Classifications

• • 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
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/20—Direct sintering or melting
  • B22F10/25—Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS]
• • 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
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/20—Direct sintering or melting
  • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• • 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
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/30—Process control
  • B22F10/36—Process control of energy beam parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
• • 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
  • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• • 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
  • C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• the present invention relates to an Fe-based alloy, an alloy component, and a method for manufacturing the alloy component.
• hot work tool steels with high high-temperature strength such as SKD8 specified in JIS G 4404, and high-speed tool steels, such as SKH51 specified in JIS G 4403, have been used for tools such as punches and dies used in hot precision press processing.
• these steels have problems with being prone to settling, wear, breakage, cracking, and heat cracking.
• Patent Document 1 discloses a high-speed tool steel having, by mass%, 0.4 to 0.9% C (carbon), 1.0% or less Si (silicon), 1.0% or less Mn (manganese), 1.5 to 6% of one or both of W (tungsten) and Mo (molybdenum) (1/2W+Mo) (however, W is 3% or less), and 0.5 to 3% of one or both of V (vanadium) and Nb (niobium) (V+Nb), wherein the average particle size of precipitated carbides dispersed in the matrix is 0.5 ⁇ m or less and the distribution density is 80 ⁇ 10 3 pieces/mm 2 or more.
• coarse primary carbides are formed in the ingot due to solidification segregation during cooling during ingot making, such as the casting or remelting process of the steel ingot.
• the presence of these coarse primary carbides promotes the generation and propagation of cracks, thereby reducing toughness and heat crack resistance.
• the precipitated carbides have a finely dispersed uniform structure. To obtain such a structure, soaking at 1200 to 1300°C for 10 to 20 hours is required. However, even if soaking is performed in this manner, quenching and tempering are performed in the subsequent process to obtain pressing tools such as dies and punches, and molds.
• coarse precipitated carbides may be precipitated, which may reduce toughness and heat crack resistance.
• the present invention aims to provide an Fe-based alloy, alloy member, and method for manufacturing an alloy member that is less susceptible to cracking and is also expected to have toughness and heat crack resistance.
• the present invention is an Fe-based alloy characterized in that it contains C, Cr, W, Mo, and V, with the remainder being Fe and unavoidable impurity elements, has an alloy structure containing an Fe-BCC phase, and the Fe-BCC phase contains, when the sum of C, Cr, W, Mo, V, and Fe is taken as 100%, C is 3.0% to 7.0%, Cr is 2.0% to 6.0%, W is 0.5% to 4.0%, Mo is 0.5% to 4.0%, V is 0.5% to 4.0%, and Fe is 75% to 93.5%, has precipitated carbides precipitated in the Fe-BCC phase, and the proportion of the Fe-BCC phase is 43.5% or more in terms of area ratio in cross-sectional structure observation.
• the Fe-based alloy as a whole contains, in mass%, C of 0.1% to 2.0%, Cr of 2.0% to 6.0%, W of 0.5% to 4.0%, Mo of 0.5% to 4.0%, V of 0.5% to 4.0%, Si of 1.0% or less, Mn of 1.0% or less, with the remainder being Fe and unavoidable impurities.
• the Fe-BCC phase contains, by mass%, C of 4.8% to 6.0%, Cr of 3.9% to 6.0%, W of 1.5% to 3.0%, Mo of 2.2% to 3.1%, and V of 1.5% to 3.0%.
• the present invention also relates to an alloy member that is at least partially composed of the above-mentioned Fe-based alloy.
• the hardness of the Fe-based alloy is 700 HV or more.
• the present invention also provides a method for producing an alloy member, which uses an alloy powder that is, by mass%, C 0.1% to 2.0%, Cr 2.0% to 6.0%, W 0.5% to 4.0%, Mo 0.5% to 4.0%, V 0.5% to 4.0%, Si 1.0% or less, Mn 1.0% or less, with the balance being Fe and unavoidable impurities, irradiates the alloy powder with an electron beam or laser beam to melt and solidify it to form a solidified layer, forms a new solidified layer on the solidified layer, and then repeats this process to obtain an alloy member having a layered structure.
• an alloy powder that is, by mass%, C 0.1% to 2.0%, Cr 2.0% to 6.0%, W 0.5% to 4.0%, Mo 0.5% to 4.0%, V 0.5% to 4.0%, Si 1.0% or less, Mn 1.0% or less, with the balance being Fe and unavoidable impurities, irradiates the alloy powder with an electron beam or laser beam to melt and solidify it to form a solidified layer, forms a
• the present invention can provide an Fe-based alloy, an alloy member, and a method for manufacturing an alloy member that is less susceptible to cracking and is also expected to have toughness and heat crack resistance.
• FIG. 1 illustrates a schematic configuration of an additive manufacturing method.
• Photograph of the structure and element mapping image of the molded body after hardening treatment Structural photographs and elemental mapping images of the molded body after quenching and tempering treatments.
• Structural photograph and element mapping image of the molded body (without heat treatment) Structural photograph and element mapping image of the molded body after tempering treatment.
• FIG. 11 is a diagram showing the Vickers hardness (HV) of each molded body.
• % indicates mass %.
• a numerical range expressed using " ⁇ " means a range that includes the numerical values written before and after " ⁇ " as the lower limit and upper limit. Furthermore, the lower limit and upper limit of the numerical range can be combined as appropriate.
• the Fe-based alloy of the present embodiment contains C, Cr, W, Mo, and V, with the balance being Fe and unavoidable impurity elements, in other words, it is a high-speed tool steel containing C, Cr, W, Mo, V, and Fe, and has an alloy structure containing an Fe-BCC phase, and the Fe-BCC phase contains, in mass %, C of 3.0% to 7.0%, Cr of 2.0% to 6.0%, W of 0.5% to 4.0%, Mo of 0.5% to 4.0%, V of 0.5% to 4.0%, and Fe of 75.0% to 93.5%, when the total of C, Cr, W, Mo, V, and Fe is taken as 100%, and has precipitated carbides in the Fe-BCC phase, and a ratio of the Fe-BCC phase is 43.5% or more in terms of area ratio in cross-sectional structure observation.
• the Fe-BCC phase is generally a structure containing ⁇ -Fe and martensite formed when an Fe-based alloy is cooled from a high temperature.
• an Fe-BCC phase obtained by a method with a high melting and solidification rate, i.e., a high cooling rate for example, an Fe-BCC phase obtained by an additive manufacturing method, it refers to a structure containing martensite of an Fe-based alloy in which C is supersaturated in solid solution, and such an Fe-BCC phase is hard.
• the Fe-BCC phase contains 3.0% to 7.0% C, 2.0% to 6.0% Cr, 0.5% to 4.0% W, 0.5% to 4.0% Mo, 0.5% to 4.0% V, and 75.0% to 93.5% Fe.
• the Fe-BCC phase can be evaluated using electron backscattering diffraction (EBSD). The evaluation method using EBSD will be described later.
• C 3.0-7.0%) C combines with elements that form carbides, such as Cr, W, Mo, and V, to precipitate carbides.
• the precipitated carbides form composite carbides in which carbides called M 6 C type and MC type are precipitated in a composite manner, and therefore have the effect of improving the wear resistance of Fe-based alloys, alloy members, and their manufactured products.
• a part of C dissolves in the matrix, thereby strengthening the matrix. Therefore, by making the C content in the Fe-BCC phase 3.0% or more, the hardness of the Fe-BCC phase can be ensured by both the strengthening of the matrix and the effect of the fine carbides formed in the crystal grains of the matrix.
• the C content in the Fe-BCC phase 7.0% or less is preferably 4.0% to 7.0%, and more preferably 4.8% to 6.0%.
• Cr 2.0-6.0% Cr combines with C to form carbides, improving wear resistance and contributing to improved hardenability.
• the Cr content in the Fe-BCC phase 2.0% or more, the amount of carbides formed within the matrix grains can be optimized, and wear resistance and hardenability can be improved.
• the Cr content in the Fe-BCC phase 6.0% or less the amount of carbides formed within the matrix grains can be suppressed from becoming excessive, and toughness can be ensured.
• the Cr content is preferably 3.0% to 6.0%, and more preferably 3.9% to 6.0%.
• Mo 0.5-4%) Mo combines with C to form carbides, improving wear resistance and contributing to improved hardenability.
• Mo content in the Fe-BCC phase 0.5% or more, it dissolves in the matrix grains and increases the heat treatment hardness, thereby improving wear resistance.
• Mo content in the Fe-BCC phase 4.0% or less, it is possible to suppress the formation of excessive carbides in the matrix grains and ensure toughness. It is preferably 1.5% to 3.5%, and more preferably 2.2% to 3.1%.
• V 0.5-4.0%
• V combines with C to form carbides, contributing to improved wear resistance and seizure resistance.
• V content in the Fe-BCC phase 0.5% or more, fine carbides that are difficult to aggregate are precipitated in the matrix grains by heat treatment, increasing softening resistance in high temperature ranges and improving high temperature yield strength.
• the matrix crystal grains are refined, improving toughness, and the A1 transformation point is raised, which, together with excellent high temperature yield strength, improves heat crack resistance.
• the V content in the Fe-BCC phase 4.0% or less it is possible to suppress the formation of excessive carbides in the matrix grains and ensure toughness. It is preferably 1.0% to 3.5%, and more preferably 1.5% to 3.0%.
• carbides containing C and at least one of Cr, W, Mo, and V (hereinafter, precipitated carbides) are precipitated.
• C and carbide-forming elements such as Cr, W, Mo, and V are combined to form hard carbides, which is effective in improving wear resistance.
• C has the effect of strengthening the matrix by dissolving in a part of the matrix.
• a phase containing precipitated carbides can be called a carbide phase.
• Cr, V, Mo, and W are concentrated in the carbide phase more than in the Fe-BCC phase, and C is the region with the largest amount of carbide.
• the carbide phase contains, for example, 12% to 15% C, 3% to 5% Cr, 3% to 9% W, 5% to 12% Mo, 15% to 45% V, and 15% to 60% Fe.
• the size of the precipitated carbides is refined to an average circle-equivalent grain size of 1.5 ⁇ m or less. It is preferably 0.50 ⁇ m to 1.45 ⁇ m, and more preferably 1.1 ⁇ m to 1.45 ⁇ m.
• the average grain size can be determined from the carbides that are visible when the observation field area (region area) is 200 x 200 ( ⁇ m) and the magnification is 400 times or more.
• the proportion of the Fe-BCC phase is 43.5% or more, preferably 43.8% or more, in terms of area ratio in cross-sectional structure observation of the alloy to be observed.
• the proportion of the Fe-BCC phase can be, for example, 60.0% or less, 50.0% or less, or 45.0% or less.
• the mechanical strength of the alloy member can be improved as the circle-equivalent average grain size of the Fe-BCC phase is finer, it is preferably 8.50 ⁇ m or less, more preferably 7.30 ⁇ m or less, even more preferably 5.50 ⁇ m or less, and even more preferably 5.30 ⁇ m or less.
• the ratio of the Fe-BCC phase and the circle-equivalent average grain size described above can be calculated as follows.
• a phase map is obtained from image data of a field of view (observation field) observed using EBSD for an arbitrary cross-section obtained by cutting in a direction perpendicular to the stacking direction.
• the arbitrary cross-section can be, for example, a Y-Z plane, where the modeling direction is X, the stacking direction is Z, and the axis perpendicular to both X and Z is Y.
• an RGB image can be used as the image data.
• the image data can be one having an observation field area of 100 ⁇ mm 2 to 500 ⁇ m 2.
• the phase map obtained by EBSD is divided into each color (red, green, blue), and only the Fe-BCC portion is extracted.
• the noise of this image is removed by a filter, and the image is binarized to black and white and the black and white of the image are inverted (for example, the original red part (Fe-BCC phase) is displayed as black).
• the Watershed method is used to segment the observation field into Fe-BCC phase portions and other portions.
• the ratio (S F /S A ) of the total area (S F ) of the Fe-BCC phase portions determined to be the Fe-BCC phase by segmentation to the area (S A ) of the observation field can be determined as the ratio of the Fe-BCC phase.
• the circle-equivalent grain size of each Fe-BCC phase in the segmented observation field is calculated and averaged to calculate the circle-equivalent average grain size forming the Fe-BCC phase (circle-equivalent average grain size of the Fe-BCC phase).
• the phase map obtained by EBSD is divided into a red area (Fe-BCC phase), a blue area (mainly Fe-FCC phase), and a green area (area that is neither Fe-BCC nor Fe-FCC phase, hereafter referred to as the zero solution area).
• the phase map By dividing (segmenting) the phase map in this way, the proportion of the structure that is occupied by the Fe-BCC phase and precipitated carbides can be determined.
• the Fe-BCC phase is displayed in white.
• the blue areas (mainly the Fe-FCC phase) and zero solution areas are displayed in white.
• the proportion of the Fe-BCC phase can be determined by dividing the total area of the Fe-BCC phase areas by the area of the observation field (e.g. 200 ⁇ m ⁇ 200 ⁇ m).
• the diameter of the circle that has the same area as each Fe-BCC phase (the circular equivalent particle size of the Fe-BCC phase) is calculated, and the circular equivalent particle size of all Fe-BCC phases present within the field of view is calculated as the arithmetic average, thereby determining the average circular equivalent particle size of the Fe-BCC phase.
• the precipitated carbides are preferably appropriately fine. By being appropriately fine, cracks are unlikely to occur, and in addition to being excellent in toughness and heat crack resistance, it is expected that the abrasion resistance is also excellent.
• the precipitated carbides are preferably 1.0 ⁇ m or more and 5.0 ⁇ m or less in circle equivalent average particle size, more preferably 1.2 ⁇ m or more and 2.5 ⁇ m or less, and even more preferably 1.35 ⁇ m or more and 2.0 ⁇ m or less.
• the ratio is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 2.5% or more. If the ratio of precipitated carbides is 0.5% or more, it is expected that the abrasion resistance is also excellent, and the higher the ratio, the more remarkable the effect.
• the zero solution portion can be displayed by subtracting the image of the divided blue portion from the black-and-white inverted image of the image in which the Fe-BCC phase is displayed in white, that is, the image in which the blue portion (mainly the Fe-FCC phase) and the zero solution portion are displayed in white.
• This zero solution portion is a portion that is neither the Fe-BCC phase nor the Fe-FCC phase, and corresponds to the precipitated carbide portion.
• the ratio of precipitated carbide can be obtained by dividing the total area occupied by the precipitated carbide portion in the observation field by the area of the observation field (for example, 200 ⁇ m ⁇ 200 ⁇ m).
• the diameter of a circle that has the same area as each precipitated carbide in the observation field (circle-equivalent grain size of precipitated carbide) is obtained, and the circle-equivalent grain size of precipitated carbide obtained from all precipitated carbides present in the field of view is arithmetically averaged to calculate the circle-equivalent average grain size of precipitated carbide.
• Each structure can be evaluated using Energy-Dispersive X-ray Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD) in conjunction with a Scanning Electron Microscope (SEM).
• EDS Energy-Dispersive X-ray Spectroscopy
• EBSD Electron Backscatter Diffraction
• SEM Scanning Electron Microscope
• the analysis conditions may be, for example, an acceleration voltage of 15 kV in the scanning electron microscope, a working distance of 10 mm from the objective lens to the surface of the object to be observed, and an observation magnification of 3000x.
• the element distribution evaluation method using EDS may obtain the element distribution by EDS surface analysis in the same field of view of the SEM mentioned above.
• the target elements when analyzing precipitated carbides, the target elements may be, for example, C, Cr, W, Mo, V, Fe, and O.
• the Fe-BCC phase may also be analyzed in the same manner as above.
• the alloy structure of the Fe-based alloy of this embodiment is made up of 43.5% or more of the Fe-BCC phase, and fine precipitated carbides are uniformly dispersed in the Fe-BCC phase, so cracks originating from the carbides are unlikely to occur, and even if cracks do occur, they are uniformly dispersed and therefore unlikely to extend. This makes it possible to improve toughness and heat crack resistance.
• the Fe-based alloy as a whole consists, in mass percent, of 0.1% to 2.0% C, 2% to 6.0% Cr, 0.5% to 4.0% W, 0.5% to 4.0% Mo, 0.5% to 4.0% V, and the remainder being Fe and unavoidable impurity elements.
• Si is 1.0% or less and Mn is 1.0% or less, by mass %.
• Si is expected to improve oxidation resistance. It is preferable to set the above range in consideration of workability.
• Mn is expected to improve wear resistance and hardenability and reduce embrittlement. It is preferable to set the above range in consideration of the effects of embrittlement due to quench cracking and residual ⁇ .
• C carbon
• carbide-forming elements such as Cr, W, Mo, and V
• C also has the effect of dissolving in a part of the matrix to strengthen the matrix.
• the C content is preferably 0.5 to 1.5%, more preferably 0.5 to 1.0%.
• Cr 2.0-6.0%) Cr (chromium) combines with C to form carbides, improving wear resistance and contributing to improved hardenability.
• Cr content 2.0% or more, the amount of carbides formed in the entire Fe-based alloy can be optimized, and wear resistance and hardenability can be improved.
• the Cr content is preferably 3.0 to 5.0%, and more preferably 4.0 to 5.0%.
• W 0.5-4.0%) W (tungsten) combines with C to form carbides, contributing to improved wear resistance. It also contributes to ensuring strength in high-temperature environments, so it is particularly effective in improving the wear resistance of dies used in high-temperature environments.
• W content in the entire Fe-based alloy 0.5% or more, it dissolves in the grains of the matrix, increasing the heat treatment hardness, and carbides are also formed on the grain boundaries of the matrix, improving wear resistance.
• the W content is preferably 1.0 to 2.5%, more preferably 1.5 to 2.0%.
• Mo molybdenum
• Mo mobdenum
• the Mo content is preferably 1.5 to 3.5%, more preferably 2.0 to 3.5%.
• V vanadium
• V vanadium
• the V content is preferably 1.5 to 3.5%, more preferably 2.0 to 3.0%.
• Si silicon
• Si silicon
• the content of Si in the entire Fe-based alloy is preferably 0.8% or less, more preferably 0.5%, in order to improve oxidation resistance and suppress deterioration of workability.
• 0.1 to 1.0% is preferable, 0.1 to 0.8% is more preferable, and 0.1 to 0.5% is even more preferable.
• Mn manganese
• Mn manganese
• the content of Mn in the entire Fe-based alloy is preferably 0.8% or less, more preferably 0.5% or less. Also, 0.1 to 0.8% is preferable, and 0.1 to 0.5% is even more preferable.
• the inevitable impurities are trace elements mixed into the raw materials, or impurities in trace amounts that are difficult to remove technically due to reactions with various components that come into contact during the manufacturing process.
• the inevitable impurities specifically refer to, for example, Al, Cu, N, Ni, O, P, S, and Co.
• the impurities that should be particularly restricted are P, S, O, and N.
• P is preferably 0.03% or less
• S is preferably 0.003% or less
• O is preferably 0.02% or less
• N is preferably 0.05% or less.
• the content of these inevitable impurities is preferably low, and 0% is even better.
• the Fe-based alloy and alloy member of the present embodiment are manufactured by irradiating an alloy powder with an electron beam or a laser beam to melt and solidify the alloy powder to form a solidified layer, forming a new solidified layer on the solidified layer, and then repeating this operation to obtain an alloy member having a layered structure.
• the alloy and alloy member are manufactured by a so-called additive manufacturing method. In this specification, the method may be referred to as an additive manufacturing (layered manufacturing) method.
• the alloy powder is an Fe-based alloy powder containing the above-mentioned predetermined composition of C, Cr, W, Mo, and V, with the balance being Fe and inevitable impurity elements.
• a predetermined amount of each element is weighed so as to obtain an alloy having a predetermined composition range, and these are mixed to prepare a raw material powder.
• This raw material powder is used to obtain an atomized powder.
• the raw material powder is loaded into a crucible, melted by high frequency, and the molten alloy is dropped from a nozzle below the crucible and sprayed with high pressure argon to prepare a gas atomized powder. This gas atomized powder can be classified to obtain an alloy powder.
• the Fe-based alloy powder of this embodiment may be alloyed by controlling the composition of the Fe-based alloy described above.
• the Fe-based alloy powder may contain, by mass%, 0.1% to 2.0% C, 2% to 6.0% Cr, 0.5% to 4.0% W, 0.5% to 4.0% Mo, 0.5% to 4.0% V, 1.0% or less Si, 1.0% or less Mn, and the balance being Fe.
• the Fe-based alloy powder contains 0.5 to 0.9% C, 4.0 to 5.0% Cr, 1.0 to 2.0 W, 2.5 to 3.5% Mo, 2.0 to 3.0 V, 0.8% or less Si, 0.3% or less Mn, and the balance being Fe and unavoidable impurities.
• C in the alloy structure of the shaped body combines with carbide-forming elements such as Cr, W, Mo, and V to generate hard composite carbides, which has the effect of improving the wear resistance of the alloy member and its manufactured products.
• C also has the effect of dissolving in a part of the matrix of the alloy structure of the shaped body to strengthen the matrix.
• the composition of the alloy powder can be analyzed, for example, using inductively coupled plasma (ICP) optical emission spectrometry.
• ICP inductively coupled plasma
• additive manufacturing methods for metal materials are roughly divided into a powder bed fusion (PBF) method and a directed energy deposition (DED) method. It can be applied to both the powder bed fusion (PBF) method and the directed energy deposition (DED) method, which are additive manufacturing methods for metal materials.
• PPF powder bed fusion
• DED directed energy deposition
• the PBF method involves spreading metal powder on a base plate (substrate) to form a powder bed, then irradiating the metal powder spread in the target area with a beam to melt and solidify the metal powder to create a shape.
• a three-dimensional object, or additive manufacturing object can be produced by repeating the lamination of the powder bed and the melting and solidification of the metal powder each time a two-dimensional model is performed on the powder bed.
• PPF powder bed fusion
• SLM selective laser melting
• SLS selective laser sintering
• SEBM selective electron beam melting
• the powder laser melting (SLM) method is a method of melting or sintering metal powder with a laser beam.
• the powder laser sintering (SLS) method is a method of sintering metal powder with a laser beam.
• the metal powder is melted and solidified in an inert atmosphere such as nitrogen gas.
• the Fe-based alloy member of this embodiment can be manufactured by repeatedly performing the melting and solidification process in which the Fe-based alloy powder described above is irradiated with a heat source such as an electron beam or laser beam to melt and solidify it and form a solidified layer, thereby stacking further solidified layers on the solidified layer.
• the powder electron beam melting (SEBM/EBM) method is a method for melting metal powder using an electron beam as a heat source.
• the EBM method which uses an electron beam, is carried out by irradiating metal powder with an electron beam and converting the kinetic energy into heat to melt the metal powder.
• the electron beam is irradiated and the metal powder is melted and solidified under a high vacuum.
• the DED method is also known as the metal deposition method.
• DED Laser Metal Deposition
• LMD Laser Metal Deposition
• the method of applying powder cladding to a base material using a laser beam is also known as laser powder cladding welding.
• the powder bed fusion (PBF) method has the advantage of high shape accuracy of the layered object.
• the directed energy deposition (DED) method has the advantage of high speed modeling.
• the powder laser melting (SLM) method allows for the selective melting and solidification of metal powder by irradiating a powder bed with a thickness of several tens of micrometers per layer with a laser with a very small beam diameter.
• powder particle size may be adjusted by mesh sieving or airflow classification to match the modeling method of the additive manufacturing method.
• the modeling powder used in powder bed fusion methods using electron beams or laser beams is melted by the laser beam, which serves as the heat source, but coarse powder that is difficult to melt must be removed to minimize the range of thermal effects.
• highly adhesive fine powder must also be removed.
• the average particle size (D50) of the alloy powder when applying to powder bed fusion (PBF), it is preferable to adjust the average particle size (D50) of the alloy powder to the range of 10 to 60 ⁇ m.
• metal powders used in directed energy deposition must have coarse powders that are difficult to melt removed in order to melt the powder using a laser beam as a heat source.
• fine powders must also be removed in order to prevent dust scattering when the powder is supplied to the heat source and ensure fluidity that allows the powder to be easily transported.
• D50 when applying the molding powder of the present invention to the directed energy deposition method, it is preferable to adjust D50 to the range of 50 to 120 ⁇ m.
• D50 when using an electron beam or plasma as a heat source, it is possible to mold using coarser metal particles, so D50 is preferably set to 75 to 250 ⁇ m.
• Figure 1 shows the schematic configuration of an additive manufacturing device 1 that uses a laser beam as a heat source for additive manufacturing using the directed energy deposition method.
• the additive manufacturing device 1 is mainly composed of a powder supply nozzle 3, a focusing lens 5, a protective lens 7, etc. Alloy powder 11 is supplied to the powder supply nozzle 3 and sprayed onto the tip of the powder supply nozzle 3 together with argon gas.
• a laser beam 9 emitted from a laser oscillator (not shown) is focused by the focusing lens 5 and irradiated near the tip of the powder supply nozzle 3.
• a protective lens 7 is provided below the focusing lens 5.
• alloy powder 11 is supplied onto the base plate 17 while the powder supply nozzle 3 is moved relative to the base plate 17 (direction A in the figure).
• the supplied alloy powder 11 is irradiated with a laser beam 9 focused by a focusing lens 5, forming a molten pool 13 in which the alloy powder 11 melts and solidifies to form a shaped body 15 (Fe-based alloy).
• This process is repeated using a program file created using CAD-CAM software to stack the shaped bodies 15 on the base plate 17, thereby forming a three-dimensional alloy part that contains at least a portion of an Fe-based alloy.
• a (3D) additive manufacturing device is used to rapidly melt the surface of a base material such as a base plate, a molded object, or a die by irradiating it with a laser, and raw material powder is supplied into the molten pool that is formed by the melting, where it is rapidly cooled and solidified. A series of processes are repeated and layered to create a molded object.
• the molded object formed on the base plate corresponds to the Fe-based alloy component of this embodiment.
• a manufactured product can be obtained.
• the additive manufacturing conditions are appropriately determined taking into consideration the particle size and composition of the raw material powder, the size, shape, and characteristics of the molded object, production efficiency, etc., and for the alloy of this embodiment, they can be selected, for example, from the following ranges.
• the thickness of one layer during additive manufacturing can be, for example, 0.1 mm to 1.0 mm, and is preferably 0.4 to 0.8 mm.
• the thickness of the first layer of Fe-based alloy formed on the surface of the base material (base plate) is 0.1 mm to 1 mm.
• the thickness of the entire layer from the interface of the base material to the surface of the Fe-based alloy is preferably 0.1 mm to 5 mm in order to prevent peeling of the Fe-based alloy from the base material and cracking of the Fe-based alloy itself.
• the dilution layer refers to a layer in which the Fe-based alloy of the first layer is melted into the base material when the Fe-based alloy of the first layer is shaped, and the compositions of both the base material and the Fe-based alloy of the first layer are mixed.
• the laser beam diameter is preferably about 3 mm at the irradiation position.
• the laser output is preferably 1500 to 2500 W.
• the laser scanning speed is preferably 500 to 1000 mm/min.
• the powder supply amount is preferably 10 to 20 g/min.
• the density of the energy input by laser irradiation to rapidly melt the raw material powder is preferably 90 to 300 J/mm, and more preferably in the range of 180 to 240 J/mm. If the energy density is too small, the defect rate will increase, and the supplied powder will not melt, making it difficult to maintain the shape of the molded object. On the other hand, if the energy density is too large, a wide area of the base plate or molded object centered on the laser irradiation position will melt, making it difficult to maintain the shape of the molded object.
• the energy density E (J/mm) can be calculated using the laser output P (W) and the laser scanning speed v (mm/min) as P/v x 60.
• the Fe-based alloy of this embodiment may be subjected to quenching treatment to improve hardness, and may be additionally subjected to tempering treatment to remove quenching stress and improve toughness if the cost and the like are within an acceptable range.
• quenching treatment the alloy may be held at 1180 to 1220°C for 10 to 60 minutes, and then cooled in oil or water. In order to prevent distortion and quench cracking, it is more preferable to cool in oil. Quenching and cooling using a salt bath may be performed.
• the tempering treatment is a heat treatment process in which the alloy is held at 400°C to 700°C, and it is preferable to hold the alloy at 560 to 580°C for 2 to 6 hours, and then cool the alloy in air.
• the hardness of the surface layer of the Fe-based alloy or alloy member of this embodiment can be evaluated by Vickers hardness HV (hereinafter referred to as hardness), and is desirably 350 HV or more, and preferably 500 HV or more.
• the hardness can be measured by setting the pressing load of a Vickers indenter to 0.5 kg, the dwell time during pressing to 10 seconds, and determining the hardness from the diagonal length of the indentation formed on the measurement surface by pressing the indenter.
• the method may further include a surface treatment step in which the obtained alloy component is subjected to a surface treatment.
• the surface treatment step is, for example, a nitriding treatment or a film formed by a PVD method on the surface layer of the Fe-based alloy, and is a nitride layer, a compound layer, or a ceramic coating layer.
• a film that is harder than the Fe-based alloy formed by additive manufacturing can be formed on the surface layer of the Fe-based alloy, and therefore the wear resistance can be improved by further strengthening the surface of the alloy component obtained by additive manufacturing.
• the raw material powder was supplied to a molten pool formed by laser irradiation on a base plate, and melted and solidified to produce a shaped body (alloy component) with a width of 3 mm, length of 80 mm, and layer height of approximately 10 mm.
• the additive manufacturing conditions were as follows: Maraging steel (YAG300 manufactured by Proterial Co., Ltd. (YAG is a registered trademark of Proterial Co., Ltd.) was used for the base plate.
• the body that had been heat-treated and bodies that had not been heat-treated were evaluated.
• the body that had only been quenched was designated F1
• the body that had been quenched and tempered was designated F2
• the body that had not been heat-treated was designated F3
• the body that had only been tempered was designated F4.
• the quenching process involved holding the body at 1200°C for 0.5 hours, followed by cooling in oil.
• the tempering process involved holding the body at 560°C for 4 hours, followed by air cooling.
• the molded bodies F1 and F2 were observed and evaluated using an SEM.
• the test pieces for evaluation were prepared by cutting a portion of the molded body into small pieces and embedding them in resin, and then polishing the cut surfaces of the embedded molded bodies to a mirror finish. The observation was performed at a magnification of 3000x.
• elemental analysis was performed in the same field of view using an EDS attached to the SEM. Eight elements were analyzed: C, Cr, Fe, Mo, O, V, and W.
• Figures 2A to 2E show examples of SEM and EDS images obtained.
• Figure 2A shows SEM and EDS images obtained by observing the cross-sectional structure of arbitrary cross sections of the alloy of body F1, which was subjected to only quenching as a heat treatment, body F2, which was subjected to quenching and tempering, body F3, which was not subjected to heat treatment, and body F4, which was subjected to only tempering.
• Figure 2E shows SEM and EDS images of forged material F0, an alloy of the same composition produced by conventional powder metallurgy. Forged material F0 was sintered from powder, forged, and subjected to the same quenching and tempering treatments as above.
• a phase map was also obtained using EBSD by the method described above.
• the field of view area also called the field of view area
• elemental analysis was performed on the Fe-BCC phase and precipitated carbides within that field of view.
• the six elemental analysis species were C, Cr, W, Mo, V, and Fe.
• Elemental analysis was performed on the Fe-BCC phase 50 at part A shown in Figures 2A, 2B, 2C, 2D, and 2E, and on the precipitated carbides 52 at part B shown in Figures 2A, 2B, 2C, 2D, and 2E.
• the Fe-BCC phase of F1 contained 84.4% Fe, 4.9% C, 4.4% Cr, 1.7% W, 2.5% Mo, and 2.2% V.
• the precipitated carbides contained 19.8% Fe, 14.7% C, 3.9% Cr, 8.3% W, 10.6% Mo, and 42.8% V.
• the Fe-BCC phase of F2 contained 82.0% Fe, 5.8% C, 4.8% Cr, 2.1% W, 3.0% Mo, and 2.3% V.
• the precipitated carbides contained 55.3% Fe, 12.2% C, 4.3% Cr, 4.0% W, 6.2% Mo, and 18.0% V.
• the Fe-BCC phase of F3 contained 83.7% Fe, 5.3% C, 3.8% Cr, 2.4% W, 2.2% Mo and 2.6% V.
• the Fe-BCC phase of F4 contained 82.5% Fe, 4.9% C, 4.7% Cr, 2.1% W, 3.3% Mo, and 2.5% V.
• the precipitated carbides contained 43.0% Fe, 11.5% C, 5.6% Cr, 6.1% W, 9.0% Mo, and 24.6% V.
• the Fe-BCC phase of F0 contained 84.9% Fe, 4.7% C, 3.8% Cr, 2.0% W, 3.2% Mo, and 1.4% V.
• the precipitated carbides contained 47.1% Fe, 12.9% C, 4.7% Cr, 6.2% W, 7.6% Mo, and 21.5% V.
• the composition of the precipitated carbides showed different trends for bodies F1 to F4. It is believed that in body F1, which was only subjected to quenching, V (vanadium) carbide and composite carbides of Mo or W with Fe were less likely to decompose, and the C derived from these carbides did not dissolve in the Fe-BCC phase, resulting in higher concentrations of V, Mo, and W in the precipitated carbides.
• molded body F4 which was only tempered, it can be assumed that it was quenched for a short time using a heat source due to the additive manufacturing process, and therefore it can be inferred that it has undergone a similar thermal history to the molded body F2, which was quenched and tempered.
• molded body F4 like F2, contains V, Mo, and W in the precipitated carbides, and in addition, carbides of the main components Fe and Cr are also precipitated, and the proportion of V, Mo, and W in the precipitated carbides is relatively lower than that of molded body F1.
• the non-heat-treated molded body F3 cooled quickly after molding, and although fine carbides precipitated locally, it is believed that their size was below the resolution of the detector.
• the forged and pressed material F0 was quenched and tempered under the same conditions as F2, and tempered under the same conditions as F4.
• the composition of the precipitated carbides was significantly different between the formed body F2 and the forged and pressed material F0. This is thought to be due to the fact that the additive manufacturing method used to create the formed body has a faster cooling rate from the molten state to the solidified state, i.e., the melting and solidification rate, than the forged and pressed material.
• the proportion of the Fe-BCC phase in terms of area percentage, was higher in the formed bodies F1 to F4 (43.8% to 56.2%) than in the forged material F0 (43.3%). Furthermore, the proportions of the Fe-BCC phase in the formed body F3, which was not subjected to heat treatment, and the formed body F4, which was subjected to only tempering, were 45.1% and 56.2%, respectively, which were higher than the proportions in the formed body F1, which was subjected to only quenching, and the formed body F2, which was subjected to quenching and tempering.
• the percentage of precipitated carbides was highest in formed body F2 at 5.95%, followed by body F1 at 2.79%, body F4 at 0.13%, and body F3 at 0.064%.
• the percentage of precipitated carbides in forged material F0 was 3.73%. From these results, it was confirmed that the percentage of precipitated carbides in formed bodies F3 and F4 was lower than in formed bodies F1, F2, and forged material F0.
• the average circle-equivalent particle size of precipitated carbides was the largest for formed body F3 at 1.42 ⁇ m, followed by formed body F2 at 1.41 ⁇ m, formed body F1 at 1.39 ⁇ m, for forged material F0 at 1.33 ⁇ m, and formed body F4 at 1.14 ⁇ m.
• the proportion of precipitated carbides or the average circle equivalent grain size was smaller in the formed bodies F3 and F4 than in the formed bodies F1 and F2.
• the cooling rate during manufacturing was high and the carbide formation time was short, so it is thought that the amount of carbides formed inside the alloy (formed body) before heat treatment was smaller than in the forged material F0.
• the proportion of the Fe-BCC phase in the formed bodies F1 to F4 is 43.5% or more in terms of area ratio, it can be said that the structure is more uniform. Also, although it is not possible to simply compare the formed bodies F1 to F4, which are additive manufactured products, with the forged material F0, the formed bodies F1 to F4 have a higher proportion of the Fe-BCC phase than F0.
• the average circle-equivalent grain size of the Fe-BCC phase is 7.0 ⁇ m or less
• the proportion of precipitated carbides exceeds 0.1%
• the size of the Fe-BCC phase is not too large
• carbides are precipitated in the Fe-BCC phase, so it is expected that they will have even better mechanical strength, toughness, heat crack resistance, and wear resistance.
• the shaped body F1 that was subjected to only quenching, the shaped body F2 that was subjected to quenching and tempering, the shaped body F3 that was not subjected to heat treatment, and the shaped body F4 that was subjected to only tempering have a proportion of Fe-BCC phase of 43.5% or more as shown in Table 4, so that the structure is uniform and it is possible to suppress the occurrence of localized distortion due to, for example, external stress, and it is expected that cracks will not easily occur.

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