EP3810820A1 - Poudres métalliques de titane sphéroïdales à microstructures personnalisées - Google Patents

Poudres métalliques de titane sphéroïdales à microstructures personnalisées

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Publication number
EP3810820A1
EP3810820A1 EP19735153.9A EP19735153A EP3810820A1 EP 3810820 A1 EP3810820 A1 EP 3810820A1 EP 19735153 A EP19735153 A EP 19735153A EP 3810820 A1 EP3810820 A1 EP 3810820A1
Authority
EP
European Patent Office
Prior art keywords
particles
spheroidized
feed material
spheroidized particles
microstructure
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.)
Pending
Application number
EP19735153.9A
Other languages
German (de)
English (en)
Inventor
Kamal Hadidi
Gregory Wrobel
Makhlouf Redjdal
Ning Duanmu
Michael C. KOZLOWSKI
Scott Turchetti
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
6K Inc
Original Assignee
6K Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from US16/012,370 external-priority patent/US10987735B2/en
Application filed by 6K Inc filed Critical 6K Inc
Publication of EP3810820A1 publication Critical patent/EP3810820A1/fr
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/42—Plasma torches using an arc with provisions for introducing materials into the plasma, e.g. powder or liquid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/065—Spherical particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • B22F1/142—Thermal or thermo-mechanical treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/30—Plasma torches using applied electromagnetic fields, e.g. high frequency or microwave energy
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
    • H05H1/461—Microwave discharges
    • H05H1/4622—Microwave discharges using waveguides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • B22F2009/086—Cooling after atomisation
    • B22F2009/0876—Cooling after atomisation by gas

Definitions

  • the present disclosure is generally directed towards producing metal spheroidal powder products. More particularly, the present disclosure is directed towards techniques for producing metal spheroidal powder products (e.g., Ti powders, Ti alloy powders, Ti compound powders) using a microwave generated plasma.
  • metal spheroidal powder products e.g., Ti powders, Ti alloy powders, Ti compound powders
  • Spherical powders are homogenous in shape, denser, less porous, have a high and consistent flowability, and high tap density. Such powders exhibit superior properties in applications such as injection molding, thermal spray coatings, additive manufacturing, etc.
  • Creating spheroidal metallic powders, especially metallic powders containing Ti, can pose a number of challenges. Achieving the desired spheroidal shape, the desired level of porosity (e.g., no porosity to very porous, and the desired composition and microstructure can be difficult.
  • thermal arc plasma An issue with thermal arc plasma is that the electrodes used to ignite the plasma are exposed to the high temperature causing degradation of the electrodes, which contaminates the plasma plume and process material.
  • thermal arc plasma plume inherently exhibit large temperature gradient.
  • the plasma is produced by a varying magnetic field that induces an electric field in the plasma gas, which in turn drives the plasma processes such as ionization, excitation, etc... to sustain the plasma in cylindrical dielectric tube.
  • Inductively coupled plasmas are known to have low coupling efficiency of the radio frequency energy into the plasma and a lower plasma temperature compared to arc and microwave generated plasmas.
  • the magnetic field responsible for generating the plasma exhibits a non-uniform profile, which leads to a plasma with a large temperature gradient, where the plasma takes a donut-like shape that exhibiting the highest temperature at the edge of the plasma (close to the dielectric tube walls) and the lowest temperature in the center of the donut.
  • metal powder particles should exhibit a spherical shape, which can be achieved through the process of spheroidization. This process involves the melting of particles in a hot environment whereby surface tension of the liquid metal shapes each particle into a spherical geometry, followed by cooling and re-solidification. Also, spherical powders can be directly produced by various techniques. In one such technique, a plasma rotating electrode (PRP) produces high flowing and packing titanium and titanium alloy powders but is deemed too expensive. Also, spheroidized titanium and titanium alloys have been produced using gas atomization, which uses a relatively complicated set up an may introduce porosity to the powder.
  • PRP plasma rotating electrode
  • Spheroidization methods of irregular shape powders include TEKNA’s (Sherbrook, Quebec, Canada) spheroidization process using inductively coupled plasma (ICP), where angular powder obtained from Hydride-Dehydride (HDH) process is entrained within a gas and injected though a hot plasma environment to melt the powder particles.
  • ICP inductively coupled plasma
  • HDH Hydride-Dehydride
  • This method suffers from non uniformity of the plasma, which leads to incomplete spheroidization of feedstock.
  • the HDH process involves several complex steps, including hydrogenation dehydrogenation, and deoxidation before the powder is submitted to spheroidization. This process is a time consuming multi-step process, which drives up the cost of metal powders made through these methods.
  • spheroidal titanium e.g., titanium and titanium alloy
  • the present disclosure relates to spheroidized particles including titanium.
  • the spheroidized particles are prepared by a process including: introducing a titanium based feed material (e.g., feed material includes titanium, such as titanium particles or titanium alloy powders) including particles into a microwave plasma torch; melting and spheroidizing the feed material within a plasma generated by the microwave plasma torch; exposing the spheroidized particles to an inert gas; and setting one or more cooling processing variables to tailor the microstructure of the spheroidized particles including titanium.
  • a titanium based feed material includes a titanium alloy.
  • the spheroidized particles are Ti A16-V4 (i.e., Ti 6-4).
  • melting and spheroidizing of the feed material occurs within a substantially uniform temperature profile between about 4,000K and 8,000K.
  • the feed material has a particle size of no less than 1.0 micrometers and no more than 300 micrometers.
  • one or more cooling processing variables are set to create a martensitic microstructure in the spheroidized particles.
  • one or more cooling processing variables are set to create a Widmanstatten microstructure in the spheroidized particles.
  • one or more cooling processing variables are set to create an equiaxed microstructure in the spheroidized particles.
  • one or more cooling processing variables are set to create at least two regions, each region having a different microstructure.
  • the at least two regions include a core portion and a skin portion.
  • the skin portion has a micro structure that is different from the feed material’s microstructure.
  • the present disclosure relates to a method of tailoring microstructure of spheroidized metallic particles.
  • the method includes introducing a metal feed material including particles into a microwave plasma torch.
  • the method also includes melting and spheroidizing the feed material within a plasma generated by the microwave plasma torch; exposing the spheroidized particles to an inert gas; and setting one or more cooling processing variables to tailor the micro structure of the spheroidized metallic particles.
  • the metal feed material includes a titanium based feed material.
  • melting and spheroidizing of the feed material occurs within a substantially uniform temperature profile between about 4,000K and 8,000K.
  • the feed material has a particle size of no less than 1.0 micrometers and no more than 300 micrometers.
  • setting one or more cooling processing variables includes selecting and controlling a cooling gas flow rate.
  • setting one or more cooling processing variables includes selecting and controlling a residence time of the particles of feed materials within the plasma.
  • setting one or more cooling processing variables includes selecting and controlling a cooling gas composition.
  • the cooling gas composition is selected to provide high thermal conductivity.
  • one or more cooling processing variables are set to create a martensitic microstructure in the spheroidized particles.
  • one or more cooling processing variables are set to create a Widmanstatten micro structure in the spheroidized particles.
  • one or more cooling processing variables are set to create an equiaxed microstructure in the spheroidized particles. In another embodiment, one or more cooling processing variables are set to create at least two regions, each region having a different microstructure. In another embodiment, the at least two regions include a core portion and a skin portion. In another embodiment, the skin portion has a microstructure that is different from the feed material’s microstructure.
  • the present disclosure relates to a method of modifying at least one of particle shape or microstructure of a titanium based feed stock.
  • the method includes selecting a composition of the titanium based metal feed stock; determining a desired microstructure for a final product; selecting cooling process parameters based upon desired microstructure and composition of the titanium based metal feed stock; melting at least a surface portion of particles of the titanium based metal feed stock in a plasma having a substantially uniform temperature profile at between 4,000K and 8,000K to spheriodize the feed stock; exposing the spheroidized particles to an inert gas; and setting and applying the selected cooling processing parameters to create spheroidized particles with the desired micro structure.
  • the above aspect includes one or more of the following features.
  • selecting the composition of the titanium based metal feed material includes determining an alloying composition of a titanium based feed stock source.
  • the particles of the titanium based metal feed stock have a particle size of no less than 1.0 micrometers and no more than 300 micrometers.
  • setting and applying the selected cooling processing parameters includes controlling a cooling gas flow rate.
  • setting and applying the selected cooling processing parameters include controlling a residence time of the particles of the titanium based metal feed stock in the plasma.
  • setting and applying the selected cooling processing parameters includes controlling a cooling gas composition.
  • the cooling gas composition is selected to provide high thermal conductivity.
  • the cooling processing parameters are selected to create a martensitic microstructure in the spheroidized particles.
  • the cooling processing parameters are selected to create a Widmanstatten microstructure in the spheroidized particles. In another embodiment, the cooling processing parameters are selected to create an equiaxed micro structure in the spheroidized particles. In another embodiment, the cooling processing parameters are selected to create at least two regions, each region having a different microstructure or crystal structure. The at least two regions can include a core portion and a skin portion. In another embodiment, the skin portion has a microstructure that is different from the feed stock’s micro structure.
  • the titanium based metal feed stock has a a-phase crystal structure and the spheroidized particles includes one or more regions of a b-phase crystal structure. In another embodiment, the titanium based metal feed stock has a single phase structure and the spheroidized particles have a multiphase structure.
  • Embodiments of the above aspects may include one or more of the following features.
  • the various spheroidized particles, processes used to create the spheroidized particles, and methods of producing metal or metal alloy powders in accordance with the present technology can provide a number of advantages.
  • the particles, processes for forming the particles and methods disclosed herein can be used in a continuous process that spheroidizes, and allows for control over the final micro structure of the particles.
  • Such embodiments can reduce the cost of spheroidizing metal powders by reducing the number of processing steps, which in turn, reduces the energy per unit volume of processed material and can increase the consistency of the final product. Reduction in the number of processing steps also reduces the possibility for contamination by oxygen and other contaminants.
  • the continuous processes disclosed herein improve the consistency of the end products by reducing or eliminating variations associated with typical batch-based processing of particles.
  • the present technology can achieve additional improvements in consistency due to the homogeneity and control of the energy source (i.e., plasma process). Specifically, if the plasma conditions are well controlled, particle agglomeration can be reduced, if not totally eliminated, thus leading to a better particle size distribution (on the same scale as the original feed materials).
  • the present methods and resulting powders have the advantage of control and the ability to tailor the micro structure of the end product. While not wishing to be bound by theory, it is believed that the methods disclosed herein provide control over heating and cooling processing conditions. As a result, by controlling and, in some embodiments, monitoring, at least one cooling processing variable (e.g., cooling gas flow rate, residence time in cooling gas, and composition of cooling gas) a desired microstructure, which may be different from the original microstructure can be obtained. Further, novel multiphase microstructures can be created. That is, spheroidal particles can be processed by controlling heating and/or cooling conditions to create a core with one microstructure and a shell with a different microstructure.
  • at least one cooling processing variable e.g., cooling gas flow rate, residence time in cooling gas, and composition of cooling gas
  • Some embodiments have the advantage of being able to modify or change the microstructure of the feed stock material to a desired microstructure, which may be a single phase or multiphase material.
  • a spheroidized particles comprising titanium prepared by a process comprising introducing a titanium based feed material comprising particles into a microwave plasma torch, melting and spheroidizing the feed material in the microwave plasma torch, exposing the spheroidized particles to an inert gas, and setting one or more cooling processing variables to tailor the micro structure of the spheroidized particles comprising titanium, the spheroidized particles including at least a first region and a second region, the first region and the second region having different microstructures.
  • the titanium based feed material comprises a titanium alloy.
  • the spheroidized particles are Ti A16-V4.
  • melting and spheroidizing of the feed material occurs within a substantially uniform temperature profile between about 4,000K and 8,000K.
  • the feed material has a particle size of no less than 1.0 micrometers and no more than 300 micrometers.
  • introducing into the microwave plasma torch comprises introducing into a plume of the microwave plasma torch and wherein melting and spheroidizing the feed material in the microwave plasma torch comprises melting and spheroidizing the feed material in the plume of the microwave plasma torch.
  • introducing into the microwave plasma torch comprises introducing into an exhaust of the microwave plasma torch and wherein melting and spheroidizing the feed material in the microwave plasma torch comprises melting and spheroidizing the feed material in the exhaust of the microwave plasma torch.
  • the titanium based feed material has a a-phase crystal structure and the spheroidized particles includes one or more regions of a b-phase crystal structure.
  • the at least two regions include a core portion and a skin portion.
  • the skin portion has a microstructure that is different from the feed material’s microstructure.
  • Also disclosed herein are embodiments of a method of tailoring micro structure of spheroidized metallic particles comprising introducing a titanium feed material comprising particles into a microwave plasma torch, melting and spheroidizing the feed material in the microwave plasma torch, exposing the spheroidized particles to an inert gas, and setting one or more cooling processing variables to tailor the micro structure of the spheroidized metallic particles, the spheroidized metallic particles including at least a first region and a second region, the first region and the second region having different microstructures.
  • melting and spheroidizing of the feed material occurs within a substantially uniform temperature profile between about 4,000K and 8,000K.
  • the feed material has a particle size of no less than 1.0 micrometers and no more than 300 micrometers.
  • setting one or more cooling processing variables comprises selecting and controlling a cooling gas flow rate. In some embodiments, setting one or more cooling processing variables comprises selecting and controlling a residence time of the particles of feed materials within the plasma. In some embodiments, setting one or more cooling processing variables comprises selecting and controlling a cooling gas composition. In some embodiments, the cooling gas composition is selected to provide high thermal conductivity.
  • introducing into the microwave plasma torch comprises introducing into a plume of the microwave plasma torch and wherein melting and spheroidizing the feed material in the microwave plasma torch comprises melting and spheroidizing the feed material in the plume of the microwave plasma torch. In some embodiments, introducing into the microwave plasma torch comprises introducing into an exhaust of the microwave plasma torch and wherein melting and spheroidizing the feed material in the microwave plasma torch comprises melting and spheroidizing the feed material in the exhaust of the microwave plasma torch.
  • the titanium based feed material has a a-phase crystal structure and the spheroidized particles includes one or more regions of a b-phase crystal structure.
  • the at least two regions include a core portion and a skin portion.
  • the skin portion has a microstructure that is different from the feed material’s microstructure.
  • a method of modifying at least one of particle shape or micro structure of a titanium based feed stock comprising selecting a composition of the titanium based metal feed stock, determining a desired microstructure for a final product, selecting cooling process parameters based upon desired microstructure and composition of the titanium based metal feed stock, melting at least a surface portion of particles of the titanium based metal feed stock in a plasma having a substantially uniform temperature profile at between 4,000K and 8,000K to spheroidize the feed stock, exposing the spheroidized particles to an inert gas, and setting and applying the selected cooling processing parameters to create spheroidized particles with the desired microstructure, the spheroidized particles including at least a first region and a second region, the first region and the second region having different microstructures.
  • selecting the composition of the titanium based metal feed material comprises determining an alloying composition of a titanium based feed stock source.
  • the particles of the titanium based metal feed stock have a particle size of no less than 1.0 micrometers and no more than 300 micrometers.
  • setting and applying the selected cooling processing parameters comprises controlling a cooling gas flow rate. In some embodiments, setting and applying the selected cooling processing parameters comprises controlling a residence time of the particles of the titanium based metal feed stock in the plasma. In some embodiments, setting and applying the selected cooling processing parameters comprises controlling a cooling gas composition. In some embodiments, the cooling gas composition is selected to provide high thermal conductivity.
  • the titanium based feed material has a a-phase crystal structure and the spheroidized particles includes one or more regions of a b-phase crystal structure.
  • the at least two regions include a core portion and a skin portion.
  • the skin portion has a microstructure that is different from the feed stock’s microstructure.
  • the titanium based metal feed stock has a single phase structure and the spheroidized particles have a multiphase structure.
  • the melting in the plasma comprises melting in a plume of the plasma. In some embodiments, the melting in the plasma comprises melting in an exhaust of the plasma. In some embodiments, the plasma comprises a microwave plasma.
  • FIG. 1 illustrates an example method of producing spheroidal metallic and metallic alloy particles according to the present disclosure, compared against a conventional method for producing similar particles.
  • FIG. 2 illustrates another example method of producing dehydrogenated spheroidal particles according to the present disclosure.
  • FIG. 3 illustrates another example method of producing dehydrogenated spheroidal particles from metal hydride material according to the present disclosure.
  • FIG. 4 illustrates an exemplary microwave plasma torch that can be used in the production of spheroidal and dehydrogenated metal or metal alloy powders, according to embodiments of the present disclosure.
  • FIGS. 5A-B illustrate embodiments of a microwave plasma torch that can be used in the production of spheroidal metal or metal alloy powders, according to a side feeding hopper embodiment of the present disclosure.
  • FIG. 6 illustrates an exemplary method of producing titanium based (e.g., titanium, titanium alloy) spheroidal particles having a desired micro structure.
  • titanium based e.g., titanium, titanium alloy
  • FIG. 7 illustrates an exemplary method of modifying a particle micro structure according to embodiments of the present disclosure.
  • FIG. 8 illustrates an exemplary particle modified according to embodiments of the present disclosure.
  • One aspect of the present disclosure involves a process of spheroidization of metals and metal alloy hydrides using a microwave generated plasma.
  • the process uses readily available existing pre-screened or non-prescreened raw materials made of metal hydrides as feedstock.
  • the feedstock can a single phase or multiphase.
  • the powder feedstock is entrained in inert and/or reducing and/or oxidizing gas environment and injected into the microwave plasma environment.
  • a hot plasma which includes the plasma itself, the plasma plume, or the plasma exhaust
  • the feedstock is simultaneously dehydrogenated and spheroidized and released into a chamber filled with an inert gas and directed into hermetically sealed drums where is it stored.
  • This process can be carried out at atmospheric pressure, in a partial vacuum, or at a slightly higher pressure than atmospheric pressure.
  • the process can be carried out in a low, medium, or high vacuum environment.
  • the process can run continuously and the drums are replaced as they fill up with spheroidized dehydrogenated and deoxidized metal or metal alloy particles.
  • the process not only spheroidizes the powders, but also eliminates the dehydrogenation steps from the traditional process of manufacturing metal and metal alloy powders using Hydride-De-hydride (HDH) process, which leads to cost reduction.
  • HDH Hydride-De-hydride
  • the Hydride-Dehydride (HDH) process is used to resize large metallic or metallic alloy pieces down to a finer particle size distribution through crushing, milling, and screening.
  • Metal and alloy powders are manufactured using the HDH process, where bulk feedstock, such as coarse metal powders or metal/metal alloy scraps, etc., are heated in a hydrogen-containing atmosphere at high temperature (-700 °C) for a few days. This leads to the formation of a brittle metal hydride, which can readily be crushed into a fine power and sifted to yield a desired size distribution determined by the end user.
  • hydrogenation may begin.
  • the furnace is filled with hydrogen gas and heated up to a few days at high temperature to fully form the metal hydride.
  • the brittle nature of the metal hydride allows the bulk material to be crushed into fine powders which are then screened into desired size distributions.
  • the next step is dehydrogenation.
  • the screen hydride powder is loaded into the vacuum furnace then heated under partial vacuum, promoting dissociation of hydrogen from the metal hydride to form H 2 gas and dehydrided metal.
  • Dehydrogenation is rapid on the particle surface where H 2 can readily leave the particles.
  • H 2 must diffuse through the bulk of the solid before it reaches surface and leave the particle. Diffusion through the bulk is a rate-limiting process“bottle-neck” requiring relatively long reaction time for complete dehydrogenation.
  • the time and processing temperatures required for dehydrogenation are sufficient to cause sintering between particles, which results in the formation of large particle agglomerations in the final product.
  • Post-process sifting eliminates the agglomerations, which adds process time and cost to the final product.
  • the powder Before the powder can be removed from the furnace, it must be sufficiently cooled to maintain safety and limit contamination. The thermal mass of the large furnaces may take many hours to sufficiently cool. The cooled powders must then be spheroidized in a separate machine. Generally this is carried out within an RF plasma, which are known to exhibit large temperature gradients resulting in partially spheroidized products.
  • the dehydrogenation and spheroidization steps of an HDH process can be simplified to a single processing step using a microwave generated plasma.
  • Such embodiments can reduce the cost of spheroidizing metal powders by reducing the number of processing steps, reducing the energy per unit volume of processed material, and increasing the consistency of the final product. Reduction in the number of processing steps also reduces the possibility for powder contamination by oxygen and other contaminants.
  • the continuous dehydrogenation processes disclosed herein improves the consistency of the end products by reducing or eliminating variations associated with typical batch-based dehydrogenation processes.
  • the rate of cooling of the dehydrogenated, deoxidized, and spheroidized metal and metal alloys can be controlled to strategically influence the microstructure of the powder.
  • rapid cooling of a-phase titanium alloys facilitates an acicular (martensite) structure.
  • Moderate cooling rates produce a Widmanstatten microstructure, and slow cooling rates form an equiaxed microstructure.
  • microstructure of the metal and metal alloys can be controlled.
  • process parameters such as power density, flow rates, and residence time of the powder in the plasma dependent on the powder material’s physical characteristics, such as, for example, the melting point, thermal conductivity, and particle size distribution.
  • the power density can range from about 20 W/cm 3 to 500 W/cm 3 .
  • the total gas flow rate can range from about 0.1 cfm (cubic feet per minute) to 50 cfm.
  • the residence time can be tuned from about 1 milliseconds to 10 seconds. The precise cooling rates required to form these structures is largely a function of the type and quantity of the alloying elements within the material.
  • the rate of cooling allows for control over the final micro structure.
  • the above methods can be applied to processing metal (e.g., titanium and titanium alloys such as Ti 6-4) feed stock.
  • metal e.g., titanium and titanium alloys such as Ti 6-4
  • the control over micro structure is not limited thereto.
  • methods of the present technology and powders created by the present technology include the use of non-hydrided sources.
  • titanium metal and various titanium metal alloys can be utilized as the feed stock source. These materials can be crushed or milled to create particles for treatment within a microwave plasma torch.
  • Cooling processing parameters include, but are not limited to, cooling gas flow rate, residence time of the spheroidized particles in the hot zone, and the composition or make of the cooling gas.
  • the cooling rate or quenching rate of the particles can be increased by increasing the rate of flow of the cooling gas. The faster the cooling gas is flowed past the spheroidized particles exiting the plasma, the higher the quenching rate-thereby allowing certain desired microstructures to be locked-in. Residence time of the particles within the hot zone of the plasma can also be adjusted to provide control over the resulting micro structure.
  • the length of time the particles are exposed to the plasma determines the extent of melting of the particle (i.e., surface of the particle melted as compared to the inner most portion or core of the particle). Consequently, the extent of melting effects the extent of cooling needed for solidification and thus it is a cooling process parameter.
  • Microstructural changes can be incorporated throughout the entire particle or just a portion thereof depending upon the extent of particle melting.
  • Residence time can be adjusted by adjusting such operating variables of particle injection rate and flow rate (and conditions, such as laminar flow or turbulent flow) within the hot zone.
  • Equipment changes can also be used to adjust residence time. For example, residence time can be adjusted by changing the cross-sectional area of the hot zone.
  • a larger cross- sectional area of the plasma torch and/or extension tube in an afterglow region (e.g., region about plasma 11 in FIG. 4, the cross-sectional area being at least partially defined by the inner wall) will lead to a lower particle velocity, whereas a smaller cross-sectional area will lead to a higher velocity, thus lowering residence time in the hot zone.
  • cooling processing parameter that can be varied or controlled is the composition of the cooling gas.
  • Certain cooling gases are more thermally conductive than others.
  • helium is considered to be a highly thermally conductive gas.
  • the higher the thermal conductivity of the cooling gas the faster the spheriodized particles can be cooled/quenched.
  • the composition of the cooling gas e.g., controlling the quantity or ratio of high thermally conductive gasses, such as helium, to lesser thermally conductive gases, such as argon
  • the cooling rate can be controlled.
  • the micro structure of a metal is determined by the composition of the metal and heating and cooling /quenching of the material.
  • the composition of the feed stock material by selecting (or knowing) the composition of the feed stock material, and then exposing the feed stock to a plasm that has the temperature profile (such as a uniform or substantially uniform temperature profile) and control there over as provided by the microwave plasma torch, followed by selecting and controlling the cooling parameters control over the microstructure of the spheroidized metallic particle is achieved.
  • the temperature profile can be between 3,000K and 8,000K (or between about 3,000K and about 8,000K) as an example.
  • the phase of the metallic material depends upon the compositions of the feed stock material (e.g., purity, composition of alloying elements, etc.) as well thermal processing. Titanium has two distinct phases known as the alpha phase (which has a hexagonal close packed crystal structure) and a beta phase which has a body centered cubic structure. Titanium can also have a mixed a + b phase. The different crystal structures yield different mechanical responses. Because titanium is allotropic it can be heat treated to yield specific contents of alpha and beta phases. The desired microstructure is not only a description of the grains (e.g., martensitic vs. equiaxed) but also the amount and location of different phases throughout.
  • inert gas is continually purged surrounding a powdered metal feed to remove oxygen within a powder-feed hopper.
  • a continuous volume of powder feed is then entrained within an inert gas and fed into the microwave generated plasma for dehydrogenation or for composition/maintaining purity of the spheroidized particles.
  • the microwave generated plasma may be generated using a microwave plasma torch, as described in U.S. Patent Publication No. US 2013/0270261, and/or U.S. Patent Publication No. US 2008/0173641 (issued as U.S. Patent 8,748,785), each of which is hereby incorporated by reference in its entirety.
  • the particles are exposed to a uniform temperature profile at between 4,000 and 8,000 K within the microwave generated plasma.
  • the powder particles are rapidly heated and melted. Liquid convection accelerates H 2 diffusion throughout the melted particle, continuously bringing hydrogen (H 2 ) to the surface of the liquid metal hydride where it leaves the particle, reducing the time each particle is required to be within the process environment relative to bulk processes.
  • an inert gas such as argon
  • the particles within the process are entrained within an inert gas, such as argon, generally contact between particles is minimal, greatly reducing the occurrence of particle agglomeration. The need for post-process sifting is thus greatly reduced or eliminated, and the resulting particle size distribution could be practically the same as the particle size distribution of the input feed materials.
  • the particle size distribution of the feed materials is maintained in the end products.
  • the melted metals are inherently spheroidized due to liquid surface tension.
  • the microwave generated plasma exhibits a substantially uniform temperature profile, though other embodiments may not be substantially uniform, more than 90% spheroidization of particles could be achieved (e.g., 91%, 93%, 95%, 97%, 99%, 100%), eliminating the need for separate dehydrogenation steps.
  • both spheroidization and tailoring e.g., changing, manipulating, controlling
  • microstructure are addressed or, in some instances, partially controlled, by treating with the microwave generated plasma.
  • Embodiments of the present disclosure are directed to producing particles that are substantially spherical or spheroidal or have undergone significant spheroidization.
  • spherical, spheroidal or spheroidized particles refer to particles having a sphericity greater than a certain threshold.
  • Particle sphericity can be calculated by calculating the surface area of a sphere A s , ideal with a volume matching that of the particle, V using the following equation:
  • particles can have a sphericity of greater than 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 0.91, 0.95, or 0.99 (or greater than about 0.5, about 0.6, about 0.7, about 0.75, about 0.8, about 0.8, about 0.91, about 0.95, or about 0.99). In some embodiments, particles can have a sphericity of 0.75 or greater or 0.91 or greater (or about 0.75 or greater or about 0.91 or greater).
  • particles can have a sphericity of less than 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 0.91, 0.95, or 0.99 (or less than about 0.5, about 0.6, about 0.7, about 0.75, about 0.8, about 0.8, about 0.91, about 0.95, or about 0.99).
  • a particle is considered to be spherical, spheroidal or spheroidized if it has a sphericity at or above any of the aforementioned sphericity values, and in some preferred embodiments, a particle is considered to be spherical if its sphericity is at or about 0.75 or greater or at or about 0.91 or greater.
  • a median sphericity of all particles within a given powder can be greater than 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 0.91, 0.95, or 0.99 (or greater than about 0.5, about 0.6, about 0.7, about 0.75, about 0.8, about 0.8, about 0.91, about 0.95, or about 0.99). In some embodiments, a median sphericity of all particles within a given powder can be less than 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 0.91, 0.95, or 0.99 (or less than about 0.5, about 0.6, about 0.7, about 0.75, about 0.8, about 0.8, about 0.91, about 0.95, or about 0.99).
  • a powder is considered to be spheroidized if all or a threshold percentage (as described by any of the fractions below) of the particles measured for the given powder have a median sphericity greater than or equal to any of the aforementioned sphericity values, and in some preferred embodiments, a powder is considered to be spheroidized if all or a threshold percentage of the particles have a median sphericity at or about 0.75 or greater or at or about 0.91 or greater.
  • the fraction of particles within a powder that can be above a given sphericity threshold can be greater than 50%, 60%, 70%, 80%, 90%, 95%, or 99% (or greater than about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, or about 99%). In some embodiments, the fraction of particles within a powder that can be above a given sphericity threshold, such as described above, can be less than 50%, 60%, 70%, 80%, 90%, 95%, or 99% (or less than about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, or about 99%).
  • Particle size distribution and sphericity may be determined by any suitable known technique such as by SEM, optical microscopy, dynamic light scattering, laser diffraction, manual measurement of dimensions using an image analysis software, for example from about 15- 30 measures per image over at least three images of the same material section or sample, and any other techniques.
  • FIG. 1 shown is a comparison of a conventional process for producing spheroidized titanium powder (100) versus a method (200) in accordance with the present technology.
  • the process flow (101) on the left of FIG. 1 presents an example process that combines a HDH process (100) with spheroidization of titanium powders.
  • the process starts with Ti raw material (step a, 105) that is hydrogenated (step b, 110), and then crushed and sifted to size (step c, 115). Pure titanium is recovered through dehydrogenation (step d, 120). It is then screened for agglomerations and impurities, and then sifted to the size specified by the customer (step e, 125).
  • the powder then goes through a deoxidation step to reduce or eliminate oxygen that it picked up during the sifting and screening processes.
  • Deoxidation is required especially for small particle sizes, such as particles below 50 microns, where the surface to volume ratio is substantial (step f, 130).
  • the titanium particles are then spheroidized (step g, 135) and collected (step h, 140).
  • a similar process can be used to create a Ti alloy, such as Ti 6-4, instead of pure titanium powder.
  • some embodiments of the present disclosure combine the dehydrogenation and spheroidization steps shown on the left side of FIG. 1 (101, 130, 135) in favor of a single step to produce spheroidized metals and/or metal alloys from corresponding hydride feedstock.
  • An example of this technique is illustrated in the process flow (201) shown on the right side of FIG. 1.
  • the method starts with a crushed and sifted metal hydride feed material (i.e., step c, 115, without performing the dehydride step).
  • the feed material is a titanium hydride powder
  • the powder resulting from process 200 is a spherical titanium powder.
  • process 200 can also be used with crushed and sifted metal alloy hydride feed material, such as titanium alloy hydride feed material, and the powder resulting from completion of process 200 is a spherical metal alloy powder, such as a spherical titanium alloy powder.
  • the powder is entrained within an inert gas and injected into a microwave generated plasma environment exhibiting a substantially uniform temperature profile, though other embodiments may not be substantially uniform, between approximately 3,000 or 4,000 K and 8,000 K (or about 3,000 or 4,000 K and 8,000 K) and under a partial vacuum.
  • the hermetically sealed chamber process can also run at atmospheric pressure or slightly above atmospheric pressure to eliminate any possibility for atmospheric oxygen to leak into the process.
  • the particles are simultaneously melted and dehydrogenated in the plasma, spheroidized due to liquid surface tension, re- solidifying after exiting the plasma (200).
  • the particles are then collected in sealed drums in an inert atmosphere (140).
  • FIG. 2 is a flow chart illustrating an exemplary method (250) for producing spherical powders, according to an embodiment of the present disclosure.
  • the process (250) begins by introducing a feed material into a plasma torch (255).
  • the plasma torch is a microwave generated plasma torch or an RF plasma torch.
  • the feed materials are exposed to a plasma causing the materials to melt, as described above (260).
  • hydrogen within the feed material dissociates from the metal, resulting in dehydrogenation (260a).
  • the melted materials are spheroidized by surface tension, as discussed above (260b).
  • step 260 includes 260a and 260b. That is, by exposing the feed material to the plasma both dehydrogenation and spheroidization are achieved; no separate or distinct processing steps are needed to achieve dehydrogenation and spheroidization. After exiting the plasma, the products cool and solidify, locking in the spherical shape and are then collected (265).
  • FIG. 3 is a flow chart illustrating another exemplary method (300) for producing spherical powders, according to another embodiment of the present disclosure.
  • the method (300) begins by introducing a substantially continuous volume of filtered metal hydride feed materials into a plasma torch.
  • the plasma torch can be a microwave generated plasma or an RF plasma torch (310).
  • an AT- 1200 rotating powder feeder (available from Thermach Inc.) allows a good control of the feed rate of the powder.
  • the powder can be fed into the plasma using other suitable means, such as a fluidized bed feeder.
  • the feed materials may be introduced at a constant rate, and the rate may be adjusted such that particles do not agglomerate during subsequent processing steps.
  • the feed materials to be processed are first sifted and classified according to their diameters, with a minimum diameter of 1 micrometers (pm) and a maximum diameter of 22 pm, or a minimum of 22 pm and a maximum of 44 pm, or a minimum of 44 pm and a maximum of 70 pm, or a minimum of 70 pm and a maximum of 106 pm, or a minimum of 106 pm and a maximum of 300 pm.
  • pm micrometers
  • these upper and lower values are provided for illustrative purposes only, and alternative size distribution values may be used in other embodiments.
  • the feed materials can be entrained within an axis-symmetric laminar and/or turbulent flow toward a microwave or RF generated plasma (320).
  • each particle within the process is entrained within an inert gas, such as argon.
  • the metal hydride materials are exposed to a partial vacuum within the plasma (330).
  • the feed materials are exposed to a substantially uniform temperature profile, though other embodiments may not be substantially uniform, and are melted (340). In one example, the feed materials are exposed to a uniform temperature profile of approximately between 4,000 and 8,000 K within the plasma.
  • the bins are under a vacuum. In one embodiment, the bins are hermetically sealed after being filled with powder generated in accordance with the present technology. In one embodiment, the bins are back filled with an inert gas, such as, for example argon. Because of the continuous nature of the process, once a bin is filled, it can be removed and replaced with an empty bin as needed without stopping the plasma process.
  • an inert gas such as, for example argon.
  • the methods and processes in accordance with the invention can be used to make spherical metal powders or spherical metal alloy powders.
  • the starting feed material is a titanium hydride material
  • the resulting powder will be a spherical titanium powder.
  • the starting feed material is a titanium alloy hydride material
  • the resulting powder will be a spherical titanium alloy powder.
  • the resulting spherical titanium alloy powder comprises spherioidized particles of Ti A16-V4, with between 4% to 7% weight aluminum (e.g., 5.5 to 6.5% Al) and 3% to 5% weight vanadium (e.g., 3.5 to 4.5% vanadium).
  • FIG. 4 illustrates an exemplary microwave plasma torch that can be used in the production of spheroidal and dehydrogenated metal or metal alloy powders, according to embodiments of the present disclosure.
  • metal hydride feed materials 9, 10 can be introduced into a microwave plasma torch 3, which sustains a microwave generated plasma 11.
  • an entrainment gas flow and a sheath flow may be injected through inlets 5 to create flow conditions within the plasma torch prior to ignition of the plasma 11 via microwave radiation source 1.
  • the entrainment flow and sheath flow are both axis-symmetric and laminar, while in other embodiments the gas flows are swirling.
  • the feed materials 9 are introduced axially into the microwave plasma torch, where they are entrained by a gas flow that directs the materials toward the plasma.
  • the gas flows can consist of a noble gas column of the periodic table, such as helium, neon, argon, etc.
  • the feed materials are melted, as discussed above, in order to dehydrogenate and spheroidize the materials.
  • Inlets 5 can be used to introduce process gases to entrain and accelerate particles 9, 10 along axis 12 towards plasma 11. First, particles 9 are accelerated by entrainment using a core laminar gas flow (upper set of arrows) created through an annular gap within the plasma torch.
  • a second laminar flow (lower set of arrows) can be created through a second annular gap to provide laminar sheathing for the inside wall of dielectric torch 3 to protect it from melting due to heat radiation from plasma 11.
  • the laminar flows direct particles 9, 10 toward the plasma 11 along a path as close as possible to axis 12, exposing them to a substantially uniform temperature within the plasma, though other embodiments may not be substantially uniform.
  • suitable flow conditions are present to keep particles 10 from reaching the inner wall of the plasma torch 3 where plasma attachment could take place.
  • Particles 9, 10 are guided by the gas flows towards microwave plasma 11 were each undergoes homogeneous thermal treatment.
  • Various parameters of the microwave generated plasma, as well as particle parameters, may be adjusted in order to achieve desired results.
  • these parameters may include microwave power, feed material size, feed material insertion rate, gas flow rates, plasma temperature, residence time and cooling rates.
  • the cooling or quenching rate is not less than 10 +3 degrees C/sec upon exiting plasma 11.
  • the gas flows are laminar; however, in alternative embodiments, swirl flows or turbulent flows may be used to direct the feed materials toward the plasma.
  • FIGS. 5A-B illustrates an exemplary microwave plasma torch that includes a side feeding hopper rather than the top feeding hopper shown in the embodiment of FIG. 4, thus allowing for downstream feeding.
  • the feedstock is injected after the microwave plasma torch applicator for processing in the“plume” or“exhaust” of the microwave plasma torch.
  • the plasma of the microwave plasma torch is engaged at the exit end of the plasma torch to allow downstream feeding of the feedstock, as opposed to the top-feeding (or upstream feeding) discussed with respect to FIG. 4.
  • This downstream feeding can advantageously extend the lifetime of the torch as the hot zone is preserved indefinitely from any material deposits on the walls of the hot zone liner.
  • the downstream approach may allow for the use of wire feedstocks instead to produce spheroidized materials such as metals which may include aluminum, Iconel, titanium, molybdenum, tungsten, and rhenium. This spheroidization method can be applied to both ceramics and metals.
  • the downstream spheroidization method can utilize two main hardware configurations to establish a stable plasma plume which are: annular torch, such as described in U.S. Pat. Pub. No. 2018/0297122, the entirety of which is incorporated by reference in its entirety, or swirl torch, such as described in U.S. Pat. No. 8,748,785 and U.S. Pat. No. 9,932,673, both of which are hereby incorporated by reference their entirety.
  • a feed system close- coupled with the plasma plume at the exit of the plasma torch is used to feed powder axisymmetrically to preserve process homogeneity.
  • Other feeding configurations may include one or several individual feeding nozzles surrounding the plasma plume.
  • the feedstock powder can enter the plasma at a specific position along the length of the plasma plume where a specific temperature has been measured and a residence time estimated for sufficient melting of the particles.
  • the melted particles exit the plasma into a sealed chamber where they are quenched then collected.
  • the feedstock can be a circular feeding system where the feedstock is fed in 180 or 360 degrees.
  • the metal feed materials 314 can be introduced into a microwave plasma torch 302.
  • a hopper 306 can be used to store the metal feed material 314 before feeding the metal feed material 314 into the microwave plasma torch 302, plume, or exhaust.
  • the feed material 314 can be injected at any angle to the longitudinal direction of the plasma torch 302. 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees.
  • the feedstock can be injected an angle of greater than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees.
  • the feedstock can be injected an angle of less than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees.
  • the feedstock can be injected along the longitudinal axis of the plasma torch.
  • the microwave radiation can be brought into the plasma torch through a waveguide 304.
  • the feed material 314 is fed into a plasma chamber 310 and is placed into contact with the plasma generated by the plasma torch 302. When in contact with the plasma, plasma plume, or plasma exhaust, the feed material melts. While still in the plasma chamber 310, the feed material 314 cools and solidifies before being collected into a container 312. Alternatively, the feed material 314 can exit the plasma chamber 310 while still in a melted phase and cool and solidify outside the plasma chamber.
  • a quenching chamber may be used, which may or may not use positive pressure. While described separately from FIG. 4, the embodiments of FIGS. 5A-B are understood to use similar features and conditions to the embodiment of FIG. 4.
  • implementation of the downstream injection method may use a downstream swirl, extended spheroidization, or quenching.
  • an additional swirl component can be introduced downstream from the plasma torch, which can keep the powder from the walls of a tube pathway.
  • the tube pathway is an extension tube which can give the powder a longer residence time (e.g., extended spheroidization).
  • it may not use a downstream swirl, extended spheroidization, or quenching.
  • it may use one of a downstream swirl, extended spheroidization, or quenching.
  • it may use two of a downstream swirl, extended spheroidization, or quenching.
  • Injection of powder from below may results in the reduction or elimination of plasma-tube coating in the microwave region.
  • the coating becomes too substantial, the microwave energy is shielded from entering the plasma hot zone and the plasma coupling is reduced. At times, the plasma may even extinguish and become unstable. Decrease of plasma intensity means decreases in spheroidization level of the powder.
  • downstream approach may allow for the method to run for long durations as the coating issue is reduced. Further, the downstream approach allows for the ability to inject more powder as there is no need to minimize coating.
  • FIG. 6 illustrates an exemplary method (500) of producing spheroidized titanium particles with a tailored or desired microstructure.
  • Method 500 includes several processing steps to treat metallic feed materials such as, for example, titanium feed materials (e.g., titanium or titanium alloys) to create spheroidized metallic particles with a desired microstructure.
  • metallic feed materials e.g., titanium based
  • metallic feed materials comprising particles are feed into a plasma torch.
  • the particles can be produced from crushing, pulverizing, or milling feed stock materials. In general, the feed stock particles have an average particle size of between 1 micron and 300 microns.
  • the feed stock particles are exposed to a microwave generated plasma to melt at least the surface portion of the particles.
  • the spheroidized particles are exposed to an inert gas such helium, nitrogen, argon or combinations/mixtures thereof.
  • the cooling processing variables/conditions are set and maintained to achieve a desired micro structure. For example, in embodiments in which a martensitic micro structure is desired throughout the entire particle, the cooling processing conditions are set for rapid cooling. As a result, the residence time of the particles in the hot zone is selected to allow for melting of the entire feedstock particle, the cooling gas flow rate is set to a fastest rate, and the amount of helium forming the composition of the cooling gas is set to a maximum available.
  • the spherical powders are collected in step 530.
  • FIG. 7 illustrates an exemplary method (600) of modifying metallic feed stock material to have a spheroidized shape and a desired microstructure.
  • the method of 600 includes several processing steps to treat metallic feed materials such as, for example, titanium feed materials (e.g., titanium or titanium alloys) to create spheroidized metallic particles with a desired microstructure.
  • metallic feed materials such as, for example, titanium feed materials (e.g., titanium or titanium alloys) to create spheroidized metallic particles with a desired microstructure.
  • knowledge of the chemical composition of the feed stock e.g., 99.9% pure titanium, Ti-6Al-4V, etc.
  • the composition of the Ti-based feed stock material is selected or analyzed to determine its composition.
  • a desired microstructure of a final product is determined. For example, it may be determined that an a-phase 99% pure Ti equiaxed microstructure throughout the spheroidized particle is desired. As a result, a slower rate of cooling will be required than that used to produce a martensitic micro structure.
  • Cooling processing parameters will be selected (step 620), such as cooling gas flow rate, residence time, and/or composition of cooling gas to achieve such a microstructure based upon the composition of the feed stock materials.
  • the micro structure of the final product will differ from the original feed stock material. That is an advantage of the present method is to be able to efficiently process feed materials to create spheroidized particles with a desired micro structure.
  • the feed stock particles are melted in the microwave generated plasma to spheriodize the particles in step 625.
  • the spheroidized particles are exposed to an inert gas (step 630) and the determined or selected cooling parameters are applied to form the desired microstructure.
  • the desired micro structure of the spheroidized particle (end product) can be tailored to meet the demands and material characteristics of its use.
  • the desired microstructure may be one that provides improved ductility (generally associated with the a-phase).
  • the desired microstructure may be associated with the inclusion of a + b phase or regions of a with islands of b phase or vice-versa.
  • FIG. 8 shows such an embodiment.
  • This figures illustrates a spheroidal particle which has two distinct regions.
  • the original titanium feed material for this particle was a pure titanium a- phase powder.
  • the feed material was exposed to the plasma under conditions (temperature, residence time, etc.) such that only a surface portion of the particle melted, so that spheriodization could occur. Cooling rates applied allowed for the transformation of the shell region to transform to b-phase, leaving the core to retain the a-phase.
  • the entire feed stock particle can be melted and cooling parameters can be selected and applied to create a crystal structure that has the same phase as the feed stock material (e.g., retains a-phase) or is transformed to a new phase or mixture of phases.
  • cooling processing parameters can be selected and applied to create spheroidal particles that have the same microstructure throughout the particle or various microstructures in two or more regions (e.g., shell region, core region).

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Abstract

L'invention concerne des méthodologies, des systèmes et des dispositifs pour produire des produits de poudre métalliques sphéroïdales. En utilisant un plasma micro-onde, une commande sur la sphéricité et la microstructure résultante peuvent être personnalisées pour satisfaire les demandes souhaitées.
EP19735153.9A 2018-06-19 2019-06-19 Poudres métalliques de titane sphéroïdales à microstructures personnalisées Pending EP3810820A1 (fr)

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PCT/US2019/037956 WO2019246242A1 (fr) 2018-06-19 2019-06-19 Poudres métalliques de titane sphéroïdales à microstructures personnalisées

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