Patent Application
20220023942
The present invention relates to metals, in particular niobium alloys, and products made from niobium alloys as well as methods of making and processing the niobium alloys.
Among its many applications, niobium alloy powder is generally used in the sputtering target industry, munition area, and space industry in view of its properties.
Currently, for example, niobium alloy powders can be primarily produced in a mechanical process. The mechanical process includes the steps of electron beam melting of niobium with one or more other metals to form an alloy ingot, hydriding the ingot, milling the hydride, and then dehydriding, crushing, and heat treating. The niobium used for instance in such a process can be of the type described in U.S. Pat. Nos. 6,051,044; 6,165,623; 6,375,704; and 6,863,750; all incorporated in their entirety by reference.
Most of the efforts in developing niobium alloy powders have been driven by the sputtering target and/or forged metal industry, where such metals were made for this specific purpose only. However, one or more properties of these niobium alloys can be generally unwanted in industries such as in additive manufacturing. Accordingly, there is a need and desire to develop niobium alloy powders that can be useful in additive manufacturing and/or other industries.
A feature of the present invention is to provide a niobium alloy powder that can be very useful in additive manufacturing or 3D printing.
Another feature of the present invention is to provide articles, products, and/or components from additive manufacturing or 3D printing using niobium alloy powder that is easier to use and/or provides one or more improved properties in such processes.
An additional feature of the present invention is to provide processes to make the niobium alloy powder as well as the articles, products, and/or components containing the niobium alloy powder.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.
To achieve these and other advantages, and in accordance with a purpose of the present invention, as embodied and broadly described herein, the present invention relates to niobium alloy powder. The niobium alloy powder includes a spherical shape wherein the powder has an average aspect ratio of from 1.0 to 1.25; a purity of niobium alloy of at least 99.9 wt % based on total weight of the niobium alloy powder, excluding gas impurities; an average particle size of from about 0.5 micron to about 250 microns; a true density of from 8.2 g/cc to 20 g/cc; an apparent density of from about 2 g/cc to about 18 g/cc; and a Hall flow rate of 20 sec or less. The niobium alloy powder can be, and preferably is plasma heat-treated.
The present invention further relates to an article or an article of manufacture (or portion thereof or part thereof) made from or formed from the niobium alloy powder of the present invention. The article or portion thereof or part thereof can be, but is not limited to, a boss for a coil set for a physical vapor deposition process, a boss that comprises open cellular structures and solid structures, a coil set or part thereof for a physical vapor deposition process, an orthopedic implant or part thereof, a dental implant or part thereof, and other medical and/or dental implants or portions thereof.
Further, the present invention relates to a method to make the niobium alloy powder of the present invention. The method can include plasma heat-treating a starting niobium alloy powder to at least partially melt at least an outer surface of said starting niobium alloy powder in an inert atmosphere to obtain a heat-treated niobium alloy powder, and cooling the heat-treated niobium alloy powder in an inert atmosphere to obtain the niobium alloy powder. The starting niobium alloy powder can be an ingot derived niobium alloy powder.
In addition, the present invention relates to a method for forming an article, wherein the method includes the step of additive manufacturing to form the article by utilizing the niobium alloy powder of the present invention to form the shape of the article or part thereof. The additive manufacturing can include or comprise laser powder bed fusion, electron beam powder bed fusion, directed energy deposition, laser cladding via a powder or wire, material jetting, sheet lamination, and/or vat photopolymerization.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
The present invention relates to novel niobium alloy powders and to articles (or portions thereof) formed from the niobium alloy powders of the present invention. The present invention further relates to methods of making the novel niobium alloy powders as well as methods to form articles (or portions thereof) utilizing additive manufacturing techniques and processes.
As opposed to other spheroidization technologies, plasma spheroidization provided the energy needed to melt the niobium alloy quickly and produces a truly spherical powder with high purity, and/or low oxygen, and/or minimal gas entrapment and/or a controlled particle size distribution (PSD).
In more detail, the niobium alloy powder of the present invention comprises, consists essentially of, consists of, or includes a spherical shape wherein the powder has an average aspect ratio of from 1.0 to 1.25; a purity of niobium alloy of at least 99.9 wt % based on total weight of the niobium alloy powder, excluding gas impurities; an average particle size of from about 0.5 micron to about 250 microns; a true density of from 8.2 g/cc to 20 g/cc; an apparent density of from about 2 g/cc to about 18 g/cc; and a Hall flow rate of 20 sec or less.
Except for the properties set forth above for the niobium alloy powder with respect to spherical shape, purity, average particle size, density and Hall flow rate, it is to be understood that there is no other critical limitations with regard to the type of niobium alloy powder, that can be used in the additive manufacturing methods of the present invention as described herein.
The niobium alloy powder of the present invention can be what is considered a salt-reduced niobium powder that is combined with one or more non-niobium metals and melted to form the niobium alloy that can be reduced to powder form or the melted metals can be processed into powders. In the alternative, the niobium alloy powders can be formed from salt-reduced niobium alloy powders such as, but not limited to, magnesium or sodium reduced niobium alloy powder. The niobium alloy powder can be a vapor phased-reduced niobium alloy or ingot-derived niobium alloy powder.
As indicated, the niobium alloy powder of the present invention has a spherical shape. This shape is defined by an average aspect ratio. The average aspect ratio of the niobium alloy powder or aspect ratio is defined herein as the ratio of the largest linear dimension of a particle (i.e., niobium alloy powder) to the smallest linear dimension of the same particle (i.e., niobium alloy powder) based on measuring randomly 50 particles or 100 particles or measuring randomly about 1% by weight to about 2% by weight of the batch of powder. The measuring of the niobium alloy particles is done using Scanning Electron Micrograph (SEM) images. True spherical particles have an aspect ratio of 1.0. For purposes of the present invention, the niobium alloy powder is considered spherical when the average aspect ratio is from 1.0 to 1.25, or from 1.0 to 1.2, or from 1.0 to 1.15, or from 1.0 to 1.1 or from 1.0 to 1.05, or from about 1.05 to about 1.25, or from 1.05 to about 1.2, or from 1.05 to about 1.1, or about 1.0.
The niobium alloy powder of the present invention is a high purity niobium alloy powder, meaning the niobium alloy powder has a purity of at least 99.9 wt % based on total weight of the niobium alloy powder, excluding gas impurities. The purity is with respect to the niobium and intentional other metal(s) and/or non-gas elements present to form the niobium alloy. The purity level can be measured by x-ray fluorescence, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) or ICP Atomic Emission Spectroscopy, or Inductively Coupled Plasma Mass Spectrometry (ICP-MS) or ICP Mass Spectrometry or Glow Discharge Mass Spectrometry (GDMS), Spark Source Mass Spec (SSMS) Analysis, or any combinations thereof. The niobium alloy purity can be at least 99 wt % niobium alloy, or at least 99.95 wt % niobium alloy, at least 99.99 wt % niobium alloy, at least 99.995 wt % niobium alloy, or from about 99.9 wt % niobium alloy to 99.9995 wt % niobium alloy, or from about 99.95 wt % niobium alloy to 99.9995 wt % niobium alloy, or from about 99.99 wt % niobium alloy to 99.9995 wt % niobium alloy or other purity values or ranges.
The niobium alloy powder has an average particle size of from about 0.5 micron to about 250 microns. The average particle size is determined by measuring randomly 50 particles using laser diffraction, or dynamic light scattering, or dynamic image analysis techniques, such as an HORIBA LA-960 or LA-300 Laser Particle Size Analyzer, or a HORIBA SZ-100 Nanopartica Instrument, or an HORIBA Camsizer or Camsizer X2 dynamic image analysis system. The average particle size can be from about 0.5 micron to about 10 microns, or from about 5 microns to about 25 microns, or from about 15 microns to about 45 microns, or from about 35 microns to about 75 microns, or from about 55 microns to about 150 microns, or from about 105 microns to about 250 microns.
The niobium alloy powder has an apparent density of from about 2 g/cc to about 18 g/cc, such as from about 2 g/cc to about 15 g/cc, or from about 2 g/cc to about 12 g/cc or from about 2 g/cc to about 10 g/cc, or from about 2 g/cc to about 8 g/cc, or 3 g/cc to about 15 g/cc, or from about 3 g/cc to about 10 g/cc, or from about 5 g/cc to about 15 g/cc, or from about 5 g/cc to about 10 g/cc, of from about 2.2 g/cc to about 7.8 g/cc or from about 3 g/cc to about 7 g/cc or from about 3.5 g/cc to about 6.5 g/cc or other apparent density numbers within these ranges. The apparent density is measured according to ASTM B212 standard.
The niobium alloy powder has a true density of from about 8.2 g/cc to about 20 g/cc, such as from about 8.2 g/cc to about 18 g/cc, or from about 8.2 g/cc to about 15 g/cc or from about 8.2 g/cc to about 12 g/cc, or from about 8.2 g/cc to about 8 g/cc, or 9 g/cc to about 15 g/cc, or from about 9 g/cc to about 20 g/cc, or from about 10 g/cc to about 18 g/cc, or from about 10 g/cc to about 20 g/cc, of from about 8.5 g/cc to about 18 g/cc or from about 8.5 g/cc to about 15 g/cc or from about 8.5 g/cc to about 15 g/cc or other apparent density numbers within these ranges. The true density is measured according to ASTM B212 standard.
The niobium alloy powder has a Hall flow rate of 20 seconds or less. The Hall Flow test is conducted according to ASTM B213 standard, where the niobium alloy powder is timed as it flows through the orifice of a Hall Flowmeter funnel. The Hall flow rate of the niobium alloy powder of the present invention can be 19 seconds or less, 15 seconds or less, 10 seconds or less, or from 4 seconds to 20 seconds, or from 5 seconds to 20 seconds, or from 6 seconds to 20 seconds, or from 4 seconds to 15 seconds, or from 4 seconds to 12 seconds, or from 5 seconds to 15 seconds, or other values in these ranges.
The niobium alloy powder can be, and preferably is plasma heat-treated.
As stated, the niobium alloy powder of the present invention is an alloy. The alloy contains a) at least niobium metal and b) i) one or more other metals and/or ii) non-metal elements and/or iii) metalloid elements. As a further option, the niobium alloy can be doped or have one or more gaseous elements present as part of the alloy and/or on the surface of the alloy. The alloy can have a single phase. The alloy can have more than one phase.
For instance, the niobium alloy powder can be a Nb—Ti alloy or a Nb—Si alloy or Nb—W alloy or Nb—Mo alloy or Nb—Re alloy or a Nb—Rh alloy, or ternary Nb alloys (e.g., containing Nb, and two or more other metals to form the metal alloy), or other Nb-metal alloys. The following one or more metals can be part of the Nb alloy powder and thus be the niobium alloy powder of the present invention: Ti, Si, W, Mo, Re, Rh, Ta, V, Th, Zr, Hf, Cr, Mn, Sc, Y, C, B, Ni, Fe, Co, Al, Sn, Au, Th, U, Pu, and/or rare earth element(s). The alloy percentages can be Nb: 30 wt % to 99.9 wt % and for the other non-Nb elements in the alloy, the wt % can be from 0.1 wt % to 70 wt %, based on the total weight of the alloy. The Nb-alloy can be niobium with one other metal or element, two other metals or elements, or three or more other metals or elements present but not as impurities. The niobium in the Nb-alloy can be the predominate metal (e.g., the niobium is the metal present in the highest percent based on the weight of the alloy). The niobium in the niobium alloy, as an option can be the lowest percent metal present or not be the predominate metal in the alloy. One further example of a Nb-alloy is C103 or C129Y. As an option, for the Nb-alloy of the present invention, tantalum is not present in the alloy.
The niobium alloy powder can have various oxygen levels. For instance, the niobium alloy powder can have an oxygen level of 2,500 ppm or less, or 1,000 ppm or less, or less than 500 ppm, or less than 400 ppm, or less than 300 ppm, or less than 250 ppm, or less than 200 ppm, such as from about 100 ppm to 495 ppm, or from about 150 ppm to about 400 ppm.
The niobium alloy powder of the present invention can have one or more other properties selected from the following:
The niobium alloy powder of the present invention can be a non-aggregated powder, wherein the properties/parameters described herein are for a non-aggregated powder.
The niobium alloy powder of the present invention can be a non-agglomerated powder, wherein the properties/parameters described herein are for a non-agglomerated powder.
As an option, the niobium alloy powder can be phosphorous doped. For instance, the phosphorous doped levels can be at least 50 ppm, or at least 100 ppm, or, for instance, from about 50 ppm to about 500 ppm, and the like. Phosphoric acid or ammonium hexafluorophosphate and the like are suggested as the forms of phosphorus.
As an option, the niobium alloy powder can be doped with other elements, such as yittrium, silica, or one or more other dopants, such as gas and/or metal dopants. The doped levels can be at least 5 ppm, at least 10 ppm, at least 25 ppm, at least 50 ppm, or at least 100 ppm, or, for instance, from about 5 ppm to about 500 ppm, and the like. One or more dopants can be used for grain stabilization and/or for other property enhancements of the powder or the resulting article made from the powder.
The niobium alloy powder of the present invention can be used to form articles or portions thereof or parts thereof.
For instance, the article can be an orthopedic implant or other medical or dental implant. The orthopedic implant can be for a replacement of a hand, ankle, shoulder, hip, knee, bone, total joint reconstruction (arthroplasty), cranial facial reconstruction, or spinal, or other part of the human or animal body. The dental implant can be for facial reconstruction including, but not limited to, mandible or maxilla. The medical or dental implant finds usefulness in humans and other animals such as dogs, cats, and other animals.
The article can be a tracer or marker such as a medical marker, for instance, a radiographic Nb marker.
The article can be a surgical tool or part thereof. The article can be an augment.
The article can be an aerospace part.
The article can be a superconducting cavity.
The article can be a piping or valves used in corrosive applications.
The article can be a boss such as a boss for a coil set used in physical vapor deposition processes. The boss can comprise open cellular structures and solid structures.
The article can be any article used in metal deposition processes, such as sputtering targets, or portions thereof, or for structures used to hold sputtering targets and the like. For instance, the article can be a coil set or part thereof for physical vapor deposition processes.
The niobium alloy powder of the present invention can be used in spraying (e.g., cold spraying) of niobium alloy for coatings and/or repairs of articles or surfaces.
The niobium alloy powder of the present invention can be used in metal injection molding applications and processes.
The niobium alloy powder of the present invention can be made using a plasma heat-treating process. For instance, a process to make the niobium alloy powder of the present invention can comprise, consists essentially of, consists of, or include step a: plasma heat-treating a starting niobium alloy powder to at least partially melt at least an outer surface of the starting niobium alloy powder in an inert atmosphere to obtain a heat-treated niobium alloy powder, and then step b: cooling the heat-treated niobium alloy powder in an inert atmosphere to obtain said niobium alloy powder. The starting niobium alloy powder can be fully melted or at least 90% by weight melted by the plasma treatment (e.g., in the plasma torch region of the plasma reactor).
In the process, the starting niobium alloy powder can be an ingot-derived niobium alloy powder or vapor phased reduced niobium alloy powder or salt-reduced niobium alloy powder, or be any other source of niobium alloy powder as mentioned herein or that is commercially available. In the process, the starting niobium alloy powder can be powder metallurgy (powder-met) derived niobium alloy powder.
For instance, vapor phase-reduced particles of niobium alloy can be obtained by contacting and reacting one or more vaporized non-niobium chlorides mixed with vaporized niobium chloride with vaporized sodium. These vapor phase-reduced particles of niobium alloy can be composed of multiple primary particles of niobium alloy formed by the reaction between one or more non-niobium chlorides mixed with vaporized niobium chloride and sodium that are encased in the sodium chloride produced by this reaction.
As an option, the starting niobium alloy powder can be non-hydrided or can be hydrided before being introduced into the plasma treatment.
In the process to make the niobium alloy powder, prior to step a), the starting niobium alloy powder can be formed by sintering a first niobium alloy powder to obtain a sintered powder (which can be in the form of a sintered mass such as a green log or other shape), and then e-beam melting of the sintered powder or mass to obtain an ingot, and then reducing the ingot to the starting niobium alloy powder. The sintering can occur at conventional sintering temperatures for niobium alloy powder. For instance, and only as an example, the niobium alloy powder can be sintered at a temperature of from about 700 deg C. to about 1,450 deg C. (or from about 800 deg C. to about 1,400 deg C., or from about 900 deg C. to about 1,300 deg C.). The sintering time can be from 1 minute to several hours, such as from about 10 minutes to 4 hours or from 10 minutes to 3 hours, or from about 15 minutes to about 2 hours or from about 20 minutes to about 1 hour or other time periods. As an option, one or more heat treatments or sinterings can occur, whether at the same temperature, same times, or at different temperatures and/or different heat treatment times. The sintering can occur in an inert atmosphere such as an argon atmosphere. The sintering can occur in a conventional furnace used for sintering of metal powders.
In the option to form a niobium alloy ingot that is then reduced to a powder, the niobium alloy ingot can have or be any volume or diameter or shape. The electron beam processing can occur at a melt rate of from about 300 lbs. to about 800 lbs. per hour using 20,000 volts to 28,000 volts and 15 amps to 40 amps, and under a vacuum of from about 1×10−3 Ton to about 1×10−6 Torr. More preferably, the melt rate is from about 400 lbs. to about 600 lbs. per hour using from 24,000 volts to 26,000 volts and 17 amps to 36 amps, and under a vacuum of from about 1×10−4 Torr to 1×10−5 Torr. With respect to the VAR processing, the melt rate is preferably of 500 lbs. to 2,000 lbs. per hour using 25 volts to 45 volts and 12,000 amps to 22,000 amps under a vacuum of 2×10−2 Torr to 1×10−4 Torr, and more preferably 800 lbs. to 1200 lbs. per hour at from 30 volts to 60 volts and 16,000 amps to 18,000 amps, and under a vacuum of from 2×10−2 Torr to 1×10−4 Torr.
The niobium alloy ingot can have a diameter of at least 4 inches or at least 8 inches, or have a diameter of at least 9½ inches, at least 11 inches, at least 12 inches, or higher. For instance, the niobium alloy ingot can have a diameter of from about 10 inches to about 20 inches or from about 9½ inches to about 13 inches, or from 10 inches to 15 inches, or from 9½ inches to 15 inches, or from 11 inches to 15 inches. The height or length of the ingot can be any amount, such as at least 5 inches or at least 10 inches or at least 20 inches, at least 30 inches, at least 40 inches, at least 45 inches, and the like. For instance, the length or height of the ingot can be from about 20 inches to about 120 inches or from about 30 inches to about 45 inches. The ingot can be cylindrical in shape, though other shapes can be used. After the formation of the ingot, optionally, the ingot can be machine cleaned using conventional techniques. For instance, the machine cleaning (off the surface) can result in a reduction in the diameter of the ingot, such as diameter reduction of from about 1% to about 10%. As a specific example, the ingot can have a nominal as-cast diameter of 12 inches and, due to machine cleaning, can have a diameter after machine cleaning of 10.75 to 11.75 inches in diameter.
The niobium alloy ingot can be reduced to a starting niobium alloy powder by making the ingot brittle and then crushing the ingot or subjecting the ingot to particle reduction steps such as milling, jaw crushing, roll crushing, cross beating and the like. To make the ingot brittle, the ingot can be hydrided such as by placing the ingot in a furnace with a hydrogen atmosphere.
With regard to the plasma heat-treating, this can also be known as plasma treatment or plasma processing. In the present invention, a RF plasma treatment or induction plasma treatment can be used. For instance, an RF thermal plasma system or an induction plasma reactor can be used, such as one from Tekna, Sherbrooke, QC, Canada, such as a PL-35LS or PL-50 or TEK-15 or other models. The central gas for the plasma can be argon, or a mixture of argon with other gases, or other gases such as helium and the like. The feed rate of the central gas can be a suitable flow such as from about 10 L/min to about 100 L/min or from about 15 L/min to about 60 L/min or other flow rates. The sheath gas for the plasma can be argon, or a mixture of argon with other gases, or other gases such as other inert gases or helium and the like. The feed rate of the sheath gas can be a suitable flow such as from about 10 L/min to about 120 L/min or from about 10 L/min to about 100 L/min or other flow rates. The carrier gas for the starting niobium alloy powder can be argon, or a mixture of argon with other gases (e.g., hydrogen can be added to increase the plasma intensity), or other gases such as other inert gases or helium and the like. The feed rate of the carrier gas can be a suitable flow such as from about 1 L/min to about 15 L/min or from about 2 L/min to about 10 L/min or other flow rates. The feeding rate of the starting niobium alloy powder into the plasma torch area can be any flow rate, such as from about 1 g/min of niobium alloy powder to about 120 g/min or from about 5 g/min to about 80 g/min of starting niobium alloy powder. Generally, a lower feed rate of the starting niobium alloy powder ensures more uniform and more complete spheroidal processing of the starting niobium alloy powder. After exiting the plasma torch area, a quench gas can be optionally used, such as through one or more quenching ports. The quench gas can be any suitable non-reactive gas, such a helium or argon. If used, the quenching gas can be fed at a variety of flow rates. For instance, the flow rate of the quench gas can be from about 25 L/min to 300 L/min or from about 50 L/min to about 200 L/min or other amounts. As an option, instead of or in addition to using a quench gas, gravity and/or a water-cooled cooling jacket can be used. The designs described in U.S. Pat. No. 5,200,595 and WO 92/19086 can be used. As an option, a passivation gas can be used after the powder is quenched or after the powder begins to cool down. The passivation gas can be oxygen, air, or a combination of air and oxygen. The flow rate of the passivation gas can be any flow rate, such as a flow rate of from about 0.1 L/min to about 1 L/min or other amounts. The chamber pressure of the plasma torch can be any suitable pressure, such as from about 0.05 MPa to about 0.15 MPa. The plate voltage can be from about 5 kV to about 7.5 kV. The frequency of the RF plasma system can be 3 MHz or other values. The plate current can be from about 2.5 A to about 4.5 A. The power can be from about 15 kW to about 35 kW. The distance from the plasma torch to the feeding nozzle or the probe position can be adjusted or varied. The distance can be 0 cm, or about 0 cm or from about 0 cm to about 8 cm. The greater the distance, the less surface evaporation of the starting powder. Thus, if the starting niobium alloy powder is very irregular and has aspect ratios of over 2 or over 3, an option is to have the distance of the feeding nozzle close to 0 cm. If the starting niobium alloy powder is more regular in shape, such as having aspect ratios of from about 1.3 to 2, the distance of the feeding nozzle can be further away from the plasma torch as an option. Also, a higher plasma powder setting can also be used to handle more irregular shaped starting niobium alloy powders.
As an option, the powder that has been plasma treated can be collected, such as collected under a protective atmosphere, such as an inert gas like argon. The collected powder can be passivated, such as using a water bath. The collected powder can be introduced into a water bath (e.g., submerged in a water bath).
As an option, the collected powder can be subjected to a sonication or other powder vibratory method to remove small particles such as nano materials deposited on the niobium alloy surface of the niobium alloy spheres (e.g., removing satellites and other loose material on the spheres). The resulting recovered niobium alloy spheres can optionally be dried, for instance, under a protective gas, such as an inert gas, like argon. This drying can be at any temperature, for instance, at a temperature of 50 deg C. to 100 deg C. for 10 mins to 24 hours, or 1 hour to 5 hours and the like. The recovered powder can be put in sealed bags such as aluminum lined anti-static bags for further use.
With the plasma treatment used in the present invention, the effort put into creating the particle size distribution of the starting niobium alloy powder and/or other morphology can carry through to the finished niobium alloy powder exiting the plasma process. Put another way, the size of the particle can be substantially maintained except for removing sharp edges and/or removing surface roughness and/or making the starting niobium alloy powder spherical or more spherical. Thus, prior to introducing the starting niobium alloy powder into the plasma treatment, the starting niobium alloy powder can be subjected to one or more steps to achieve desirable particle size distributions and/or other particle characteristics. For instance, the particle size distribution of the starting niobium alloy powder can be such that the D10 and/or D90 are within 50%, or within 40%, or within 30%, or within 25%, or within 20%, or within 15%, or within 10% or within 5% of the D50 of that starting niobium alloy powder.
The starting niobium alloy powder prior to being introduced into the plasma treatment can be subjected to one or more sieving steps or other particle screening steps, for instance to obtain a particle size distribution as described above or other sieve cuts, such as, but not limited to, a minus 200 mesh cut, a minus 225 mesh cut, a minus 250 mesh cut, a minus 275 mesh cut, a minus 300 mesh cut, and so on (with mesh being US Mesh sizes).
The starting niobium alloy powder, prior to plasma treating, can have one of the following particle size ranges: the average particle size can be from about 0.5 micron to about 10 microns, or from about 5 microns to about 25 microns, or from about 15 microns to about 45 microns, or from about 35 microns to about 75 microns, or from about 55 microns to about 150 microns, or from about 105 microns to about 250 microns.
In the process to make the niobium alloy powder, the starting niobium alloy powder can have a first particle size distribution, and the resulting (or finished) niobium alloy powder (e.g., after plasma treatment) can have a second particle size distribution, and the first particle size distribution and the second particle size distribution are within 15% of each other, within 10% of each other, or within 5% of each other, or within 2.5% of each other or within 1% of each other.
The starting niobium alloy powder prior to being introduced into the plasma treatment can be subjected to deoxidation treatments to remove oxygen from the niobium alloy powder.
The starting niobium alloy powder prior to plasma treating can be classified or sieved to remove various sizes, for instance, removing particles less than 20 microns, less than 15 microns, less than 10 microns, or less than 5 microns.
After exiting the plasma treatment, the plasma-treated niobium alloy powder can be subjected to one or more post-processing steps.
For instance, one post-processing step can be passing the plasma-treated niobium alloy powder through one or more sieves to remove certain sized plasma-treated niobium alloy powder.
For instance, one post-processing step can be sonicating or using other vibratory techniques to remove imperfections from the niobium alloy spheres. For instance, the niobium alloy spheres from the plasma treatment can be put in a water bath and sonicated to remove nano materials of on the niobium alloy spheres and then the niobium alloy spheres can be recovered.
For instance, one post-processing step can be optionally subjecting the plasma-treated niobium alloy to at least one deoxidation or ‘deox’ step. The deoxidation can involve subjecting the plasma-treated niobium alloy to a temperature of from about 500° C. to about 1,000° C. in the presence of at least one oxygen getter. For instance, the oxygen getter can be a magnesium metal or compound. The magnesium metal can be in the form of plates, pellets, or powder. Other oxygen getter material can be used.
For instance, one post-processing step can be optionally subjecting the plasma-treated niobium alloy to one or more heat treatment steps or annealing steps. With regard to the heat treating step of the plasma-treated niobium alloy, the heat treating can occur in a conventional oven under vacuum or under inert temperature. The heat treatment temperature is generally at least 800° C., or at least 1,000° C., or from about 800° C. to about 1,450° C., or from about 1,000° C. to about 1,450° C., and the like. While any heat treatment time can be used, examples include, but are not limited to, at least 10 minutes, at least 30 minutes, from about 10 minutes to about 2 hours, or more. As an option, one or more heat treatments can occur, whether at the same temperature, same times, or at different temperatures and/or different heat treatment times. After heat-treatment, if used, the plasma-treated niobium alloy can maintain the Hall flow rate achieved prior to the heat-treatment or be within 20% or within 10% or within 5% of that Hall flow rate.
For instance, one post-processing step can be subjecting the plasma-treated niobium alloy to acid leaching, such as using conventional techniques or other suitable methods. The various processes described in U.S. Pat. Nos. 6,312,642 and 5,993,513, for example, can be used herein and are incorporated in their entireties by references herein. The acid leaching can be performed using an aqueous acid solution comprising a strong mineral acid as the predominant acid, for example, nitric acid, sulfuric acid, hydrochloric acid, and the like. Also, a hydrofluoric acid (e.g., HF) in minor amounts (e.g., less than 10% by weight, or less than 5% by weight, or less than 1% by weight based on the total weight of acid) can be used. The mineral acid concentration (e.g., HNO3 concentration) can range from about 20% by weight to about 75% by weight in the acid solution. The acid leach can be conducted at elevated temperatures (above room temperature to about 100° C.) or at room temperature, using acid compositions and techniques as shown, for example, in U.S. Pat. No. 6,312,642 B1. The acid leach step typically is performed under normal atmospheric conditions (e.g., approximately 760 mm Hg). The acid leach step performed using conventional acid compositions and pressure conditions, such as indicated, can remove soluble metal oxides from the deoxidized powder for those conditions.
As an option, the plasma-treated niobium alloy can be nitrogen doped. With respect to nitrogen, the nitrogen can be in any state, such as a gas, liquid, or solid. The powders of the present invention, can have any amount of nitrogen present as a dopant or otherwise present. Nitrogen can be present as a crystalline form and/or solid solution form at any ratio. Nitrogen doped levels can be from 5 ppm to 5,000 ppm nitrogen or higher.
The plasma-treated niobium alloy of the present invention can be used in a number of ways. For instance, the plasma-treated niobium alloy can be used in additive manufacturing or processing which is sometimes referred to as 3-D printing to form an article or part of an article. The plasma-treated niobium alloy powder of the present invention can be used in processes or devices that permit the use of metal powders. With the plasma-treated powder of the present invention, the ease of conducting additive manufacturing is achieved. In addition or alternatively, with the plasma-treated powder of the present invention, the feed of the powder to the additive manufacturing devices is improved and/or the resulting article is more accurately obtained from the design programmed into the printing device.
The additive processes that can utilize the plasma-treated niobium alloy powder of the present invention include laser powder bed fusion, electron beam powder bed fusion, directed energy deposition, laser cladding via a powder or wire, material jetting, sheet lamination, or vat photopolymerization.
Some of these additive processes are referred to as laser metal fusion, laser sintering, metal laser melting, or direct metal printing, or direct metal laser sintering. In this process, a high power laser beam is scanned over a bed of powder, sintering the powder in the required shape, in the path of the laser beam. After each layer, the bed is lowered by a short distance and a new layer of powder applied. The entire process runs in a sealed chamber with a controlled gas atmosphere which is either inert (e.g. argon) or active to fine-tune material/product properties.
Some of these additive processes are referred to as laser metal deposition (LMD) or near net shape. In this process, a high-power laser beam is used, connected to a robot or gantry system, to form a melt pool on a metallic substrate into which powder or metal wire is fed. In LMD, the powder is contained in a carrier gas and directed to the substrate through a nozzle that is concentric with the laser beam. Alternatively, a wire can be fed from the side. The powder or wire is melted to form a deposit that is bonded to the substrate and grown layer-by-layer. An additional gas jet, concentric with the laser beam, can provide additional shield or process gas protection.
Some of these additive processes are referred to as gas-metal arc welding and plasma welding techniques to melt the metal powder to form a 3D shape layer by layer. In this process, metal wire is added as the electrode melts in the arc and its droplets form layers on the substrate. Processes with lower heat input, such as controlled short-circuit metal transfer, are preferred given the heat sensitivity of most materials used in additive manufacturing. Shielding gases protect the layers against ambient air.
Plasma additive manufacturing is similar to laser metal deposition, where powder is guided towards the substrate in a gas stream and fused by the plasma heat.
Some of these additive processes are referred to as thermal spraying. In this process, molten, heated powder particles or droplets from molten wires are accelerated in a gas stream towards the substrate, where local adherence is ensured by kinetic energy and heat. When used for additive manufacturing, thermal spraying is applied layer-by-layer to build up components without geometrical complexity, e.g. tubes or reducers. Process gases protect the hot material against ambient atmospheric gases and help to fine-tune material properties.
Some of these additive processes are referred to as electron beam melting or a powder bed fusion process using an electron beam in a vacuum. This process is similar to laser sintering.
The additive manufacturing device or process used to form the articles can have one or more of the following settings: a laser power of from 150 W to about 175 W or from 155 W to 165 W; a scan speed of from about 100 mm/s to about 500 mm/s, such as from about 300 mm/s to about 400 mm/s; hatch spacing of from about 30 microns to about 100 microns, such as from about 80 microns to about 90 microns; a layer thickness of from about 10 microns to about 50 microns, such as from about 30 microns to about 40 microns; and/or an energy density of from about 3 J/mm2 to about 20 J/mm2, such as from about 4 J/mm2 to about 6 J/mm2. Sometimes, a lower than maximum laser setting can be utilized so as to reduce thermal input and/or minimize thermal stress and/or minimize part deformation.
For additive manufacturing, preferably a niobium alloy baseplate is utilized but other base plates such as stainless steel or stainless steel alloys can be used. Niobium alloy baseplates can minimize the difference of Coefficient of Thermal Expansion (CTE) and/or the difference in thermal conductivities between the part and base plant. The effect can minimize thermal residual stresses in the part and/or can prevent lift-up of the part from the plate.
With the niobium alloy powder of the present invention and utilizing additive manufacturing processes, it was discovered that desirable tensile properties of the resulting article formed from the niobium alloy powder of the present invention can be achieved. One or more of these properties can be enhanced if the article is annealed such as at a temperature of from about 800 deg C. to about 2,000 deg C. (for instance for 10 mins to 10 hours, or from 30 minutes to 3 hours, or from 1 hour to 2 hours).
One or more of the following properties can be achieved with the present invention in forming additive manufactured (AM) objects or articles. Ultimate tensile strength (UTS) can be at least 50% or at least 100% greater than wrought Nb of the same shape. The UTS can be over 50 KSI, over 70 KSI, over 80 KSI, or over 90 KSI, such as from about 50 KSI to about 100 KSI. The Yield Stress can be at least 50% or at least 100% greater than wrought Nb of the same shape. The Yield Stress can be over 35 KSI, over 40 KSI, over 50 KSI, or over 80 KSI, such as from about 35 KSI to about 90 KSI. An annealed AM article of the present invention showed improved Yield Stress. An annealed AM article of the present invention showed improved Yield Stress without compromising the UTS. Elongation can be from about 1% to about 50%, such as from about 3 to 40% or from 5% to 35%. An annealed AM article of the present invention showed improved elongation. With the present invention, a balance of acceptable and/or good UTS, Yield and Elongation are possible.
With the plasma-treated niobium alloy powder utilized in additive manufacturing, various articles are possible and the quality and accuracy of the article can be excellent. For instance, the article can be an orthopedic implant or other medical or dental implant. The orthopedic implant can be for a replacement of a hand, ankle, shoulder, hip, knee, bone, total joint reconstruction (arthroplasty), cranial facial reconstruction, or spinal, or other part of the human or animal body. The dental implant can be for facial reconstruction including but not limited to mandible or maxilla. The medical or dental implant finds usefulness in humans and other animals such as dogs, cats and other animals.
The article can be a boss such as a boss for a coil set used in physical vapor deposition processes. The boss can comprise open cellular structures and solid structures.
The article can be any article used in metal deposition processes, such as sputtering targets, or portions thereof, or for structures used to hold sputtering targets and the like. For instance, the article can be a coil set or part thereof for physical vapor deposition processes.
As an option, the plasma-treated niobium alloy can be further processed to form a capacitor electrode (e.g., capacitor anode). This can be done, for example, by compressing the plasma treated powder to form a body, sintering the body to form a porous body, and anodizing the porous body. The pressing of the powder can be achieved by any conventional techniques such as placing the powder in a mold and subjecting the powder to a compression by use of a press, for instance, to form a pressed body or green body. Various press densities can be used, and include, but are not limited to, from about 1.0 g/cm3 to about 7.5 g/cm3. The powder can be sintered, anodized, and/or impregnated with an electrolyte in any conventional manner. For instance, the sintering, anodizing, and impregnation techniques described in U.S. Pat. Nos. 6,870,727; 6,849,292; 6,813,140; 6,699,767; 6,643,121; 4,945,452; 6,896,782; 6,804,109; 5,837,121; 5,935,408; 6,072,694; 6,136,176; 6,162,345; and 6,191,013 can be used herein and these patents are incorporated in their entirety by reference herein. The sintered anode pellet can be, for example, deoxidized in a process similar to that described above for the powder. The anodized porous body further can be impregnated with manganese nitrate solution, and calcined to form a manganese oxide film thereon. Wet valve metal capacitors can use a liquid electrolyte as a cathode in conjunction with their casing. The application of the cathode plate can be provided by pyrolysis of manganese nitrate into manganese dioxide. The pellet can be, for example, dipped into an aqueous solution of manganese nitrate, and then baked in an oven at approximately 250° C. or other suitable temperatures to produce the manganese dioxide coat. This process can be repeated several times through varying specific gravities of nitrate to build up a thick coat over all internal and external surfaces of the pellet. The pellet optionally can be then dipped into graphite and silver to provide an enhanced connection to the manganese dioxide cathode plate. Electrical contact can be established, for example, by deposition of carbon onto the surface of the cathode. The carbon can then be coated with a conductive material to facilitate connection to an external cathode termination. From this point the packaging of the capacitor can be carried out in a conventional manner, and can include, for example, chip manufacture, resin encapsulation, molding, leads, and so forth.
As part of forming an anode, for example, a binder, such as camphor (C10H16O) and the like, can be added to the powder, for instance, in the amount of 3-5 wt % based on 100 wt % of the powder and the mixture can be charged into a form, compression-molded, and sintered by heating for 0.3-1 hour at 1,000-1,400° C. while still in a compressed state. Such a molding method makes it possible to obtain pellets consisting of sintered porous bodies.
When a pellet obtained using the above-described molding process is employed as a capacitor anode, before the powder is compression-molded, it is preferable to embed lead wires into the powder in order to integrate the lead wires into the pellet.
The capacitor can be manufactured using the above-described pellet. A capacitor equipped with an anode can be obtained by oxidizing the surface of the pellet, a cathode facing the anode, and a solid electrolyte layer disposed between the anode and cathode.
A cathode terminal is connected to the cathode by soldering and the like. In addition, an exterior resin shell is formed around a member composed of the anode, cathode, and solid electrolyte layer. Examples of materials used to form the cathode include graphite, silver, and the like. Examples of materials used to form the solid electrolyte layer include manganese dioxide, lead oxide, electrically conductive polymers, and the like.
When oxidizing the surface of a pellet, for example, a method can be used that involves treating the pellet for 1-3 hours in an electrolyte solution such as nitric acid, phosphoric acid and the like with a concentration of 0.1 wt % at a temperature of 30-90° C. by increasing the voltage to 20-60V at a current density of 40-120 mA/g. A dielectric oxide film is formed in the portion oxidized at such time.
As indicated, the plasma-treated niobium alloy of the present invention can be used to form a capacitor anode (e.g., wet anode or solid anode). The capacitor anode and capacitor (wet electrolytic capacitor, solid state capacitor, etc.) can be formed by any method and/or have one or more of the components/designs, for example, as described in U.S. Pat. Nos. 6,870,727; 6,813,140; 6,699,757; 7,190,571; 7,172,985; 6,804,109; 6,788,523; 6,527,937 B2; 6,462,934 B2; 6,420,043 B1; 6,375,704 B1; 6,338,816 B1; 6,322,912 B1; 6,616,623; 6,051,044; 5,580,367; 5,448,447; 5,412,533; 5,306,462; 5,245,514; 5,217,526; 5,211,741; 4,805,704; and 4,940,490, all of which are incorporated herein in their entireties by reference. The powder can be formed into a green body and sintered to form a sintered compact body, and the sintered compact body can be anodized using conventional techniques. It is believed that capacitor anodes made from the powder produced according to the present invention have improved electrical leakage characteristics. The capacitors of the present invention can be used in a variety of end uses such as automotive electronics; cellular phones; smart phones; computers, such as monitors, mother boards, and the like; consumer electronics including TVs and CRTs; printers/copiers; power supplies; modems; computer notebooks; and disk drives.
Further details of the starting niobium alloy powder, the plasma-treated niobium alloy powder, and components formed from the niobium alloy powder are provided below and further form optional aspects of the present invention.
With the methods of the present invention, the niobium alloy powder can be made that can have:
The niobium alloy powder can have at least one of the following properties:
For purposes of the present invention, at least one of these properties, at least two, at least three, at least four, or all five properties can be present.
In at least one embodiment of the present invention, the plasma-treated niobium alloy powder (or starting niobium alloy powder) can have the following characteristics, but it is to be understood that the powder can have characteristics outside of these ranges:
Purity levels:
The plasma treated powder (or starting niobium alloy powder) (primary, secondary, or tertiary) can have a particle size distribution (based on overall %) as follows, based on mesh size:
The plasma-treated niobium alloy powder of the present invention can also have a pore size distribution which can be unimodal or multi-modal, such as bi-modal.
The plasma-treated niobium alloy powders of the present invention can have a BET surface area of from about 0.01 m2/g to about 20 m2/g, and more preferably from about 0.05 m2/g to about 5 m2/g such as from about 0.1 m2/g to about 0.5 m2/g.
The starting niobium alloy powder may comprise primary particles that have an average size in the range of 1 nm to about 500 nm, or 10 nm to 300 nm, or 15 nm to 175 nm, or 20 nm to 150 nm, or 25 nm to 100 nm, or 30 nm to 90 nm, or other sizes. The average size and distribution of the primary particles sizes can depend on the method of preparation. The primary particles may tend to form clusters or agglomerates of larger size than the primary particles. The shapes of raw or starting niobium alloy powder particles may include, but are not limited to, flaked, angular, nodular, or spherical, and any combinations thereof or variations thereof. The raw powder used to practice the present invention can have any purity with respect to the niobium alloy metal with higher purities being preferred. For instance, the niobium alloy purity (e.g., by wt %) of the raw or starting powder can be 95% Nb-alloy or greater, or 99% Nb-alloy or greater such as from about 99.5% Nb-alloy or greater and more preferably 99.95% Nb-alloy or greater and even more preferably 99.99% Nb-alloy or greater, or 99.995% Nb-alloy or greater or 99.999% Nb-alloy or greater.
At any stage, before or after plasma-treatment, the niobium alloy powder can be passivated using an oxygen-containing gas, such as air, as part of the plasma-treated niobium alloy powder production process of the present invention. Passivation typically is used to form a stabilizing oxide film on the powder during processing and in advance of sintered body formation using the powder. A powder production process of the present invention therefore can include hydrogen doping and passivating operations.
Passivating the niobium alloy powder can be by any suitable method. Passivation can be achieved in any suitable container, for example, in a retort, a furnace, a vacuum chamber, or a vacuum furnace. Passivation can be achieved in any of the equipment used in processing, such as heat treating, deoxidizing, nitriding, delubing, granulating, milling, and/or sintering, the metal powder. The passivating of the metal powder can be achieved under vacuum. Passivation can include backfilling of the container with an oxygen containing gas to a specified gas pressure, and holding the gas in the container for a specified time. The oxygen content level of the gas used in powder passivation can be from 1 to 100 wt % oxygen, or from 1 to 90 wt %, or from 1 to 75 wt %, or from 1 to 50 wt %, or from 1 to 30 wt %, or from 20 to 30 wt %, or an oxygen content that is the same as or greater than that of air or atmospheric air, or other content levels. The oxygen can be used in combination with an inert gas, such as nitrogen, argon, or combinations of these, or other inert gases. The inert gas does not react with the niobium alloy during the passivation process. The inert gas, such as nitrogen gas and/or argon gas, preferably can compose all or essentially all (e.g., >98%) of the remaining portion of the passivating gas other than the oxygen. Air can be used as the passivating gas. Air can refer to atmospheric air or dry air. The composition of dry air typically is nitrogen (about 75.5 wt %), oxygen (about 23.2 wt %), argon (about 1.3 wt %), and the rest in a total amount of less than about 0.05%. The content level of hydrogen in dry air is about 0.00005 vol %.
Additional techniques that may be employed for the passivation process can be adapted from those disclosed in U.S. Pat. No. 7,803,235, which is incorporated in its entirety by reference herein.
The present invention includes the following aspects/embodiments/features in any order and/or in any combination:
The present invention can include any combination of these various features or embodiments above and/or below as set forth in sentences and/or paragraphs. Any combination of disclosed features herein is considered part of the present invention and no limitation is intended with respect to combinable features.
Applicant specifically incorporates the entire contents of all cited references in this disclosure. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.
Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein. It is intended that the present specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims and equivalents thereof.
This application claims the benefit under 35 U.S.C. § 119(e) of prior U.S. Provisional Patent Application No. 62/778,377, filed Dec. 12, 2018, which is incorporated in its entirety by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2019/064810 | 12/6/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62778377 | Dec 2018 | US |
