Fe-BASED ALLOY, ALLOY MEMBER, PRODUCT, AND METHOD FOR MANUFACTURING ALLOY MEMBER

Abstract

To provide an Fe-based alloy having excellent mechanical properties as well as excellent wear resistance, an alloy member, a product, and a method for manufacturing the alloy member.SOLUTION: This Fe-based alloy has an alloy structure including C, Cr, W, Mo, and V, with the remainder made up by Fe and unavoidable impurities, and including an Fe-BCC phase and a W-Mo-concentrated phase. By mass, the Fe-BCC phase contains 3-7% of C, 2-6% of Cr, 0.5-8% of W, 3-20% of Mo, 2-20% of V, and 60-90% of Fe, and the W-Mo-concentrated phase contains 5-13% of C, 2-12% of Cr, 7-17% of W, 11-22% of Mo, 3-19% of V, and 40-50% of Fe. The W-Mo-concentrated phase is formed so as to surround the Fe-BCC phase.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present invention relates to an Fe-based alloy, an alloy member, a product, and a method for manufacturing an alloy member. [Background technology]

[0002] Conventionally, tools such as punches and dies used in hot precision press working have been made of 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. However, these steels have problems such as being prone to settling, wear, breakage, cracking, and heat cracking.

[0003] For example, Patent Document 1 discloses a high-speed tool steel produced by powder metallurgy, which contains, by mass, 0.8-3.95% C, 30-50% total of W and twice the amount of Mo, 3.0-5.0% Cr, 1.0-10.0% V, 5-15% Co, and the remainder being Fe and impurities. Patent Document 1 discloses a high-speed tool steel that contains a large amount of residual carbides during quenching, and has excellent cutting durability by uniformly and finely dispersing the residual carbides in the matrix, thereby combining high wear resistance and high toughness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 51-072906 Summary of the Invention [Problem to be solved by the invention]

[0005] The tool steel of Patent Document 1 is an alloy formed by powder metallurgy, and therefore, compared with the case of solidifying normal molten metal, it is less likely to cause precipitation or segregation of primary crystals, and it is easier to form a uniform structure both microscopically and macroscopically. In general, a uniform structure is effective for mechanical properties, and wear resistance can be obtained by dispersing carbides uniformly. However, when used in dies and the like, there is a risk of adhesive wear, especially on the sliding surface, and higher wear resistance has been required.

[0006] Therefore, an object of the present invention is to provide an Fe-based alloy, an alloy member, a product, and a method for manufacturing an alloy member, which are excellent in both mechanical properties and wear resistance. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a first invention is an Fe-based alloy comprising C, Cr, W, Mo, and V with the balance being Fe and unavoidable impurity elements, and having an alloy structure including an Fe-BCC phase and a W-Mo concentrated phase, wherein, in mass%, the Fe-BCC phase contains 3% or more and 7% or less of C, 2% or more and 6% or less of Cr, 0.5% or more and 8% or less of W, 3% or more and 8% or less of Mo, 2% or more and 20% or less of V, and 60% or more and 90% or less of Fe; the W-Mo concentrated phase contains 5% or more and 13% or less of C, 2% or more and 12% or less of Cr, 7% or more and 17% or less of W, 11% or more and 22% or less of Mo, 3% or more and 19% or less of V, and 40% or more and 50% or less of Fe; and the W-Mo concentrated phase is formed so as to surround the Fe-BCC phase.

[0008] The Fe-based alloy as a whole preferably contains, by mass, C of 0.3% or more and 2.8% or less, Cr of 3.0% or more and 10.0% or less, W of 1.5% or more and 10.5% or less, Mo of 2.0% or more and 9.0% or less, V of 1.0% or more and 8.0% or less, with the balance being Fe and unavoidable impurity elements.

[0009] It is preferable that the material further contains either Si or Mn, or both, and that, in mass %, Si is 1.0% or less, and Mn is 0.1% or more and 1.0% or less.

[0010] It is desirable that the Fe-based alloy as a whole further contains, by mass%, 10.5% or less of Co, the Fe-BCC phase further contains 9% or more and 13% or less of Co, and the W-Mo concentrated phase further contains 6% or more and 11% or less of Co.

[0011] The W-Mo concentrated phase desirably has a lamellar structure or approximately annular precipitates.

[0012] According to the first invention, an alloy with excellent mechanical properties can be obtained. In addition, since the alloy has an Fe-BCC phase and a W-Mo concentrated phase, and the W-Mo concentrated phase is formed so as to surround the Fe-BCC phase, for example, when a die slides, the relatively soft Fe-BCC phase wears preferentially, and the worn portion is formed in a dimple shape. Oil such as lubricant is retained in the dimple-shaped portion, and the occurrence of adhesive wear can be suppressed. Therefore, the alloy has excellent wear resistance.

[0013] Such alloys can be obtained by forming metal powder of the desired composition using additive manufacturing (hereinafter referred to as metal additive manufacturing or simply additive manufacturing).

[0014] In addition, the W-Mo concentrated phase forms a lamellar structure or approximately annular precipitates, so that high mechanical properties and wear resistance can be obtained more reliably.

[0015] A second aspect of the present invention is an alloy member comprising at least a part of the Fe-based alloy according to the first aspect of the present invention.

[0016] The Fe-based alloy is preferably formed on the surface of a base material of an alloy part, the thickness of the surface layer from the interface of the base material to the surface of the Fe-based alloy being 0.1 to 2 mm, the hardness of the surface layer being 700 HV or more, and the average crystal grain size of the Fe-BCC phase being 3.0 μm or more.

[0017] The Fe-based alloy may be provided as an alloy member having at least one of a nitride layer, a compound layer, and a ceramic coating layer on a surface thereof.

[0018] According to the second aspect of the present invention, it is possible to obtain an alloy part which is excellent in mechanical properties and wear resistance.

[0019] Moreover, by forming an alloy layer made of the Fe-based alloy according to the first invention on the surface of the base material, a member having wear resistance on the surface can be obtained. Even if a part of the surface is damaged, for example, it can be easily repaired by forming an alloy layer again only on the damaged part by build-up, and an alloy member having excellent mechanical properties and excellent wear resistance can be obtained.

[0020] Furthermore, by further forming a nitride layer or the like on the surface, higher durability can be obtained.

[0021] A third invention is a manufactured product comprising, at least in part, the alloy part according to the second invention.

[0022] According to the third aspect of the present invention, a product having excellent mechanical properties and excellent wear resistance can be obtained.

[0023] Hot stamping dies, cold forging dies or cold pressing dies are particularly suitable for such production.

[0024] The fourth invention is a method for producing an alloy part, characterized in that an alloy powder containing, by mass%, C of 0.3% or more and 2.8% or less, Cr of 3.0% or more and 10.0% or less, W of 1.5% or more and 10.5% or less, Mo of 2.0% or more and 9.0% or less, V of 1.0% or more and 8.0% or less, with the balance being Fe and unavoidable impurities, is irradiated with an electron beam or a laser beam to melt and solidify the alloy powder to form a solidified layer, a new solidified layer is formed on the solidified layer, and then this operation is repeated to obtain an alloy part having a layered structure.

[0025] It is also preferable that the alloy powder further contains Co, and the Co content is 10.5% or less by mass.

[0026] The method may further include a surface treatment step of performing a surface treatment on the obtained alloy member, and the surface treatment step may be a nitriding treatment or film formation by a PVD method.

[0027] According to the fourth aspect of the present invention, it is possible to obtain an alloy part having excellent mechanical properties and excellent wear resistance.

[0028] Furthermore, by carrying out a surface treatment step of forming a nitride layer or the like on the surface, higher durability can be obtained. Effect of the Invention

[0029] According to the present invention, it is possible to provide an Fe-based alloy, an alloy member, a product, and a method for manufacturing an alloy member, which are excellent in both mechanical properties and wear resistance. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a laser additive manufacturing method. [Figure 2A] 4 is a photograph of the structure of the alloy part of the present invention after laser additive manufacturing. [Figure 2B] FIG. 2B is a microstructure photograph of the alloy member in FIG. 2A after tempering. [Figure 2C] FIG. 2B is a microstructure photograph of the alloy member in FIG. 2A after quenching. [Figure 2D] FIG. 2C is a microstructure photograph of the alloy part after tempering. [Figure 2E] A micrograph of the structure of forged material F0 after quenching and tempering. [Diagram 3] Elemental mapping image of the alloy member of the present invention after laser additive manufacturing. [Figure 4] A diagram showing HV0.5 of each alloy member. [Figure 5A] 13 is a photograph of the structure of an alloy part according to another embodiment of the present invention after laser additive manufacturing. [Figure 5B] FIG. 5B is a microstructure photograph of the alloy member in FIG. 5A after tempering. [Figure 5C] FIG. 5B is a microstructure photograph of the alloy member in FIG. 5A after quenching. [Figure 5D] FIG. 5C is a microstructure photograph of the alloy member after tempering. [Figure 5E] Microstructure photograph of the forged material F01 after quenching and tempering. [Figure 6] Element mapping image of the alloy member of the present invention after laser additive manufacturing.

Mode for Carrying Out the Invention

[0031] Hereinafter, an embodiment of the present invention will be described. First, the Fe-based alloy will be described, and then the additive manufacturing method will be described. In the following description, % represents mass%. In addition, in this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0032] <Fe-based alloy> The Fe-based alloy of this embodiment contains C, Cr, W, Mo, and V, and the balance consists of Fe and inevitable impurity elements, and has an alloy structure including an Fe-BCC phase and a W-Mo enriched phase. By mass%, in the Fe-BCC phase, C is 3% to 7%, Cr is 2% to 6%, W is 0.5% to 8%, Mo is 3% to 8%, V is 2 to 20%, and Fe is 60% to 90%. In the W-Mo enriched phase, C is 5% to 13%, Cr is 2% to 12%, W is 7% to 17%, Mo is 11% to 22%, V is 3% to 19%, and Fe is 40% to 50%. The W-Mo enriched phase is formed so as to surround the Fe-BCC phase.

[0033] In addition, the Fe-based alloy of this embodiment further contains Co of 10.5% or less by mass%. In the Fe-BCC phase, it is preferable that Co contains 9% or more and 13% or less. In the W-Mo enriched phase, it is preferable that Co contains 6% or more and 11% or less. More preferably, it is 3% to 11%, and even more preferably 6% to 10%.

[0034] In the Fe-based alloy of this embodiment, the W-Mo concentrated phase is continuously formed in a substantially annular shape, or the W-Mo concentrated phase is divided but arranged in a substantially annular shape, so that a structure in which the W-Mo concentrated phase surrounds the Fe-BCC phase can be obtained. In this way, a microscopically non-uniform structure, that is, a structure in which the W-Mo concentrated phase and the Fe-BCC phase are not completely mixed and a distribution occurs, is obtained. When this is made into a sliding surface, the relatively soft Fe-BCC phase wears preferentially over the relatively hard W-Mo concentrated phase, so that the Fe-BCC phase surrounded by the W-Mo concentrated phase wears in a dimple shape. However, the lubricating oil is held in this dimple-shaped portion, and the wear resistance can be improved. In addition, since such dimple-shaped portions are formed in a dispersed manner, the occurrence of adhesive wear can be suppressed.

[0035] The Fe-based alloy as a whole has, in mass%, C of 0.3% to 2.8%, Cr of 3.0% to 10.0%, W of 1.5% to 10.5%, Mo of 2.0% to 9.0%, V of 1.0% to 8.0%, Co of 10.5%, and the balance of Fe and inevitable impurity elements. It further contains either Si or Mn, or both, and it is preferable that, in mass%, Si is 1.0% or less and Mn is 0.1% to 1.0%. 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. On the other hand, it is preferable to set the above range in consideration of the influence of embrittlement due to quench cracking and residual γ.

[0036] In the alloy of this embodiment, the average grain size of the Fe-BCC phase is preferably 3.0 μm or more, and more preferably 5.0 μm or more. The Fe-BCC phase is a phase in which Fe in the BCC phase, C, Cr, W, Mo, V, and Co are in the component ranges described above. The method for calculating the average grain size of the Fe-BCC phase will be described later.

[0037] (W-Mo concentrated phase) The W-Mo enriched phase is a region where W and Mo are enriched compared to the Fe-BCC phase. The W-Mo enriched phase preferably forms a network-like lamellar structure or precipitates. The network-like lamellar structure and precipitates contain particularly large amounts of W and Mo. For example, the lower limit of the total amount of W and Mo (W+Mo) is preferably 15% or more, more preferably 20% or more, and even more preferably 26% or more. Also, the upper limit of the total amount of W and Mo (W+Mo) is preferably 60.0% or less, more preferably 52.0% or less, and even more preferably 45.0% or less. Further, for example, the lower limit of the ratio ((W+Mo) / Fe) of the total amount of W and Mo (W+Mo) to Fe in the W-Mo enriched phase is preferably 0.25 or more, more preferably 0.60 or more. The upper limit of the ratio ((W+Mo) / Fe) of the total amount of W and Mo (W+Mo) to Fe is preferably 2.50 or less, more preferably 2.40 or less.

[0038] The Fe-BCC phase is formed within a region surrounded by the network-like lamellar structure or substantially circular precipitates of the W-Mo enriched phase. That is, the W-Mo enriched phase is formed continuously in a substantially circular shape so as to surround the Fe-BCC phase (and other phases). The W-Mo enriched phase formed continuously in a substantially circular shape is often formed in a substantially circular shape with an equivalent circle diameter of about 10 μm, and preferably has an equivalent circle diameter of 5 μm to 20 μm.

[0039] The lower limit of the average crystal grain size of the Fe-BCC phase formed within the region surrounded by the W-Mo enriched phase is 3.0 μm, preferably 4.8 μm, and more preferably 5.0 μm. The upper limit is not particularly limited, but is 8.0 μm or less, preferably 6.5 μm or less, and more preferably 5.5 μm or less.

[0040] Note that the W-Mo enriched phase may not be completely continuous and may be segmented. For example, in the alloy of the present embodiment, when quenching treatment or quenching treatment and tempering treatment are performed, precipitates with a particle size of about 1 μm are formed by being arranged in a substantially circular shape with an equivalent circle diameter of 5 to 20 μm.

[0041] The precipitates with a grain size of about 1 μm are presumed to be carbide phases formed by the W-Mo concentrated phase being dissolved in the matrix by quenching, and carbide-forming elements such as V, W, and Mo being precipitated as carbides during the cooling process and tempering process after quenching. Even in this case, the W-Mo concentrated phase is not uniformly dispersed, but may be arranged in a predetermined direction so as to be substantially annular as a whole. This form is referred to as "formed to surround the Fe-BCC phase" or "formed substantially annular". The area surrounded by the W-Mo concentrated phase may have fine precipitates with a grain size of about 0.1 to 0.5 μm.

[0042] The carbide phase described above is a region in which V, Mo, and W are more concentrated than in the Fe-BCC phase, and where there is a large amount of C. An example of the composition of the carbide phase is, in mass%, 10% to 16% C, 1% to 5% Cr, 8% to 25% W, 13% to 23% Mo, 25% to 35% V, 0% to 5% Co, and 3% to 35% Fe.

[0043] Each structure can be evaluated using Energy-Dispersive X-ray Spectroscopy (EDS) and Electron Back Scattering Diffraction (EBSD) associated with a Scanning Electron Microscope (SEM). For example, a test piece used for analysis is prepared by embedding a part of the alloy in resin, and then polishing the cut surface of the embedded alloy to a mirror finish.

[0044] The analysis conditions may be, for example, an acceleration voltage of 15 kV in the SEM, a working distance from the objective lens to the observation surface of 10 mm, and an observation magnification of 3000 times. The element distribution evaluation method using EDS may be performed by obtaining an element mapping image by surface analysis in the same field of view of the SEM as described above. For example, when analyzing the W-Mo enriched phase, the target elements may be, for example, eight types of elements, C, Co, Cr, Fe, Mo, O, V, and W. The Fe-BCC phase can also be analyzed in the same manner as described above. The phase evaluation method using EBSD may be performed by obtaining a phase mapping image in a field of view of 200 μm × 200 μm at a magnification of 400 times.

[0045] (Average grain size of Fe-BCC phase) The average grain size of the Fe-BCC phase mentioned above can be calculated as follows. First, the phase map obtained by EBSD (e.g., RGB image, 200 x 200 μm) 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 and inverted (e.g., the original red portion (Fe-BCC phase) is displayed as black). After that, the Fe-BCC phase portion is segmented using the watershed method, and the grain size forming the Fe-BCC phase within the segmented field of view is calculated and averaged to calculate the average grain size forming the Fe-BCC phase (average grain size of the Fe-BCC phase).

[0046] Specifically, first, the phase map obtained by EBSD is divided into a red part (Fe-BCC phase), a blue part (mainly Fe-FCC phase), and a green part (part that is neither Fe-BCC phase nor Fe-FCC phase, hereinafter referred to as the zero solution part). By dividing the phase map in this way, the ratio of the Fe-BCC phase and precipitated carbides in the structure can be obtained. By displaying the image of the divided red part in black and white, the Fe-BCC phase is displayed in white. By inverting this black and white display, the blue and green parts are displayed in white. Here, when the total area is the sum of the areas of the red part, the blue part, and the green part, the value obtained by dividing the red part (Fe-BCC phase) by the total area can be rephrased as the area ratio.

[0047] The zero solution area can be displayed by subtracting the image of the divided blue area from this black and white inverted image. This zero solution area is neither the Fe-BCC nor Fe-FCC phase, and corresponds to the precipitated carbide area. After that, the average area of ​​the precipitated carbide area in the field of view is calculated, and the circle equivalent diameter of that area is calculated, so that the circle equivalent average grain size of the precipitated carbide in the Fe-BCC phase can be calculated.

[0048] (Inevitable impurities) 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. In the case of the alloy of this embodiment, the inevitable impurities specifically refer to, for example, Al, Cu, N, Ni, O, P, S, and Ti. Among these impurities, the impurities that should be particularly restricted are P, S, O, and N. In terms of mass%, P is preferably 0.03% or less, S is preferably less than 0.003%, O is preferably 0.02% or less, and N is preferably 0.05% or less. Of course, the content of these inevitable impurities is preferably low, and 0% is even better.

[0049] <Method of manufacturing alloy member> The Fe-based alloy of this embodiment uses an alloy powder, which is irradiated with an electron beam or a laser beam to melt and solidify to form a solidified layer, and a new solidified layer is formed on the solidified layer. This process is then repeated to obtain an alloy member having a layered structure. In other words, the alloy is manufactured by a so-called additive manufacturing method.

[0050] (Alloy powder) Here, the alloy powder is an Fe-based alloy powder containing the above-mentioned predetermined composition of C, Cr, W, Mo, V, and Co, with the balance being Fe and inevitable impurity elements. First, 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. For example, the raw material powder is loaded into a crucible, melted by high frequency, and the molten alloy is dropped from a nozzle under 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.

[0051] [Particle size] The additive manufacturing method is a manufacturing method in which individual powders are repeatedly melted and solidified to give them a shape. If the grain size of the alloy powder is less than 5 μm, it is difficult to obtain a volume required for one melting and solidification, making it difficult to obtain a sound additive manufacturing product. On the other hand, if the grain size of the alloy powder exceeds 250 μm, the volume required for one melting and solidification is too large, making it difficult to obtain a sound additive manufacturing product. Therefore, the grain size of the alloy powder is preferably 5 to 250 μm. More preferably, it is 10 μm to 150 μm. In addition, powder obtained by a gas atomization method that can obtain a spherical shape is preferable. In addition, the grain size of the powder may be measured by using, for example, a laser diffraction grain size distribution measuring device.

[0052] For example, by additive manufacturing method, the thickness is preferably 10 μm to 53 μm in the selective laser melting (SLM) method, and 45 μm to 105 μm in the electron beam melting (EBM) method. Also, the thickness is preferably 53 μm to 150 μm in the laser metal deposition (LMD) method, and more preferably 53 μm to 106 μm.

[0053] In addition, in an integrated distribution curve showing the relationship between particle diameter and volume integration from the small particle diameter side, obtained by laser diffraction method, when an integrated frequency of 50 volume % is defined as D50, D50 is preferably 50 μm to 100 μm, and more preferably 70 μm to 80 μm.

[0054] As described above, the Fe-based alloy powder preferably contains, by mass, 0.3% to 2.8% C, 3.0% to 10.0% Cr, 1.5% to 10.5% W, 2.0% to 9.0% Mo, 1.0% to 8.0% V, and the balance is Fe. It is also preferable that the powder further contains either one or both of Si and Mn. Note that, when Co is contained, the content may be 10.5% or less.

[0055] For example, an Fe-based alloy powder containing, in mass%, 0.3% to 2.8% C, more than 0% and not more than 1.0%, 0.1% to 1.0% Mn, 3.0% to 10.0% Cr, 1.5% to 10.5% W, 2.0% to 9.0% Mo, 1.0% to 8.0% V, and the balance being Fe and unavoidable impurity elements, can be used.

[0056] The Fe-based alloy powder may also contain Co. In this case, an Fe-based alloy powder containing 0.3% to 2.8% C, more than 0% and not more than 1.0% Si, 0.1% to 1.0% Mn, 3.0% to 10.0% Cr, 1.5% to 10.5% W, 2.0% to 9.0% Mo, 1.0% to 8.0% V, more than 0% and not more than 10.5% Co, and the balance being Fe and unavoidable impurity elements can be used.

[0057] The composition of the alloy powder can be analyzed, for example, by using inductively coupled plasma (ICP) emission spectrometry.

[0058] As an embodiment of the invention in which an electron beam or laser beam is irradiated and the material is melted and solidified to form a shape, methods such as Powder Bed Fusion (PBF) and Directed Energy Deposition (DED), which are additive manufacturing methods (referred to as additive manufacturing in this invention) for metal materials, can be applied.

[0059] FIG. 1 is a diagram showing the schematic configuration of an additive manufacturing apparatus 1 that performs additive manufacturing using a laser as a heat source in a directed energy deposition method. The additive manufacturing apparatus 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 injected into 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.

[0060] In additive manufacturing, alloy powder 11 is supplied onto a base plate 17 while a powder supply nozzle 3 is moved relative to the base plate 17 (direction A in FIG. 1 ). A laser beam 9 focused by a focusing lens 5 is irradiated onto the supplied alloy powder 11, and a molten pool 13 is formed in which the alloy powder 11 is melted, and the molten pool 13 is solidified to form a molded object 15 (Fe-based alloy). This process is repeated as necessary to stack the molded object 15 on the base plate 17, thereby forming a three-dimensional alloy part at least partially comprising an Fe-based alloy.

[0061] In the directed energy deposition method, alloy powder is sprayed onto a base material while moving it, and the sprayed alloy powder is irradiated with an electron beam or a laser beam to melt and solidify it to form a solidified layer, and a new solidified layer is formed on the solidified layer. This operation is then repeated to obtain an alloy member (modeled body) with a layered structure. Specifically, a three-dimensional additive manufacturing machine is used to rapidly melt the surface of a base plate or a modeled body by irradiating it with a laser, and raw material powder is supplied into the molten pool formed by the melting, and then rapidly cooled and solidified. This series of processes is repeated to produce a modeled body. The modeled body formed on the base plate is the Fe-based alloy of this embodiment. 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 modeled body, production efficiency, etc., and can be selected from the following ranges for the alloy of this embodiment.

[0062] The thickness of one layer in the additive manufacturing is, for example, 0.1 to 1.0 mm, and preferably 0.4 to 0.5 mm. The thickness of the first layer of Fe-based alloy formed on the surface of the base material (base plate) (thickness from the interface of the base material to the surface of the first layer of Fe-based alloy, including the diffusion layer near the interface) is 0.1 to 1 mm, and the total thickness from the interface of the base material to the surface of the Fe-based alloy (thickness including the diffusion layer near the interface) is 0.1 to 2 mm. 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.

[0063] The density of the energy input by laser irradiation to rapidly melt the raw material powder (energy density of the heat source: J / mm) is preferably 90 to 300 J / mm, more preferably 180 to 240 J / mm. If the energy density is too small, the defect rate increases, and furthermore, the supplied powder does not melt, making it difficult to maintain the shape of the molded body. On the other hand, if the energy density is too large, a wide range of the base plate or molded body centered on the laser irradiation position melts, and it also becomes difficult to maintain the shape of the molded body. The energy density E (J / mm) can be calculated from Equation 1 using the laser output P (W) and the laser scanning speed v (mm / min).

[0064] [Formula 1] E = P / v × 60 (1)

[0065] <Heat treatment> The alloy of this embodiment can be used as it is without heat treatment. This is the basic principle, but additional heat treatment may be performed within the allowable range of costs, etc. As the heat treatment, for example, only one of quenching and tempering, or both, may be performed. However, it is preferable to perform only tempering without performing high-temperature quenching.

[0066] As for the heat treatment conditions, for example, in the case of quenching, the material can 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 quenching cracks, it is more preferable to cool in oil. Quenching and cooling using a salt bath may be performed. Tempering is a heat treatment process in which the material is held at 400°C to 700°C, and it is preferable to hold the material at 560 to 580°C for 2 to 6 hours, and then cooled in air.

[0067] <Surface treatment> The obtained alloy member may be subjected to a surface treatment. The surface treatment process for performing the surface treatment on the alloy member includes, for example, nitriding or film formation by a PVD method on the surface layer of the Fe-based alloy to form a nitride layer, a compound layer, or a ceramic coating layer. When performing the surface treatment, it is sufficient to select at least one of the nitride layer, the compound layer, and the ceramic coating layer.

[0068] (Hardness) The hardness of the surface layer of the alloy member can be evaluated by Vickers hardness HV (hereinafter referred to as hardness), and is desirably 350HV or more, preferably 500HV or more, more preferably 700HV or more, even more preferably 800HV or more, and even more preferably 900HV or more. When no heat treatment is performed, 350HV or more is obtained, and preferably 500HV or more. When heat treatment is performed, 700HV or more is obtained, preferably 800HV or more, and more preferably 900HV or more is obtained.

[0069] The Vickers hardness HV can be measured, for example, by setting the indentation load of a Vickers indenter to 0.5 kg and the dwell time during indentation to 10 seconds, and determining the hardness from the diagonal length of the indentation formed on the measurement surface by indenting the indenter.

[0070] <Product> The product having at least a part of the alloy member thus obtained is not particularly limited, but is particularly suitable for hot stamping dies, cold forging dies, and cold press dies. In this case, even if a part of the surface of the die is damaged, the damaged part can be easily repaired by forming the alloy layer of the present invention by build-up. In this case, the Fe-based alloy according to this embodiment does not adhere and has excellent mechanical properties and wear resistance. EXAMPLES

[0071] (Experiment 1) In the example, a raw material was prepared by weighing and mixing the respective elements in a predetermined amount so as to obtain a shaped body of the desired composition, and the raw material was loaded into a crucible, melted by high frequency in a vacuum, and the molten alloy was dropped from a nozzle with a diameter of 5 mm under the crucible and sprayed with high pressure argon to produce a gas atomized powder. This gas atomized powder was classified to obtain an iron-based (Fe-based) alloy powder (raw material powder) with a size of 53 to 106 μm and a D50 of 71 μm. The composition of the obtained iron-based alloy powder is shown in Tables 1 and 2.

[0072] [Table 1]

[0073] [Table 2]

[0074] Next, using a 3D additive manufacturing machine with directed energy deposition (LASERTEC65 3D Hybrid manufactured by DMG Mori Seiki Co., Ltd.), the raw material powder was fed into a molten pool formed by laser irradiation on a base plate, and was rapidly melted and rapidly solidified to produce a molded object with a width of 3 mm, length of 80 mm, and a layer height of approximately 10 mm. The additive manufacturing conditions were as follows. Maraging steel (YAG 300 manufactured by Proterial Co., Ltd. (YAG is a registered trademark of Proterial Co., Ltd.)) was used for the base plate.

[0075] -Layer thickness when additive manufacturing: 0.45mm Laser beam diameter: approx. 3mm Laser power: 2400W Laser scanning speed: 600mm / s Energy density: 240J / mm

[0076] As the shaped bodies, those without heat treatment and those with heat treatment were evaluated. As the heat treatments, only tempering, only quenching, and quenching + tempering were evaluated. The shaped body with only shaping (without heat treatment) was designated as F1, the shaped body with only tempering was designated as F2, the shaped body with only quenching was designated as F3, and the shaped body with both quenching and tempering was designated as F4. Note that, as the heat treatment of the shaped body, the quenching treatment was carried out by holding at 1200°C for 0.5 hours and then cooling in oil. The tempering treatment was carried out by holding at 560°C for 4 hours and then air-cooling. Through such heat treatment, the shaped body of the Fe-based alloy according to this example was obtained.

[0077] The obtained shaped bodies F1 to F4 of the Fe-based alloy of each example were observed and evaluated using SEM and EDS. As the test piece for observation, a part of the shaped body was cut into small pieces and embedded in resin, and then the cut surface of the embedded shaped body was polished to a mirror finish. The observation magnification was 3000 times. Also, using EDS, an elemental mapping image was obtained with the same field of view as the SEM image at a magnification of 3000 times. The analysis elements were eight types: C, Co, Cr, Fe, Mo, O, V, and W.

[0078] Figures 2A to 2E show an example of the obtained SEM images. Figure 2A shows the shaped body F1 without heat treatment (no heat treatment), Figure 2B shows the shaped body F2 with tempering as the heat treatment, Figure 2C shows the shaped body F3 with only quenching as the heat treatment, Figure 2D shows the shaped body F4 with quenching + tempering as the heat treatment, and Figure 2E shows, for comparison, the structure of an alloy with the same composition but after sintering and forging the powder by the conventional powder metallurgy method and heat treatment (a sample with quenching + tempering. Hereinafter, this forged material is designated as F0). Figure 3 shows an example of the elemental mapping image (W, Mo, Fe, Cr) mapping obtained for the shaped body F1. The elemental mapping image had a field of view area of 46 μm × 35 μm and a magnification of 3000 times.

[0079] 2A to 2E, it was confirmed from SEM images that a mesh-like lamellar structure 50 exists in the molded body F1 that was not subjected to heat treatment as molded, and in the molded body F2 that was subjected to only tempering treatment after molding. It was also confirmed from the element mapping image of Fig. 3 that a structure containing Mo and W forms a mesh-like lamellar structure. Although the mesh-like lamellar structure and the gray region 52 surrounded by the W-Mo concentrated phase can be confirmed, it cannot be determined that the entire gray region 52 is the Fe-BCC phase. Therefore, the grain size of the Fe-BCC phase is calculated by the method described above.

[0080] As shown in Figures 2A and 3, the mesh-like lamellar structure can be observed as a striped pattern. From the element mapping image shown in Figure 3, it was confirmed that the mesh-like lamellar structure 50 observed as this striped pattern contains Fe, Mo, and W, and that a portion with a relatively low Fe element concentration and relatively high Mo and W element concentrations is adjacent to a portion with a relatively high Fe element concentration and relatively low Mo and W element concentrations, resulting in a structure that can be observed as a mesh. It was also confirmed that the lamellar structure 50 is a W-Mo concentrated phase in which W and Mo are concentrated compared to the portions other than the lamellar structure.

[0081] It was also confirmed that the formed body F1 had fine precipitates 56 with a grain size of about 0.1 to 0.5 μm inside the Fe-BCC phase 52 (inside the black frame in the figure) surrounded by a lamellar structure, i.e., a W-Mo concentrated phase. It was also confirmed from the element mapping image in FIG. 3 that these precipitates also contained Mo and W.

[0082] In the shaped body F3, which was subjected to quenching after shaping, and the shaped body F4, which was subjected to quenching and tempering, SEM images confirmed that precipitates 54 with a grain size of about 1 μm were arranged in rings with a circle equivalent diameter of 5 μm to 20 μm. Element mapping images were also obtained for the shaped bodies F3 and F4 in the same manner as for the shaped body F1, and the element mapping images confirmed that the precipitates 54 arranged in rings were a W-Mo concentrated phase containing Mo and W. In addition, fine precipitates 56 with a grain size of about 0.1 to 0.5 μm were present inside the Fe-BCC phase 52 (within the black frame in the figure) surrounded by precipitates 54 with a grain size of about 1 μm, and the element mapping images confirmed that these precipitates also contained Mo and W.

[0083] Table 3 shows the composition of each phase of the unheat-treated body F1. In FIG. 2A, the Fe-BCC phase was analyzed in part A, the W-Mo concentrated phase in part B, and the carbides in part C. As shown in Table 3, the W-Mo concentrated phase (part B) of body F1 contained 15.6% W and 14.5% Mo, and the total amount of W and Mo (W+Mo) was 30.1%. In addition, since Fe was 44.9%, the ratio of the total amount of W and Mo to Fe in the concentrated phase ((W+Mo) / Fe) was 0.67.

[0084] [Table 3]

[0085] The Fe-BCC phase was mainly composed of Fe, and contained Cr, W, Mo, V, Co, C, etc. within specified ranges. By measuring the electron diffraction pattern generated when the surface of the molded body sample was irradiated with an electron beam using EBSD, it was possible to determine that the Fe-BCC phase had a BCC structure.

[0086] Meanwhile, Table 4 shows the composition of each phase in the forged material F0. As in the case of the unheat-treated shaped body F1, the Fe-BCC phase was analyzed in part A, the W and Mo concentrated phase in part B, and the carbides in part C in Fig. 2E. As shown in Table 4, the W and Mo concentrated phase (part B) of the forged material F0 contained 30.5% W and 22.6% Mo, and the total amount of W and Mo (W+Mo) was 53.1%. As Fe was 22.1%, the ratio of the total amount of W and Mo to Fe in the concentrated phase ((W+Mo) / Fe) was 2.40.

[0087] [Table 4]

[0088] The Fe-BCC phase shows a composition similar to that of the shaped bodies of the examples, but the composition of the W and Mo concentrated phase of the forged material F0 is significantly different from that of the shaped bodies F1 to F4. That is, the W and Mo concentrated phase exists in the forged material F0, but the W and Mo concentrated phase in the forged material F0 has less Fe and more W and Mo than the shaped bodies F1 to F4. In addition, when focusing on V, which has a high carbide forming ability, the W-Mo concentrated phase of the shaped body F1 has 5.2%, while the W and Mo concentrated phase of the forged material F0 has 8.2%, so that the V of the forged material F0 has a higher concentration. From this, it is presumed that the formation of carbides is promoted in the W and Mo concentrated phase of the forged material F0 compared to the W-Mo concentrated phase of the shaped body F1 without heat treatment.

[0089] Therefore, the W, Mo concentrated phase of the forged material F0 is harder than, for example, the W-Mo concentrated phase in the unheat-treated molded body F1. In the forged material F0, as shown in FIG. 2E, this hard W-Mo concentrated phase is uniformly dispersed together with the Fe-BCC phase, so when this surface becomes a sliding surface, it wears uniformly, resulting in the oil film on the sliding surface being cut off, making it prone to adhesive wear.

[0090] Next, the average crystal grain size of the Fe-BCC phase was evaluated. Table 5 shows the results of calculating the average crystal grain size of the Fe-BCC phase for each of F1 to F4 and the forged material F0 using the method described above. As shown in Table 5, the average crystal grain size of the Fe-BCC phase was 5.28 μm for the shaped body F1 without heat treatment, 5.33 μm for the shaped body F2 that had been tempered, 4.65 μm for the shaped body F3 that had been quenched, and 4.57 μm for the shaped body F4 that had been quenched and tempered. The forged material F0 had a grain size of 5.17 μm.

[0091] [Table 5]

[0092] Generally, the mechanical properties are improved by making the structure finer and more uniform. Forged materials are obtained by sintering powder, forging, and then heat treating it to avoid weight segregation and obtain a uniform structure. With this method, as mentioned above, it is possible to obtain a structure in which the Fe-BCC phase is relatively small and the W-Mo concentrated phase and the Fe-BCC phase are uniformly dispersed even at the microscopic level.

[0093] On the other hand, in this embodiment, the W-Mo concentrated phase is continuously formed in a substantially annular shape like a lamellar structure, or the W-Mo concentrated phase is divided but arranged in a substantially annular shape, so that a structure in which the W-Mo concentrated phase surrounds the Fe-BCC phase can be obtained. In this way, a microscopically non-uniform structure (a structure in which the W-Mo concentrated phase and the Fe-BCC phase are not completely mixed and a distribution occurs) is obtained, but when this is used as a sliding surface, the relatively soft Fe-BCC phase wears preferentially over the relatively hard W-Mo concentrated phase, so that the Fe-BCC phase surrounded by the W-Mo concentrated phase wears into a dimple shape with a circle equivalent diameter of 3.0 μm or more. For this reason, the lubricating oil is held in the dimple-shaped part, and the wear resistance can be improved. In addition, since such dimple-shaped parts are formed in a dispersed manner, the occurrence of adhesion can be suppressed.

[0094] On the other hand, the forged material F0 has a high overall hardness as described above, but since the W-Mo concentrated phase and the Fe-BCC phase are uniformly dispersed, wear progresses approximately uniformly and simultaneously throughout. As a result, dimples and the like do not occur, and grease tends to run out, which may lead to adhesion. In this way, according to this embodiment, adhesion and the like can be efficiently suppressed.

[0095] [Hardness] The hardness of the resulting Fe-based alloy molded bodies F1 to F4 was measured using a Vickers hardness tester. The measurement conditions were a Vickers indenter pressing load of 0.5 kg and a dwell time of 10 seconds, and the hardness was calculated from the length of the diagonal line of the indentation formed on the measurement surface by pressing the indenter. Five measurements were taken, and the average value was calculated. The results are shown in Table 6, and a comparison with the forged material F0 is shown in Figure 4.

[0096] [Table 6]

[0097] It was confirmed that the molded body F1, which was not heat-treated as it was, exhibited a high hardness of 916HV. This is thought to be the effect of the mesh-like lamellar structure. In addition, it was confirmed that the molded body F2, which was only tempered after molding, had a hardness of 944HV, the molded body F3, which was quenched after molding, had a hardness of 983HV, and the molded body F4, which was quenched and tempered after molding, had a hardness of 946HV. The forged material F0, which was quenched and tempered, had the highest hardness, but since the forged material would have a hardness of less than half if quenching and tempering were not performed, it can be said that the molded body has a higher hardness. From the above, in this embodiment, regardless of whether or not heat treatment was performed, a sufficient hardness of 900HV or more could be obtained.

[0098] As described above, the shaped bodies F1 and F2 have a mesh-like lamellar structure and are expected to have high toughness. As shown in Fig. 2C and Fig. 2D, the shaped bodies F3 and F4 also have ring-shaped precipitates 54 containing Mo and W, which causes the Fe-BCC phase and precipitates 54 to be distributed unevenly. As a result, hard parts and relatively soft parts coexist in the structure, and thus the shaped bodies F3 and F4 are expected to have high toughness, similar to F1 and F2.

[0099] In the above-mentioned examples, the shaped bodies containing Co were evaluated, but Co is not necessarily essential. By including a certain amount of Co, high mechanical properties can be obtained without heat treatment, but as in Experiment 2 described later, even if the material does not contain Co, sufficient mechanical properties can be obtained by performing heat treatment such as quenching.

[0100] (Experiment 2) Next, a shaped body was produced using an iron-based alloy powder with the alloy composition shown in Table 7. As in Experiment 1, the raw materials were loaded into a crucible by weighing and mixing the respective elements in a predetermined amount so as to obtain a shaped body with the desired composition, and melted by high frequency in a vacuum. The molten alloy was dropped from a nozzle with a diameter of 5 mm below the crucible and sprayed with high pressure argon to produce a gas atomized powder. This gas atomized powder was classified to obtain an iron-based (Fe-based) alloy powder with a diameter of 53 to 106 μm and a D50 of 73 μm. Co was considered to be contained as an inevitable impurity element.

[0101] [Table 7]

[0102] Next, using a 3D additive manufacturing machine with a directed energy deposition method (LASERTEC65 3D Hybrid manufactured by DMG Mori Seiki Co., Ltd.), the raw material powder was fed into a molten pool formed by laser irradiation on a base plate, and was rapidly melted and rapidly solidified to produce a molded object with a width of 3 mm, length of 80 mm, and a layer height of approximately 10 mm. The additive manufacturing conditions were the same as those in Experiment 1 described above. Maraging steel (YAG 300 manufactured by Proterial Co., Ltd. (YAG is a registered trademark of Proterial Co., Ltd.)) was used for the base plate.

[0103] The shaped bodies were evaluated with and without heat treatment. The heat treatments evaluated were tempering only, quenching only, and quenching + tempering. The shaped body only (without heat treatment) was named F11, the shaped body only tempered F12, the shaped body only quenched F13, and the shaped body quenched and tempered F14. The heat treatment of the shaped bodies was the same as in Experiment 1, with the quenching treatment held at 1200°C for 0.5 hours and then cooled in oil. The tempering treatment was held at 560°C for 4 hours and then air cooled.

[0104] The obtained Fe-based alloy molded bodies F11 to F14 were observed and evaluated using SEM and EDS. The test pieces for observation were prepared by cutting a part of the molded body into small pieces, embedding them in resin, and polishing the cut surface of the embedded molded body to a mirror finish. The observation was performed at a magnification of 3000 times. In addition, an element mapping image was obtained using EDS at a magnification of 3000 times with the same field of view as the SEM image. Eight elements were analyzed: C, Co, Cr, Fe, Mo, O, V, and W.

[0105] 5A to 5E show examples of the acquired SEM images. FIG. 5A shows a shaped body F11 that was not subjected to heat treatment (no heat treatment), FIG. 5B shows a shaped body F12 that was subjected to tempering as heat treatment, FIG. 5C shows a shaped body F13 that was subjected to only quenching as heat treatment, FIG. 5D shows a shaped body F14 that was subjected to quenching + tempering as heat treatment, and FIG. 5E shows the structure of an alloy of the same composition, but sintered powder by a conventional powder metallurgy method, forged and pressed, and then subjected to heat treatment (quenching + tempering. Hereinafter, this forged material will be referred to as F01). FIG. 6 shows an example of element mapping image (W, Mo, Fe, Cr) acquired for the shaped body F11. The element mapping image had a field area of ​​46 μm × 35 μm and a magnification of 3000 times.

[0106] The grain size of the Fe-BCC phase was calculated by the method described above. As shown in Fig. 5A and Fig. 5B, the presence of a mesh-like lamellar structure 50 was confirmed from the SEM images of the molded body F11 that was not subjected to heat treatment as molded and the molded body F12 that was subjected to only tempering treatment after molding.

[0107] From the results of confirming the EDS surface analysis image, it was confirmed that this mesh-like lamellar structure 50 contains Fe, Mo, and W, and that a portion with a relatively low Fe element concentration and a relatively high Mo and W element concentration is adjacent to a portion with a relatively high Fe element concentration and a relatively low Mo and W element concentration, thereby forming a structure that can be observed as a mesh. It was also confirmed that the lamellar structure 50 is a W-Mo concentrated phase in which W and Mo are concentrated compared to the portion other than the lamellar structure. From the element mapping image shown in FIG. 6, it was also confirmed that the structure containing Mo and W was formed as a lamellar structure or a mesh.

[0108] As shown in FIG. 5C, which is an SEM image of the molded body F13 that was quenched after molding, and FIG. 5D, which is an SEM image of the molded body F14 that was quenched and tempered, it was confirmed that precipitates 54 with a grain size of about 1 μm to 2 μm were arranged in rings with an equivalent circle diameter of 5 μm to 20 μm. Furthermore, as a result of checking the EDS area analysis image, it was confirmed that the precipitates 54 were a W-Mo concentrated phase containing Mo and W. In addition, fine precipitates 56 with a grain size of about 0.1 to 0.5 μm were present, and it was confirmed from the results of the EDS area analysis image that these precipitates also contained Mo and W.

[0109] Table 8 shows the composition of each phase of the formed body F11 as an example. In FIG. 5A, the Fe-BCC phase was analyzed at part A, the W-Mo concentrated phase at part B, and the carbides at part C. As shown in Table 8, the W-Mo concentrated phase (part B) of the formed body F11 contained 7.9% W and 17.4% Mo, and the total amount of W and Mo (W+Mo) was 25.3%. In addition, since Fe was 43.0%, the ratio of the total amount of W and Mo to Fe in the concentrated phase ((W+Mo) / Fe) was 0.59.

[0110] [Table 8]

[0111] The Fe-BCC phase was mainly composed of Fe, with the contents of Cr, W, Mo, V, Co, C, etc. falling within the prescribed ranges. By measuring the electron diffraction pattern generated when the surface of the molded body sample was irradiated with an electron beam using EBSD, it was possible to determine that the Fe-BCC phase had a BCC structure.

[0112] Meanwhile, Table 9 shows the composition of each phase for the forged material F01. As in the case of the non-heat-treated shaped body F11, the Fe-BCC phase was analyzed in part A, the W-Mo concentrated phase in part B, and the carbides in part C in FIG. 5E. As shown in Table 9, the W-Mo concentrated phase (part B) of the forged material F01 contained 6.3% W and 10.6% Mo, and the total amount of W and Mo (W+Mo) was 16.9%. Since Fe was 48.1%, the ratio of the total amount of W and Mo to Fe in the concentrated phase ((W+Mo) / Fe) was 0.35.

[0113] [Table 9]

[0114] The Fe-BCC phase has a composition similar to that of the shaped bodies of the examples, but the forged material F01 has a different composition of the W-Mo concentrated phase compared to the shaped body F11. More specifically, the W-Mo concentrated phase in the forged material F01 has more Fe and less W and Mo compared to the shaped body F11.

[0115] Therefore, the W-Mo concentrated phase of the forged material F01 is harder than the W-Mo concentrated phase in the unheat-treated shaped body F11, for example. In the forged material F01, as shown in FIG. 5E, this hard W-Mo concentrated phase is uniformly dispersed with the Fe-BCC phase, so when this surface becomes a sliding surface, it wears uniformly without partially wearing into a dimple shape, which results in the oil film on the sliding surface being broken, making it prone to adhesive wear.

[0116] Next, the average grain size of the Fe-BCC phase was evaluated. Table 10 shows the results of calculating the average grain size of the Fe-BCC phase for each of F11 to F14 and the forged material F01 by the above-mentioned method. As shown in Table 10, the average grain size of the Fe-BCC phase of the shaped body F11 without heat treatment and the shaped body F12 with only tempering treatment was 5.34 μm for F11, 5.18 μm for F12, 5.05 μm for F13, and 4.84 μm for F14. The average grain size of the Fe-BCC phase of the forged material F01 was 4.62 μm. The proportion of precipitated carbides in F12 to F14 was 0.6% or more and 2.4% or less. The proportion of the Fe-BCC phase was 45.0% or more in F11 to F14, and the proportion of precipitated carbides precipitated in the Fe-BCC phase was 0.5% or more.

[0117] [Table 10]

[0118] Generally, the mechanical properties are improved by making the structure finer and more uniform. Forged materials are obtained by sintering powder, forging, and then heat treating it to avoid weight segregation and obtain a uniform structure. With this method, as mentioned above, it is possible to obtain a structure in which the Fe-BCC phase is relatively small and the W-Mo concentrated phase and the Fe-BCC phase are uniformly dispersed even at the microscopic level.

[0119] On the other hand, in this embodiment, the W-Mo concentrated phase is continuously formed in a substantially annular shape (lamellar structure), or the W-Mo concentrated phase is divided but arranged in a substantially annular shape, so that a structure in which the W-Mo concentrated phase surrounds the Fe-BCC phase can be obtained. Although this results in a microscopically non-uniform structure (a structure in which the W-Mo concentrated phase and the Fe-BCC phase are not completely mixed and are distributed), when this is used as a sliding surface, the relatively soft Fe-BCC phase wears preferentially over the relatively hard W-Mo concentrated phase, so that the Fe-BCC phase surrounded by the W-Mo concentrated phase wears into dimples with a circle equivalent diameter of 4.8 μm or more. Therefore, oil is retained in the dimple-shaped parts, and wear resistance can be improved. In addition, since such dimple-shaped parts are formed in a dispersed manner, the occurrence of adhesion can be suppressed.

[0120] On the other hand, the forged material F01 has a high hardness overall, but the W-Mo concentrated phase and the Fe-BCC phase are dispersed, so that wear progresses uniformly and simultaneously throughout the material. As a result, dimples and the like do not occur, and the oil film is easily broken, which may lead to adhesion. Thus, according to this embodiment, adhesion and the like can be efficiently suppressed.

[0121] [Hardness] The hardness of the resulting Fe-based alloy molded body was measured using a Vickers hardness tester. The measurement conditions were a Vickers indenter pressing load of 0.5 kg and a dwell time of 10 seconds, and the hardness was calculated from the length of the diagonal line of the indentation formed on the measurement surface by pressing the indenter. Five measurements were taken, and the average value was calculated. The results are shown in Table 11.

[0122] [Table 11]

[0123] The hardness of the molded body F11, which was not heat-treated after molding, was 360 HV, the hardness of the molded body F12, which was only tempered after molding, was 837 HV, the hardness of the molded body F13, which was hardened after molding, was 804 HV, and the hardness of the molded body F14, which was hardened and tempered after molding, was 748 HV.

[0124] As described above, the formed body F11, which was not subjected to heat treatment as it was formed, and the formed body F12, which was subjected to only tempering treatment after forming, had a mesh-like lamellar structure. As shown in Figures 5C and 5D, the formed body F13, which was subjected to quenching treatment after forming, and the formed body F14, which was subjected to quenching treatment and tempering treatment, also have ring-shaped precipitates 54 containing Mo and W, and the Fe-BCC phase and precipitates 54 are distributed unevenly. As a result, hard parts and relatively soft parts coexist in the structure, and it is expected that these will exhibit high toughness similar to F1 and F2.

[0125] In the above-mentioned examples, a shaped body containing Co was evaluated, but Co is not necessarily required. By containing a certain amount of Co, high mechanical properties can be obtained without heat treatment, but even if Co is not contained, sufficient mechanical properties can be obtained by performing heat treatment such as quenching. [Explanation of symbols]

[0126] 1. Additive manufacturing device 3: Powder supply nozzle 5. Focusing lens 7. Protective lens 9...Laser beam 11...Alloy powder 13. Molten pool 15……Sculptures 17...Base plate 50...Lamellar structure 52‥‥‥Fe-BCC phase 54‥‥‥Precipitate 56. Fine precipitates

Claims

1. In mass%, C is 0.3% or more and 2.8% or less, Cr is 3.0% or more and 10.0% or less, W is 1.5% or more and 10.5% or less, Mo is 2.0% or more and 9.0% or less, V is 1.0% or more and 8.0% or less, Si is 1.0% or less, Co is more than 0% and 10.5% or less, the balance being Fe and inevitable impurity elements, Fe-BCC phase and W-Mo concentrated phase are included, The alloy structure has an Fe-BCC phase ratio of 44.8% or more, the average crystal grain size of the Fe-BCC phase is 3.0 μm or more and 8.0 μm or less, The Fe-based alloy is characterized in that the W—Mo-enriched phase is continuous and annular or approximately annular with an equivalent circle diameter of 5 μm to 20 μm, and is formed so as to surround the Fe-BCC phase.

2. 2. The Fe-based alloy according to claim 1, wherein the W-Mo concentrated phase has a total amount of W and Mo (W+Mo) in mass % of 15% to 60%.

3. 2. The Fe-based alloy according to claim 1, wherein the W-Mo enriched phase has a lamellar structure and includes annular or approximately annular precipitates.

4. 2. The Fe-based alloy according to claim 1, wherein the C content is, in mass %, 1.30% to 2.8%.

5. 2. The Fe-based alloy according to claim 1, wherein the Mn content is 0.1% or more and 1.0% or less.

6. The Fe-based alloy according to claim 1, characterized in that the W-Mo concentrated phase has a ratio of the total amount of W and Mo to Fe ((W+Mo) / Fe) of 0.60 to 2.50%.

7. The Fe-based alloy according to claim 1, characterized in that the W-Mo concentrated phase has, in mass%, W of 7% or more and 17% or less, Mo of 11% or more and 22% or less, and Fe of 40% or more and 50% or less.

8. 2. The Fe-based alloy according to claim 1, characterized in that the surface is provided with at least one of a nitride layer, a compound layer, and a ceramic coating layer.

9. An alloy member comprising at least a portion of the Fe-based alloy according to any one of claims 1 to 8.

10. A manufactured product comprising at least a part of the alloy member according to claim 9.

11. 11. The article of manufacture according to claim 10, which is a hot stamping die, a cold forging die or a cold pressing die.

12. In mass%, C is 0.3% or more and 2.8% or less, Cr is 3.0% or more and 10.0% or less, W is 1.5% or more and 10.5% or less, Mo is 2.0% or more and 9.0% or less, V is 1.0% or more and 8.0% or less, Si is 1.0% or less, Co is more than 0% and 10.5% or less, Only alloy powder is used, with the balance being Fe and unavoidable impurities, The alloy powder is irradiated with an electron beam or a laser beam of 1500 to 2500 W to melt and solidify the alloy powder to form a solidified layer, and a new solidified layer is formed on the solidified layer. This process is then repeated to obtain a laminated structure. A method for producing an alloy member containing the following Fe-BCC phase and W-Mo concentrated phase: [a] The proportion of the Fe-BCC phase is 44.8% or more, [b] the average crystal grain size of the Fe-BCC phase is 3.0 μm or more and 8.0 μm or less; [c] The W--Mo concentrated phase has a lamellar structure, is continuous in an annular or approximately annular shape with an equivalent circle diameter of 5 μm to 20 μm, and is formed so as to surround the Fe-BCC phase.

13. The method for producing an alloy member according to claim 12, wherein the alloy powder further contains 0.1% to 1.0% of Mn.

14. The method for manufacturing an alloy member according to claim 12, characterized in that the C content is 1.30% or more and 2.8% or less by mass %.

15. The method for manufacturing an alloy member according to any one of claims 12 to 14, further comprising a surface treatment step of performing a surface treatment on the obtained alloy member, wherein the surface treatment step is a nitriding treatment or film formation by a PVD method.

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