide compounds; glasses, etc. Thus, for e~ample, Si3N4 bodies having a disk interposed between them consisting of W, Mo, Cr or Co are bonded together by pressure welding. The products thus obtained, however, show the formation of cracks in the boundary layer. The ~oining of the Si3N~ bodies with the help of successive graduated layers of Si3~4 and ~ powders has seemed more promising: In this case, a faultless bond with shear strengths from lO0 to 200 MPa was obtained.
Various solders have been mentioned in the literature for insertion between Si3N4 workpieces to produce a joint.
Active solders or brazing compounds made from the elements Ag, Ti, Zr, Be, Cu, etc. have been found useful in this regard.
The:eutectics thereby formed indeed have good wettlng properties, but the temperature stability of such compositions is small, however.
Substantial strength values were successfully reached by means of glasses of the SiO2~A1203+Y203 or SiO2+Al203~MgO
c~mpGsi~ions. The Si3N4 surfac2 rcacted w'th the glass mel~s at temperatures around ~600C (pressure: 200 KPa;
time: 45 minutes). The Si2N20 thereby formed grew out from the Si3N4 surface into the weld seam. At the same time, the melt diffused along the grain boundaries into the Si3N4. Up to 800C a 4-point bending strength (~4B) of ~ 450 MPa was measured. With rise of the temperature, this value grew _z_ ~3~ 0~
~tlll fureher, but at 1000C- it nevertheless sank to zero.
Si3N4 was bonded in accordance with another proce~s by means of Si02~Ca0~Tl02 glasses. Breaking s~rength experiments sho~ed, however, that ~he ~ ~ value3 of the joint seam that was about 20 ~m thick did not go above 280 MPa~
The~ejoiningprocesses, whether worked with or ~ithout a foreign substance in the region of the joint, are not fully satisfactory, because either no convincingly good bond is obtained or else the nitriding cannot be obtained uni~ormly over the eneire region of the joint, or else a ~ea~ening of the bo~ndary layer is to be expected particularly on account of the effect of temperature on strength.
SUM~ARY OF THE INVENTION
-It is accordingly an obJect of the invention to provide a process by which a uniformly good bond of the molded parts can be obtalned across and beyond the joint region, a bond which is not subject to weakening in the joint seam as a result of the presence of foreign materials.
Briefly, at least on one of the surfaces to be joined a sputtered layer of silicon nitride is -applied before hot pressing which has an excess of nitrogen in its composition and the~, in hot pressing for joinlng the parts, measures are taken to provide a complementary nitrogen deficiency in the joint region In other words, in accordance with the invention, measures are taken to provide a ni~rogen excess in the region of the boundary layers growing together and a nitrogen deiciency in the material itself, so that merely by reactive sorting out and di~fusion into each other of the complementary layers, a growing together of the bodies can take place across _ -3-~3~6~
the boundary layer, by which the sea~ practically vanishes.
The ni~roge~ e~cess is produced by buildlng up an Si3N4+ layer by sputterlng of silicon in a regul&ted n~trogen colltalning atmosphere. "Sputterlng of silicon" is to be understood, in the contex~ of the foregoing description, as also including plasma ~upported processes in which the silicon is brought forth in the reaction chamber either as such or in the form of a compound.
The corresponding nitrogen deficiency can be for~ed either by a surface layer consisting only of silicon or likewise by sputtering of an obtainable Si3N4 layer. In particular, these layers or sputtered coatingsprovided on the finely polished surfaces of the molded bodies are thinner than about 2 ~m, and layer thicknesses exceeding the v~lue of the maximum surface roughness of the bodies to be bonded are of minor interest.
Thick~esses in the region from 0.1 to 0.3 ~m are particularly desired and sought.
The atomic composition of the sputtered layer which is built up by sputtering in nitrogen depends,wi.th relatively great sensiti~ity~ on the nitrogen pressure that prevails during the sputtering of the silicon, and,in fact, especially in the deficiency region while an approximate saturation is established in the nitrogen excess region, all of which leads more or less to compositions corresponding to Si3N5 59 SO that the buildlng up of these same nitrogen-excess silicon nitride layers seems particularly practical.
It further seems useful to provide immediately on top of such nitrogen-excess layers a deposit of silicon of about half the thickness, so that later when two analogously pre~
treated molded bodies are ~oined, a growing together across the .:: . . . , ., . ... ,.. .: . : .. ., .,:,:,: .,:;,: .:,:, ., , .. , . , .... .:
( --~3~6~
location of the ~olnt seam can be obtained by melting together and i~erpenetrating reaction.
Good results are also obtained, however, by generating a nitrogen~deflciency l~yer of the composition Si3N2-5 which is complementary to the Si3N5 S Such a nitrogen deficiency layer can be obtained by sputtertng silicon in a correspondlngly reduced (rarefied) nitrogen atmosphere.
The formation of such silicon nitride sputteredlayers by silicon sputter~ng is in itself known and the desired production of a nitrogen excess or of a nitrogen deficiency, dependent upon the prevailing nitrogen pressure and the other conditions, such as absolute pressure, spacing between sputtering electrode and substrate, applied voltage, Ptc., can be determined directly and simply by a preliminary run of the operation. In particular, and by way of example, nitrogen pressures in the region from 10 3 to 10 1 mbar are useful and applied voltages between a Eew hundred volts and durations of sputtering between 10 and 100 minutes.
Further details of experimental information regarding sputtering nitrogenous silicon films are published in our article in Thin Solid Films (1987), pp. 223-233.
Immediately before the application of such sputtered layers, ehe surfaces to be ~oined are preferably cleaned by "bombardment" with argon ions ("argon-etched").
~5 The joinlng procedure is carried out most successfully at temperatures in the region from 1500 to 1750 C and pressures applied to press the parts together are preferably in the region from ~0 to 30 MPa, for application for 20 to 120 minutes or somewhat more in a press which i~ evacuated and flushed wlth N2.
When Si3N4 molded parts of ~PSN material are used which have been produced with addition of a small amount of Y203, the yttrium oxide present in the surface appears to have - 3L3~
an effect as an aide to consolidation. - -The lnvention will now be degcribed by way of - -illustration wlth reerence ~o an example of performance of the process.
S EXAMPLE:
~3~E____ion of Samples Prismatic samp~es measuring 12 x 12 x 5 mm or 16.3 x 16.3 x 5 mm (both sizes have been usea in this example) were polished at their faces which wereto be ~oined (12 ~ 12 mm or 16.3 x 16.3 mm as the case may be). These samples were of HP quality Si3N4 obtalned from tbe Hertel-International firm in Germany. The polished samples, before the application of layers thereto, were then cleaned in an ultrasonic bath and dried. Immediately before sputtering on of the SiNX layers, lS the polished surfaces were etched with Ar~ ions in situ after having been installed in the sputtering apparatus through vacuum locks. Thin fllms were applied by reactiva sputtering of a silicon target in the presence of N2. For this purpose a sputtering apparatus with a planar HF magnetron cathode was used (Type Z 400 of the Leybold-Heraeus firm of Germany~.
Joining of Samples For joining together the Si3N4 samples, two varieties of làyers were provided to the parts for different joining conditions, as the following table shows.
Test ~ Joint layers produced Layer Temp. Time Pressing No. by sputtering thickness Cmin ~orce ,um MPa S~3N5, 5/Si3Nz ~ 5 ~ , / , 3 1650 120 30 2 - Si3N5 ~ Si/Si3Ns 5 0,2/0-,l/~,l/012 1600 ~ 0 30-~3'~6~
The sputtered pairs of samples were joined toge~her in a laboratory hot pressO During the pressing operation, the S~3N4 samples were located in a graph$te guide structure in order toprevent lateral shifting. For avoiding a chemical reaction between metallic pre~sing dies and ~he sample, the contact surfaces were isolated from each other by graphite cylinders or SiC dis~so The press chamber was evacuated and flushed with N2 several t~mes before hot pressing. In each case an ~2 pressure of 40 KPa was established bafore pressing. The test samples were cut perpendicularly to the joint seam and then were examined with a light microscope as well as with an electron beam microsonde, by which it was established that the joint seam was no longer recognizable.
Although the invention has been described with reference to a particular example, it will be recognized that ~ariations and modifications are possible within the inventive concept.
~IL3~61!DO r IN THE UNITED STATES PATENT AND TRADEMA~K OF~IC~
"PROCESS FOR JOINING MOLDED SILICON NITRIDE~ =
PA~TS"
:, ' The invention concerns a process for Joining toge~her ; by isostatic hot pressing molded parts having a silicon nitride surface at least in the region of the ~oi~t, in which process polished surfaces to be ~oined, with or without an interposed silicon layer, are bonded together at pressures of at least 10 MPa and temperatures above 1300 C.
Various processes are known for joining Si3N4 ceramic parts. These can in a general ~ay be subdivided into two groups of processes which respectively operate with and without addition of other (foreign) matter.
In the first group is a joining process in which the bonding of molded parts made o isostatically hot pressed silicon r~itride (HPSN) or reaction bonded Si3N4 tRBSN) is intended to be obtained by nitriding an interposed silicon lS disk. According to another process, the bond between ~PSN or ~3~0~ ~
RBSN ceramics is produced by hot press~ng(H~ or lsostatic hot pressing (HIP) with an interpos~d layer of Si3~4 powder or an interposed RBSN disk. After isostatic hot pressing, bending s~rength values up to 276 MPa at room ~emperature are obtained.
In the second group, there are processes using intermediate layers of individual metals, alloys9 oxide compounds; glasses, etc. Thus, for e~ample, Si3N4 bodies having a disk interposed between them consisting of W, Mo, Cr or Co are bonded together by pressure welding. The products thus obtained, however, show the formation of cracks in the boundary layer. The ~oining of the Si3N~ bodies with the help of successive graduated layers of Si3~4 and ~ powders has seemed more promising: In this case, a faultless bond with shear strengths from lO0 to 200 MPa was obtained.
Various solders have been mentioned in the literature for insertion between Si3N4 workpieces to produce a joint.
Active solders or brazing compounds made from the elements Ag, Ti, Zr, Be, Cu, etc. have been found useful in this regard.
The:eutectics thereby formed indeed have good wettlng properties, but the temperature stability of such compositions is small, however.
Substantial strength values were successfully reached by means of glasses of the SiO2~A1203+Y203 or SiO2+Al203~MgO
c~mpGsi~ions. The Si3N4 surfac2 rcacted w'th the glass mel~s at temperatures around ~600C (pressure: 200 KPa;
time: 45 minutes). The Si2N20 thereby formed grew out from the Si3N4 surface into the weld seam. At the same time, the melt diffused along the grain boundaries into the Si3N4. Up to 800C a 4-point bending strength (~4B) of ~ 450 MPa was measured. With rise of the temperature, this value grew _z_ ~3~ 0~
~tlll fureher, but at 1000C- it nevertheless sank to zero.
Si3N4 was bonded in accordance with another proce~s by means of Si02~Ca0~Tl02 glasses. Breaking s~rength experiments sho~ed, however, that ~he ~ ~ value3 of the joint seam that was about 20 ~m thick did not go above 280 MPa~
The~ejoiningprocesses, whether worked with or ~ithout a foreign substance in the region of the joint, are not fully satisfactory, because either no convincingly good bond is obtained or else the nitriding cannot be obtained uni~ormly over the eneire region of the joint, or else a ~ea~ening of the bo~ndary layer is to be expected particularly on account of the effect of temperature on strength.
SUM~ARY OF THE INVENTION
-It is accordingly an obJect of the invention to provide a process by which a uniformly good bond of the molded parts can be obtalned across and beyond the joint region, a bond which is not subject to weakening in the joint seam as a result of the presence of foreign materials.
Briefly, at least on one of the surfaces to be joined a sputtered layer of silicon nitride is -applied before hot pressing which has an excess of nitrogen in its composition and the~, in hot pressing for joinlng the parts, measures are taken to provide a complementary nitrogen deficiency in the joint region In other words, in accordance with the invention, measures are taken to provide a ni~rogen excess in the region of the boundary layers growing together and a nitrogen deiciency in the material itself, so that merely by reactive sorting out and di~fusion into each other of the complementary layers, a growing together of the bodies can take place across _ -3-~3~6~
the boundary layer, by which the sea~ practically vanishes.
The ni~roge~ e~cess is produced by buildlng up an Si3N4+ layer by sputterlng of silicon in a regul&ted n~trogen colltalning atmosphere. "Sputterlng of silicon" is to be understood, in the contex~ of the foregoing description, as also including plasma ~upported processes in which the silicon is brought forth in the reaction chamber either as such or in the form of a compound.
The corresponding nitrogen deficiency can be for~ed either by a surface layer consisting only of silicon or likewise by sputtering of an obtainable Si3N4 layer. In particular, these layers or sputtered coatingsprovided on the finely polished surfaces of the molded bodies are thinner than about 2 ~m, and layer thicknesses exceeding the v~lue of the maximum surface roughness of the bodies to be bonded are of minor interest.
Thick~esses in the region from 0.1 to 0.3 ~m are particularly desired and sought.
The atomic composition of the sputtered layer which is built up by sputtering in nitrogen depends,wi.th relatively great sensiti~ity~ on the nitrogen pressure that prevails during the sputtering of the silicon, and,in fact, especially in the deficiency region while an approximate saturation is established in the nitrogen excess region, all of which leads more or less to compositions corresponding to Si3N5 59 SO that the buildlng up of these same nitrogen-excess silicon nitride layers seems particularly practical.
It further seems useful to provide immediately on top of such nitrogen-excess layers a deposit of silicon of about half the thickness, so that later when two analogously pre~
treated molded bodies are ~oined, a growing together across the .:: . . . , ., . ... ,.. .: . : .. ., .,:,:,: .,:;,: .:,:, ., , .. , . , .... .:
( --~3~6~
location of the ~olnt seam can be obtained by melting together and i~erpenetrating reaction.
Good results are also obtained, however, by generating a nitrogen~deflciency l~yer of the composition Si3N2-5 which is complementary to the Si3N5 S Such a nitrogen deficiency layer can be obtained by sputtertng silicon in a correspondlngly reduced (rarefied) nitrogen atmosphere.
The formation of such silicon nitride sputteredlayers by silicon sputter~ng is in itself known and the desired production of a nitrogen excess or of a nitrogen deficiency, dependent upon the prevailing nitrogen pressure and the other conditions, such as absolute pressure, spacing between sputtering electrode and substrate, applied voltage, Ptc., can be determined directly and simply by a preliminary run of the operation. In particular, and by way of example, nitrogen pressures in the region from 10 3 to 10 1 mbar are useful and applied voltages between a Eew hundred volts and durations of sputtering between 10 and 100 minutes.
Further details of experimental information regarding sputtering nitrogenous silicon films are published in our article in Thin Solid Films (1987), pp. 223-233.
Immediately before the application of such sputtered layers, ehe surfaces to be ~oined are preferably cleaned by "bombardment" with argon ions ("argon-etched").
~5 The joinlng procedure is carried out most successfully at temperatures in the region from 1500 to 1750 C and pressures applied to press the parts together are preferably in the region from ~0 to 30 MPa, for application for 20 to 120 minutes or somewhat more in a press which i~ evacuated and flushed wlth N2.
When Si3N4 molded parts of ~PSN material are used which have been produced with addition of a small amount of Y203, the yttrium oxide present in the surface appears to have - 3L3~
an effect as an aide to consolidation. - -The lnvention will now be degcribed by way of - -illustration wlth reerence ~o an example of performance of the process.
S EXAMPLE:
~3~E____ion of Samples Prismatic samp~es measuring 12 x 12 x 5 mm or 16.3 x 16.3 x 5 mm (both sizes have been usea in this example) were polished at their faces which wereto be ~oined (12 ~ 12 mm or 16.3 x 16.3 mm as the case may be). These samples were of HP quality Si3N4 obtalned from tbe Hertel-International firm in Germany. The polished samples, before the application of layers thereto, were then cleaned in an ultrasonic bath and dried. Immediately before sputtering on of the SiNX layers, lS the polished surfaces were etched with Ar~ ions in situ after having been installed in the sputtering apparatus through vacuum locks. Thin fllms were applied by reactiva sputtering of a silicon target in the presence of N2. For this purpose a sputtering apparatus with a planar HF magnetron cathode was used (Type Z 400 of the Leybold-Heraeus firm of Germany~.
Joining of Samples For joining together the Si3N4 samples, two varieties of làyers were provided to the parts for different joining conditions, as the following table shows.
Test ~ Joint layers produced Layer Temp. Time Pressing No. by sputtering thickness Cmin ~orce ,um MPa S~3N5, 5/Si3Nz ~ 5 ~ , / , 3 1650 120 30 2 - Si3N5 ~ Si/Si3Ns 5 0,2/0-,l/~,l/012 1600 ~ 0 30-~3'~6~
The sputtered pairs of samples were joined toge~her in a laboratory hot pressO During the pressing operation, the S~3N4 samples were located in a graph$te guide structure in order toprevent lateral shifting. For avoiding a chemical reaction between metallic pre~sing dies and ~he sample, the contact surfaces were isolated from each other by graphite cylinders or SiC dis~so The press chamber was evacuated and flushed with N2 several t~mes before hot pressing. In each case an ~2 pressure of 40 KPa was established bafore pressing. The test samples were cut perpendicularly to the joint seam and then were examined with a light microscope as well as with an electron beam microsonde, by which it was established that the joint seam was no longer recognizable.
Although the invention has been described with reference to a particular example, it will be recognized that ~ariations and modifications are possible within the inventive concept.
Claims (10)
1. Process of joining together,by isostatic hot pressing, molded parts having a silicon nitride surface at least in the portions of said respective parts, adjoining the intended joint, comprising the steps of;
polishing the silicon nitride surfaces which are to be joined together;
applying by sputtering a silicon nitride layer having a nitrogen content exceeding the Si3N4 stoichiometric ratio on at least one of said surfaces which are to be joined together, and isostatically hot pressing together said surfaces which are to be joined with provision between said surfaces of a complementary nitrogen deficiency relative to silicon for establishment of an at least approximate stoichiometric ratio of nitrogen to silicon in and across said joint by diffusive migration during hot pressing.
polishing the silicon nitride surfaces which are to be joined together;
applying by sputtering a silicon nitride layer having a nitrogen content exceeding the Si3N4 stoichiometric ratio on at least one of said surfaces which are to be joined together, and isostatically hot pressing together said surfaces which are to be joined with provision between said surfaces of a complementary nitrogen deficiency relative to silicon for establishment of an at least approximate stoichiometric ratio of nitrogen to silicon in and across said joint by diffusive migration during hot pressing.
2. Process as defined in claim 1, wherein a said nitride layer having a nitrogen content exceeding the Si3N4 stoichiometric ratio, having an approximate composition of Si3N5.5, and having a thickness not greater than 1 µm, is applied on both of said surfaces which are to be joined together and the said provision between said surfaces of a complementary nitrogen deficiency relative to silicon is performed by providing a silicon layer of about half the thickness of said Si3N5.5 layer immediately adjoining each said Si3N5.5 layer before said surfaces are hot pressed together.
3. Process as defined in claim 1, wherein a said silicon nitride layer having a nitrogen content exceeding the Si3N4 stoichiometric ratio is applied by sputtering on one of said polished silicon nitride surfaces which are to be joined together and,on the silicon nitride surface which is to be joined with said one silicon nitride surface,there is applied by sputtering a nitrogen deficient silicon nitride layer of substantially the same thickness as said silicon nitride layer having excess nitrogen content, said silicon nitride layer having excess nitrogen content being applied under sputtering conditions producing an approximate layer composition of Si3N5.5 and said nitrogen deficient silicon nitride layer being applied under sputtering conditions producing an approximate layer composition of Si3N2.5 whereby said complementary nitrogen deficiency relative to silicon is established between said surfaces, both said layers being applied prior to hot pressing said polished silicon nitride surfaces of said molded parts together.
4. Process as defined in claim 3, wherein both said silicon nitride layer having excess nitrogen content and said nitrogen deficient silicon nitride layer have a thickness of about 0.3 µm.
5. Process as defined in claim 2, wherein both of said silicon nitride layers having an approximate composition of Si3N5.5 have a thickness of about 0.2 µm and wherein the total thickness of silicon interposed between them likewise has a thickness of about 0.2 µm.
6. Process as defined in claim 2, wherein said molded parts to be joined together are formed by silicon nitride containing Y2O3.
7. Process as defined in claim 3, wherein said molded parts to be joined together are formed by silicon nitride containing Y2O3.
8. Process as defined in claim 4, wherein said molded parts to be joined together are formed by silicon nitride containing Y2O3.
9. Process as defined in claim 1, wherein the step of applying a silicon nitride layer by sputtering is preceded by argon etching the polished silicon nitride surface on which a silicon nitride layer is to be applied, said argon etching being performed by argon ion bombardment.
10. Process as defined in claim 1, wherein the step of isostatically hot pressing together said surfaces which are to be joined is performed at a temperature in the range from 1500 to 1750°C and at pressures in the range from 10 to 30 MPa for from 20 to 120 minutes in a nitrogen atmosphere.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000552831A CA1306100C (en) | 1987-11-26 | 1987-11-26 | Process for joining molded silicon nitride parts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000552831A CA1306100C (en) | 1987-11-26 | 1987-11-26 | Process for joining molded silicon nitride parts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1306100C true CA1306100C (en) | 1992-08-11 |
Family
ID=4136939
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000552831A Expired - Lifetime CA1306100C (en) | 1987-11-26 | 1987-11-26 | Process for joining molded silicon nitride parts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1306100C (en) |
-
1987
- 1987-11-26 CA CA000552831A patent/CA1306100C/en not_active Expired - Lifetime
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