US4812272A
Expired / Lapsed
US
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Process by compacting a porous structural member for hot isostatic pressing
Assignee: Deutsches Zentrum für Luft- und Raumfahrt eV
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Filing: 1987-02-05
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Granted: 1989-03-14
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Expires: 2007-02-05
Abstract
Abstract A process for compacting a porous ceramic structural member having a compated shape and an optional size by encapsulation with material of the same type and capable of sintering and subsequently subjected to hot-isostatic pressing; immersing the preformed body in a suspension of a material of the same type in a solvent but which contains no sintering aid and forming a first encapsulating layer; evaporating the solvent; immersing the thus obtained body in a second suspension of a material in a solvent of the same type capable of sintering and which contains one or more sintering aids, and forming a second encapsulating layer; evaporating the solvent; subjecting the thus obtained body at an elevated temperature in an atmosphere of a protective gas for a sufficient period of time to sinter the same; isostatically compacting the body provided with a tight-sintered surface; and mechanically removing the encapsulating layers.
Inventors
- 👤 Jurgen Heinrich
- 👤 Manfred Bohmer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:03
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/645; C04B35/6455; B; B22; B22F; B22F3/00; B22F3/12; B22F3/1208; B22F3/1216; B22F3/1241; B22F3/125; B22F3/1258; B22F3/1266; C04B35/515; C04B35/56; C04B35/565; C04B35/575; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
250 words
A process for compacting a structural member having a complicated shape and an optional size and which is made of porous ceramic material by encapsulation of said member with porous ceramic material of the same type and which is capable of being sintered and subsequently subjected to hot-isostatic pressing, comprising the steps of: (a) immersing a preformed porous ceramic body in a suspension of a porous ceramic material of the same type and which has substantially the same coefficient of thermal expansion as said preformed porous ceramic body in a solvent and which contains no sintering aid, and forming a first encapsulating layer on said body; (b) evaporating the solvent; (c) immersing the thus obtained body in a second suspension of a porous ceramic material of the same type and which has substantially the same coefficient of thermal expansion as said preformed porous ceramic body in a solvent and which is capable of being sintered and which contains at least one sintering aid, and forming a second encapsulating layer on said body; (d) evaporating the solvent; (e) subjecting the thus obtained body to an elevated temperature in an atmosphere of a protective gas for a sufficient period of time to sinter said body substantially completely; (f) isostatically compacting said body provided with a tight-sintered surface at pressures in a range of from about 10 MPa to about 300 MPa and temperatures in a range of from about 1600° C. to about 2300° C.; (g) mechanically removing the two encapsulating layers.
Claim 2
Dependent Claim
250 words
A process for compacting a structural member having a complicated shape and an optional size and which is made of porous ceramic material by encapsulation of said member with porous ceramic material of the same type and which is capable of being sintered and subsequently subjected to hot-isostatic pressing, comprising the steps of: (a) immersing a preformed porous ceramic body in a suspension of a porous ceramic material of the same type and which has substantially the same coefficient of thermal expansion as said preformed porous ceramic body in a solvent and which contains no sintering aid, and forming a first encapsulating layer on said body; (b) evaporating the solvent; (c) immersing the thus obtained body in a second suspension of a porous ceramic material of the same type and which has substantially the same coefficient of thermal expansion as said preformed porous ceramic body in a solvent and which is capable of being sintered and which contains at least one sintering aid, and forming a second encapsulating layer on said body; (d) evaporating the solvent; (e) subjecting the thus obtained body to an elevated temperature in an atmosphere of a protective gas for a sufficient period of time to sinter said body substantially completely; (f) isostatically compacting said body provided with a tight-sintered surface at pressures in a range of from about 10 MPa to about 300 MPa and temperatures in a range of from about 1600° C. to about 2300° C.; (g) mechanically removing the two encapsulating layers.
Claim 3
Dependent Claim
18 words
A process according to claim 1, wherein the preformed, porous ceramic body is made of non-oxide ceramic material.
Claim 4
Dependent Claim
17 words
A process according to claim 1 wherein the preformed, porous ceramic body is made of silicon nitride.
Claim 5
Dependent Claim
17 words
A process according to claim 1 wherein the preformed, porous ceramic body is made of silicon carbide.
Claim 6
Dependent Claim
17 words
A process according to claim 1 wherein the preformed, porous ceramic body is made of boron nitride.
Claim 7
Dependent Claim
17 words
A process according to claim 1 wherein the preformed, porous ceramic body is made of boron carbide.
Claim 8
Dependent Claim
67 words
A process according to claim 1 wherein a suspension consisting of from about 30 to about 70% by weight of a powder of porous ceramic material of the same type as the porous ceramic material of which the structural member is made but containing no sintering aid, and from about 70 to about 30% by weight of a solvent, is employed to form the first encapsulating layer.
Claim 9
Dependent Claim
38 words
A process according to claim 1 wherein the same porous ceramic material of which the porous ceramic structural member consists is employed in the form of a powder as the solid material to form the first encapsulating layer.
Claim 10
Dependent Claim
15 words
A process according to claim 1 wherein the solvent is a readily volatile organic solvent.
Claim 11
Dependent Claim
11 words
A process according to claim 1 wherein the solvent is isopropanol.
Claim 12
Dependent Claim
19 words
A process according to claim 1 wherein the solvent is evaporated at an elevated temperature in a drying chamber.
Claim 13
Dependent Claim
17 words
A process according to claim 1 wherein the solvent is evaporated in a stream of hot air.
Claim 14
Dependent Claim
30 words
A process according to claim 1 wherein the solvent is evaporated by allowing the molded article coated with a first encapsulating layer to be exposed to air at room temperature.
Claim 15
Dependent Claim
41 words
A process according to claim 1 wherein the first encapsulating layer while still wet is coated with a powdery material capable of sintering and the particle size of which is in excess of the particle size of the first encapsulating layer.
Claim 16
Dependent Claim
27 words
A process according to claim 14 wherein the materials employed for the first encapsulating layer and the powdery material are the same but have different particle sizes.
Claim 17
Dependent Claim
48 words
A process according to claim 1 wherein a suspension consisting of from about 30 to about 70% by weight of a solid proportion of porous ceramic material and from about 70 to about 30% by weight of a solvent proportion is employed to form the second encapsulating layer.
Claim 18
Dependent Claim
36 words
A process according to claim 16 wherein the ratio of the solid proportion to the solvent proportion in the suspension employed to form the second encapsulating layer is adjusted to a ratio by weight of 1:1.
Claim 19
Dependent Claim
45 words
A process according to claim 16 wherein the solid proportion of the suspension consists of from about 50 to 99% by weight of a powdery porous ceramic material capable of sintering and from about 1 to 50% by weight of at least one sintering aid.
Claim 20
Dependent Claim
38 words
A process according to claim 1 wherein the same material of which the preform and the first encapsulating layer consists is employed as the solid material capable of sintering on the material to form the second encapsulating layer.
Claim 21
Dependent Claim
26 words
A process according to claim 1 wherein the solvent employed in the formation of the second encapsulating layer is evaporated in a stream of hot air.
Claim 22
Dependent Claim
42 words
A process according to claim 1 wherein the solvent employed in the formation of the second encapsulating layer is evaporated under vacuum and at increased temperature in a pressure oven which is employed for the subsequent steps of sintering and hot-isostatic pressing.
Claim 23
Dependent Claim
39 words
A process according to claim 1 wherein the steps of applying a second encapsulating layer containing at least one sintering aid to the preformed porous ceramic body and the subsequent drying of said body are repeated, optionally, several times.
Claim 24
Dependent Claim
18 words
A processing according to claim 1 wherein nitrogen is employed as the protective gas in the sintering procedure.
Claim 25
Dependent Claim
20 words
A process according to claim 1 wherein the sintering procedure is carried out for a period of about 10 minutes.
Claim 26
Dependent Claim
16 words
A process according to claim 1 wherein the two encapsulsating layers are mechanically removed by sand-blasting.
References Cited (Backward Citations)
US4112143A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-13 | 1992-09-12 | 1993-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-13 | 1996-09-12 | 1997-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-13 | 2000-09-12 | 2001-03-14 | $7700.00 | Window Closed / Lapsed |