US20240100594A1 - Method for producing titanium alloy sintered part, and titanium alloy sintered part - Google Patents

Method for producing titanium alloy sintered part, and titanium alloy sintered part Download PDF

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Publication number
US20240100594A1
US20240100594A1 US18/462,844 US202318462844A US2024100594A1 US 20240100594 A1 US20240100594 A1 US 20240100594A1 US 202318462844 A US202318462844 A US 202318462844A US 2024100594 A1 US2024100594 A1 US 2024100594A1
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titanium alloy
alloy sintered
sintered part
sintering
producing
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Masahiro Kimura
Atsushi Yamamoto
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Nippon Piston Ring Co Ltd
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Nippon Piston Ring Co Ltd
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Assigned to NIPPON PISTON RING CO., LTD. reassignment NIPPON PISTON RING CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KIMURA, MASAHIRO, YAMAMOTO, ATSUSHI
Publication of US20240100594A1 publication Critical patent/US20240100594A1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/045—Alloys based on refractory metals
    • C22C1/0458—Alloys based on titanium, zirconium or hafnium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/1017—Multiple heating or additional steps
    • B22F3/1021—Removal of binder or filler
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/004—Filling molds with powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
    • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2201/00—Treatment under specific atmosphere
    • B22F2201/20—Use of vacuum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/20—Refractory metals
    • B22F2301/205—Titanium, zirconium or hafnium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only

Definitions

  • the present invention relates to a method for producing a titanium alloy sintered part, and a titanium alloy sintered part, and particularly relates to a method for producing a titanium alloy sintered part which can be made to have a low oxygen content, and the titanium alloy sintered part.
  • titanium is an element for which the amount of deposits is largest after aluminum, iron, and magnesium, and titanium is known as a metal which is light in weight, has high strength, and is excellent in corrosion resistance, and is also known to have little adverse effect on the human body.
  • titanium has a hexagonal close-packed structure at room temperature, it is difficult to subject titanium to processing that is accompanied by a change in shape, and it is also not simple to subject titanium to machining due to its high strength, and consequently there has been the problem that it is difficult to keep down the cost of production.
  • MIM metal injection molding
  • a method for producing a titanium alloy sintered part which is a method that produces a member by powder metallurgy using titanium or a titanium alloy in which a green body is formed using a metal powder constituted by titanium or a titanium alloy and the green body is then compressed and solidified in a sintering stage, in which, in order to form the green body, a metal powder constituted by titanium or a titanium alloy which has an average particle size of less than 25 ⁇ m that is measured using laser light scattering in accordance with ASTM Standard B822-10 is used, and the sintering stage is performed at a sintering temperature up to a maximum of 1100° C. for a sintering time of five hours or less in an atmosphere under a reduced pressure in comparison to normal
  • a titanium alloy sintered part is known that is characterized by having a mean grain size at the surface within a range of more than 30 ⁇ m to 500 ⁇ m or less, and having a Vickers hardness at the surface within a range of 300 or more to 800 or less.
  • a titanium alloy sintered part According to the aforementioned titanium alloy sintered part, deterioration does not occur at the surface even when exposed to a harsh environment over a long time period, and as a result, a titanium alloy sintered part having high specularity (design properties) can be provided.
  • titanium alloy sintered bodies it is known that the tensile strength and elongation properties change depending on the oxygen content in the titanium alloy sintered part, and it is known that as the oxygen content increases, the tensile strength increases and the elongation decreases.
  • titanium alloy sintered bodies produced by a conventional method for producing a titanium alloy sintered part there has been the problem that it is difficult to suppress the oxygen content to 0.2% by mass or less, and it is difficult to increase the fatigue strength.
  • the present invention has been made in view of the situation described above, and an objective of the present invention is to provide a method for producing a titanium alloy sintered part in which the oxygen content is reduced and the fatigue strength is enhanced, and the titanium alloy sintered part.
  • a method for producing a titanium alloy sintered part according to the present invention is a method for producing a titanium alloy sintered part by a metal injection molding method, including: a mixing process of producing a compound of a metal powder and a binder; an injection process of subjecting the compound to injection molding to produce a green part; a degreasing process of degreasing the green part to remove the binder; and a sintering process of sintering the green part from which the binder is removed to obtain a sintered body; wherein the sintering process is performed at a sintering temperature of 800 to 995° C. for a sintering time of 6 to 200 hours.
  • the sintering process is performed under vacuum, and in the vacuum, an atmospheric pressure during sintering is 1 ⁇ 10 ⁇ 3 Pa or less.
  • a low-oxygen metal powder is used as the metal powder.
  • a titanium alloy sintered part according to the present invention consists of, in mass %, aluminum: 5.50 to 6.50%, vanadium: 3.50 to 4.50%, iron: 0.40% or less, oxygen: 0.2% or less, carbon: 0.08% or less, nitrogen: 0.05% or less, and hydrogen: 0.015% or less, with the balance being titanium, and has a relative density of 97.0% or more.
  • a mean grain size is 5.0 to 50.0 ⁇ m, and an aspect ratio of a crystal structure is 3 or less.
  • the sintering temperature is set to 980° C. and the sintering time is set to 48 hours, and therefore a sintered titanium alloy with low oxygen content can be obtained.
  • the relative density is 97.0% or more and the oxygen content is 0.2% by mass or less, it is possible to provide a titanium alloy sintered part that has high fatigue strength.
  • FIG. 1 is a flowchart of a method for producing a titanium alloy sintered part according to an embodiment of the present invention
  • FIG. 2 is a multiple view drawing showing results of microstructure observation, in which (A) is a view showing an observation result with respect to a titanium alloy sintered part according to the present embodiment, and (B) is a view showing an observation result with respect to a Comparative Example;
  • FIG. 3 is a graph illustrating the relation between sintering time and relative density with respect to the titanium alloy sintered part according to the present embodiment and the Comparative Example.
  • FIG. 4 is a multiple view drawing showing graphs that show tensile strength test results obtained with respect to the titanium alloy sintered part according to an embodiment of the present invention and the Comparative Example.
  • FIG. 1 is a flowchart of a method for producing a titanium alloy sintered part according to an embodiment of the present invention.
  • FIG. 2 is a multiple view drawing showing results of microstructure observation, in which (A) is a view showing an observation result with respect to a titanium alloy sintered part according to the present embodiment, and (B) is a view showing an observation result with respect to a Comparative Example.
  • FIG. 3 is a graph illustrating the relation between sintering time and relative density with respect to the titanium alloy sintered part according to the present embodiment and the Comparative Example.
  • FIG. 4 is a multiple view drawing showing graphs that show tensile strength test results obtained with respect to the titanium alloy sintered part according to an embodiment of the present invention and the Comparative Example.
  • the method for producing a titanium alloy sintered part includes: a step of producing a compound of a metal powder and a binder (S 101 ); a step of subjecting the compound to injection molding to produce a green part (S 102 ); a step of degreasing the green part to remove the binder (S 103 ); a step of sintering the green part from which the binder is removed to obtain a titanium alloy sintered part (S 104 ); and a step of subjecting the titanium alloy sintered part to post processing and inspection (S 105 ).
  • a metal powder and a binder are kneaded together to produce a compound.
  • the metal powder pure titanium or a titanium alloy which is conventionally known is preferably used, and a low-oxygen powder in which the oxygen content is 0.13% by mass or less is more preferably used.
  • a powder corresponding to ASTM grade 23 Extra Low-Interstitial is preferable.
  • the binder is an additive agent that provides fluidity that is necessary for injection molding which is described later, and a material obtained by adding a lubricant and a plasticizer to a binding agent consisting of a general-purpose synthetic resin is preferably used.
  • the ratio between the metal powder and the binder can be appropriately adjusted according to the properties and shape or the like of the titanium alloy sintered part to be produced, and for example it is suitable to make the ratio between the metal powder and the binder a ratio of 60 vol %:40 vol %.
  • Production of the compound is performed by adding the binder to the metal powder, performing heating, pressurizing, and mixing, and thereafter subjecting the cooled and solidified compound to pulverization and granulation to obtain a compound having fluidity.
  • the compound In the step of subjecting the compound to injection molding to produce a green part (S 102 ), the compound is injection-molded into a mold, and thereafter is caused to cool and solidify to produce a green part having a desired shape.
  • a mold corresponding to the shape of a green part that is conventionally known can be used as the mold to be utilized for the injection molding.
  • the step of degreasing the green part to remove the binder is a step in which, prior to sintering which is described later, the binder contained in the green part is removed to obtain a degreased body.
  • a thermal degreasing treatment in which the green part is heated under an inert gas flow to evaporate and thermally decompose the binder, or a solvent degreasing treatment in which the binder is extracted using an organic solvent or the like is performed.
  • the degreased body is heated and sintered at a temperature in a range from 800 to 995° C., more preferably a temperature of about 980° C., under vacuum of 1 ⁇ 10 ⁇ 3 Pa or less for 6 to 200 hours, and more preferably for 48 hours. Note that, any remaining binder contained in the degreased body is removed in the step in which the degreased body is heated by sintering. Because the binder is removed from the green part by performing degreasing and sintering in this way, the sintered body shrinks by about 10 to 20% compared to the green part.
  • a setter made of zirconia is arranged inside a case made of molybdenum, the degreased body is placed on the setter, the case is sealed with a lid made of molybdenum, and thereafter the inside of the case is evacuated and sintering is performed.
  • the step of subjecting the titanium alloy sintered part to post processing and inspection is a step in which post processing and inspection or the like of the titanium alloy sintered part obtained by sintering is performed, and specifically, in this step the titanium alloy sintered part is subjected to a heat treatment, and polishing or the like to secure the dimensional accuracy is performed.
  • a titanium alloy powder was used which consisted of, in mass %, aluminum: 6.22%, vanadium: 4.04%, iron: 0.2%, oxygen: 0.091%, carbon: 0.004%, nitrogen: 0.012%, and hydrogen: 0.002%, with the balance being titanium, and which had a mean particle size of 27.3
  • a binder described in Japanese Patent No. 5163596 was used as the binder, and was mixed at a ratio of 40 vol % with respect to the titanium alloy powder and kneaded.
  • the step of subjecting the compound to injection molding to produce a green part (S 102 ) was performed, and the step of degreasing the green part to remove the binder (S 103 ) was performed by thermal degreasing.
  • the temperature of the degreased body was increased to 980° C. by heating, and sintering was performed at 980° C. for 48 hours. Because the binder was removed from the green part by performing the degreasing and sintering, the sintered body shrunk by about 15% compared to the green part. Further, the relative density of the titanium alloy sintered part was 97.5%.
  • a setter made of zirconia was arranged inside a case made of molybdenum, the degreased body was placed on the setter, the case was sealed with a lid made of molybdenum, and thereafter the inside of the case was evacuated and sintering was performed.
  • the titanium alloy sintered part obtained by sintering was subjected to cutting and polishing to obtain a fatigue test specimen.
  • a tensile test specimen was only inspected, and was not subjected to post processing.
  • the Example of the titanium alloy sintered part according to the present embodiment and a Comparative Example were subjected to a grain size observation test.
  • the Comparative Example was a sintered body obtained by forming a compound using a normal metal powder having a large oxygen content in comparison to the low-oxygen powder used in the titanium alloy sintered part according to the present embodiment, and performing sintering at a sintering temperature of 1100° C. for a sintering time of six hours.
  • the value of the length of the longest portion among the lengths of the object was determined.
  • the value of the shortest distance between two straight lines when the object was sandwiched between the two straight lines in parallel to the absolute maximum length was determined.
  • the aspect ratio a value obtained by dividing the absolute maximum length by the diagonal width was used.
  • the grains in the microstructure were observed as being round overall in comparison to the conventional Comparative Example.
  • the aspect ratio of the crystal structure in the microfibers of the titanium alloy sintered part according to the present embodiment is 3.0 or less.
  • the crystal structure is elongated overall, indicating that the aspect ratio is 3.0 or more, and it can be confirmed that, the crystal structure of the titanium alloy sintered part according to the present embodiment is fine and round overall in comparison to the Comparative Example.
  • the nitrogen content and carbon content were on an equal level to the nitrogen content and carbon content in the Comparative Example, and it was found that the oxygen content was 0.18% which was lower by a large margin in comparison to the oxygen content in the Comparative Example. This satisfies the conditions for a wrought material of Grade 60 of the JIS standard and Grade 5 of the ASTM standard.
  • the gauge length was set to 15 mm. As shown in FIG. 4 , it can be confirmed that the tensile strength of the Example was on an equal level to the tensile strength of the Comparative Example, and the elongation of the Example was higher than the elongation of the Comparative Example.
  • the fatigue strength test was conducted under the following test conditions.
  • the results of the fatigue strength test showed that the fatigue strength at 1.0 ⁇ 10 7 cycles was 350 MPa in the Example, and was 280 MPa in the Comparative Example.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
US18/462,844 2022-09-22 2023-09-07 Method for producing titanium alloy sintered part, and titanium alloy sintered part Pending US20240100594A1 (en)

Applications Claiming Priority (2)

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JP2022-151959 2022-09-22
JP2022151959A JP2024046523A (ja) 2022-09-22 2022-09-22 チタン合金焼結体の製造方法及びチタン合金焼結体

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Publication number Priority date Publication date Assignee Title
JP5617381B2 (ja) * 2010-06-28 2014-11-05 セイコーエプソン株式会社 チタン焼結体およびチタン焼結体の製造方法
EP3655558A4 (en) * 2017-07-18 2020-11-04 Carpenter Technology Corporation CUSTOM TITANIUM ALLOY, TI-64, 23+

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