WO2019084045A1

WO2019084045A1 - Electrolytic-based methods for recycling titanium particles

Info

Publication number: WO2019084045A1
Application number: PCT/US2018/057159
Authority: WO
Inventors: Jen C. Lin
Original assignee: Arconic Inc.
Priority date: 2017-10-23
Filing date: 2018-10-23
Publication date: 2019-05-02

Abstract

A method is disclosed for recycling of titanium particles, including titanium alloy powders used in additive manufacturing processes. The method includes receiving a feedstock comprising titanium particles. The as-received titanium particles include oxygen and have a surface oxide layer thereon. The method also includes exposing the feedstock to reducing conditions in an electrolytic cell. The exposing includes reducing the surface oxide layer of the titanium particles. The exposing also includes decreasing the oxygen of the as-received titanium particles by at least 10%. The method also includes recovering a purified feedstock from the electrolytic cell. The as-recovered titanium particles comprise at least 10% less oxygen as compared to the as-received titanium particles.

Description

ELECTROLYTIC-BASED METHODS FOR RECYCLING

TITANIUM PARTICLES

FIELD OF THE INVENTION

[001] The present disclosure is directed towards electrolytic-based methods for recycling titanium particles.

BACKGROUND

[002] Titanium particles are required to meet strict specifications for oxygen content for use in powder metallurgy processes. These requirements are laid out in ASTM B988-13.

SUMMARY OF THE INVENTION

[003] Broadly, the present disclosure relates to methods for recycling titanium metal-based particles, including, for example and without limitation, titanium alloy powders, as may be used in powder metallurgy or additive manufacturing (AM) processes. Due to titanium metal's affinity for oxygen, titanium particles tend to accumulate oxygen during their use and/or storage. The accumulated oxygen may, for instance, be in the form of titanium oxides, such as titanium dioxide (T1O2), building-up as a surface oxide layer upon a titanium-based core body. In AM processes, for example, oxygen content of the titanium particles may accumulate to such an extent that the titanium particles may no longer be used in those processes due to their oxygen content becoming excessive and, thus, outside of allowed oxygen limits.

I. Overview of the Method

[004] The present disclosure relates to recycling titanium-based particles for reuse in AM processes, powder metallurgy, and other systems, methods and apparatuses where titanium- based particles may be used. In one approach, a method may include receiving a feedstock comprising titanium particles (e.g., titanium metal particles; titanium alloy particles). The as- received titanium particles may comprise oxygen and have a surface oxide layer thereon. The method may include exposing the feedstock to reducing conditions in an electrolytic cell. The method may include reducing the surface oxide layer of the titanium particles, thereby decreasing the oxygen of the as-received titanium particles by at least 10%. The method may include recovering a purified feedstock from the electrolytic cell. In one embodiment, the as- recovered titanium particles generally have at least 10% less oxygen as compared to the as- received titanium particles. [005] As used herein, "additive manufacturing" means "a process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies," as defined in ASTM F2792-12A entitled "Standard Terminology for Additive Manufacturing Technologies." Such materials may be manufactured via any appropriate additive manufacturing technique described in ASTM F2792-12A, such as binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, or sheet lamination, among others.

[006] As used herein, a "particle" means a distinct fragment of matter. A particle may be produced, for example, via gas atomization. A particle may be jagged or spherical. A jagged particle may be spherodized by any suitable known process. A particle may be of any suitable size, including of a size suitable for use in an additive manufacturing environment, as well as very small (e.g., fines) or very large (e.g., chips) fragments of matter.

[007] As used herein, "titanium particles" means particles based on titanium. The titanium particles may be titanium metal particles, titanium alloy particles, and/or titanium aluminide particles, as defined below.

[008] As used herein, "titanium metal particles" means commercially pure (CP) titanium particles, as defined in ASTM B988-13 (2013).

[009] As used herein, "titanium alloy particles" means particles of a titanium alloy, where titanium is the predominant alloying element, or particles of a titanium aluminide.

[0010] As used herein, "titanium aluminide particles" means particles having titanium and aluminum as the predominant alloying elements.

[0011] The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0012] Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive. [0013] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases "in one embodiment" and "in some embodiments" as used herein do not necessarily refer to the same embodiment s), though they may. Furthermore, the phrases "in another embodiment" and "in some other embodiments" as used herein do not necessarily refer to a different embodiment, although they may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0014] In addition, as used herein, the term "or" is an inclusive "or" operator, and is equivalent to the term "and/or," unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references, unless the context clearly dictates otherwise. The meaning of "in" includes "in" and "on", unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a schematic diagram of one embodiment of an electrolysis-based process for recycling titanium particles for use in one or more additive manufacturing processes.

[0016] FIG. 2a is a flow chart illustrating one embodiment of the receiving, preparing, exposing, and recovering steps of FIG. 1.

[0017] FIG 2b is a schematic diagram illustrating various optional embodiments of the receiving step of FIG 1.

[0018] FIG. 2c is a schematic diagram illustrating various optional embodiments of the preparing step of FIG 1.

[0019] FIG. 2d is a schematic diagram illustrating various optional embodiments of the exposing step of FIG 1.

[0020] FIG. 2e is a schematic diagram illustrating an optional embodiment of the recovering step of FIG 1.

[0021] FIG. 3a is a schematic cross-sectional diagram of one embodiment of an as-received titanium particle of the as-received feedstock of FIG. 1.

[0022] FIG. 3b is a schematic cross-sectional diagram of one embodiment of an as-recovered titanium particle of the purified feedstock of FIG. 1.

[0023] FIG. 4 is a flow chart illustrating embodiments of the exposing and recovering steps of FIG. 1. [0024] FIG. 5 is a flow chart illustrating one embodiment of the process of FIG. 1.

DETAILED DESCRIPTION

II. Feedstock

[0025] In one approach, and referring now to FIG. 1, a method (100) may be implemented, at least in part, through an electrolysis-based process (101). The method (100) may include receiving (102) a feedstock at an electrolytic cell (104). In one embodiment, the feedstock may include titanium particles. Examples of titanium particles in the as-received feedstock may include titanium alloy particles (e.g., Ti₆Al4 particles), titanium aluminide particles, and titanium metal particles (e.g., commercially pure (CP) titanium particles, as defined in ASTM B988-13 (2013), which is incorporated herein by reference in its entirety). The as-received feedstock may include any mixture of two or more of the types of titanium particles described above.

[0026] The feedstock of titanium particles may be received (102) from one or more AM processes (106). In one embodiment, the AM processes (106) may utilize the titanium particles only one time. In such embodiments, the titanium particles (e.g., the same batch of powder material provided to a powder bed of an AM apparatus, not shown) may not be reused in a subsequent run of one or more of the AM processes (106). In another embodiment, the AM processes (106) may utilize the same batch of titanium particles two or more times. In these embodiments, a single batch of titanium particles may be reused in one or more subsequent runs of the AM process(es) (106).

[0027] The number of times that one batch of titanium particles may be reused may be based on one or more process and/or design considerations. In one embodiment, the AM apparatus may not include sufficient capability to maintain a controlled atmosphere chamber under which the titanium particles are positioned for the AM process (106). Accordingly, the titanium particles may be oxidized and accumulate oxygen at a faster rate as compared to cases in which the controlled atmosphere may limit the rate of oxidation of the titanium particles. In another embodiment, the AM apparatus may include a capability to maintain a controlled atmosphere (e.g., inert gas(es) or vacuum) chamber under which the titanium particles are positioned for the AM process (106). Accordingly, the titanium particles may be oxidized and accumulate oxygen at a slower rate, and the same batch of titanium particles may be reused for a greater number of runs of the AM process (106) relative to cases where the AM apparatus being used has a lesser developed atmosphere control capability to limit the oxidation rate of the titanium particles. Based upon, for example, the particular application for which the AM process (106) is being used and/or for the particular type of titanium particles being employed in the AM process (106), the permitted level of oxygen content of the titanium particles may be stringently controlled for quality control and/or specification compliance purposes. Thus, it may be necessary for the titanium particles to only be reused in AM processes (106) for at most a specified number (including zero) of times.

[0028] Referring now to FIGS. 2a-2e and 3a, a method (200) may include receiving (102) the titanium particles (301) (shown in FIG. 3a) which may include oxygen and may have a surface oxide layer (302a) thereon. The oxygen content of the as-received titanium particles (301) may be determined as an average oxygen content value of the as-received feedstock. For example, the oxygen content of the as-received titanium particles (301) may be determined using the ASTM E1409-13 (2013) test method, which is incorporated by reference herein in its entirety. The as-received titanium particles may include from 100 ppm (0.01 weight (wt.) %) to 5000 ppm (0.5 wt. %) oxygen. In one embodiment, the as-received titanium particles (301) may include at least 100 ppm oxygen. In another embodiment, the as-received titanium particles (301) may include at least 200 ppm oxygen. In yet another embodiment, the as-received titanium particles (301) may include at least 300 ppm oxygen. In still another embodiment, the as-received titanium particles (301) may include at least 500 ppm oxygen. In another embodiment, the as-received titanium particles (301) may include at least 1,000 ppm oxygen. In yet another embodiment, the as-received titanium particles (301) may include at least 2,000 ppm oxygen. In still another embodiment, the as-received titanium particles (301) may include at least 2,500 ppm oxygen. In yet another embodiment, the as-received titanium particles (301) may include at least 5,000 ppm oxygen. In one embodiment, the as-received titanium particles (301) may include less than or equal to 5,000 ppm oxygen. In one embodiment, an amount of the oxygen of the as-received titanium particles (301) is greater than a predetermined oxygen content specification (206b) (e.g., greater than the oxygen content allowed by ASTM B988-13).

[0029] The oxygen in the surface oxide layers (302a) of the as-received titanium particles (301) may be present as one or more oxides of the titanium metal and/or the other alloying elements of the as-received titanium particles (301). In one embodiment, the oxygen may include one or more oxides of titanium (e.g., T1O2) (202b). In another embodiment, the surface oxide layers (302a) of the as-received titanium particles (301) may contain one or more of hydrogen (water, hydrated oxides), nitrogen (e.g., nitrides, oxynitrides), carbon (e.g., carbides, organic residues), and sulfur (e.g., sulfides). In yet another embodiment, the hydrogen, nitrogen, carbon, and/or sulfur may be present in the surface oxide layers (302a) either instead of or in addition to oxygen. In one embodiment, a surface oxide layer (302a) of at least one of the as-received titanium particles (301) may consist essentially of oxygen and hydrogen (212b). Without being bound by any particular theory or mechanism, it is believed that the reducing conditions of the electrolytic cell (104) during the exposing step (110) may facilitate decreasing the content of hydrogen, nitrogen, carbon, and/or sulfur in the surface oxide layers (302a). One or more of the mechanisms described in International Patent Application No. PCT/GB99/01781 ("Removal of Oxygen from Metal Oxides and Solid Solutions by Electrolysis in a Fused Salt," International Publication No. WO 99/64638, which is incorporated herein by reference in its entirety) may be involved during the exposing (110) step to reduce the content of oxygen and, where present, the content of hydrogen, nitrogen, carbon, and/or sulfur, in the surface oxide layers (302a) of the as-received titanium particles (301).

[0030] In addition to the as-received titanium particles (301) containing oxygen in the surface oxide layers (302a), the oxygen may be present in the surface oxide layers (302a) and/or the cores (308) of the as-received titanium particles (301) as interstitial (e.g., dissolved) oxygen. Where present, the hydrogen, nitrogen, carbon, and/or sulfur may be present in the surface oxide layers (302a) and/or the cores (308) of the as-received titanium particles (301) as interstitial (e.g., dissolved) species. Without being bound by any particular theory or mechanism, it is believed that the reducing conditions of the electrolytic cell (104) during the exposing step (110) may facilitate decreasing the content of interstitial oxygen and, where present, the content of interstitial species of hydrogen, nitrogen, carbon, and/or sulfur, in the surface oxide layers (302a) and/or the cores (308). One or more of the mechanisms described in PCT/GB99/01781 may be involved during the exposing (110) step to reduce the content of interstitial oxygen and, where present, the content of interstitial species of hydrogen, nitrogen, carbon, and/or sulfur in the surface oxide layers (302a) and/or the cores (308) of the as-received titanium particles (301).

[0031] The oxygen of the as-received titanium particles (301) may be contained predominantly (204b) in the surface oxide layer (302a). The surface oxide layer (302a) may contain from 50% to 100% of the oxygen of the as-received titanium particles (301). In one embodiment, at least 50% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a). In another embodiment, at least 75% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a). In yet another embodiment, at least 90% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a). In still another embodiment, at least 95% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302aY In another embodiment, at least 97% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a). In yet another embodiment, at least 99% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a). In still another embodiment, at least 99.5% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a). In another embodiment, 100% of the oxygen of the as-received titanium particles (301) may be contained in the surface oxide layer (302a).

[0032] The as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 10 μιη to 150 μιη (208b). The as-received titanium particles (301) have an as- received particle size distribution (PSD) which may be expressed as a range of diameters along with the D50 value (304a). The surface oxide layer (302a) of the as-received titanium particles (301) may have an as-received thickness (306a). Provided with reasonably accurate values determined for D50 (304a) and/or PSD, along with the average oxygen content of the as-received titanium particles (301), the average value of the as-received thickness (306a) of the surface oxide layer (302a) may be determined under the assumption that the oxygen is predominantly (204b) contained in the surface oxide layer (302a). In one embodiment, the as- received thickness (306a) of the surface oxide layer may be from 0.50 to 12.50 nm (210b).

[0033] As noted above, the as-received titanium particles (301) may have an as-received mean diameter (D50) (304a) of from 10 μιη to 150 μιη (208b). In one embodiment, the as- received titanium particles (301) have a mean diameter (D50) (304a) of at least 10 μιη. In another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of at least 15 μιη. In yet another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of at least 20 μιη. In another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of at least 25 μιη. In yet another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of at least 30 μιη. In one embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of not greater than 125 μιη. In another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of not greater than 100 μιη. In yet another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of not greater than 85 μιη. In yet another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of not greater than 60 μιη. In yet another embodiment, the as-received titanium particles (301) have a mean diameter (D50) (304a) of not greater than 50 μιη. Other particle size distributions may be used.

[0034] In one embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D50) (304a) of from 15 μιη to 125 μιη (208b). In another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D50) (304a) of from 20 μιη to 100 μιη (208b). In yet another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 20 μιη to 85 μιη (208b). In another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 20 μιη to 60 μιη (208b). In yet another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 25 μιη to 60 μιη (208b). In another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 25 μιη to 50 μιη (208b). In yet another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 30 μιη to 50 μιη (208b). In another embodiment, the as- received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 50 μιη to 100 μιη (208b). In yet another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 75 μιη to 100 μιη (208b). In another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 25 μιη to 125 μιη (208b). In yet another embodiment, the as-received titanium particles (301) may have an as-received mean diameter (D₅₀) (304a) of from 75 μιη to 150 μιη (208b).

[0035] As noted above, the as-received thickness (306a) of the surface oxide layer may be from 0.5 to 12.50 nm (210b). In one embodiment, the as-received thickness (306a) of the surface oxide layer is at least 0.5 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is at least 1.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is at least 1.25 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is at least 1.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is at least 1.67 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is at least 2.0 nm (210b). In one embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 12.5 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 11.75 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 11.0 nm (210b). In another embodiment, the as- received thickness (306a) of the surface oxide layer is not greater than 10.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 10.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 9.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 9.0 nm (210b). In another embodiment, the as-received thickness i306a^") of the surface oxide layer is not greater than 8.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 8.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 7.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 7.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 6.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 6.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 5.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 5.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 4.5 nm (210b). In yet another embodiment, the as- received thickness (306a) of the surface oxide layer is not greater than 4.25 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 4.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 3.75 nm (210b). In another embodiment, the as- received thickness (306a) of the surface oxide layer is not greater than 3.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 3.25 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 3.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is not greater than 2.8 nm (210b).

[0036] As noted above, the as-received thickness (306a) of the surface oxide layer may be from 0.5 to 12.50 nm (210b). In one embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 11.75 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 11.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 10.5 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 10.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 9.5 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 9.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 0.5 to 8.5 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.0 to 8.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.0 to 8.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.25 to 7.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.25 to 7.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.25 to 6.5 nm (210b). In yet another embodiment, the as- received thickness (306a) of the surface oxide layer is from 1.25 to 6.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.25 to 5.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.25 to 5.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.5 to 5.0 nm (210b). In yet another embodiment, the as- received thickness (306a) of the surface oxide layer is from 1.5 to 4.5 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.5 to 4.25 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.5 to 4.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.67 to 4.0 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.67 to 3.75 nm (210b). In yet another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.67 to 3.5 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.67 to 3.25 nm (210b). In yet another embodiment, the as- received thickness (306a) of the surface oxide layer is from 1.67 to 3.0 nm (210b). In another embodiment, the as-received thickness (306a) of the surface oxide layer is from 1.67 to 2.8 nm (210b).

[0037] The as-received titanium particles (301) may comprise a titanium-based core (308). The titanium -based core (308) may contain the majority of the mass of the titanium particle (301) and may contain all of the material of the titanium particle (301) other than the surface oxide layer (302a). The titanium of the titanium particle (301) may be contained predominantly in the titanium-based core (308). The surface oxide layer (302a) of the as- received titanium particles (301) may include the surface oxide layer (302a) deposited on the surface of the titanium -based core (308). The oxygen-containing surface oxide layer (302a) may at least partially encapsulate the titanium-based core (308).

[0038] Although the received feedstocks disclosed in this section have been described in the context of additive manufacturing, feedstocks may be received (102) from other titanium particle producing systems, methods and apparatuses, such as, for instance, powder metallurgy processes, mining processes, and other industrial processes where titanium-based particles are produced.

III. Preparation of the Feedstock

[0039] Referring to FIGS. 1 and 2a-2e, the method (100) may include a preparing step (108). The preparing step (108) may include dispensing C201c) the as-received feedstock of titanium particles (301) into the electrolytic cell (104). In one embodiment, the as-received titanium particles (301) may be dispensed (201c) into one electrolytic cell (104), which may be suitably sized to accommodate all or a portion of the quantity of the titanium particles (301) received (102). In another embodiment, the as-received titanium particles (301) may be dispensed (201c) into a plurality of electrolytic cells (104). The structure and configuration of the electrolytic cell(s) (104) may be those described PCT/GB99/01781.

[0040] In the method (200), prior to and/or after the receiving (102) step, the as-received feedstock of titanium particles (301) may be subjected to one of more preparatory steps prior to and/or during the preparing (108) step. In one embodiment, the preparing step (108) may include a blending (202c) step. During the blending (202c) step, at least a portion of the as- received feedstock of titanium particles (301) may be blended using a blending machine (not shown in FIG. 2c). The blending (202c) step may provide a consistent mixture of the as- received titanium particles (301) to be dispensed (201c) into the one or more electrolytic cells (104). The blending (202c) step may be beneficial in cases where, for example, the as- received feedstock of titanium particles (301) is being supplied from more than one source. The blending (202c) step may also be beneficial where the as-received titanium particles (301) may have an incompletely characterized composition, PSD, oxygen content, surface oxide layer (302a) thickness (306a), and/or D50 (304a).

[0041] In another embodiment, the preparing step (108) may include a deagglomerating (204c) step. During the deagglomerating (204c) step, at least a portion of the as-received feedstock of titanium particles (301) may be deagglomerated (204c) using a deagglomerating machine (not shown in FIG. 2c). In one embodiment, the apparatus employed for the deagglomerating (204c) step may be the same machine used for the blending step (202c). In another embodiment, separate machines may be utilized for the deagglomerating (204) and blending (202c) steps. The deagglomerating (204c) step may provide a deagglomerated mixture of the as-received titanium particles (301) which may be dispensed (201c) into the electrolytic cell(s) (104). The deagglomerating (204c) step may be beneficial in cases where, for example, at least a portion of the as-received feedstock of titanium particles (301) may be agglomerated and where such a state of agglomeration may be undesirable during subsequent steps of process (101) and/or may negatively impact the quality of a final product of process (101).

[0042] In yet another embodiment, the preparing step (108) may include a treating (206c) step. During the treating (206c) step, at least a portion of the as-received feedstock of titanium particles (301) may be subjected to one or more chemical treatments prior to and/or after the deagglomerating (204c) and blending C202c) steps. The treating (206c) step may be accomplished using a treatment apparatus (not shown in FIG. 2c). In one embodiment, the apparatus employed for the treating (206c) step may be the same machine used for the blending (202c) and/or deagglomerating (204c) steps. In another embodiment, separate machines are utilized for the deagglomerating (204c), blending (202c), and treating (206c) steps.

[0043] The treating (206c) step may include a plurality of steps. In one embodiment, the treating (206c) step may include a cleaning (208c) step. During the cleaning (208c) step, at least a portion of the as-received feedstock of titanium particles (301) may be cleaned with a suitable solvent and/or other method to remove, or at least decrease, a level of contamination present in the as-received feedstock of titanium particles (301). For example, the cleaning (208c) step may include contacting the as-received titanium particles (301) with a cleaning solvent to dissolve organic residues that may be present. The cleaning (208c) step may include more extensive purification of the as-received feedstock of titanium particles (301). For example, the cleaning (208c) step may include wet and/or dry separation steps to remove undesired particulate matter (e.g., dirt and/or non-metallic particles) from the as-received feedstock of titanium particles (301). After the cleaning (208c) step, solvents and other cleaning agents may be rinsed from the titanium particles (301) in preparation for subsequent steps of process (101). The cleaning (208c) step may provide an at least partially purified mixture of the as-received titanium particles (301) to be dispensed (201c) into the electrolytic cell(s) (104). The cleaning (208c) step may be beneficial in cases where, for example, at least a portion of the as-received feedstock of titanium particles (301) is known to contain undesirable levels of extraneous matter and/or residues which may diminish the efficiency and/or effectiveness of subsequent unit operations of process (101), and/or may negatively impact the quality of the final product of process (101).

[0044] In another embodiment, the treating (206c) step may include a deoxidizing (210c) step. During the deoxidizing (210c) step, at least a portion of the as-received feedstock of titanium particles (301) may be deoxidized with a suitable chemical agent and/or may be subjected to any other suitably deoxidizing condition(s). For example, the deoxidizing (210c) may include contacting the as-received titanium particles (301) with a suitably diluted acidic solution to dissolve, perforate, and/or soften the surface oxide layer (302a) of the as-received titanium particles (301). The deoxidizing (210) step may include initially deoxidizing the as- received titanium particles (301) to a predetermined extent. After the deoxidizing (210c) step, deoxidizing agents may be rinsed from the titanium particles (301) in preparation for subsequent steps of process (101). The deoxidizing (210c) step may provide an at least partially deoxidized mixture of the as-received titanium particles (301) to be dispensed (201c) into the electrolytic cell(s) (104). The deoxidizing (210c) step may be beneficial in cases where, for example, at least a portion of the as-received feedstock of titanium particles (301) is known to contain undesirable high levels of oxygen contained in the surface oxide layer (302a) which may diminish the effectiveness of subsequent unit operations of process (101).

[0045] Referring now to FIG. 4, the electrolytic cell (104) may include an electrolyte (402). In one embodiment, the electrolyte may comprise at least one of a liquid, gel, sponge or porous solid material (405) In the method (400), the preparing (108) step may include suspending (412) the as-received titanium particles (301) in the electrolyte (402). The electrolyte (402) may be those described in PCT/GB99/01781. The suspending (412) step may be accomplished as described in PCT/GB99/01781.

IV. Removal of Oxygen Via Electrolysis

[0046] Referring back to FIG. 1 the method (100) may include an exposing (110) step. During the exposing (110) step, the feedstock of titanium particles (301) prepared (108) for the electrolytic cell (104) may be exposed (110) to reducing conditions in the electrolytic cell (104). The reducing conditions in the electrolytic cell (104) may include one or more physical, chemical, and electrical conditions. In one embodiment, the reducing conditions in the electrolytic cell (104) may include the configuration(s) of the electrodes (403). In another embodiment, the reducing conditions may include the position(s) of the electrodes (403). In yet another embodiment, the reducing conditions may include the material(s) of the electrodes (403). In still another embodiment, the reducing conditions may include the temperatures at which the electrolyte (402) is maintained. In another embodiment, the reducing conditions may include the duration of the exposing (110) step. In yet another embodiment, the reducing conditions may include the composition of the electrolyte (402). In still another embodiment, the reducing conditions may include the magnitude(s), waveform(s) and/or rate(s) of change of voltage(s) and/or current(s) induced across the electrodes (403) and flowing through the electrolyte (402), respectively, during the exposing (110) step. In another embodiment, the reducing conditions of the electrolytic cell (104) during the exposing (110) step may include one or more of those conditions described in PCT/GB99/01781.

[0047] Referring now to FIGS. 1 and 2d, the exposing (110) step may include reducing the surface oxide layer (302a) of the as-received titanium particles (301). The exposing (110) step may include decreasing the amount of oxygen (212d) contained in the as-received titanium particles (301). In one embodiment, the oxygen contained in the as-received titanium particles (301) may be decreased by at least 10% during the exposing (110) step. In another embodiment, the oxygen contained in the as-received titanium particles (301) may be decreased by at least 25% during the exposing (110) step. In yet another embodiment, the oxygen contained in the as-received titanium particles (301) may be decreased by at least 50% during the exposing (110) step. In yet another embodiment, the oxygen contained in the as-received titanium particles (301) may be decreased by at least 75% during the exposing (110) step. In still another embodiment, the oxygen contained in the as-received titanium particles (301) may be decreased by at least 90% during the exposing (110) step. In another embodiment, the oxygen contained in the as-received titanium particles (301) may be decreased to less than 2000 ppm during the exposing (110) step. The exposing (110) step may include decreasing (210d) the as-received thickness (306a) of the as-received surface oxide layer (302a).

[0048] Referring now to FIG. 4, the exposing (110) step may include controlling (404) one or more of the reducing conditions of the electrolytic cell (104). In one embodiment, the controlling (404) step may include establishing and controlling the reducing conditions of the electrolytic cell (104) to maintain the titanium -based core (308) while reducing or eliminating the oxygen-containing surface oxide layer (302a) of the as-received titanium particles (301) during the exposing (110) step. In another embodiment, the controlling (404) step may include establishing and controlling the reducing conditions of the electrolytic cell (104) to maintain the size of the titanium-based core (308) during the exposing (110) step. In yet another embodiment, the controlling (404) step may include establishing and controlling the reducing conditions of the electrolytic cell (104) to maintain the composition of the titanium- based core (308) during the exposing (110) step. In still another embodiment, the controlling (404) step may include establishing and controlling the reducing conditions of the electrolytic cell (104) to maintain the morphology of the titanium -based core (308) during the exposing (110) step. In another embodiment, the controlling (404) step may include establishing and controlling the reducing conditions of the electrolytic cell (104) to maintain the surface topology of the titanium -based core (308) during the exposing (110) step. In another embodiment, the controlling (404) step may include establishing and controlling the reducing conditions of the electrolytic cell (104) to maintain the size and/or diameter of the titanium- based core (308) during the exposing (110) step.

[0049] Additionally, the controlling (404) step may be employed to accomplish the desired extent of decreasing the oxygen content and as-received surface oxide layer (302a) thickness (306a) of the as-received titanium particles (301). The parameters and variables of the process (101) upon which the controlling (404) step may be implemented may be specific to the particular nature of the as-received feedstock of titanium particles (301). If used in the process (101), the nature and extent the treating C206c), deagglomerating (204c), and/or blending (202c) step(s) may also influence how, when, and to what extent the controlling (404) step may be implemented during the exposing (110) step. In one embodiment, the parameters and variables of process (101) which may be targeted by the controlling (404) step may be predetermined prior to the receiving (102) and/or exposing (110) step(s). In another embodiment, the parameters and variables of process (101) which may be targeted by the controlling (404) step may be determined prior to the receiving (102) and/or exposing (110) step(s) based on one or more analytical characterizations of the as-received feedstock of titanium particles (301). In yet another embodiment, the parameters and variables of process (101) which may be targeted by the controlling (404) step may be determined continuously and/or in an in-process manner during the exposing (110) step as, for example, by monitoring (406) one or more of the reducing conditions of the electrolytic cell (104) and/or one or more characteristics of the titanium particles as the exposing (110) step progresses. In still another embodiment, the parameters and variables of process (101) may be targeted by the controlling (404) step using a combination of two or more of the targeting schemes described above. In another embodiment, the parameters and variables of process (101) may be targeted by the controlling (404) step using one or more of the schemes described in PCT/GB99/01781.

[0050] The titanium-based core (308) may have a first size (e.g., characterized by a volume, a diameter, a major radius, and/or a minor radius) prior to reducing or eliminating the oxygen- containing surface oxide layer (302a) during the exposing (110) step. After reducing or eliminating the oxygen-containing surface oxide layer (302a) during the exposing (110) step, the titanium-based core (308) may have a second size. In one embodiment, after the exposing (110) step, the second size of the titanium-based core (308) may be from 75% to 100%) of the first size of the titanium-based core (308). In one embodiment, the second size of the titanium-based core (308) may be within 75% of the first size of the titanium-based core (308) after the exposing (110) step. In another embodiment, the second size of the titanium-based core (308) may be within 80%> of the first size of the titanium-based core (308) after the exposing (110) step. In yet another embodiment, the second size of the titanium-based core (308) may be within 85%> of the first size of the titanium-based core (308) after the exposing (110) step. In still another embodiment, the second size of the titanium-based core (308) may be within 90% of the first size of the titanium-based core (308) after the exposing (110) step. In another embodiment, the second size of the titanium- based core (308) may be within 95% of the first size of the titanium-based core (308) after the exposing (110) step. In yet another embodiment, the second size of the titanium-based core (308) may be within 97% of the first size of the titanium-based core (308) after the exposing (110) step. In still another embodiment, the second size of the titanium-based core (308) may be within 99% of the first size of the titanium-based core (308) after the exposing (110) step. In another embodiment, the second size of the titanium-based core (308) may be within 99.5% of the first size of the titanium-based core (308) after the exposing (110) step. In yet another embodiment, the second size of the titanium-based core (308) may be equal to the first size of the titanium-based core (308) after the exposing (110) step. The exposing (110) step may be performed in the absence of changing the PSD (208d) (FIG. 2d) of the as- received titanium particles (301).

[0051] In certain applications for the as-recovered titanium particles (310), it may be desirable and beneficial to prevent decreasing the as-received thickness of the surface oxide layer (306a) below a predetermined thickness threshold value. In such cases, the exposing (110) step may also include a maintaining step, which may be accomplished by way of the controlling (404) step. In one embodiment, the maintaining step may include maintaining a predetermined portion (214d) (FIG. 2d) of the as-received surface oxide layer (302a). In another embodiment, the maintaining step may include maintaining a predetermined fraction of the as-received thickness (306a) of the as-received surface oxide layer (302a). In yet another embodiment, the maintaining step may include maintaining the as-received surface oxide layer (302a) at a thickness value that may be approximately equal to a native oxide layer thickness.

[0052] After the exposing (110) step, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be from 0.5 nm to 3.0 nm. In one embodiment, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be at least 0.5 nm after the exposing (110) step. In another embodiment, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be at least 1.0 nm after the exposing (110) step. In yet another embodiment, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be at least 1.5 nm after the exposing (110) step. In still another embodiment, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be at least 2.0 nm after the exposing (110) step. In another embodiment, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be at least 2.5 nm after the exposing (110) step. In yet another embodiment, the final thickness (306b) of the as-exposed surface oxide layer (302b) may be not greater than 3.0 nm after the exposing (110) step.

[0053] Referring now to FIGS. 1, 2d and 4, the exposing (110) step may be performed in the absence of changing the morphology (202d) of the as-received titanium particles (301). In one embodiment, both the as-received (301) and the as-recovered (310) titanium particles may have a spheroid morphology. In another embodiment, both the as-received (301) and the as-recovered (310) titanium particles may have an ellipsoid morphology. In yet another embodiment, both the as-received (301) and the as-recovered (310) titanium particles may have an equiaxed morphology. In one embodiment, the morphology of the as-received titanium particles (301) may be substantially the same as the morphology of the as-recovered (310) titanium particles.

[0054] The exposing (110) step may be performed in the absence of changing the surface topology (204d) of the as-received titanium particles (301). In one embodiment, both the as- received (301) and the as-recovered (310) titanium particles may have a rough surface topology. In another embodiment, both the as-received (301) and the as-recovered (310) titanium particles may have a smooth surface topology. In yet another embodiment, both the as-received (301) and the as-recovered (310) titanium particles may have a surface topology having an intermediate level of roughness. In one embodiment, the surface topology of the as-received titanium particles (301) may be substantially the same as the surface topology of the as-recovered (310) titanium particles. The exposing (110) step may be performed in the absence of sintering (206d) the as-received titanium particles (301). The exposing (110) step may be performed in the absence of deposition (420) of titanium (e.g., as titanium metal) of the as-received titanium particles (301) on one or more electrodes (403) of the electrolytic cell (104).

[0055] Without being bound by any particular theory or mechanism, it is believed that the reducing conditions of the electrolytic cell (104) during the exposing step (110) may facilitate decreasing the oxygen content of the as-received titanium particles (301) and decreasing the as-received thickness (306a) of the as-received surface oxide layer (302a). One or more of the mechanisms described in PCT/GB99/01781 may be involved during the exposing (110) step. However, PCT/GB99/01781 mainly discloses reduction of material composed primarily of Ti02 to titanium metal, where it is beneficial to achieve as full a deoxidization of the starting feedstock as possible to obtain the desired metallic end product. In contrast, the methods described herein begin with the as-received feedstock of oxidized as-received titanium particles (301) having a titanium-based core (308) and a surface oxide layer (302a). Thus, while one or more electrolytic cell (104) configurations and structures and/or one or more of the reducing conditions described in PCT/GB99/01781 may be employed in one or more embodiments of process (101), the present disclosure is directed to decreasing the oxygen content and as-received surface oxide layer (302a) thickness (306a) of a primarily metallic, titanium-containing particulate starting material. V. Recovery/Recycling of Purified Feedstock & Subsequent Use

[0056] Referring now to FIGS. 1, 2e and 4, upon achieving the desired decrease in the oxygen content of the as-received titanium particles (301) and/or the desired decrease in the as-received thickness (306a) of the as-received surface oxide layer (302a), the method (100) may proceed from the exposing (110) step to a recovering (112) step. During the recovering (112) step, a purified feedstock of as-recovered titanium particles (310) may be recovered from the electrolytic cell (104). Due to the exposing (110) step, the as-recovered titanium particles (310) may include at least 10% less oxygen as compared (202e) to the as-received titanium particles (301). The amount of the oxygen of the as-recovered titanium particles (310) may be decreased to less than or equal to the predetermined oxygen content specification (e.g., less than the oxygen content allowed by ASTM B998-13) during the exposing (110) step. As shown in FIGS. 3a and 3b, an as-exposed surface oxide layer (302b) of the as-recovered titanium particles (310) may have a final thickness (306b). In one embodiment, after the exposing (110) step, and in consequence thereof, the final thickness (306b) of the surface oxide layer (302b) may be less than the initial thickness (306a) of the as-received titanium particles (301).

[0057] The as-recovered titanium particles (310) may have an as-recovered mean diameter (D50) (304b) of from 10 μπι to 150 μπι, such as any of the D50 ranges described above relative to the as-received titanium particles (304a). The as-recovered titanium particles (310) may have an as-recovered PSD which may be expressed as a range of diameters along with the as-recovered D50 value (304b). Provided with reasonably accurate values determined for as-recovered D50 (304b) and/or as-recovered PSD, along with the average oxygen content of the as-recovered titanium particles (310), the average value of the as- exposed thickness (306b) of the surface oxide layer (302b) may be determined under the assumption that the oxygen is predominantly contained in the surface oxide layer (302b).

[0058] Referring to FIG. 4, the recovering (112) step may include a separating (414) step. In one embodiment, the separating (414) step may include removing the titanium particles from the electrolytic cell (104) to yield the as-recovered titanium particles (310). In another embodiment, the separating (414) step may include removing the titanium particles from the electrolyte (402) to yield the as-recovered titanium particles (310). In yet another embodiment, the separating (414) step may include removing the electrolyte (402) from the titanium particles to yield the as-recovered titanium particles (310).

[0059] The recovering (112) step may include a rinsing (416) step. Depending on the nature and type of the electrolyte(s) (402) utilized in the electrolytic cell (104) during the exposing

(110) step, the rinsing (416) step mav utilize one or more suitable rinsing solvents to accomplish sufficient removal of residual electrolyte (402) from the as-recovered titanium particles (310). In one embodiment, the rinsing (416) step is performed one time. In another embodiment, the rinsing (416) is performed two or more times, including using either the same or different rinsing solvents for each repetition of the rinsing (416) step during the recovering (112) step. In yet another embodiment, one or more repetitions of the rinsing (416) step are performed until such time when an amount and/or level of the residual electrolyte (402) associated with the as-recovered titanium particles (310) is decreased to at or below a predetermined threshold value.

[0060] The recovering (112) step may include a drying (418) step. Depending on the nature and type of the electrolyte(s) (402) and/or rinsing solvent(s) utilized in the electrolytic cell (104) during the exposing (110) and/or rinsing (416) step(s), respectively, the drying (418) step may utilize one or more drying methods under one or more drying conditions (e.g., time, temperature, atmosphere, pressure, etc.). In one embodiment, one or more repetitions of the drying (418) step may be performed until such time when an amount and/or level of residual rinsing solvent(s) associated with the as-recovered titanium particles (310) is decreased to at or below a predetermined threshold value. In yet another embodiment, the recovering (112) step may not include the rinsing (416) step, and any residual electrolyte (402) associated with the as-recovered titanium particles (310) may be decreased to at or below the predetermined threshold value through the drying (418) step alone.

[0061] The methods disclosed herein may be performed, either in whole or in part, as either batch process(es), semi-continuous process(es), and/or continuous process(es). In the method

(500), shown in FIG. 5, the method (500) may include a recycling (114) step. In one embodiment, the as-received titanium particles (301) may be scrap titanium particles (501) from at least a first additive manufacturing (AM) process (106a), and method (500) may include recycling the purified feedstock from the recovering (112) step for use in a second

AM process (106b). In one embodiment, method (500) may include recycling the purified feedstock from the recovering (112) step for use in powder metallurgy processes. In another embodiment, method (500) may include recycling the purified feedstock from the recovering

(112) step for use in manufacturing pigments, additives and coatings. In yet another embodiment, method (500) may include recycling the purified feedstock from the recovering

(112) step for use in producing pharmaceuticals. In another embodiment, method (500) may include recycling the purified feedstock from the recovering (112) step for use in producing cosmetics. In yet another embodiment, method (500) may include recycling the purified feedstock from the recovering (112) step for use in other end-use applications that utilize titanium-based particles. The scrap titanium oarticles (501) may include titanium particles rejected for use in one or more AM processes (106) (e.g., for having too much oxygen, but still having a composition that is within a predetermined specification for all other elements beside oxygen). During the recycling (1 14) step, at least a portion of the purified as- recovered feedstock of titanium particles (310) may be recycled to one or more AM process(es) (106). In one embodiment, the recovering (1 12) and/or recycling (1 14) steps may include a characterizing step. During the characterizing step, properties of the as-recovered titanium particles (310) may be identified and/or determined in order to assess their suitability for use as a recycled feedstock to the one or more AM processes (106). If the identified and/or determined properties of the as-recovered titanium particles (310) indicate they are suitable as a recycled feedstock for use in the first AM process (106a), but not in the second manufacturing process (106b), the as-recovered titanium particles (310) may be delivered directly to the first AM process (106).

[0062] The first (106a) and second (106b) AM processes may be located in the same facility. In one embodiment, the first (106a) AM process may be the same as the second (106b) AM processes (510). For example, the facility may include two or more of the same type of AM apparatus which may use the same purified and recycled feedstock of as-recovered titanium particles (310). In another embodiment, the first (106a) AM process may not be the same as the second (106b) AM process, although the first (106a) and second (106b) AM processes may be co-located (508). For example, a single AM facility may include two or more different AM machines which may use different purified and recycled feedstocks of as- recovered titanium particles (310) having different properties and characteristics.

[0063] The first (106a) and second (106b) AM processes may be located in and may be performed in different locations that may not share the same facility (512). In one embodiment, although they may not be co-located, the first (106a) AM process may be the same as the second (106b) AM processes. For example, a first facility in a first location may include one or more of the type of AM apparatus for the same AM process performed by one of more of the same type of AM apparatus for the same AM process performed in a second facility in a second location. The AM machines for the first (106a) and second (106b) AM processes occurring in the first and second facilities, respectively, may use the same purified and recycled feedstock of as-recovered titanium particles (310). In another embodiment, the first AM process (106a) performed in the first location may not be the same as the second AM process (106b) performed in the second location. For example, the first facility may include one or more AM machines which may use different purified and recycled feedstocks of as-recovered titanium particles (310) having different properties and characteristics than the as-recovered titanium particles (310) used bv one or more AM machines in the second facility. Similarly, the electrolytic cell (104) may be either co-located with or located in a different location relative to where the AM process(es) (106) are performed.

[0064] The recycling (114) step may include a maintaining (502) step. After the recovering (112) step, the maintaining (502) step may include storing the as-recovered titanium particles (310) under controlled conditions such that they retain their desirable properties and characteristics (e.g., decreased oxygen content) attained through the exposing (110) step. The recycling (114) step may include a refining (504) step. After the recovering (112) step, it may be determined (e.g., by the aforementioned characterizing step) that the as-recovered titanium particles (310) do not meet all requirements for use as a recycled feedstock in one or more AM processes (106). The refining (504) step may be beneficial in such cases to ensure that the as-recovered titanium particles (310) may be used as a recycled feedstock in the one or more AM processes (106). In one embodiment, the refining (504) step may include a chemical treatment, such as a chemical deoxidizing, which may be similar to those described above with reference to the treating (206c) step. In another embodiment, the refining (504) step may include a mechanical treatment, which may be similar to those described above with reference to the blending (202c) and/or deagglomerating (204c) steps. In yet another embodiment, the refining (504) step may include at least one additional iteration of the methods (e.g. methods 100/200), as described above. The refining (504) step may be performed by apparatuses and/or systems that may be either co-located with or located in a different location relative to where either the exposing (110) step or the AM process(es) (106) are performed.

[0065] The recycling (114) step may include a delivering (506) step. In one embodiment, the delivering (506) step may be performed, at least in part, concurrently with the maintaining

(502) step. The delivering (506) step may include transporting the as-recovered feedstock of titanium particles (310) from the location of the electrolytic cell(s) (104) used for the exposing (110) step to one more other locations which may either be in close proximity to the electrolytic cell(s) (104) in the same facility or may be some distance from where the exposing (110) step was performed, including in one or more different facilities for AM process(es) (106). In one embodiment, the delivering (506) step may include transporting the as-recovered feedstock of titanium particles (310) directly from the location where the exposing (110) step was performed to the location where the as-recovered titanium particles

(310) may be used as a recycled feedstock for the AM process(es) (106).

[0066] The delivering (506) step may include one or more intervening step(s). In one embodiment, the one or more intervening step(s) of the delivering (506) step may include the refining (504) step. In another embodiment, the one or more intervening step(s) of the delivering (506) step may include receiving additional feedstock(s) of as-recovered titanium particles (310) from additional locations where the exposing (110) step was performed. In such embodiments, the delivering (506) step may include additional steps similar to the blending (202c) and/or deagglomerating (204c) step(s) to provide a consistent recycled feedstock for use in one or more AM process(es) (106) meeting the predetermined requirements and specifications.

[0067] The new titanium alloy particles produced by the methods described herein may be utilized to produce a variety of titanium alloy products. The titanium alloy products may be suitable in aerospace and/or automotive applications. Non-limiting examples of aerospace applications may include heat exchangers and turbines. In one embodiment, a titanium alloy product is in the form of a compressor component (e.g., turbocharger impeller wheels). Non- limiting examples of automotive applications may include interior or exterior trim/appliques, pistons, valves, and/or turbochargers. Other examples include any components close to a hot area of the vehicle, such as engine components and/or exhaust components, such as the manifold. Titanium alloy products may be in the form of an engine component for an aerospace or automotive vehicle, wherein the method comprises incorporating the engine component into the aerospace or automotive vehicle. A method may include operating such an aerospace or automotive vehicle. In any of the above embodiments, the final titanium alloy particles may be used in a compressor wheel for a turbocharger. In any of the above embodiments, the final titanium alloy product may be one of a heat exchanger and a piston.

[0068] Aside from the applications described above, the titanium alloy products may also be utilized in a variety of consumer products, such as any consumer electronic products, including laptops, cell phones, cameras, mobile music players, handheld devices, computers, televisions, microwave, cookware, washer/dryer, refrigerator, sporting goods, or any other consumer electronic product requiring durability and selective visual appearance. In one embodiment, the visual appearance of the consumer electronic product meets consumer acceptance standards.

[0069] In some embodiments, the titanium alloy products may be utilized in a variety of products including non-consumer products including the likes of medical devices, transportation systems and security systems, to name a few. In other embodiments, the titanium alloy products may be incorporated in goods including the likes of car panels, media players, bottles and cans, office supplies, packages and containers, among others.

[0070] While the above-described embodiments have been disclosed as being applicable to feedstocks comprising titanium particles (e.g., titanium-based powders), those described embodiments are given only as examples. Other tvoes of feedstocks may be used, and in addition to or in lieu of titanium particles. Examples of other types of suitable titanium feedstocks include chips and wires, among others. Without being bound by any particular theory or mechanism, it is anticipated that the above-described electrolytic-based methods may be applicable for reducing the thicknesses of surface oxide layers (e.g., reducing the oxygen content) of other metal-based particles (e.g., metal-based powders other than titanium-based powders). Similarly, the electrolytic-based recycling methods provided herein may be applicable to metal-based particles other than the described titanium particles for purposes of recycling them for re-use in AM processes and other environments where accumulated oxygen in surface oxide layers may be undesirable for similar reasons as described above. Such other feedstocks for the herein-described electrolytic-based methods may include metal-based particles, as well as semi-metal-based particles, based in one or more (including, e.g., alloys) of the following elements: Al, Ni, Co, Cu, Mg, U, Nd, Sm, Ge, Si, refractory metals, including, without limitation, Ta, W, Nb, Mo, HE, Zr, Cr, and other rare earths. As explained previously, any of these feedstocks may be used to produce purified feedstock. Whereas particular embodiments of this disclosure have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations on the details of the present disclosure may be made without departing from the scope of the disclosure as defined in the appended claims.

[0071] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.

Claims

CLAIMS What is claimed is:

1. A method comprising:

(a) receiving a feedstock comprising titanium particles;

(i) wherein the as-received titanium particles comprise oxygen and have a surface oxide layer thereon;

(b) exposing the feedstock to reducing conditions in an electrolytic cell, wherein the exposing comprises:

(i) reducing the surface oxide layer of the titanium particles; and

(ii) decreasing the oxygen of the as-received titanium particles by at least 10%; and

(c) recovering a purified feedstock from the electrolytic cell;

(i) wherein the as-recovered titanium particles comprise at least 10% less oxygen as compared to the as-received titanium particles.

2. The method of claim 1, wherein the as-received titanium particles comprise at least 500 ppm oxygen.

3. The method of claim 2, wherein the as-received titanium particles comprise at least 1000 ppm oxygen.

4. The method of claim 3, wherein the as-received titanium particles comprise at least 2000 ppm oxygen.

5. The method of claim 4, wherein the as-received titanium particles comprise at least 2500 ppm oxygen.

6. The method of any of the preceding claims, wherein:

an amount of the oxygen of the as-received titanium particles is greater than a predetermined oxygen content specification; and

after the exposing step (b), the amount of the oxygen of the as-recovered titanium particles is less than or equal to the predetermined oxygen content specification.

7. The method of any of the preceding claims, wherein the exposing step (b) comprises decreasing the oxygen by at least 25%.

8. The method of claim 7, wherein the exposing step (b) comprises decreasing the oxygen by at least 50%.

9. The method of claim 8, wherein the exposing step (b) comprises decreasing the oxygen by at least 75%.

10. The method of claim 9, wherein the exposing step (b) comprises decreasing the oxygen by at least 90%.

11. The method of any of the preceding claims, wherein the exposing step (b) comprises decreasing the oxygen to less than 2000 ppm.

12. The method of any of the preceding claims, wherein the surface oxide layer consists essentially of oxygen and hydrogen.

13. The method of any of the preceding claims, wherein the surface oxide layer comprises at least one of hydrogen, nitrogen, carbon, and sulfur.

14. The method of any of the preceding claims, wherein:

the surface oxide layer of the as-received titanium particles has an initial thickness; the surface oxide layer of the as-recovered titanium particles has a final thickness; and after the exposing step (b), the final thickness is less than the initial thickness.

15. The method of any of the preceding claims, wherein:

the oxygen of the titanium particles is contained predominately in the surface oxide layer; and

the exposing step (b) comprises decreasing a thickness of the surface oxide layer of the as-received titanium particles.

16. The method of any of claims 14 and 15, wherein, after the exposing step (b), the thickness of the surface oxide layer is not greater than 3.0 nm.

17. The method of any of the preceding claims, wherein: the as-received titanium particles have a mean diameter (D50) of from 10 μιη to 150 μιη; and

the exposing step (b) is performed in the absence of changing a particle size distribution of the as-received titanium particles.

18. The method of any of the preceding claims, wherein:

the titanium particles comprise a titanium-based core;

the oxygen-containing surface oxide layer at least partially encapsulates the titanium- based core; and

the method comprises controlling the reducing conditions to maintain the titanium- based core while reducing or eliminating the oxygen-containing surface oxide layer.

19. The method of claim 18, wherein:

the titanium-based core has a first size prior to the reducing or eliminating;

the titanium-based core has a second size after the reducing or eliminating; and the second size is within 95% of the first size.

20. The method of claim 19, wherein the second size is within 97% of the first size.

21. The method of claim 20, wherein the second size is within 99% of the first size.

22. The method of claim 21, wherein the second size is equal to the first size.

23. The method of any of the preceding claims, wherein the exposing step (b) is performed in the absence of changing a morphology of the as-received titanium particles.

24. The method of any of the preceding claims, wherein the exposing step (b) is performed in the absence of changing a surface topology of the as-received titanium particles.

25. The method of any of the preceding claims, wherein the exposing step (b) is performed in the absence of sintering the as-received titanium particles.

26. The method of any of the preceding claims, wherein the exposing step (b) is performed in the absence of deposition of titanium on an electrode of the electrolytic cell.

27. The method of any of the preceding claims, wherein:

the as-received titanium particles are scrap particles from a first additive manufacturing process; and

the method comprises recycling the purified feedstock for use in a second additive manufacturing process.