DEOXIDATION OF METAL POWDERS

Abstract

Systems, methods, and compositions disclosed herein provide for low-oxygen metal powders. These metal powders, such as very-fine powders and spherical powders of titanium and titanium alloys, can be effectively deoxidized through use of vapor deoxidation without requiring the powder to undergo re-sizing or re-shaping subsequent to the deoxidation. Systems, methods, and compositions in accordance with the present disclosure can produce low-cost, low-oxygen, metal powders, such as very-fine powders and spherical powders of, for example, titanium and titanium alloys. Moreover, systems, methods, and compositions in accordance with the present disclosure can provide for reducing the number of processes or cost of processes required to produce these low-oxygen metal powders.

Claims

1-32. (canceled)

33. A very-fine-powder cake prepared by a process comprising: obtaining a high-oxygen very-fine powder including titanium; adding an amount of deoxidant to the high-oxygen very-fine powder to thereby produce a powder blend; applying a vacuum to the powder blend; heating the powder blend to a predetermined temperature sufficient to at least partially vaporize the deoxidant at a pressure of the vacuum; vapor deoxidizing the high-oxygen very-fine powder using the vaporized deoxidant to produce a low-oxygen very-fine powder and an oxidized deoxidant; wherein the low-oxygen very-fine powder has an oxygen content less than the high-oxygen very-fine powder; and maintaining the powder blend at the predetermined temperature for a predetermined time to produce the very-fine-powder cake, the very-fine-powder cake including a low-oxygen very-fine powder and an oxidized deoxidant, the low-oxygen very-fine powder including the titanium, the predetermined time being sufficient to convert the high-oxygen very-fine powder to a low-oxygen very-fine powder.

34. The very-fine-powder cake of claim 33, wherein the low-oxygen very-fine powder has an oxygen content of less than about 1300 parts-per-million.

35-38. (canceled)

39. The very-fine-powder cake of claim 33, wherein the high-oxygen very-fine powder is spent powder.

40-41. (canceled)

42. The very-fine-powder cake of claim 33, wherein the high-oxygen very-fine powder defines a first particle-size distribution and the low-oxygen very-fine powder defines a second particle-size distribution that is substantially equal to the first particle-size distribution.

43-75. (canceled)

76. A spherical-powder cake prepared by a process comprising: obtaining a high-oxygen spherical powder including titanium, the high-oxygen spherical powder defining a first particle-size distribution; adding an amount of deoxidant to the high-oxygen spherical powder to thereby produce a powder blend; applying a vacuum to the powder blend; heating the powder blend to a predetermined temperature sufficient to at least partially vaporize the deoxidant at a pressure of the vacuum; vapor deoxidizing the high-oxygen spherical powder using the vaporized deoxidant to produce a low-oxygen spherical powder and an oxidized deoxidant; wherein the low-oxygen spherical powder has an oxygen content less than the high-oxygen spherical powder; and maintaining the powder blend at the predetermined temperature for a predetermined time to produce the spherical-powder cake, the spherical-powder cake including a low-oxygen spherical powder and an oxidized deoxidant, the low-oxygen spherical powder including the titanium, the low-oxygen spherical powder defining a second particle-size distribution that is substantially equal to the first particle-size distribution, the predetermined time being sufficient to convert the high-oxygen spherical powder to the low-oxygen spherical powder.

77. The spherical-powder cake of claim 76, wherein the low-oxygen spherical powder has an oxygen content of less than about 1300 parts-per-million.

78. The spherical-powder cake of claim 76, wherein the low-oxygen spherical powder has an oxygen content of less than about 1100 parts-per-million.

79. The spherical-powder cake of claim 76, wherein the low-oxygen spherical powder has an oxygen content of less than about 800 parts-per-million.

80. The spherical-powder cake of claim 76, wherein the low-oxygen spherical powder has an oxygen content of less than about 500 parts-per-million.

81. The spherical-powder cake of claim 76, wherein the high-oxygen spherical powder is spent powder.

82. The spherical-powder cake of claim 76, wherein the predetermined temperature is less than about 1700° F.

83. The spherical-powder cake of claim 76, wherein the predetermined temperature is less than about 1500° F.

84. The spherical-powder cake of claim 76, wherein the low-oxygen spherical powder has an oxygen content of less than about 2,000 parts-per-million such that the low-oxygen spherical powder is configured for use in additive manufacturing processes without further alteration to physical properties of powder particles.

85. The spherical-powder cake of claim 76, wherein the high-oxygen spherical powder defines an average particle size of less than about 105 μm.

86. The spherical-powder cake of claim 76, wherein the high-oxygen spherical powder defines an average particle size of less than about 63 μm.

87. The spherical-powder cake of claim 76, wherein the high-oxygen spherical powder defines an average particle size of less than about 45 μm.

88. The spherical-powder cake of claim 76, wherein the high-oxygen spherical powder defines an average particle size of less than about 25 μm.

89. The very-fine-powder cake of claim 33, wherein the low-oxygen very-fine powder has an oxygen content of less than about 2000 parts-per-million.

90. A spherical-powder cake prepared by a process comprising: obtaining a high-oxygen spherical powder including titanium; wherein the high-oxygen spherical powder includes spent powder from an additive manufacturing process; adding an amount of deoxidant to the high-oxygen spherical powder to thereby produce a powder blend; applying a vacuum to the powder blend; heating the powder blend to a predetermined temperature sufficient to at least partially vaporize the deoxidant at a pressure of the vacuum to produce a vaporized deoxidant; vapor deoxidizing the high-oxygen spherical powder using the vaporized deoxidant to produce a low-oxygen spherical powder and an oxidized deoxidant; wherein the low-oxygen spherical powder has an oxygen content less than the high-oxygen spherical powder; and maintaining the powder blend at the predetermined temperature for a predetermined time to produce a spherical-powder cake, the spherical-powder cake including the low-oxygen spherical powder and the oxidized deoxidant, the low-oxygen spherical powder including the titanium, the predetermined time being sufficient to convert the high-oxygen spherical powder to the low-oxygen spherical powder.

91. The spherical-powder cake of claim 90, wherein the low-oxygen spherical powder has an oxygen content of less than about 2000 parts-per-million.

Description

DETAILED DESCRIPTION

[0115] Systems, methods, and compositions in accordance with the present disclosure can produce low-cost, low-oxygen, very-fine powders of, for example, titanium and titanium alloys. “Very-fine powders” are powders that have an average particle size less than about 105 μm. In some aspects, the average particle size of the very-fine powder is less than about 63 μm, less than about 45 μm, or even less than about 25 μm. As particle size decreases, the ratio of surface area to volume increases, which generally increases the oxygen content of the powder.

[0116] Deoxidation processes can lead to fusion of the powders. If fusion occurs, the particles will have to be subjected to subsequent processes, such as re-sizing or re-shaping, which can increase the oxygen content of the powders. Accordingly, fusion during deoxidation can increase batch-to-batch variability of oxygen content or even render the deoxidation wholly superfluous.

[0117] In accordance with the present disclosure, relatively low-temperature vapor-phase deoxidation is employed to deoxidize very-fine powders while inhibiting fusion of the powders. Beneficially, the vapor-phase deoxidation allows lower-cost manufacturing processes to be employed that would otherwise produce very-fine powders having high oxygen concentrations. Further, in accordance with the present disclosure, the overall number of processes performed on the very-fine powders may be optimized to reduce the cost of producing the low-oxygen very-fine powders. Yet further, in accordance with the present disclosure, the number of processes performed subsequent to deoxidation of the powders may be optimized to reduce the amount of interstitial oxygen in the resultant very-fine powder.

[0118] According to aspects of the present disclosure, a low-cost, low-oxygen, very-fine powder is produced from titanium metal or other forms of titanium including, for example, solids, turnings, cobbles, sponge, combinations thereof, and the like. The titanium is processed to produce a high-oxygen very-fine powder.

[0119] In some aspects, the titanium metal or other forms of titanium may be processed using hydride-milling-dehydride (“HDH”) processing of titanium to produce the high-oxygen very-fine powder in the form of an angular-titanium powder. For example, the oxygen content of many HDH-produced powders is approximately 10,000 parts-per-million. Optionally, the angular-titanium powder may be converted to a spherical-titanium powder using, for example, plasma spheroidization.

[0120] The high-oxygen very-fine powder is then mixed with an amount of deoxidant to produce a powder blend. The deoxidant is configured to remove oxygen from the high-oxygen very-fine powder by having a higher affinity for oxygen than the very-fine powder. In some aspects, the deoxidant is an alkaline earth metal. In some aspects, the deoxidant is calcium such as granulated calcium metal. For example, under given reaction conditions, calcium vapor has a higher affinity for oxygen than titanium powder and, thus, is able remove oxygen from the very-fine powder by forming calcium oxide.

[0121] The powder blend is placed into a container and a vacuum is applied. A pressure of the vacuum is selected to provide for vaporization of the deoxidant below a predetermined temperature and to provide for deoxidation of the high-oxygen very-fine powder within a predetermined time period that will not substantially fuse particles of the high-oxygen very-fine powder. In some aspects, the pressure of the vacuum is less than about 300 torra. In some aspects, the pressure of the vacuum is less than about 100 torra. In some aspects, the pressure of the vacuum is less than about 1 torra.

[0122] Beneficially, as the vacuum increases (e.g., absolute pressure decreases), the temperature of vaporization for the deoxidant decreases. This reduced temperature also reduces the probability of sintering or diffusion bonding of the very-fine powders because the lower temperatures make forming diffusion bonds more difficult. In some aspects, the predetermined temperature is less than about 1900° F. In some aspects, the predetermined temperature is less than about 1700° F. In some aspects, the predetermined temperature is less than about 1500° F.

[0123] Surprisingly, the time period required for deoxidation is decreased through use of vaporized deoxidant. Surprisingly, it is believed that vaporization of the deoxidant contributes to faster removal of oxygen as compared to, for example, melting of the deoxidant. While not being bound by theory, the vapor is more effective than a liquid to reach the surface area thoroughly and quickly to perform the deoxidation function at a faster reaction rate. Beneficially, this faster reaction time reduces the amount of time that the powder is exposed to the heat and, thus, reduces the probability of the metal particles sintering or fusing to one another through diffusion bonding. In some aspects, the predetermined time period is less than about 10 hours. In some aspects, the predetermined time period is less than about 5 hours. In some aspects, the predetermined time period is less than about 2 hours.

[0124] While under vacuum, the powder blend is heated to the predetermined temperature and maintained at that predetermined temperature for the predetermined time. This produces a very-fine-powder cake including a low-oxygen very-fine powder and an oxidized deoxidant. In some aspects, the low-oxygen very-fine powder has an oxygen content of less than about 2000 parts-per-million. In some further aspects, the low-oxygen very-fine powder has an oxygen content of less than about 1300 parts-per-million. In some yet further aspects, the low-oxygen very-fine powder has an oxygen content of less than about 1100 parts-per-million. In some still yet further aspects, the low-oxygen very-fine powder has an oxygen content of less than about 800 parts-per-million. In some additional aspects, the low-oxygen very-fine powder has an oxygen content of less than about 600 parts-per-million. In some yet additional aspects, the low-oxygen very-fine powder has an oxygen content of less than about 500 parts-per-million.

[0125] In some aspects, the deoxidation is carried out in an abundance of deoxidant. In some aspects, the amount of oxygen to be removed is calculated and an amount of deoxidant in slight excess to that needed to remove that amount of oxygen is added to the very-fine powder. While not being bound by theory, it is believed that the oxidized deoxidant, which has a higher vaporization point than the deoxidant, acts as a coating on the metal particles. Surprisingly, this further reduces the probability of the metal particles fusing.

[0126] The very-fine-powder cake is milled to produce a low-oxygen very-fine-powder blend. If the very-fine powder includes any satellites, these satellites can be removed simultaneously with the milling to produce a uniform particle-size distribution with a more uniform surface area-to-volume ratio distribution. Beneficially, this reduces the overall number of steps required to produce the low-oxygen very-fine powder and, thus, reduces the overall time and cost of manufacturing the low-oxygen very-fine powder.

[0127] After milling, the deoxidant residue is removed from the low-oxygen very-fine-powder blend to thereby produce the low-oxygen very-fine powder. In some aspects, the low-oxygen very-fine-powder blend is treated chemically to remove the oxidized deoxidant. The resultant low-oxygen very-fine powder has an oxygen content of less than about 800 parts-per-million. In some aspects, the low-oxygen very-fine powder has an oxygen content of less than about 600 parts-per-million. In some aspects, the low-oxygen very-fine powder has an oxygen content of less than about 500 parts-per-million. The low-oxygen very-fine powder may then be packaged without increasing the interstitial oxygen content.

[0128] For use in additive manufacturing processes, titanium powders need an oxygen concentration no more than, for example, 2000 parts-per-million. Because titanium powders used in additive manufacturing processes will scavenge oxygen when exposed to elevated temperatures, titanium powders for use in additive manufacturing processes have an oxygen concentration that is generally less than half the maximum acceptable oxygen concentration. Beneficially, low-oxygen very-fine powders produced in accordance with the present disclosure may provide increased longevity of very-fine powders prior to the very-fine powder becoming a spent powder by providing oxygen concentrations that are much less than half the maximum oxygen concentration.

[0129] According to additional aspects of the present disclosure, a low-cost, low-oxygen, very-fine powder is produced from spent powder used in additive manufacturing. In some aspects, the high-oxygen very-fine powder is spent powder that is obtained after use in additive manufacturing processes. The oxygen content of these spent powders is necessarily near or above the upper limit of allowable specifications for use in additive manufacturing. Surprisingly, the spent powder can be mixed with an amount of deoxidant, placed under vacuum, heated, milled, and the deoxidant residues removed as described above to produce a low-oxygen very-fine powder that is suitable in applications such as feedstock for additive manufacturing. Beneficially, processing spent powders in accordance with the present disclosure may reduce the oxygen content of the spent powder without substantially altering other characteristics of the spent powder, such as particle-size distributions or shapes.

[0130] Systems, methods, and compositions in accordance with the present disclosure can produce low cost, low oxygen spherical powders of, for example, titanium and titanium alloys. High-oxygen spherical powders may be obtained from titanium metal or other forms of titanium, or may be obtained from spent powders. Surprisingly, the high-oxygen spherical powders can be mixed with an amount of deoxidant, placed under vacuum, heated, milled, and the deoxidant residues removed as described above to produce a low-oxygen spherical powder. Beneficially, processing spherical powders in accordance with the present disclosure may produce low-oxygen spherical powders without substantially altering beneficial characteristics of the high-oxygen spherical powders, such as particle-size distributions or shapes. In addition to the benefits described above, processing spherical powders in accordance with the present disclosure also provides for lower overall oxygen content of the produced low-oxygen spherical powder because higher temperature processes such as plasma spheroidization, which can increase oxygen content, are performed prior to deoxidizing.

[0131] While the above aspects have been described with respect to titanium and titanium alloys, the disclosure is not so limited. It is contemplated that the above-described aspects have applicability to other metals such as zirconium, hafnium, vanadium, niobium, tantalum, combinations thereof, and the like.

[0132] All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, in some circumstances, “about” indicates variations of ±10%. In some further circumstances, “about” indicates variations of ±5%.

[0133] All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “substantially” whether or not “substantially” actually appears before the numerical value. “Substantially” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “substantially” is not otherwise understood in the art with this ordinary meaning, then “substantially” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, in some circumstances, “substantially” indicates variations of ±2.5%. In some further circumstances, “substantially” indicates variations of ±1%.

[0134] While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims.