USH1075H - Tungsten heavy alloys - Google Patents
Tungsten heavy alloys Download PDFInfo
- Publication number
- USH1075H USH1075H US07/830,215 US83021592A USH1075H US H1075 H USH1075 H US H1075H US 83021592 A US83021592 A US 83021592A US H1075 H USH1075 H US H1075H
- Authority
- US
- United States
- Prior art keywords
- tungsten
- alloy
- alloys
- powdered
- heavy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
- C22C27/04—Alloys based on tungsten or molybdenum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/045—Alloys based on refractory metals
Definitions
- the invention relates to heavy alloys of tungsten and methods of producing such alloys.
- Tungsten heavy alloys which are of great value in counter weights for aircraft, in ballistics, and in other applications, are conventionally produced by liquid phase sintering of mixed elemental powders. Alloys produced by this method are generally two-phase composites consisting of rounded tungsten grains dispersed in an alloy metrix.
- tungsten heavy alloys are strongly dependent upon their specific microstructural features: for example, the grain size, contiguity, dihedral angle and the volume fraction of the tungsten phase.
- the optimal microstructure exhibits low contiguity, small grain size, and strong W-W grain boundary and W-matrix interface.
- Solid state sintering is a known means for obtaining finer alloy microstructures.
- the microstructure of solid state sintered heavy alloys using tungsten powder of spherical morphology exhibit low continguity and finer grain size in comparison with materials produced by liquid phase sintering.
- the mechanical properties of these solid state-produced materials, especially their ductility, is very low.
- the probable cause of low ductilities in these materials is the weak interphase and interface boundaries of their composite microstructure.
- Still another object of the present invention is to provide methods for producing and fabricating tungsten heavy alloys exhibiting the properties described hereinabove.
- the present invention resides, briefly stated, in the use of plasma rapid solidification technology to fabricate improved tungsten/tungsten alloys of spherical morphology.
- the composition of the alloys by weight is based on the following generic formula:
- the alloys are produced by introducing elemental or alloy powders into a thermal spray plasma gun, melting the powders in the hot zone of the gun and then spraying the molten material into a collecting chamber where they are cooled by the gas in the chamber, whereupon the resulting powder is collected.
- tungsten heavy alloys refers to alloys of tungsten which have a density greater than 13 g/cc.
- well-mixed metallic powder comprising from about 80 to about 99% by weight tungsten and from about 1 to about 20% by weight of at least one alloying metal selected from the group consisting of molybdenum, tantalum, niobium, hafnium, rhenium, and chromium is fed by internal or external feed into a thermal spray plasma kgun, for example, a Baystate Model PG-100 plasma gun (Baystate Co., Westboro, Mass.). That gun has a power rating of 28 klowatts and an internal feed nozzle.
- the ionized gas plume in a thermal spray plasma gun can reach temperatures of 10,000° Kelvin and is particularly suitable for melting tungsten, which has the highest melting point of any metal (3410° C.).
- the mixed metallic powder is passed rapidly through the gas plume of the plasma gun, which plume may comprise ionized inert gases, such as argon, together with a small amount of helium or hydrogen.
- the powder melts almost instantaneously in the extremely hot gas plume, becoming a stream of molten metal alloy droplets.
- the molten alloy is then sprayed in droplet form into a collecting chamber having an atmosphere composed of one or more relatively cool, inert gases, for example, argon, helium or nitrogen.
- the temperature of the atmosphere in the chamber is prefereably ambient or near-ambient, but may be any temperature low enough to cause rapid solidification of the metal droplets.
- the molten alloy droplets solidify or "freeze" into tungsten alloy powder granules in the collecting chamber, and the powder is collected.
- the resultant powder has an average grain size of from about 5 to about 30um, and preferably from about 15 to about 25 um.
- the tungsten alloy powders are further treated in a heated hydrogen-containing atmosphere, preferably at about 600°-900° C., to thoroughly clean and reduce any surface oxides.
- the clean alloy powders can then be intermixed with elemental or alloy powders of at least one metal selected from the group consisting of copper, iron, nickel, cobalt and tantalum in a weight ratio of from about 90 to about 100% tungsten alloy powder and from about 1 to about 10% of the other metal powders.
- the intermixed powder may be compacted by dynamic or explosive compaction to form near full density metallic compacts.
- Dynamic or explosive compaction produces a very small amount of incipient melting around the tungsten particles for a very short time. The presence of this liquid strongly improves the interface strength, but since the quantity of the melt and the time period is extremely small, any measurable grain growth of tungsten is prevented.
- the near full density compact can be further thermomechanically processed by, for example, extrusion, swaging or rolling to improve the properties of the material.
- the fully dense tungsten heavy alloy materials produced according to the foregoing process exhibit a fine-grained microstructure, low continguity and improved interface strength and ductility in comparison with prior art materials.
- the novel tungsten heavy alloys are extremely valuable for kinetic energy penetrator applications, and may substantially improve the performance of kinetic energy warheads.
- compositions and methods which achieve the various objects of the invention and which are well adapted to meet the conditions of practical use.
Abstract
Tungsten heavy alloys comprising by weight from about 80 to about 100% tuten and from about 0 to about 20% of one or more heavy alloying metals are produced by introducing powders of tungsten and the alloying metals into a thermal spray plasma gun, melting the powders in the hot zone of the gun to form a molten alloy and then spraying the molten alloy in droplet form into a collecting chamber where the droplets are solidified, and the resultant alloy in powdered form is collected. The powdered alloy can be further mixed with powdered copper, iron, nickel, cobalt or tantalum and compacted by dynamic or explosive compaction to form a near full density material. Full density materials are produced by further thermomechanical processing of the compact.
Description
The invention described herein may be manufactured, used, and licensed by or for the Government for Government purposes without payment to me of any royalties thereon.
1. Field of the Invention
The invention relates to heavy alloys of tungsten and methods of producing such alloys.
2. Description of the Prior Art
Tungsten heavy alloys, which are of great value in counter weights for aircraft, in ballistics, and in other applications, are conventionally produced by liquid phase sintering of mixed elemental powders. Alloys produced by this method are generally two-phase composites consisting of rounded tungsten grains dispersed in an alloy metrix.
The mechanical properties of tungsten heavy alloys are strongly dependent upon their specific microstructural features: for example, the grain size, contiguity, dihedral angle and the volume fraction of the tungsten phase. For a given tungsten content, the optimal microstructure exhibits low contiguity, small grain size, and strong W-W grain boundary and W-matrix interface.
There are serious drawbacks associated with the fabrication of tungsten heavy alloys by liquid phase sintering, one of the principal problems being that such alloys almost always exhibit excessive grain growth.
Solid state sintering is a known means for obtaining finer alloy microstructures. In fact, the microstructure of solid state sintered heavy alloys using tungsten powder of spherical morphology exhibit low continguity and finer grain size in comparison with materials produced by liquid phase sintering. However, the mechanical properties of these solid state-produced materials, especially their ductility, is very low. The probable cause of low ductilities in these materials is the weak interphase and interface boundaries of their composite microstructure.
Improved tungsten heavy alloys and improved methods for producing the same are required.
1. Objects of the Invention
It is an object of the present invention to provide tungsten heavy alloys with improved microstructural features and mechanical properties in comparison with prior art alloys.
It is another object of the present invention to provide such alloys with fine grain size, low contiguity, strong W-W grain boundary and W-matrix interface.
It is a further object of the present invention to provide tungsten heavy alloys with higher strength and ductility than solid state-processed materials.
Still another object of the present invention is to provide methods for producing and fabricating tungsten heavy alloys exhibiting the properties described hereinabove.
2. Brief Description of the Invention
In keeping with the foregoing objects and others which will become hereinafter aparent, the present invention resides, briefly stated, in the use of plasma rapid solidification technology to fabricate improved tungsten/tungsten alloys of spherical morphology. The composition of the alloys by weight is based on the following generic formula:
W.sub.100-x --(Mo, Ta, Nb, Hf, Re, Cr).sub.x
The alloys are produced by introducing elemental or alloy powders into a thermal spray plasma gun, melting the powders in the hot zone of the gun and then spraying the molten material into a collecting chamber where they are cooled by the gas in the chamber, whereupon the resulting powder is collected.
As used herein, the phrase "tungsten heavy alloys" refers to alloys of tungsten which have a density greater than 13 g/cc. To produce the novel tungsten heavy alloys, well-mixed metallic powder comprising from about 80 to about 99% by weight tungsten and from about 1 to about 20% by weight of at least one alloying metal selected from the group consisting of molybdenum, tantalum, niobium, hafnium, rhenium, and chromium is fed by internal or external feed into a thermal spray plasma kgun, for example, a Baystate Model PG-100 plasma gun (Baystate Co., Westboro, Mass.). That gun has a power rating of 28 klowatts and an internal feed nozzle.
The ionized gas plume in a thermal spray plasma gun can reach temperatures of 10,000° Kelvin and is particularly suitable for melting tungsten, which has the highest melting point of any metal (3410° C.).
The mixed metallic powder is passed rapidly through the gas plume of the plasma gun, which plume may comprise ionized inert gases, such as argon, together with a small amount of helium or hydrogen. The powder melts almost instantaneously in the extremely hot gas plume, becoming a stream of molten metal alloy droplets.
The molten alloy is then sprayed in droplet form into a collecting chamber having an atmosphere composed of one or more relatively cool, inert gases, for example, argon, helium or nitrogen. The temperature of the atmosphere in the chamber is prefereably ambient or near-ambient, but may be any temperature low enough to cause rapid solidification of the metal droplets. The molten alloy droplets solidify or "freeze" into tungsten alloy powder granules in the collecting chamber, and the powder is collected. The resultant powder has an average grain size of from about 5 to about 30um, and preferably from about 15 to about 25 um.
The tungsten alloy powders are further treated in a heated hydrogen-containing atmosphere, preferably at about 600°-900° C., to thoroughly clean and reduce any surface oxides. The clean alloy powders can then be intermixed with elemental or alloy powders of at least one metal selected from the group consisting of copper, iron, nickel, cobalt and tantalum in a weight ratio of from about 90 to about 100% tungsten alloy powder and from about 1 to about 10% of the other metal powders.
The intermixed powder may be compacted by dynamic or explosive compaction to form near full density metallic compacts. Dynamic or explosive compaction produces a very small amount of incipient melting around the tungsten particles for a very short time. The presence of this liquid strongly improves the interface strength, but since the quantity of the melt and the time period is extremely small, any measurable grain growth of tungsten is prevented.
The near full density compact can be further thermomechanically processed by, for example, extrusion, swaging or rolling to improve the properties of the material.
The fully dense tungsten heavy alloy materials produced according to the foregoing process exhibit a fine-grained microstructure, low continguity and improved interface strength and ductility in comparison with prior art materials. The novel tungsten heavy alloys are extremely valuable for kinetic energy penetrator applications, and may substantially improve the performance of kinetic energy warheads.
It has thus been shown that there are provided compositions and methods which achieve the various objects of the invention and which are well adapted to meet the conditions of practical use.
As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments set forth above, it is to be understood that all matters herein described are to be interpreted as illustrative and not in a limiting sense.
Claims (2)
1. In an improved tungsten heavy alloy having a density greater than 15g/cc, the improvement consisting essentially of said tungsten alloy containing up to about 20% by weight of either molybdenum, tantalum, niobium, hafnium, rhenium or chrominum and mixtures thereof, said alloy being of spherical shape having an average grain size between about 5 and 30 um.
2. The improved tungsten alloy of claim 1 in powder form containing up to at least 10% by weight of either copper, iron, nickle, cobalt or tantalum forming a full density material having comparatively fine-grained microstructure, low contiguity, greater interface strength and ductility relative to known tungsten alloys of the art.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/830,215 USH1075H (en) | 1992-01-24 | 1992-01-24 | Tungsten heavy alloys |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/830,215 USH1075H (en) | 1992-01-24 | 1992-01-24 | Tungsten heavy alloys |
Publications (1)
Publication Number | Publication Date |
---|---|
USH1075H true USH1075H (en) | 1992-07-07 |
Family
ID=25256548
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US07/830,215 Abandoned USH1075H (en) | 1992-01-24 | 1992-01-24 | Tungsten heavy alloys |
Country Status (1)
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US (1) | USH1075H (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5740516A (en) * | 1996-12-31 | 1998-04-14 | Remington Arms Company, Inc. | Firearm bolt |
US5760317A (en) * | 1995-10-27 | 1998-06-02 | The United States Of America As Represented By The Secretary Of The Army | Flow softening tungsten based composites |
US6045601A (en) * | 1999-09-09 | 2000-04-04 | Advanced Materials Technologies, Pte, Ltd. | Non-magnetic, high density alloy |
FR2825718A1 (en) * | 2001-06-11 | 2002-12-13 | Gen Electric | Anti-diffusion barrier material used for profile elements and other gas turbine motor components contains chromium together with tungsten or rhenium or ruthenium or combinations of these elements to prevent aluminum migration |
US6960319B1 (en) * | 1995-10-27 | 2005-11-01 | The United States Of America As Represented By The Secretary Of The Army | Tungsten alloys for penetrator application and method of making the same |
US7107715B2 (en) | 2003-05-23 | 2006-09-19 | Ra Brands, L.L.C. | Bolt assembly with locking system |
CN107541633B (en) * | 2017-08-15 | 2019-04-26 | 清华大学 | Tungsten alloy and preparation method thereof |
-
1992
- 1992-01-24 US US07/830,215 patent/USH1075H/en not_active Abandoned
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5760317A (en) * | 1995-10-27 | 1998-06-02 | The United States Of America As Represented By The Secretary Of The Army | Flow softening tungsten based composites |
US6960319B1 (en) * | 1995-10-27 | 2005-11-01 | The United States Of America As Represented By The Secretary Of The Army | Tungsten alloys for penetrator application and method of making the same |
US5740516A (en) * | 1996-12-31 | 1998-04-14 | Remington Arms Company, Inc. | Firearm bolt |
US6045601A (en) * | 1999-09-09 | 2000-04-04 | Advanced Materials Technologies, Pte, Ltd. | Non-magnetic, high density alloy |
SG82681A1 (en) * | 1999-09-09 | 2001-08-21 | Lye King Tan | Non-magnetic, high density alloy |
FR2825718A1 (en) * | 2001-06-11 | 2002-12-13 | Gen Electric | Anti-diffusion barrier material used for profile elements and other gas turbine motor components contains chromium together with tungsten or rhenium or ruthenium or combinations of these elements to prevent aluminum migration |
US6746782B2 (en) * | 2001-06-11 | 2004-06-08 | General Electric Company | Diffusion barrier coatings, and related articles and processes |
US7107715B2 (en) | 2003-05-23 | 2006-09-19 | Ra Brands, L.L.C. | Bolt assembly with locking system |
US20070107290A1 (en) * | 2003-05-23 | 2007-05-17 | Ra Brands, L.L.C. | Bolt assembly with locking system |
CN107541633B (en) * | 2017-08-15 | 2019-04-26 | 清华大学 | Tungsten alloy and preparation method thereof |
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