Claims
- 1. An apparatus for heating powders or powder compacts for consolidation comprising:
- a presure vessel having a chamber, said powder or compact disposed in said chamber and essentially isolated therein such that fluidic pressure can act on a majority of the surface area of the powder or compact; p1 means for directly induction heating the powder or compact, said heating means disposed in said chamber between said powder or compact and said vessel, said heating means requiring no independent cooling; and
- means for compacting powder or powder compact, said compacting means in communication with said chamber.
- 2. An apparatus as described in Claim 1 wherein the induction heating means includes induction coils disposed in the chamber, and an RF generator electrically connected to the induction coils such that induction heating is provided to the powder or powder compact.
- 3. An apparatus as described in claim 2 wherein the compacting means includes means for applying a shear stress to the powder or powder compact.
- 4. An apparatus as described in claim 3 wherein the compacting means includes means for applying an isostatic stress to the powder or powder compact.
- 5. An apparatus as described in claim 4 wherein the RF generator includes a variable frequency RF generator.
- 6. An apparatus as described in claim 5 wherein the isostatic stress is in excess of 5 KSI.
- 7. An apparatus as described in claim 2 wherein the compacting means includes means for applying an isostatic stress to the powder or powder compact.
- 8. An apparatus as described in claim 7 wherein the compacting means includes a stand disposed in the chamber to support the powder or powder compact therein.
- 9. An apparatus as described in claim 1 wherein the apparatus has no cooling feedthroughs.
- 10. A method for heating powders or powder compacts for consolidation comprising the steps of:
- disposing the powder or powder compact within a pressure vessel such that it is essentially isolated therein and fluidic pressure can act on a majority of the surface area of the powder or compact;
- heating the powder or powder compact directly by induction heating means which requires no cooling and which is disposed within the pressure vessel between the vessel and the powder or powder compact; and
- pressurizing the vessel in excess of 5 KSI such that the powder or powder compact is isostatically stressed.
- 11. A method as described in claim 10 wherein after the heating step there is the step of applying a shear stress to the powder or powder compact.
FIELD OF THE INVENTION
This is a continuation of copending application Ser. No. 07/544,745 filed on Jun. 27, 1990 now abandoned.
The present invention is related to the consolidation of powders or powder compacts. More specifically, the present invention is related to the consolidation of powders or powder compacts using induction heating.
The theory [Kaysser, W. A., "Present State of Modeling of Hot Isostatic Pressing, " Second International Conference on Hot Isostatic Pressing--Theories and Applications, Gaithersburg, Md., Jun. 7-9, 1989] and technology [Fujikawa, T. and N. Kawai, "Recent Trends in HIP Process in Japan," Second International Conference on Hot Isostatic Pressing--Theories and Applications, Gaithersburg, Md., Jun. 7-9, 1989] of hot isostatic pressing (HIPing) have recently been reviewed at the Second International Conference on Hot Isostatic Pressing--Theories and Applications. Several modifications to the basic HIPing process for consolidation of particulates and composites have also been recently explored. Two such modifications involve altering the state of stress and strain during compaction. The first of these is sinter forging [Raj, R., "Enhancement of Strength through Sinter Forging, " J. Am. Ceram. Soc., 70 [7], pp. 514-520, 1987], which has been used to increase the fracture resistance of alumina; the second is hot triaxial compaction (HTC) [Piehler, H. R. and D. M. Watkins, "Hot Triaxial Compaction: Apparatus Description and Initial Experimental Results, " Second International Conference on Hot Isostatic Pressing--Theories and Applications, Gaithersburg, Md., Jun. 7-9, 1989], which has been used by Piehler and Watkins to enhance the densification of Ti-6A1-4V spherical powder compacts.
An essential problem in hot isostatic pressing (HIPing) of metallic powders or powder compacts is the rapid and uniform heating of these powders or powder compacts to a required temperature. Recent work in microwave sintering of ceramics [Sutton, W. H. , "Microwave Processing of Ceramic Materials," Ceramic Bulletin, 68 [2], pp. 376-386, 1989] suggests that a method of heating the specimen from within would be highly desirable. Radio-frequency induction heating is a well established method of heating all types of metals and alloys for surface hardening, welding [Zinn, S. and S. L. Semiatin, Elements of Induction Heating: Design, Control, and Applications, ASM International, Metals Park, Ohio, 1988], etc. To date, no one has solved all of the problems associated with the application of radio-frequency induction heating technology to the sinter forging, HIPing, or HTCing processes. The successful implementation of R.F. induction heating to these processes could yield results superior to those achievable using radiative heating for the following reasons:
The present invention pertains to an apparatus for heating powders or powder compacts for consolidation. The apparatus comprises a pressure vessel having a chamber. There is means for directly induction heating the powder or powder compact. Additionally, the apparatus is comprised of means for consolidating a powder or powder compact. The means for directly induction heating the powder or powder compact essentially provides uniform heating to the powder while the compacting means consolidates the powder or powder compact in the chamber of the pressure vessel.
A method for consolidation of powders or powder compacts which has the steps of heating directly by induction the powder or powder compact, and applying an isostatic stress to the powder or powder compact.
US Referenced Citations (9)
Continuations (1)
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Number |
Date |
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544745 |
Jun 1990 |
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Patent Grant
5134260
