US20160122840A1 - Methods for processing nanostructured ferritic alloys, and articles produced thereby - Google Patents

Methods for processing nanostructured ferritic alloys, and articles produced thereby Download PDF

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Publication number
US20160122840A1
US20160122840A1 US14/533,145 US201414533145A US2016122840A1 US 20160122840 A1 US20160122840 A1 US 20160122840A1 US 201414533145 A US201414533145 A US 201414533145A US 2016122840 A1 US2016122840 A1 US 2016122840A1
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workpiece
temperature
weight percent
degrees fahrenheit
strained
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Laura Cerully Dial
Richard DiDomizio
Shenyan Huang
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General Electric Co
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General Electric Co
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Assigned to GENERAL ELECTRIC COMPANY reassignment GENERAL ELECTRIC COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DIDOMIZIO, RICHARD, DIAL, LAURA CERULLY, HUANG, SHENYAN
Priority to FR1559757A priority patent/FR3027922A1/fr
Priority to JP2015208497A priority patent/JP2016108658A/ja
Priority to DE102015118873.2A priority patent/DE102015118873A1/de
Priority to CN201510743322.XA priority patent/CN105567927A/zh
Publication of US20160122840A1 publication Critical patent/US20160122840A1/en
Abandoned legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
    • F01D5/286—Particular treatment of blades, e.g. to increase durability or resistance against corrosion or erosion
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/40—Heat treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/60—Properties or characteristics given to material by treatment or manufacturing
    • F05D2300/608—Microstructure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/60—Properties or characteristics given to material by treatment or manufacturing
    • F05D2300/609—Grain size

Definitions

  • the present disclosure relates to nanostructured ferritic alloys (NFAs), and more particularly, methods for processing the same utilizing high temperature processing methods.
  • the disclosure also relates to an article comprising a nanostructured ferritic alloy (NFA) that is formed by using such a method.
  • Gas turbines operate in extreme environments, exposing the turbine components, especially those in the turbine hot section, to high operating temperatures and stresses. In order for the turbine components to endure these conditions, they are necessarily manufactured from a material capable of withstanding these severe conditions. In other words, a material used for the turbine components limits the temperature range that can be used without inducing a significant degradation in the mechanical properties of the material.
  • Nickel-based superalloys have been used in these demanding applications because they maintain their strength at up to 90% of their melting temperature and have excellent environmental resistance.
  • Nickel-based superalloys in particular, have been used extensively throughout the gas turbine engines, e.g., in turbine blade, nozzle, wheel, spacer, disk, spool, blisk, and shroud applications.
  • steels may be used for turbine components.
  • use of conventional steels is often limited in high temperature and high stress applications because they fail to meet necessary mechanical property requirements and/or design requirements.
  • Nanostructured ferritic alloys are an emerging class of iron-based alloys that exhibit exceptional high temperature properties. These alloys are typically derived from nanometer-sized oxide particulates or clusters that precipitate during hot consolidation following a mechanical alloying step. These oxide particulates or clusters are present at high temperatures, providing a strong and stable microstructure during service.
  • the NFAs are a powder metallurgy alloy that is typically consolidated through hot iso static pressing (HIP), and then hot-worked to manufacture a desired article.
  • HIP hot iso static pressing
  • processing an as-HIP NFA at a high temperature typically leads to a change in its final microstructure and thus results in the degradation of its mechanical properties.
  • This change in microstructure at the high temperatures limits (1) the use of these NFA materials at desired temperatures and stresses, for example in a heavy duty gas turbine, and (2) the use of the high strain rate processing techniques that may be economically beneficial for manufacturing an article.
  • the material should desirably be capable of being manufactured into the desired article without sacrificing its mechanical properties. It may additionally be desirable to process the material at high temperatures and high strain rates.
  • a method for forming an article comprising a nanostructured ferritic alloy includes introducing a quantity of strain into a workpiece at a first temperature to form a strained workpiece, heating the strained workpiece to a second temperature, and deforming the strained workpiece at the second temperature.
  • the workpiece includes a nanostructured ferritic alloy.
  • the first temperature is below about 1900 degrees Fahrenheit and the second temperature is at least about 1900 degrees Fahrenheit.
  • the quantity of strain introduced into the workpiece at the first temperature is effective to substantially inhibit grain growth in the strained workpiece during the subsequent heating and the deforming at the second temperature.
  • an article comprising a nanostructured ferritic alloy, which may be formed by the method.
  • the article may be a turbomachinery component.
  • a method of forming a turbomachinery component comprising a nanostructured ferritic alloy includes introducing a quantity of strain into a workpiece at a first temperature to form a strained workpiece, heating the strained workpiece to a second temperature, and forging the strained workpiece at the second temperature at a strain rate of at least about 1 inch/inch/sec.
  • the workpiece includes a nanostructured ferritic alloy.
  • the first temperature is below 1900 degrees Fahrenheit and the second temperature is higher than 1900 degrees Fahrenheit.
  • the quantity of strain introduced into the workpiece at the first temperature is effective to substantially inhibit grain growth in the strained workpiece during the subsequent heating and the forging at the second temperature.
  • FIG. 1A shows scanning electron microscope (SEM) micrograph of an “as-consolidated” NFA workpiece.
  • FIG. 1B shows SEM micrograph of the NFA workpiece after heating the workpiece at 2000 Fahrenheit for 24 hours after the consolidation.
  • FIG. 2A shows SEM micrograph of a NFA workpiece that is extruded at 1700 degrees Fahrenheit, in accordance with some embodiments of the invention.
  • FIG. 2B shows SEM micrograph after heating the extruded NFA workpiece at 2000 degrees Fahrenheit, in accordance with some embodiments of the invention.
  • FIG. 3 shows stress-strain curves for NFA workpieces that are processed with high strain rates at 1900 degrees Fahrenheit and 2100 degrees Fahrenheit, in accordance with some embodiments of the invention.
  • ranges are inclusive and independently combinable (e.g., ranges of “up to about 25 wt. %, or, more specifically, about 5 wt. % to about 20 wt. %,” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt. % to about 25 wt. %,” etc.).
  • the modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity).
  • some embodiments of the invention include a method for processing a nanostructured ferritic alloy (NFA) that allows the alloy (NFA) to be processed at a high temperature, a high strain rate, or both at high temperature and high strain rate while maintaining a desired microstructure.
  • Some embodiments provide articles (also referred to as “formed articles”) manufactured by the present method.
  • the formed article is made of a nanostructured ferritic alloy (NFA), wherein the article is formed at a high temperature, a high strain rate, or both.
  • the formed article may be any article desirably comprising the NFA and the properties conferred thereto by the NFA.
  • One illustrative class of articles that may find particular benefit from application of the principles described herein includes turbomachinery components, and in particular, those that experience high operating temperatures (for example, greater than 850° F.) and/or high stresses during use.
  • the formed article may advantageously comprise a component of a gas turbine or a steam turbine.
  • Some exemplary articles are bolts, studs, blades, wheels, and spacers.
  • the nanostructured ferritic alloys are a class of alloys that comprise a stainless steel matrix that is dispersion strengthened by a very high density, for example, at least about 10 18 m ⁇ 3 of nanometer (nm)-scale, i.e., from about 1 nanometer to about 100 nanometers, of nanofeatures comprising titanium oxide (Ti—O) and at least one other metal element from the oxide used to prepare the NFA or the alloy matrix.
  • yttrium oxide, aluminum oxide, zirconium oxide, hafnium oxide may be used to prepare the NFAs, in which case, the nanofeatures may comprise yttrium (Y), aluminum (Al), zirconium (Zr), hafnium (Hf) or combinations of these.
  • Transition metals such as iron (Fe), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), silicon (Si), niobium (Nb), aluminum (Al), nickel (Ni), or tantalum (Ta) from the alloy matrix can also participate in the creation of the nanofeatures.
  • an average size of nanofeatures ranges from about 1 nanometer to about 50 nanometers. In certain instances, the average size ranges from about 1 nanometer to about 10 nanometers.
  • the density of nanofeatures in some instances, is at least about 10 20 m ⁇ 3 , and in some certain instances, at least about 10 22 m ⁇ 3 .
  • oxide dispersion strengthened (ODS) alloys generally contain refined, but larger, oxide phases, and the oxide additive is stable throughout the powder metallurgy process, i.e., if yttrium oxide were added to the matrix alloy, ytrrium oxide would be present after the alloying step and there would be no significant formation of the nanofeatures (NFs) described above.
  • ODS oxide dispersion strengthened
  • NFs nanofeatures
  • an NFA at least the majority, and in some cases substantially all, of the added oxide is dissolved into the alloy matrix during powder attrition and participates in the formation of the aforementioned nanofeatures when the powder is raised to a temperature during the compaction process, for example hot isostatic pressing (HIP).
  • the new oxide in the NFA may comprise one or more transition metals present in the base alloy as well as the metallic element(s) of the initial oxide addition.
  • the nanostructured ferritic alloy comprises a ferritic stainless steel.
  • a martensitic, duplex, austenitic stainless steel or precipitation hardened steel are also potential matrix alloys. The nature of the steel matrix phase may affect to some degree the environmental resistance and the material ductility of the resultant NFA.
  • the NFA includes chromium.
  • Chromium can be important for ensuring corrosion resistance, and may thus be included in the NFA in amounts of at least about 5 weight percent, and in some embodiments, at least about 9 weight percent. Amounts of up to about 30 weight percent, and in some instances up to about 20 weight percent can be included.
  • both chromium and iron, the basis of the NFA are readily available and relatively low in cost, in particular as compared to the nickel-based superalloys which the NFAs may replace in some applications.
  • the NFA includes molybdenum.
  • An amount of up to about 30 weight percent, and in some instances, up to about 20 weight percent can be included. In some instances, the amount of molybdenum ranges from about 3 weight percent to about 10 weight percent. In some other instances, the amount of molybdenum ranges from about 1 weight percent to about 5 weight percent.
  • the NFA may further include titanium. Titanium may participate in the formation of the precipitated oxide, and so, amounts of titanium of from about 0.1 weight percent to about 2 weight percent, and in some instances, from about 0.1 weight percent to about 1 weight percent, and in certain instances, from about 0.1 weight percent to about 0.5 weight percent, are desirably included in the NFA.
  • the composition of the nanofeature(s) will depend, in part, upon the oxide utilized to prepare the NFA and/or the alloy matrix.
  • the nanofeatures comprise titanium, oxygen and one or more additional element such as Y, Zr, Hf, Fe, Cr, Mo, W, Mn, Si, Nb, Al, Ni, Ta, or any combination of aforementioned.
  • an NFA as described herein comprises at least about 0.1% oxygen by weight.
  • the amount of oxygen present in the alloy determines in part the resultant type and concentration of nanofeatures present in the alloy.
  • the oxygen content is in a range from about 0.1% to about 0.5%, and in particular embodiments, the range is from about 0.1% to about 0.3%, where all percentages are by total weight of the alloy.
  • One illustrative NFA suitable for use in the formation of the article comprises from about 5 weight percent to about 30 weight percent chromium, from about 0.1 weight percent to about 2 weight percent titanium, from about 0 weight percent to about 10 weight percent molybdenum, from about 0 weight percent to about 5 weight percent tungsten, from about 0 weight percent to about 5 weight percent manganese, from about 0 weight percent to about 5 weight percent silicon, from about 0 weight percent to about 2 weight percent niobium, from about 0 weight percent to about 2 weight percent aluminum, from about 0 weight percent to about 8 weight percent nickel, from about 0 weight percent to about 2 weight percent tantalum, from about 0 weight percent to about 0.5 weight percent carbon, and from about 0 weight percent to about 0.5 weight percent nitrogen, with the balance being iron and incidental impurities; and a number density of at least about 10 18 m ⁇ 3 nanofeatures comprising titanium, oxygen, and at least one element derived from the oxide added during the preparation of the NFA or from the alloy matrix.
  • the NFA comprises from about 9 weight percent to about 20 weight percent chromium, from about 0.1 weight percent to about 1 weight percent titanium, from about 0 weight percent to about 10 weight percent molybdenum, from about 0 weight percent to about 4 weight percent tungsten, from about 0 weight percent to about 2.5 weight percent manganese, from about 0 weight percent to about 2.5 weight percent silicon, from about 0 weight percent to about 1 weight percent niobium, from about 0 weight percent to about 1 weight percent aluminum, from about 0 weight percent to about 4 weight percent nickel, from about 0 weight percent to about 1 weight percent tantalum, from about 0 weight percent to about 0.2 weight percent carbon, and from about 0 weight percent to about 0.2 weight percent nitrogen, with the balance being iron and incidental impurities; and a number density of at least about 10 20 m ⁇ 3 nanofeatures comprising titanium, oxygen and at least one element derived from the oxide added during the preparation of the NFA or from the alloy matrix.
  • the NFA comprises from about 9 weight percent to about 14 weight percent chromium, from about 0.1 weight percent to about 0.5 weight percent titanium, from about 0 weight percent to about 10 weight percent molybdenum, from about 0 weight percent to about 3 weight percent tungsten, from about 0 weight percent to about 1 weight percent manganese, from about 0 weight percent to about 1 weight percent silicon, from about 0 weight percent to about 0.5 weight percent niobium, from about 0 weight percent to about 0.5 weight percent aluminum, from about 0 weight percent to about 2 weight percent nickel, from about 0 weight percent to about 0.5 weight percent tantalum, from about 0 weight percent to about 0.1 weight percent carbon, and from about 0 weight percent to about 0.1 weight percent nitrogen, with the balance being iron and incidental impurities; wherein the NFA comprises a number density of at least about 10 22 m ⁇ 3 nanofeatures comprising titanium, oxygen and at least one element derived from the oxide added during preparation of the NFA or from the alloy matrix.
  • an “as-prepared” or “as-consolidated” NFA workpiece has a fine microstructure having an average grain size less than about 2 microns. In certain instances, the average grain size is between about 1 micron and 2 microns. In this fine microstructure, a percentage of coarse grains (grains larger than about 1 micron) may be low, for example less than about 5 percent based on the total grains in the microstructure.
  • FIG. 1A and FIG. 1B show the effect of a high temperature on the microstructure of a NFA workpiece.
  • FIG. 1A is a scanning electron microscope (SEM) micrograph of an “as-consolidated” workpiece (i.e. without a heat treatment); and
  • FIG. 1B is a SEM micrograph of the workpiece after heating it at 2000 degrees Fahrenheit for 24 hours.
  • FIG. 1B clearly shows a grain growth (i.e., an increase in percentage of coarse that is large grains) in the NFA workpiece with the increase in temperature.
  • SEM scanning electron microscope
  • the percentage of coarse grains (that have grain size greater than about 1 micron, and in some certain instances, greater than about 5 microns) in the NFA workpiece after heating it up to 2000 degrees Fahrenheit is significantly larger ( ⁇ 4 times) than the percentage of coarse grains in the alloy of the workpiece at about 1800 degrees Fahrenheit. After heating the workpiece at 2000 degrees Fahrenheit, for about 24 hours, the average grain size of the NFA workpiece is up to about 50 microns.
  • This grain growth with the rise of temperature limits the processing of the NFA at high temperatures, i.e. at temperatures higher than about 1900 degrees Fahrenheit.
  • processing NFAs with coarsening grains by using a high strain rate technique may lead to cracking, and thus damaging the resulting article.
  • the present method enables the processing of the NFAs at high temperatures (more than about 1900° F.) and/or at high strain rates without a significant degradation in the mechanical properties of a resulting article at an operating temperature.
  • An operating temperature, at which these articles are used is generally lower than a processing temperature, at which the NFAs are processed.
  • the ability to process the NFAs at high temperatures and/or high strain rates advantageously enables the use of the conventional high strain rate processing techniques for manufacturing a desired article from the NFA and thus maintaining low manufacturing costs.
  • the present method includes steps of introducing a quantity of strain into a workpiece that includes a nanostructured ferritic alloy (NFA) at a first temperature below about 1900 degrees Fahrenheit to form a strained workpiece, heating the strained workpiece to a second temperature and deforming the strained workpiece at the second temperature.
  • the second temperature is at least about 1900 degrees Fahrenheit.
  • the quantity of strain is first introduced into the NFA workpiece at a temperature below about 1900 degrees Fahrenheit before heating and/or processing (i.e., hot-working) the workpiece at a higher temperature.
  • the quantity of strain introduced into the workpiece at the first temperature is effective to substantially inhibit grain growth in the strained workpiece during the subsequent heating and the deforming at the second temperature.
  • This introduction of strain into the workpiece at the first temperature enables the deforming and/or the heating of the workpiece at a subsequent higher temperature, and thus the workpiece can be processed or hot-worked at high temperatures while preserving the microstructure to procure the desired mechanical properties.
  • the workpiece may be fabricated by consolidating a powder of a nanostructured ferritic alloy (NFA) (as discussed previously) by any technique as known in the art.
  • the workpiece is fabricated by hot isostatic pressing (HIP).
  • HIP hot isostatic pressing
  • Other compaction techniques include hot compaction, extrusion, or roll compaction.
  • a quantity of strain is first introduced into the NFA workpiece at a first temperature below about 1900 degrees Fahrenheit.
  • the workpiece is deformed at the first temperature.
  • a retained plastic strain interacts with the stable nanofeatures and effectively pins grain boundaries.
  • This pinning of the grain boundaries does not allow the grains of the fine microstructure of the workpiece to substantially grow in size, and thus substantially inhibits grain growth of the microstructure of the strained workpiece during the heating, the processing, or both at a second temperature.
  • the microstructure of the strained workpiece does not substantially change on heating or with a rise in temperature, and is maintained or stabilized for any further heating or processing, for example high strain rate processing at a high temperature.
  • a substantial growth may refer to an increase of up to about 10 percent in the percentage of coarse grains in the microstructure. In some embodiments, the increase in the percentage of coarse grains in the microstructure is in a range from about 1 percent to about 5 percent during the heating or the processing at the second temperature.
  • FIGS. 2B show SEM micrographs of a workpiece, respectively, after extruding the workpiece at 1700 degrees Fahrenheit and after heating the extruded workpiece at 2000 degrees Fahrenheit for about 24 hours. No significant change in the grain size of the workpiece was observed with the heat treatment at the high temperature after the extrusion at 1700 degrees Fahrenheit.
  • the stability of the microstructure of the strained workpiece may depend specifically on the first temperature in conjunction with the quantity of strain introduced into the workpiece.
  • the quantity of strain introduced into the workpiece at the first temperature is effective to substantially inhibit grain growth in the strained workpiece during the heating and the deforming at the second temperature.
  • the effectiveness of the strain introduced into the workpiece may be a result of an amount of a strain applied to the workpiece and a strain rate at which the strain is applied to the workpiece. That is, the workpiece may be deformed at the first temperature by applying a specific strain with a specific strain rate.
  • the workpiece may be deformed by any technique including forging, compaction, extrusion, and rolling. In certain embodiments, the workpiece is deformed by extrusion at the first temperature.
  • At least about 40 percent strain with a strain rate of less than about 1 inch/inch/sec is applied on the workpiece. In some embodiments, a strain ranging from about 40 percent to about 70 percent is desirable for effectively inhibiting the grain growth. In some embodiments, the strain is applied at a strain rate ranging from about 0.005 inch/inch/sec to about 0.9 inch/inch/sec.
  • the first temperature is generally below 1900 degrees Fahrenheit. In some embodiments, the first temperature ranges from about 1600 degrees Fahrenheit to about 1900 degrees Fahrenheit, and in some certain embodiments, from about 1700 degrees Fahrenheit to about 1800 degrees Fahrenheit.
  • the strained workpiece having the stabilized microstructure can be processed at a high temperature (i.e., a high processing temperature) and/or at a high strain rate for forming an article.
  • a high temperature refers to a temperature equal to or higher than 1900 degrees Fahrenheit.
  • a high strain rate refers to a strain rate higher than about 1 inch/inch/sec. In some embodiments, the strain rate is higher than about 5 inch/inch/sec, and in particular embodiments, higher than about 10 inch/inch/sec.
  • the strained workpiece after introducing a quantity of strain into the workpiece, the strained workpiece may be first heated to the second temperature and then deformed at the second temperature.
  • the strained workpiece is deformed at a second temperature that is at least about 1900 degrees Fahrenheit. In some embodiments, the second temperature ranges from about 1950 degrees Fahrenheit to about 2300 degrees Fahrenheit, and in certain embodiments, from about 2000 degrees Fahrenheit to about 2200 degrees Fahrenheit.
  • the step of deforming at the second temperature may be performed to form an article from the strained workpiece.
  • the deforming step may include deforming the strained workpiece with a high strain rate technique, for example high strain rate forging.
  • the strained workpiece is deformed with a strain rate in a range from about 10 inch/inch/sec to about 30 inch/inch/sec.
  • Other suitable techniques may include extrusion, compaction, or rolling.
  • a workpiece is first extruded at the first temperature and then processed by forging at the second temperature.
  • a turbomachinery component such as a bolt, may be manufactured by the disclosed method.
  • FIG. 3 shows flow stress curves for the NFA workpiece samples that were compressed at 1900 degrees Fahrenheit and 2100 degrees Fahrenheit. Each of these samples was first extruded at 1700 degrees Fahrenheit and then subsequently compressed at a strain rate of 20 inch/inch/sec. It was observed that a sample that was first extruded at 1700 degrees Fahrenheit and subsequently compressed at 1700 degrees Fahrenheit, was cracked.

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US14/533,145 2014-11-05 2014-11-05 Methods for processing nanostructured ferritic alloys, and articles produced thereby Abandoned US20160122840A1 (en)

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Application Number Priority Date Filing Date Title
US14/533,145 US20160122840A1 (en) 2014-11-05 2014-11-05 Methods for processing nanostructured ferritic alloys, and articles produced thereby
FR1559757A FR3027922A1 (fr) 2014-11-05 2015-10-14 Procedes pour transformer des alliages ferritiques nanostructures, et articles fabriques de cette facon
JP2015208497A JP2016108658A (ja) 2014-11-05 2015-10-23 ナノ組織鉄合金を処理する方法及びそれによって生産される物品
DE102015118873.2A DE102015118873A1 (de) 2014-11-05 2015-11-04 Verfahren zur Verarbeitung von nanostrukturierten ferritischen Legierungen und dabei hergestellte Produkte
CN201510743322.XA CN105567927A (zh) 2014-11-05 2015-11-05 用于加工纳米结构铁素体合金的方法和由此产生的物品

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN107893154A (zh) * 2017-11-22 2018-04-10 西南大学 一种高强高韧梯度马氏体奥氏体双相钢的制备方法

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