Patent Publication Number: US-2023150027-A1

Title: Systems and methods for high strength titanium rod additive manufacturing

Description:
FIELD 
     The disclosure generally relates to the manufacture of feedstock for producing aerospace components via additive manufacturing processes and more particularly to methods of manufacture for rod feedstock being produced from titanium and other metallic powders. 
     BACKGROUND 
     Aircraft landing gear designs incorporate large structural components made from high strength titanium alloys. Powder based additive manufacturing techniques, such as powder bed, for titanium alloy landing gear components are unsuited for producing large parts. Rod deposition additive manufacturing techniques may be used to form large parts. However, existing rod feedstocks for titanium alloys are high cost and tend to have reduced tensile and/or fatigue strength in comparison to wrought processed material. 
     SUMMARY 
     A method of titanium rod additive manufacturing is disclosed herein. The method may comprise: mixing a plurality of powdered metals comprising titanium, iron, vanadium, and aluminum to produce a powder blend; isostatic pressing the powder blend to form a billet having a cross-sectional profile; cutting the billet to form a rod feedstock having the first cross-sectional profile; loading the rod feedstock into an additive manufacturing machine configured to deposit the rod feedstock; and producing a metallic component from the rod feedstock. 
     In various embodiments, the titanium is a titanium hydride powder. The powder blend may comprise between 4% and 6% by weight iron, between 0.5% to 2% by weight aluminum, and between 6% to 9% by weight vanadium. The method may further comprise sintering the powder blend after the isostatic pressing, wherein the sintering is performed between 900° F. (482° C.) and 1600° F. (871° C.) and under a vacuum. The isostatic pressing may be performed within a temperature range between 1652° F. (900° C.) and 2,282° F. (1,250° C.). The additive manufacturing machine may comprise a rotating tool having an aperture disposed therethrough. The rod feedstock may be fed through the aperture of the rotating tool. A first density of the rod feedstock may be less than 100% of a second density for a known specification of a wrought metal alloy associated with a material composition of the powder blend. The cross-sectional profile of the rod feedstock may be a substantially square shape. Each side length of the rod feedstock may be between 0.25 inches (0.635 cm) and 0.5 inches (1.27 cm). Loading the rod feedstock may further comprise applying an axial force to the rod feedstock to translate the rod feedstock through an aperture of a rotating tool. 
     An article of manufacture including a metallic component additively manufactured from a rod feedstock by a stir friction welding additive manufacturing machine is disclosed herein. The rod feedstock may comprise a rod feedstock from a sintered billet of powdered metals including a material composition, the rod feedstock comprising a first density less than 100% of a known density for a wrought metal alloy of the material composition, and the powdered metals comprising titanium hydride, iron, vanadium, and aluminum. 
     In various embodiments, the material composition may comprise between 4% and 6% by weight iron, between 0.5% to 2% by weight aluminum, and between 6% to 9% by weight vanadium. The metallic component may comprise between 0.1% and 1.0% by weight oxygen and between 0.001% and 0.015% by weight hydrogen. The metallic component may be heat treated by at least one of annealing, solutionizing, or aging. The metallic component may undergo at least one of a beta phase transformation, a beta anneal, or an alpha beta anneal during the at least one of annealing, solutionizing, or aging. 
     A method of forming a rod feedstock for titanium stir friction welding additive manufacturing is disclosed herein. The method may comprise: mixing a plurality of powdered metals comprising titanium, iron, vanadium, and aluminum to produce a powder blend; isostatic pressing the powder blend to form a billet having a first cross-sectional profile; and cutting the billet to form a rod feedstock having the first cross-sectional profile to form a worked rod feedstock. 
     In various embodiments, the titanium is a titanium hydride powder. The powder blend may comprise between 4% and 6% by weight iron, between 0.5% to 2% by weight aluminum, and between 6% to 9% by weight vanadium. The method may further comprise sintering the powder blend after the isostatic pressing, wherein the sintering is performed between 900° F. and 1600° F. and under a vacuum. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated herein otherwise. These features and elements as well as the operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosures, however, may best be obtained by referring to the detailed description and claims when considered in connection with the figures, wherein like numerals denote like elements. 
         FIG.  1    illustrates an exemplary aircraft, in accordance with various embodiments; 
         FIG.  2 A  illustrates a method for titanium rod additive manufacturing, in accordance with various embodiments; and 
         FIG.  2 B  illustrates a continuation of a method from  FIG.  2 A  for titanium rod additive manufacturing, in accordance with various embodiments. 
         FIG.  3    illustrates an additive manufacturing machine for use in the method of  FIGS.  2 A and  2 B . 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosures, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosures. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
     Titanium alloy Ti-185 has a relatively high tensile strength; however, the high iron percentage of the alloy causes segregation during conventional melting. Powder metallurgy techniques such as, for example, pressing and sintering may overcome the segregation issues induced in conventional melt metallurgy thereby enabling a lower cost part. Alloying powder may be either elemental powders (e.g., Ti, Fe, V, Al), master alloy powders, or a combination thereof. Sintered billets may be drawn or otherwise worked into a rod feedstock for additive manufacturing operations. In this regard, large high strength titanium alloy components such as, for example, pistons, bogie beams, torque links, brake rods, and/or the like may be produced at reduced cost. Additionally, additive manufacturing according to the process described herein may tend to overcome macro segregation issues encountered in conventional melt metallurgy and benefit of enhanced fatigue and ultimate strength. 
     In various embodiments, methods and/or processes disclosed herein may tend to eliminate thermomechanical processing prior to a stir friction weld process. In this regard, feedstock for a stir friction weld process may be manufactured in an inexpensive and efficient manner and maintain structural capabilities of the feedstock, in accordance with various embodiments. 
     With reference to  FIG.  1   , an aircraft  10  in accordance with various embodiments may comprise aircraft systems and components. For example, aircraft  10  may comprise one or more landing gear such as landing gear  12 , landing gear  14  and landing gear  16 . Landing gear  12 , landing gear  14  and landing gear  16  may generally support aircraft  10  when aircraft  10  is not flying, allowing aircraft  10  to taxi, take off, and land without damage and may comprise wheels and an oleo strut, also referred to as a shock strut, comprising a strut cylinder and a strut piston filled with a hydraulic fluid. For example, landing gear  12  may include wheels  18  coupled by an axle  20  and a shock strut  22 . In operation, aircraft landing gear may experience significant forces such as landing loads and aerodynamic loads and may tend to benefit from high performance alloy construction. In various embodiments, aircraft  10  components such as landing gear  12  and shock strut  22  may comprise complex geometries tending to benefit from additive manufacturing techniques. 
     With additional reference to  FIG.  2 A , a method for titanium rod additive manufacturing is illustrated according to various embodiments. A plurality of powdered metals  202  comprising titanium and iron are added to powder blender  204  and blended to consistency to powder blend  206 . In various embodiments, powder blend  206  may comprise titanium and iron and any of oxygen, aluminum, vanadium, and/or hydrogen. Powdered metals  202  may include titanium hydride powder. Powder blend  206  may be between 4% and 6% by weight iron, between 0.5% to 2% by weight aluminum, and between 6% to 9% by weight vanadium. The input powders may contain oxygen and hydrogen levels between 0.01 and 1.0% by weight. In various embodiments, powdered metals comprise of Al—V master alloy and Fe elemental powder blended with TiH 2  powder. In various embodiments, powder metals may consist of Al—V master alloy and Fe elemental powder blended with TiH 2  powder. The billet elemental weight percent may be adjusted to account for vaporization of elements such as aluminum during the rod-fed additive process, tending thereby to ensure the additive manufactured part is within a desired weight percent limit. In various embodiments, the billet shape may be a solid round or other shape as appropriate to input stock for rod drawing. 
     Powder blend  206  is loaded into a forming mold  308 , which is subjected to a near-uniform hydrostatic pressure  310  to compact the powder blend  206  to achieve a uniform, or near uniform, density. “Near uniform” as described herein refers to a variation in local density less than 10% of an average density, or less than 5% of an average density. In this regard, powder blend  206  is subjected to a cold isostatic pressing (CIP) process. In various embodiments, the forming mold  308  may comprise a flexible bag, such as a polymeric bag or the like. In various embodiments, the forming mold  308  is submerged in a pressure vessel  312  containing a pressurizing fluid, such as a soluble oil or the like. In various embodiments, the forming mold  308  is fixed in the pressure vessel  312  and loaded with a gas, such as air or the like. Thus, the pressure vessel  312  may be configured for a wet bag process or a dry bag process. In various embodiments, temperatures for a CIP process may be between ambient (approximately 70° F. [21° C.]) and 200° F. [93° C.]. 
     Although described herein with respect to the CIP process, the present disclosure is not limited in this regard. For example, in various embodiments, hot isostatic pressing (HIP) of the powder blend  206  may be performed in the pressure vessel  312 . In this regard, the pressure vessel  312  may be heated to an elevated temperature (e.g., between 1652° F. [900° C.] and 2,282° F. [1,250° C.]). 
     Pressed powder blend  306  is loaded into sintering furnace  208 , which applies force  210  to compact the pressed powder blend  306  and heat to sinter the pressed powder blend  306 , thereby forming billet  212 . In various embodiments, the pressed powder blend  306  may be loaded into sintering furnace  208  after the CIP process. In various embodiments, by utilizing a HIP process as described above, the sintering step may be eliminated. In various embodiments, the HIP process may be performed after sintering. The present disclosure is not limited in this regard. 
     In various embodiments, sintering furnace  208  may be a vacuum sintering furnace and pressed powder blend  306  may be compressed and heated under a vacuum or near vacuum. In various embodiments, the compressed pressed powder blend  306  may be heated to between 900° F. [483° C.] and 1600° F. [871° C.] for the sintering operation. In this regard, the sintered billet may undergo beta phase transformation. Sintering the pressed powder blend  306  may include removing gasses evolved from the pressed powder blend  306  during sintering and sintering furnace  208  may include a gas removal system and/or control system. In various embodiments, oxygen, nitrogen, and/or hydrogen may be removed from the pressed powder blend  306  during sintering. In various embodiments, billet  212  may undergo an annealing cycle after sintering. In various embodiments, the annealing cycle temperatures may be between 1200° F. [649° C.] and 1400° F. [760° C.]. 
     In various embodiments, in response to sintering the pressed powder blend  306 , a billet  212  having a cross-sectional profile  214  may be formed. The cross-sectional profile  214  may correspond directly to a feedstock cross-sectional profile for an additive manufacturing machine. 
     In various embodiments, the cross-sectional profile  214  may be substantially square. “Substantially square” as described herein refers to a cross-sectional shape with four right angles plus or minus 5 degrees. Additionally, “substantially square” as referred to herein includes rounded corners, chamfered corners or any other type of corner. Although described herein as having a square cross-sectional shape, the present disclosure is not limited in this regard. For example, circular, rectangular, oval, or any other cross-sectional shape for feedstock is within the scope of this disclosure. In various embodiments, each side of the cross-sectional profile  214  may be between 0.25 inches (0.635 cm) and 0.5 inches (1.27 cm), or approximately 0.375 inches. 
     The process described herein may be directly used in an additive manufacturing machine after a worked rod  230  is formed after sintering. In various embodiments, further conditioning (e.g., via a subtractive component  232 , such as a die grinder, a mill, a bench grinder, a tool bit, a milling cutter, or the like) of the worked rod  230  may be performed if tight tolerances are desired. In this regard, conditioning may be optionally performed to further facilitate a feedstock cross-sectional profile  214  that is substantially complimentary to a feed aperture cross-sectional profile, in accordance with various embodiments. 
     Billet  212  may be sintered to any length with the cross-sectional profile  214 . In various embodiments, the length may be a multiple of a uniform length for use as feedstock in a stir friction welding process as described further herein. In this regard, the billet  212  may be cut after being sintered to a length between 3 feet (0.9 m) and 6 feet (1.8 m), or between 4 feet (1.2 m) and 5 feet (1.5 m). Billet  212  may be cut into a plurality of feedstock (or a plurality of the worked rod  230 ) for use with an additive manufacturing machine as described further herein. 
     In various embodiments, a density of the billet  212  may be less than a density of a known specification for a wrought metal alloy (e.g., Titanium alloy Ti-185 as described previously herein). For example, the density of the billet  212  may be between 90% and 100% of the density of the known specification, or between 95% and 100% of the known specification. In this regard, due to the strength of Titanium ally Ti-185, a solid metal billet  212  having a density of less than 100% may exceed a desired strength for an additive manufacturing process as described further herein. 
     In various embodiments, the plurality of rod feedstock  234  may be fed into an additive manufacturing machine  242 . With brief reference to  FIG.  3   , the additive manufacturing machine  242  is illustrated in accordance with various embodiments. In various embodiments, the additive manufacturing machine  242  comprises a rotating tool  322  comprising an aperture  324  disposed therethrough. The aperture  324  comprises a cross-sectional profile  325  complimentary to the cross-sectional profile  214  from  FIG.  2 A . In this regard, the cross-sectional profile  214   from  FIG.  2 A  corresponds to the cross-sectional profile  325  of the rotating tool  322  of the additive manufacturing machine  242  to receive the rod feedstock  234  during a stir friction welding process, in accordance with various embodiments. In this regard, the rod feedstock  234  is fed through the aperture  324  of the additive manufacturing machine to facilitate adding additional material to a respective previously laid layer or the like. 
     In various embodiments, the process disclosed herein may tend to eliminate utilization of induction coils for hot rolling, drawing, and/or coiling feedstock bar or wire. In various embodiments, conditioning may also be eliminated as sintering may be performed under a vacuum, preventing mill defects. In various embodiments, the process described herein may eliminate thermomechanical work of a billet prior to input into an additive manufacturing system. 
     Rod feedstock  234  may be loaded in the additive manufacturing machine  242  configured for rod feedstock  234 . The additive manufacturing machine  242  may comprise hardware and/or software configured to perform additive manuring of an aerospace component. In various embodiments additive manufacturing may include friction stir welding additive manufacturing. In various embodiments, additive manufacturing machine  242  may be configured to deposit the rod feedstock  234  on a substrate (e.g., substrate  330  as shown in  FIG.  3   ). For example, the additive manufacturing machine  242  may be configured with the rotating tool  322  of  FIG.  3   . In various embodiments, the additive manufacturing machine  242  may incorporate a single or a multiple rod feed system and be capable of delivering the rod feedstock  234  at a rate of 0.5 in/min [1.27 cm/min] to 25 in/min [63.5 cm/min] and may have deposition rates between 1 and 20 lbs/hour [0.45 and 9 kg/hr]. The additive manufacturing machine  242  may further be configured to supply an axial force to the rod feedstock  234  to cause the rod feedstock  234  to translate through the rotating tool  322 . 
     Additive manufacturing machine  242  may produce a metallic aerospace component  244  from rod feedstock  234 . Metallic aerospace component  244  may undergo a component heat treat process  245 . In this regard, crack formation and oxide formation for the metallic aerospace component  244  may be reduced. Heat treatment operations may include solutionizing heat treatment, aging, and/or annealing. In various embodiments, heat treatments may include a beta anneal and an alpha beta anneal. For example, annealing between 1550° F. [843° C.] and 1600° F. [871° C.] or annealing between 1200° F. [649° C.] and 1400° F. [760° C.]. In various embodiments, a solutionizing heat treatment may be between 1350° F. [732° C.] and 1450° F. [788° C.]. In various embodiments, an aging heat treatment may be between 800° F. [427° C.] and 1100° F. [593° C.] or may be adjusted to achieve a desired material property for metallic aerospace component manufacture. In various embodiments, the heat-treated metallic aerospace component may have between 0.001% and 0.015% by weight hydrogen and may have between 0.1% and 1.0% by weight oxygen. 
     Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosures. 
     The scope of the disclosures is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
     Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in an alternative embodiment. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element is intended to invoke 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.