Alloy molded body, manufactured article, and method for manufacturing alloy molded body

Abstract

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 a 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, 3-8% 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.

Description

Technical Field

[0001] The present invention relates to Fe-based alloys, alloy members, products, a method for manufacturing alloy members, and the like.

Background Art

[0002] Conventionally, for tools such as punches and dies for hot precision press working, hot work tool steels such as SKD8 defined in JIS G 4404 with high high-temperature strength and high-speed tool steels such as SKH51 defined in JIS G 4403 have been used. However, there has been a problem that they are prone to sagging, wear, breakage, cracking, and heat cracks.

[0003] For example, Patent Document 1 discloses a high-speed tool steel made by powder metallurgy in which, by mass ratio, C is 0.8 to 3.95%, the total amount of W and twice the amount of Mo is 30 to 50%, Cr is 3.0 to 5.0%, V is 1.0 to 10.0%, Co is 5 to 15%, and the balance is Fe and impurities. Patent Document 1 discloses a high-speed tool steel having excellent cutting durability with high wear resistance and high toughness by containing a large amount of retained carbides and uniformly and finely dispersing the retained carbides in the matrix during quenching.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since the tool steel of Patent Document 1 is formed by powder metallurgy, compared with the case of solidifying ordinary molten metal, primary crystal sedimentation, segregation, etc. are less likely to occur, and it is easy to form a uniform structure both microscopically and macroscopically. Generally, a uniform structure is effective for mechanical properties, and wear resistance can also be obtained by dispersing uniform carbides. However, when used for molds and the like, especially the sliding surface is prone to adhesive wear, 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 manufactured product, and a method for manufacturing an alloy member, which are excellent in mechanical properties and also excellent in wear resistance.

Means for Solving the Problems

[0007] To achieve the above-described object, a first invention includes C, Cr, W, Mo, and V, the balance being composed of Fe and inevitable impurity elements, includes an Fe-BCC phase and a W-Mo enriched phase, and has an alloy structure in which the proportion of the Fe-BCC phase is 44.8% or more. By mass, in the Fe-BCC phase, C is 3% or more and 7% or less, Cr is 2% or more and 6% or less, W is 0.5% or more and 8% or less, Mo is 3% or more and 8% or less, V is 2% or more 2.7 % or less and less than that of V in the W-Mo enriched phase, and Fe is 60% or more and 90% or less , the average crystal grain size of the Fe-BCC phase is 3.0 μm or more and 8.0 μm or less, The W-Mo enriched phase is an alloy shaped body made of an Fe-based alloy, characterized in that C is 5% or more and 13% or less, Cr is 2% or more and 12% or less, W is 7% or more and 17% or less, Mo is 11% or more and 22% or less, V is 3% or more and 19% or less, Fe is 40% or more and 50% or less, and the W-Mo enriched phase is formed so as to surround the Fe-BCC phase. The W-Mo enriched phase has a lamellar structure and is continuous in an annular or substantially annular shape with an equivalent circle diameter of 5 μm to 20 μm.

[0008] As for the entire Fe-based alloy, by 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, and the balance is composed of Fe and inevitable impurity elements .

[0009] Further contains either one or both of Si and Mn, and desirably, in terms of mass%, Si is 1.0% or less and Mn is 0.1% or more and 1.0% or less.

[0010] As the entire Fe-based alloy, in terms of mass%, further contains Co of 10.5% or less, the Fe-BCC phase further contains Co of 9% or more and 13% or less, and the W-Mo enriched phase further contains Co of 6% or more and 11% or less, which is desirable.

[0011] It is desirable that the W-Mo enriched phase has a lamellar structure or substantially circular precipitates.

[0012] According to the first invention, an alloy excellent in mechanical properties can be obtained. In addition, since it has an Fe-BCC phase and a W-Mo enriched phase, and the W-Mo enriched phase is formed so as to surround the Fe-BCC phase, for example, when the mold slides, the relatively soft Fe-BCC phase is preferentially worn, and the worn portion is formed into a dimpled shape. Oil such as lubricating oil is retained in the dimpled portion, and the occurrence of seizure wear can be suppressed. Therefore, it is excellent in wear resistance.

[0013] Such an alloy can be obtained by forming metal powder of a desired composition by an additive manufacturing method (hereinafter referred to as metal additive manufacturing or simply additive manufacturing).

[0014] In addition, since the W-Mo enriched phase forms a lamellar structure or substantially circular precipitates, higher mechanical properties and wear resistance can be obtained more reliably.

[0015] The first invention is an alloy characterized by comprising at least a part of the Fe-based alloy according to each of the above inventions formed body is.

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

[0017] The alloy member may be provided with one or more of a nitride layer, a compound layer, or a ceramic coating layer on the surface of the Fe-based alloy.

[0018] According to the first invention, an alloy excellent in mechanical properties and wear resistance formed body can be obtained.

[0019] Also, 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. Further, for example, even if a part of the surface is damaged, by re-forming the alloy layer only on the damaged part by overlaying, repair can be easily performed, and an alloy member excellent in mechanical properties and wear resistance can be obtained.

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

[0021] The second invention is a product characterized by comprising at least a part of the alloy according to the first invention. formed body is provided.

[0022] Second According to the invention, a product excellent in mechanical properties and wear resistance can be obtained.

[0023] As such a product, a die for hot stamping, a die for cold forging, or a die for cold pressing is particularly suitable.

[0024] The third invention is, in mass%, C is 1.30It is 2.8% or less and more than 0%, Cr is 10.0% or less and 3.0% or more, W is 10.5% or less and 1.5% or more, Mo is 9.0% or less and 2.0% or more, V is 8.0% or less and 1.0% or more, and the balance is an alloy powder composed of Fe and inevitable impurities. The alloy powder is irradiated with an electron beam or a laser beam of 1500~2 5 00W and melted and solidified to form a solidified layer, a new solidified layer is formed on the solidified layer, and this operation is repeated thereafter to obtain an alloy formed body having a laminated structure, and an Fe-based alloy having an alloy structure containing the following Fe-BCC phase and W-Mo enriched phase. A method for manufacturing an alloy formed body, characterized in that [a] The proportion of the Fe-BCC phase is 44.8%, [b] In mass%, the Fe-BCC phase has C of 7% or less and 3% or more, Cr of 6% or less and 2% or more, W of 8% or less and 0.5% or more, Mo of 8% or less and 3% or more, V of 2.7 % or less and less than that of V in the W-Mo enriched phase, Fe is 90% or less and 60% or more, the average crystal grain size of the Fe-BCC phase is 8.0 μm or less and 3.0 μm or more, [c] In mass%, the W-Mo enriched phase has C of 13% or less and 5% or more, Cr of 12% or less and 2% or more, W of 17% or less and 7% or more, Mo of 22% or less and 11% or more, V of [d] The W-Mo enriched phase forms a lamellar structure and is continuous in an annular or substantially annular shape with a circle equivalent diameter of 5 μm to 20 μm, and is formed so as to surround the Fe-BCC phase.

[0025] Further, the alloy powder further contains Co, and preferably, in mass%, the Co is 10.5% or less.

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

[0027] According to the third invention, an alloy excellent in mechanical properties and wear resistance can be obtained. formed body

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

Advantages of the Invention

[0029] According to the present invention, it is possible to provide an Fe-based alloy, an alloy member, a manufactured product, and a method for manufacturing an alloy member that are excellent in mechanical properties and also excellent in wear resistance.

Brief Description of the Drawings

[0030]

Figure 1

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Figure 2E

Figure 3

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Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 5E

Figure 6

Embodiments 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%. Also, 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 is composed of Fe and inevitable impurity elements, and has a microstructure including an Fe-BCC phase and a W-Mo enriched phase. In 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] Further, 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 case of the Fe-based alloy of this embodiment, since the W-Mo enriched phase is formed continuously in a substantially circular shape or the W-Mo enriched phase is segmented but arranged in a substantially circular shape, a structure in which the W-Mo enriched phase surrounds the Fe-BCC phase can be obtained. Microscopically, such a non-uniform structure, that is, a structure in which the W-Mo enriched phase and the Fe-BCC phase are not completely mixed and a distribution occurs. However, when this becomes the sliding surface, the relatively soft Fe-BCC phase preferentially wears against the relatively hard W-Mo enriched phase, so that the Fe-BCC phase surrounded by the W-Mo enriched phase wears in a dimple shape. However, lubricating oil is retained in this dimpled portion, and the wear resistance can be improved. Further, since such dimpled portions are formed dispersedly, the occurrence of adhesive wear can be suppressed.

[0035] Also, as for the entire Fe-based alloy, in terms of 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, Co is 10.5% or less, and the balance is composed of Fe and inevitable impurity elements. Further, it is desirable to further contain either one or both of Si and Mn, and in terms of mass%, Si is 1.0% or less and Mn is 0.1% or more and 1.0% or less. Si can be expected to improve oxidation resistance. It is desirable to set the above ranges in consideration of workability. Mn can be expected to improve wear resistance, hardenability, and reduce embrittlement. On the other hand, considering the influence of embrittlement due to burn cracking and residual γ, it is desirable to set the above ranges.

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

[0037] (W-Mo enriched 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 the equivalent circle diameter is 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. Also, the upper limit is not particularly limited, but it 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 this 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 precipitate with a particle size of about 1 μm is presumed to be a carbide phase in which the W-Mo enrichment phase once dissolves in the matrix by quenching, and carbide-forming elements such as V, W, and Mo precipitate as carbides during the cooling process or tempering process after quenching. Even in this case, it is only necessary that the W-Mo enrichment phase is not uniformly dispersed but is formed to be arranged in a predetermined direction so as to be substantially annular as a whole. Such a form shall be regarded as "formed so as to surround the Fe-BCC phase" or "formed in a substantially annular shape". Note that the region surrounded by the W-Mo enrichment phase may have fine precipitates with a particle size of about 0.1 to 0.5 μm.

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

[0043] Each structure can be evaluated using energy-dispersive X-ray spectroscopy (EDS) and electron backscattering diffraction (EBSD) attached to a scanning electron microscope (SEM). For example, as a test piece used for analysis, after embedding a part of the alloy in resin, a cut surface of the embedded alloy polished to a mirror surface is used.

[0044] As analysis conditions, for example, the acceleration voltage in SEM may be 15 kV, the working distance from the objective lens to the observation surface may be 10 mm, and the observation magnification may be 3000 times. The method for evaluating the element distribution using EDS may be to obtain an element mapping image by surface analysis in the same field of view of the above SEM. For example, when analyzing the W-Mo enrichment phase, the target elements may be, for example, 8 types including C, Co, Cr, Fe, Mo, O, V, and W. The Fe-BCC phase can also be analyzed in the same manner as above. The method for evaluating the phase using EBSD may be to obtain a phase mapping image of a field of view of 200 μm × 200 μm with a magnification of 400 times.

[0045] (Average crystal grain size of Fe-BCC phase) In addition, the average crystal grain size of the Fe-BCC phase described above can be calculated as follows. First, the phase map obtained by EBSD (for example, an RGB image, 200 × 200 μm) is divided into each color (red, green, blue), and only the Fe-BCC part is extracted. The noise of this image is removed by applying a filter, and it is binarized into black and white and the black and white of the image is inverted (for example, the original red part (Fe-BCC phase) is displayed in black). Then, using the Watershed method, the Fe-BCC phase part is segmented, and the crystal grain size forming the Fe-BCC phase in the segmented field of view is calculated and averaged to calculate the average crystal grain size forming the Fe-BCC phase (average crystal 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 (a part that is neither Fe-BCC phase nor Fe-FCC phase, hereinafter referred to as the zero-resolution part). By such a division operation of the phase map, the proportion of the Fe-BCC phase and the 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 part and the green part are displayed in white. Here, when the total area of the red part, the blue part, and the green part is defined as the total area, the value obtained by dividing the red part (Fe-BCC phase) by the total area can be rephrased as the area ratio.

[0047] By subtracting the image of the divided blue part from this black-and-white inverted image, the zero-resolution part can be displayed. This zero-resolution part is a part that is neither Fe-BCC phase nor Fe-FCC phase and corresponds to the part of the precipitated carbides. Then, by calculating the average area of the precipitated carbide part within the field of view and calculating the equivalent circle diameter of that area, the equivalent average particle diameter of the precipitated carbides in the Fe-BCC phase can be calculated.

[0048] (Inevitable impurities) Inevitable impurities refer to trace amounts of impurities that are mixed into the raw materials or caused by reactions with various members contacted during the manufacturing process and are technically difficult to remove. In the case of the alloy of this embodiment, specifically, inevitable impurities 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, N, etc. 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, it is preferable that the content of these inevitable impurities is less, and it is even better if it is 0%.

[0049] <Method for manufacturing an alloy member> The Fe-based alloy of this embodiment uses alloy powder, irradiates the alloy powder with an electron beam or a 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 operation to obtain an alloy member with a laminated structure. That is, it is manufactured by a so-called additive manufacturing method.

[0050] (Alloy powder) Here, the alloy powder is an Fe-based alloy powder containing C, Cr, W, Mo, V, and Co having the predetermined composition described above, with the balance being Fe and inevitable impurity elements. First, the feed materials of each element are weighed in a predetermined amount so as to obtain an alloy within a predetermined composition range, and these are mixed to produce a raw material powder. Atomized powder is obtained using this raw material powder. For example, the raw material powder is loaded into a crucible, melted by high-frequency melting, the molten alloy is dropped from a nozzle below the crucible, and sprayed with high-pressure argon to produce 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 that imparts a shape by repeating melting and solidification for each individual powder. However, if the particle size of the alloy powder is less than 5 μm, it becomes difficult to obtain the volume required for one-time melting and solidification, and it is difficult to obtain a sound additive manufactured product. On the other hand, if the particle size of the alloy powder exceeds 250 μm, the volume required for one-time melting and solidification is too large, and it is difficult to obtain a sound additive manufactured product. Therefore, the particle 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 the gas atomization method that can obtain a spherical shape is preferred. Also, regarding the particle size of the powder, for example, the particle size distribution may be measured using a laser diffraction particle size distribution measuring device.

[0052] Illustrated by additive manufacturing method, in the Selective Laser Melting (SLM) method, 10 μm to 53 μm is more preferable, and in the Electron Beam Melting (EBM) method, 45 μm to 105 μm is more preferable. Also, in the Laser Metal Deposition (LMD) method, it is good to be 53 μm to 150 μm, and more preferably 53 μm to 106 μm.

[0053] Also, in the cumulative distribution curve showing the relationship between the particle size and the volume integration from the small particle size side obtained by the laser diffraction method, when the cumulative frequency of 50 volume% is defined as D50, it is preferable that D50 is 50 μm to 100 μm, and more preferably 70 μm to 80 μm.

[0054] As described above, the Fe-based alloy powder preferably contains 0.3% to 2.8% of C, 3.0% to 10.0% of Cr, 1.5% to 10.5% of W, 2.0% to 9.0% of Mo, 1.0% to 8.0% of V by mass ratio, and the balance is preferably composed of Fe. Furthermore, it is preferable to contain either one or both of Si and Mn. When Co is contained, it can be 10.5% or less.

[0055] For example, by mass%, Fe-based alloy powders such as those with C being 0.3% to 2.8%, Si being more than 0% and 1.0% or less, Mn being 0.1% to 1.0%, Cr being 3.0% to 10.0%, W being 1.5% to 10.5%, Mo being 2.0% to 9.0%, V being 1.0% to 8.0%, and the balance being Fe and inevitable impurity elements can be used.

[0056] Also, as the Fe-based alloy powder, Co may be contained. In this case, Fe-based alloy powders with C being 0.3% to 2.8%, Si being more than 0% and 1.0% or less, Mn being 0.1% to 1.0%, Cr being 3.0% to 10.0%, W being 1.5% to 10.5%, Mo being 2.0% to 9.0%, V being 1.0% to 8.0%, Co being more than 0% and 10.5% or less, and the balance being Fe and inevitable impurity elements can be used.

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

[0058] As an embodiment of performing shaping by irradiating with an electron beam or a laser beam and melting and solidifying, methods such as a powder bed fusion method (PBF: Powder Bed Fusion) and a directed energy deposition method (DED: Directed Energy Deposition), which are additive manufacturing methods for metal materials (referred to as a layered manufacturing method in the present invention), can also be applied.

[0059] FIG. 1 is a diagram showing a schematic configuration of a layered manufacturing apparatus 1 for layered manufacturing using a laser as a heat source among directed energy deposition methods. The layered manufacturing apparatus 1 mainly includes a powder supply nozzle 3, a focusing lens 5, a protective lens 7, and the like. Alloy powder 11 is supplied to the powder supply nozzle 3 and is ejected from 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 layered manufacturing, while supplying the alloy powder 11 onto the base plate 17, the powder supply nozzle 3 is relatively moved with respect to the base plate 17 (in the direction A in FIG. 1). The supplied alloy powder 11 is irradiated with the laser beam 9 focused by the focusing lens 5 to form a molten pool 13 in which the alloy powder 11 is melted and solidified, thereby forming a shaped article 15 (Fe-based alloy). If necessary, this process is repeated to stack the shaped article 15 on the base plate 17, thereby shaping a three-dimensional alloy member having at least a part made of an Fe-based alloy.

[0061] In the directional energy deposition method, alloy powder is sprayed while moving on a substrate, and the sprayed alloy powder is irradiated with an electron beam or a laser beam to be melted and solidified to form a solidified layer. A new solidified layer is formed on the formed solidified layer, and this operation is repeated thereafter to obtain an alloy member (formed body) having a laminated structure. Specifically, using a three-dimensional laminating machine, the surface of a base plate or a formed body is rapidly melted by laser irradiation, raw material powder is supplied into the melted pool formed by melting, and rapid solidification is performed. A formed body is produced by repeating a series of processes. The formed body formed on the base plate is the Fe-based alloy of this embodiment. The lamination forming conditions are appropriately determined in consideration of the particle size and composition of the raw material powder, the size, shape, and characteristics of the formed body, the production efficiency, etc. For the alloy of this embodiment, it can be selected from the following ranges.

[0062] When laminating and forming, the thickness of one layer is, for example, 0.1 to 1.0 mm, 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) (the thickness including the diffusion layer near the interface from the interface of the base material to the surface of the first layer of Fe-based alloy) 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 (the thickness including the diffusion layer near the interface) is 0.1 to 2 mm. The beam diameter of the laser is preferably about 3 mm at the irradiated 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 energy density (energy density of heat source: J / mm) input by laser irradiation to rapidly melt the raw material powder is preferably 90 to 300 J / mm, more preferably in the range of 180 to 240 J / mm. If the energy density is too small, the defect rate will increase, and furthermore, the supplied powder will not melt, making it difficult to maintain the shape of the formed body. On the other hand, if the energy density is too large, a wide range of the base plate or the formed body centered on the laser irradiation position will melt, and it will also be difficult to maintain the shape of the formed body. The energy density E (J / mm) can be obtained from Equation 1 using the laser output P (W) and the laser scanning speed v (mm / min).

[0064] [Equation 1] E = P / v × 60 ···(1)

[0065] <Heat treatment> The alloy of this embodiment can be used as it is after being formed without performing heat treatment. Based on this, if it is within the allowable range such as cost, additional heat treatment may be performed. As the heat treatment, for example, only one of quenching treatment and tempering treatment, or both of them may be performed. However, it is preferable to perform only the tempering treatment without performing high-temperature quenching treatment.

[0066] As the heat treatment conditions, for example, in the case of quenching treatment, it can be held at 1180 to 1220 °C for 10 to 60 minutes and then cooled in oil or water. To prevent distortion and cracking, it is more preferable to cool in oil. Quenching and cooling using a salt bath may also be performed. The tempering treatment is a heat treatment step of holding at 400 °C or higher and 700 °C or lower. For example, it is preferably held at 560 to 580 °C for 2 to 6 hours and then air-cooled.

[0067] <Surface treatment> In addition, surface treatment may be performed on the obtained alloy member. The surface treatment process for performing surface treatment on the alloy member includes, for example, nitriding treatment or film formation by 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 surface treatment, any one or more of the nitride layer, the compound layer, or the ceramic coating layer may be selected.

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

[0069] As a method for measuring Vickers hardness HV, for example, the indentation load of the Vickers indenter is 0.5 kg, the dwell time during indentation is 10 seconds, and the hardness can be obtained from the length of the diagonal line of the indentation formed on the measurement surface by pressing the indenter.

[0070] <Product> The product having at least a part of the alloy member obtained in this way is not particularly limited, but is particularly suitable for, for example, 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 alloy layer of the present invention can be easily repaired by forming it only on the damaged part by build-up welding. At this time, the Fe-based alloy according to this embodiment does not cause adhesion, etc., has excellent mechanical properties, and also has excellent wear resistance.

Examples

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

[0072]

Table 1

[0073]

Table 2

[0074] Next, using a three-dimensional laminating rapid prototyping machine (LASERTEC65 3D Hybrid manufactured by DMG MORI SEIKI CO., LTD.) of the directed energy deposition method, the raw material powder was supplied to the molten pool formed by laser irradiation on the base plate, and rapidly melted and rapidly solidified to produce a shaped body with a width of 3 mm, a length of 80 mm, and a laminated height of about 10 mm. The laminating rapid prototyping conditions were as follows. Maraging steel (YAG (YAG is a registered trademark of Proterial Co., Ltd.) 300 manufactured by Proterial) was used for the base plate.

[0075] · Thickness of one layer during laminating rapid prototyping: 0.45 mm · Laser beam diameter: about 3 mm · Laser output: 2400 W · Laser scanning speed: 600 mm / s · Energy density: 240 J / mm

[0076] As the shaped bodies, those without heat treatment and those with heat treatment were evaluated. As the heat treatments, only annealing, only quenching, and quenching + annealing were evaluated. The shaped body with only shaping (without heat treatment) was designated as F1, the shaped body with only annealing was designated as F2, the shaped body with only quenching was designated as F3, and the shaped body with both quenching and annealing 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 annealing 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 analyzed elements were 8 types: C, Co, Cr, Fe, Mo, O, V, and W.

[0078] Figs. 2A to 2E show an example of the obtained SEM images. Fig. 2A shows the shaped body F1 without heat treatment (no heat treatment), Fig. 2B shows the shaped body F2 with annealing as the heat treatment, Fig. 2C shows the shaped body F3 with only quenching as the heat treatment, Fig. 2D shows the shaped body F4 with quenching + annealing as the heat treatment, and Fig. 2E shows, for comparison, the structure of an alloy with the same composition but obtained by sintering and forging powder by the conventional powder metallurgy method and then heat treatment (a sample with quenching + annealing. Hereinafter, this forged material is designated as F0). Fig. 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] Referring to FIGS. 2A to 2E, in the as-shaped body F1 that has not been heat-treated while maintaining the shape and the as-shaped body F2 that has only been annealed after shaping, it was confirmed from the SEM image that a network-like lamellar structure 50 exists. Even when looking at FIG. 3 showing the elemental mapping image, it was confirmed that the structure containing Mo and W forms a network-like lamellar structure. In addition, although the region 52 shown in gray surrounded by the network-like lamellar structure and the W-Mo enrichment phase can be confirmed, it cannot be determined that all of the region 52 shown in gray is the Fe-BCC phase. Therefore, the crystal grain size forming the Fe-BCC phase is calculated by the method described above.

[0080] As shown in FIGS. 2A and 3, the network-like lamellar structure can be observed in a striped pattern. From the elemental mapping image shown in FIG. 3, the network-like lamellar structure 50 observed in this striped pattern contains Fe, Mo, and W, and is arranged such that a portion with a relatively low Fe elemental concentration and relatively high Mo and W elemental concentrations is adjacent to a portion with a relatively high Fe elemental concentration and relatively low Mo and W elemental concentrations, so that it can be confirmed that it is a structure that can be observed in a network pattern. Also, it was confirmed that the lamellar structure 50 is a W-Mo enrichment phase in which W and Mo are enriched compared to the portions other than the lamellar structure.

[0081] Regarding the as-shaped body F1, it was confirmed that there are fine precipitates 56 with a particle size of about 0.1 to 0.5 μm inside the lamellar structure, that is, the Fe-BCC phase 52 (inside the black frame in the figure) surrounded by the W-Mo enrichment phase. Also, from the elemental mapping image in FIG. 3, it was confirmed that these precipitates also contain Mo and W.

[0082] In the formed body F3 that was quenched after shaping, and the formed body F4 that was quenched and tempered, it was confirmed from the SEM image that precipitates 54 with a particle size of about 1 μm were arranged in a circular shape with an equivalent circle diameter of 5 μm to 20 μm. For the formed body F3 and the formed body F4 as well, elemental mapping images were obtained in the same manner as for the formed body F1, and it was confirmed from the elemental mapping images that the precipitates 54 arranged in a circular shape were a W-Mo enriched phase containing Mo and W. Further, fine precipitates 56 with a particle size of about 0.1 to 0.5 μm were present inside the Fe-BCC phase 52 (inside the black frame in the figure) surrounded by the precipitates 54 with a particle size of about 1 μm, and it was confirmed from the elemental mapping images that these precipitates also contained Mo and W.

[0083] Table 3 shows the composition of each phase of the formed body F1 without heat treatment. In Fig. 2A, the Fe-BCC phase was analyzed in part A, the W-Mo enriched phase was analyzed in part B, and the carbide was analyzed in part C. As shown in Table 3, the W-Mo enriched phase (part B) of the formed body F1 contained 15.6% of W and 14.5% of Mo, and the total amount of W and Mo (W + Mo) was 30.1%. Further, since Fe was 44.9%, the ratio of the total amount of W and Mo to Fe ((W + Mo) / Fe) in the enriched phase was 0.67.

[0084]

Table 3

[0085] Further, the Fe-BCC phase mainly consisted of Fe, and Cr, W, Mo, V, Co, C, etc. were contained within a predetermined range. By measuring the electron diffraction pattern generated during electron beam irradiation on the surface of the formed body sample by EBSD, it was possible to ascertain 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 forging material F0 by 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 as-formed body F1 without heat treatment, 5.33 μm for the as-formed body F2 subjected to tempering treatment, 4.65 μm for the as-formed body F3 subjected to quenching treatment, and 4.57 μm for the as-formed body F4 subjected to quenching and tempering treatment. Further, the forging material F0 was 5.17 μm.

[0091]

Table 5

[0092] Generally, as a method for improving mechanical properties, refinement and homogenization of the structure are carried out. The forging material is obtained by sintering powder, forging it, and further performing heat treatment in order to avoid weight segregation and obtain a uniform structure. According to this method, as described above, a structure in which the Fe-BCC phase is relatively small and the W-Mo enrichment phase and the Fe-BCC phase are uniformly dispersed microscopically can be obtained.

[0093] On the other hand, in this example, since the W-Mo enrichment phase is formed continuously in a substantially annular shape like a lamellar structure, or the W-Mo enrichment phase is segmented but arranged in a substantially annular shape, a structure in which the Fe-BCC phase is surrounded by the W-Mo enrichment phase can be obtained. In this way, a microscopically non-uniform structure (a structure in which the W-Mo enrichment phase and the Fe-BCC phase are not completely mixed and a distribution occurs) is formed. However, when this becomes the sliding surface, the relatively soft Fe-BCC phase preferentially wears against the relatively hard W-Mo enrichment phase. Therefore, the Fe-BCC phase surrounded by the W-Mo enrichment phase wears in a dimple shape with a circle equivalent diameter of 3.0 μm or more. For this reason, lubricating oil is retained in this dimple-shaped portion, and the wear resistance can be improved. Further, since such dimple-shaped portions are dispersed and formed, the occurrence of adhesion can be suppressed.

[0094] On the one hand, as described above, the forging material F0 has a high overall hardness. However, since the W-Mo enriched phase and the Fe-BCC phase are uniformly dispersed, wear progresses simultaneously in a substantially uniform manner throughout. For this reason, dimples and the like do not occur, galling is likely to occur, and there is a risk of adhesion. Thus, according to this embodiment, adhesion and the like can be efficiently suppressed.

[0095] [Hardness] Using a Vickers hardness tester, the hardness of the obtained shaped bodies F1 to F4 of the Fe-based alloy was measured. The measurement conditions were such that the indentation load of the Vickers indenter was 0.5 kg and the dwell time during indentation was 10 seconds, and the hardness was determined from the length of the diagonal of the indentation formed on the measurement surface by the indentation of the indenter. The number of measurement points was 5, and the average value was obtained. The results are shown in Table 6, and a comparison with the forging material F0 is shown in FIG. 4.

[0096]

Table 6

[0097] It was confirmed that the as-shaped body F1, which had not been heat-treated, showed a high hardness of 916 HV. This is considered to be the effect of the network-like lamellar structure. Also, it was confirmed that the shaped body F2, which had only been annealed after shaping, had a hardness of 944 HV, the shaped body F3, which had been quenched after shaping, had a hardness of 983 HV, and the shaped body F4, which had been quenched and annealed after shaping, had a hardness of 946 HV. The forging material F0, which had been quenched and annealed, had the highest hardness. However, in the forging material, the hardness would be less than half without quenching and annealing. Therefore, it can be said that the shaped body has a higher hardness. From the above, in this embodiment, sufficient hardness of 900 HV or more could be obtained regardless of the presence or absence of heat treatment.

[0098] As described above, the formed bodies F1 and F2 have a mesh-like lamellar structure and can be expected to have high toughness. Further, as shown in FIGS. 2C and 2D, regarding the formed bodies F3 and F4 as well, due to the presence of the annular precipitates 54 containing Mo and W, the Fe-BCC phase and the precipitates 54 are unevenly distributed. As a result, since hard portions and relatively soft portions coexist in the structure, it can be expected to exhibit high toughness similar to F1 and F2.

[0099] In the above-described examples, formed bodies containing Co were evaluated, but Co is not necessarily essential. By containing a predetermined amount of Co, high mechanical properties can be obtained without performing heat treatment. However, as in Experiment 2 described later, even when Co is not contained, sufficient mechanical properties can be obtained by performing heat treatment such as quenching.

[0100] (Experiment 2) Next, formed bodies were produced using iron-based alloy powders having the alloy compositions shown in Table 7. Similar to Experiment 1, a raw material obtained by weighing and mixing supply materials of each element in a predetermined amount so as to obtain a formed body having the target composition was loaded into a crucible, melted by high frequency in a vacuum, and the molten alloy was dropped from a nozzle having a diameter of 5 mm below the crucible and sprayed with high-pressure argon to produce gas atomized powder. This gas atomized powder was classified to obtain an iron-based (Fe-based) alloy powder having a particle size of 53 to 106 μm and a D50 of 73 μm. Co is considered to be contained as an inevitable impurity element.

[0101]

Table 7

[0102] Next, using a three-dimensional layered manufacturing machine (LASERTEC65 3D Hybrid manufactured by DMG MORI SEIKI CO., LTD.) with a directed energy deposition method, raw material powder was supplied to a molten pool formed by laser irradiation on a base plate, and was rapidly melted and rapidly solidified to fabricate a formed body with a width of 3 mm, a length of 80 mm, and a laminated height of approximately 10 mm. The layered manufacturing conditions were the same as those in Experiment 1 described above. As the base plate, maraging steel (YAG (YAG is a registered trademark of Proterial Co., Ltd.) 300 manufactured by Proterial Co., Ltd.) was used.

[0103] As the formed bodies, those without heat treatment and those with heat treatment were evaluated. As the heat treatment, only annealing, only quenching, and quenching + annealing were evaluated. The formed body with only shaping (without heat treatment) was designated as F11, the formed body with only annealing was designated as F12, the formed body with only quenching was designated as F13, and the formed body with quenching and annealing was designated as F14. Note that for the heat treatment of the formed bodies, similar to the conditions in Experiment 1, for the quenching treatment, it was held at 1200 °C for 0.5 hours and then cooled in oil. For the annealing treatment, it was held at 560 °C for 4 hours and then air-cooled.

[0104] The obtained formed bodies F11 to F14 of the Fe-based alloy were observed and evaluated using SEM and EDS. As test pieces for observation, a part of the formed body was cut into small pieces, embedded in resin, and then the cut surface of the embedded formed 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 analyzed elements were eight types: C, Co, Cr, Fe, Mo, O, V, and W.

[0105] Figs. 5A to 5E show an example of the obtained SEM images. Fig. 5A shows the as-formed body F11 without heat treatment (no heat treatment), Fig. 5B shows the as-formed body F12 subjected to tempering as heat treatment, Fig. 5C shows the as-formed body F13 subjected only to quenching as heat treatment, Fig. 5D shows the as-formed body F14 subjected to quenching + tempering as heat treatment, and Fig. 5E shows, for comparison, a sample of an alloy with the same composition but sintered and forged by the conventional powder metallurgy method and subjected to heat treatment (quenching + tempering. Hereinafter, this forged material is referred to as F01). Fig. 6 shows an example of the obtained element mapping images (W, Mo, Fe, Cr) mapping of the as-formed body F11. The element mapping images had a field-of-view area of 46 μm × 35 μm and a magnification of 3000 times.

[0106] The crystal grain size forming the Fe-BCC phase was calculated by the method described above. Also, as shown in Figs. 5A and 5B, in the as-formed body F11 that was not heat-treated as-formed and the as-formed body F12 that was only subjected to tempering treatment after forming, it was confirmed from the SEM images that a network-like lamellar structure 50 exists.

[0107] From the results of confirming the EDS surface analysis images, this network-like lamellar structure 50 contains Fe, Mo, and W, and is arranged such that portions with a relatively low Fe element concentration and relatively high Mo and W element concentrations are adjacent to portions with a relatively high Fe element concentration and relatively low Mo and W element concentrations, so that it can be observed as a network-like structure. Also, it was confirmed that the lamellar structure 50 is a W-Mo enriched phase in which W and Mo are enriched compared to portions other than the lamellar structure. Looking at the element mapping images shown in Fig. 6, it was also confirmed that the tissue containing Mo and W is formed in a lamellar or network-like pattern.

[0108] As shown in Fig. 5C, which is an SEM image of the shaped body F13 after quenching treatment, and Fig. 5D, which is an SEM image of the shaped body F14 after quenching and tempering treatments, it was confirmed that precipitates 54 with a particle size of about 1 μm to 2 μm were arranged in a circular equivalent diameter of 5 μm to 20 μm in a ring shape. Also, as a result of confirming the EDS surface analysis image, it was confirmed that the precipitate 54 is a W-Mo enriched phase containing Mo and W. Further, fine precipitates 56 with a particle size of about 0.1 to 0.5 μm were present, and from the results of the EDS surface analysis image, it was confirmed that these precipitates also contain Mo and W.

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

[0110]

Table 8

[0111] Also, the Fe-BCC phase mainly consisted of Fe, and Cr, W, Mo, V, Co, C, etc. were within a predetermined range. By measuring the electron diffraction pattern generated during electron beam irradiation on the surface of the shaped body sample with EBSD, it was possible to grasp that the Fe-BCC phase has a BCC structure.

[0112] On the one hand, Table 9 shows the composition of each phase of the forged material F01. Similar to the case of the as-formed body F11 without heat treatment, in Fig. 5E, the Fe-BCC phase was analyzed in part A, the W-Mo enriched phase was analyzed in part B, and the carbide was analyzed in part C. Also, as shown in Table 9, the W-Mo enriched 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 ((W + Mo) / Fe) in the enriched phase was 0.35.

[0113]

Table 9

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

[0115] Therefore, the W-Mo enriched phase of the forged material F01 is harder than, for example, the W-Mo enriched phase in the as-formed body F11 without heat treatment. In the forged material F01, according to Fig. 5E, since this hard W-Mo enriched phase is uniformly dispersed with the Fe-BCC phase, when this surface becomes a sliding surface, it wears uniformly without partially wearing in a dimple shape. As a result, the oil film on the sliding surface breaks, and adhesive wear is likely to occur.

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

[0117]

Table 10

[0118] Generally, as a method for improving mechanical properties, refinement and homogenization of the structure are carried out. The forging material is obtained by sintering powder, forging it, and further performing heat treatment in order to avoid weight segregation and obtain a uniform structure. According to this method, as described above, a structure in which the Fe-BCC phase is relatively small and the W-Mo enriched phase and the Fe-BCC phase are uniformly dispersed microscopically can be obtained.

[0119] On the one hand, in this embodiment, the W-Mo enriched phase is continuously formed in a substantially circular shape (lamellar structure), or although the W-Mo enriched phase is segmented, it is arranged in a substantially circular shape. Therefore, a structure can be obtained in which the Fe-BCC phase is surrounded by the W-Mo enriched phase. Microscopically, such a non-uniform structure (a structure in which the W-Mo enriched phase and the Fe-BCC phase are not completely mixed and a distribution occurs) is formed. However, when this becomes the sliding surface, the relatively soft Fe-BCC phase preferentially wears against the relatively hard W-Mo enriched phase. As a result, the Fe-BCC phase surrounded by the W-Mo enriched phase wears in the form of dimples with a circular equivalent diameter of 4.8 μm or more. Therefore, oil is retained in this dimpled portion, and the wear resistance can be improved. In addition, since such dimpled portions are formed dispersedly, the occurrence of adhesion can be suppressed.

[0120] On the other hand, although the forging material F01 has a high hardness as a whole, since the W-Mo enriched phase and the Fe-BCC phase are dispersed, wear progresses substantially uniformly and simultaneously as a whole. For this reason, dimples or the like do not occur, oil film breakdown easily occurs, and there is a risk of adhesion. Thus, according to this embodiment, adhesion and the like can be efficiently suppressed.

[0121] [Hardness] The hardness of the obtained shaped body of the Fe-based alloy was measured using a Vickers hardness tester. The measurement conditions were as follows: the pressing load of the Vickers indenter was 0.5 kg, the dwell time during pressing was 10 seconds, and the hardness was determined from the length of the diagonal of the indentation formed on the measurement surface by pressing the indenter. The number of measurement points was 5, and the average value was obtained. The results are shown in Table 11.

[0122]

Table 11

[0123] The as-formed body F11 without heat treatment had a hardness of 360 HV, the as-formed body F12 with only tempering treatment after forming had a hardness of 837 HV, the as-formed body F13 with quenching treatment after forming had a hardness of 804 HV, and the as-formed body F14 with both quenching and tempering treatments after forming had a hardness of 748 HV.

[0124] As described above, the as-formed body F11 without heat treatment and the as-formed body F12 with only tempering treatment after forming had a reticular lamellar structure. Also, as shown in FIGS. 5C and 5D, for the as-formed body F13 with quenching treatment after forming and the as-formed body F14 with both quenching and tempering treatments, due to the presence of the annular precipitate 54 containing Mo and W, the Fe-BCC phase and the precipitate 54 were unevenly distributed. As a result, since hard and relatively soft parts coexist in the structure, it can be expected to exhibit high toughness similar to F1 and F2.

[0125] In the above-described embodiments, the as-formed bodies containing Co were evaluated, but Co is not necessarily essential. By containing a predetermined amount of Co, high mechanical properties can be obtained without heat treatment. However, even when Co is not contained, sufficient mechanical properties can be obtained by performing heat treatment such as quenching.

Explanation of Reference Numerals

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

Claims

1. An Fe-based alloy containing C, Cr, W, Mo, and V, with the balance consisting of Fe and unavoidable impurities In terms of mass percentage of the entire Fe-based alloy, C is 1.30% 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, Further containing either one or both of Si and Mn. In terms of mass percentage of the entire Fe-based alloy, Si is 1.0% or less and Mn is 0.1% or more and 1.0% or less, An alloy-shaped body composed of an Fe-based alloy in which the balance consists of Fe and unavoidable impurity elements, Containing an Fe-BCC phase and a W-Mo enriched phase, and having an alloy structure in which the proportion of the Fe-BCC phase is 44.8% or more, The Fe-BCC phase contains, in terms of mass percentage, C of 3% or more and 7% or less, Cr of 2% or more and 6% or less, W of 0.5% or more and 8% or less, Mo of 3% or more and 8% or less, V of 2% or more and 2.7% or less and less than that of V in the W-Mo enriched phase, and Fe of 60% or more and 90% or less. The average crystal grain size of the Fe-BCC phase is 3.0 μm or more and 8.0 μm or less, The W-Mo enriched phase contains, in terms of mass percentage, C of 5% or more and 13% or less, Cr of 2% or more and 12% or less, W of 7% or more and 17% or less, Mo of 11% or more and 22% or less, V of 3% or more and 19% or less, and Fe of 40% or more and 50% or less, The alloy-shaped body is characterized in that the W-Mo enriched phase forms a lamellar structure and is annular or substantially annular with an equivalent circle diameter of 5 μm to 20 μm and continuous, and is formed so as to surround the Fe-BCC phase.

2. In terms of mass percentage of the entire Fe-based alloy, further containing Co of 10.5% or less, The alloy-shaped body according to claim 1, wherein the Fe-BCC phase contains Co of 9% or more and 13% or less, and the W-Mo enriched phase contains Co of 6% or more and 11% or less.

3. The alloy-shaped body according to claim 1, wherein the W-Mo enriched phase has a lamellar structure and annular or substantially annular precipitates.

4. The alloy-shaped body according to claim 1, wherein the W-Mo enriched phase forms an annular or substantially annular continuous phase, and the Fe-BCC phase forms a dispersed phase and is arranged so as to be surrounded by the W-Mo enriched phase.

5. The Fe-based alloy is formed on the surface of the base material of the alloy member, the thickness of the surface layer from the interface between the base material and the Fe-based alloy to the surface of the Fe-based alloy is 0.1 to 2 mm, the hardness of the surface layer is 700 HV or more, and the average crystal grain size of the Fe-BCC phase is 3.0 μm or more. The alloy molded body according to claim 1, characterized in that.

6. The alloy molded body according to claim 1, characterized in that any one or more of a nitride layer, a compound layer, or a ceramic coating layer is provided on the surface of the Fe-based alloy.

7. A product characterized by comprising at least a part of the alloy molded body according to any one of claims 1 to 6.

8. The product according to claim 7, characterized in that it is a mold for hot stamping, a mold for cold forging, or a mold for cold pressing.

9. In mass%, C is 1.30% 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, Either one or both of Si and Mn are further included, and as the entire Fe-based alloy, in mass%, Si is 1.0% or less and Mn is 0.1% or more and 1.0% or less, Only an alloy powder composed of the balance Fe and inevitable impurities is used, The alloy powder is irradiated with an electron beam or a laser beam of 1500 to 2500 W to be melted and solidified to form a solidified layer, a new solidified layer is formed on the solidified layer, and this operation is repeated thereafter to obtain an alloy molded body having a laminated structure. A method for manufacturing an alloy molded body including the following Fe-BCC phase and W-Mo enriched phase. [a]The proportion of the Fe-BCC phase is 44.8% or more, [b]In mass%, the Fe-BCC phase has C of 3% or more and 7% or less, Cr of 2% or more and 6% or less, W of 0.5% or more and 8% or less, Mo of 3% or more and 8% or less, V of 2% or more and 2.7% or less and less than that of V in the W-Mo enriched phase, Fe of 60% or more and 90% or less, and the average crystal grain size of the Fe-BCC phase is 3.0 μm or more and 8.0 μm or less. [c]In mass%, the W-Mo enriched phase has C of 5% or more and 13% or less, Cr of 2% or more and 12% or less, W of 7% or more and 17% or less, Mo of 11% or more and 22% or less, V of 3% or more and 19% or less, and Fe of 40% or more and 50% or less. [d]The W-Mo enriched phase forms a lamellar structure and is continuous in an annular or substantially annular shape with a circle equivalent diameter of 5 μm to 20 μm and is formed so as to surround the Fe-BCC phase.

10. The method for manufacturing an alloy shaped body according to claim 9, further comprising Co in the alloy powder, wherein the Co is 10.5% or less by mass%.

11. The method for manufacturing an alloy shaped body according to claim 9 or 10, further comprising a surface treatment step of performing a surface treatment on the obtained alloy member, wherein the surface treatment step is nitriding treatment or film formation by a PVD method.

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