Molded article made of Ni-based alloy

Abstract

The purpose of the present invention is to provide a molded article which has high hardness that can be achieved with a short heat treatment time, and which is formed from an Ni-based alloy in which an alpha Cr phase and a gamma phase and / or a gamma'phase are precipitated in layers, and which does not contain particulate precipitates having a particle diameter of 400 nm or more in terms of an equivalent circle diameter.

Description

Technical Field

[0001] This invention relates to Ni-based alloy molded objects formed by molding methods such as three-dimensional additive manufacturing. Background Technology

[0002] NiCrAl alloys, exhibiting wear resistance and corrosion resistance, have long been used in engine parts and other applications. Examples of NiCrAl alloys include high-strength, heat-resistant Ni-based alloys with the following composition: by mass percent, containing C: 0.1% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr: 30–45%, and Al: 3.1–5%, with the balance consisting of unavoidable impurities and Ni, and strengthened through the combined precipitation of γ' and α phases (see Patent Document 1).

[0003] This alloy material attempts to achieve hardness by precipitating lamellar α-Cr and γ' phases.

[0004] In recent years, NiCrAl alloys have also been applied to metal additive manufacturing. As a metal laminate model using NiCrAl alloys, examples include Ni-based alloy products that use Ni-based alloy powder containing C: 0.3 to 1.0%, Cr: 36.0 to 50.0%, Al: 3.0 to 7.0%, with the balance consisting of Ni and unavoidable impurities (see Patent Document 2).

[0005] This alloy attempts to achieve hardness by adding C to the NiCrAl alloy to induce carbide formation.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2002-69557

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-188069

[0010] Non-patent literature 1: Electrical Steel, Vol. 77, No. 2, p. 134, Fig. 1 (a) Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] While these documents describe NiCrAl alloys that prioritize hardness and corrosion resistance, the precipitation of lamellar structures requires time. For example, in Patent Document 2, an aging time of approximately 16–20 hours is needed. Therefore, the time and cost of heat treatment present a manufacturing challenge.

[0013] Therefore, the problem to be solved by the present invention is to provide a model formed of a Ni-based alloy such as NiCrAl alloy, which has high hardness that can be achieved with a short heat treatment time.

[0014] Problem-solving methods

[0015] Through the results of our intensive research, we discovered that by directly aging a model obtained from Ni-based alloy powder such as NiCrAl alloy powder without solution treatment, the resulting Ni-based alloy model does not contain granular precipitates with a particle size of 400 nm or more in terms of equivalent circular diameter, and has a lamellar structure of γ phase and / or γ' phase and αCr phase, thus completing the present invention.

[0016] That is, the present invention provides the following shapes.

[0017] [1] A model made of a Ni-based alloy, wherein the αCr phase, γ phase and / or γ' phase are precipitated in layers, and the model does not contain granular precipitates with a particle size of 400 nm or more in terms of equivalent circular diameter.

[0018] [2] According to the shape described in [1], the original γ particle size is less than 100 μm.

[0019] [3] The shape according to [1] or [2], wherein the Rockwell hardness is 50.0 HRC or higher.

[0020] [4] The shape according to any one of [1] to [3], wherein the Vickers hardness is 513 HV or higher.

[0021] [5] The model according to any one of [1] to [4], wherein the Ni-based alloy has the following composition: by mass % Cr: 30.0 to 45.0%, Al: 2.5 to 5.0%, C: 0 to 0.2%, and balance: Ni and unavoidable impurities.

[0022] [6] A shape according to any one of [1] to [5], wherein the shape is a layered shape.

[0023] The effects of the invention

[0024] For molded objects obtained using Ni-based alloy powder (e.g., NiCrAl alloy powder), without solution treatment, a short-term (e.g., within 10 hours) aging treatment can be performed to obtain Ni-based alloy molded objects (e.g., NiCrAl alloy) with high hardness, such as a Rockwell hardness of 50.0 HRC or higher (especially 59.5 HRC or higher) and a Vickers hardness of 513 HV or higher (especially 700 HV or higher). Therefore, according to the present invention, it is possible to provide a molded object that has high hardness while having low energy costs in manufacturing.

[0025] According to the present invention, the precipitate of the αCr phase, γ phase and / or γ' phase in a layered manner, and without containing granular precipitates with a particle size of 400 nm or more in terms of equivalent circular diameter, can achieve high hardness such as Rockwell hardness of 50.0 HRC or more (especially 59.5 HRC or more) and Vickers hardness of 513 HV or more (especially 700 HV or more) without particularly impairing mechanical properties such as toughness. Attached Figure Description

[0026] Figure 1 The image shows the SEM image of the microstructure of the stacked model of the present invention, obtained by air cooling after holding the unheat-treated stacked model at 700°C for 4 hours.

[0027] Figure 2 The image shows the SEM image of the microstructure of the stacked model of the present invention, obtained by air cooling after holding the unheat-treated stacked model at 500°C for 8 hours.

[0028] Figure 3 This is a SEM image of the microstructure of a laminated object obtained by solution treatment (holding at 1150℃ for 30 minutes followed by water cooling) followed by holding at 500℃ for 2 hours and then air cooling. The arrows indicate the growth direction of the lamellars and show the cessation of lamellar growth due to granular precipitates. Detailed Implementation

[0029] The following describes the design of the present invention.

[0030] [Element]

[0031] The shapes of the present invention are formed from Ni-based alloys. The Ni-based alloys used in the present invention preferably have the following composition: Cr: 30.0–45.0%, Al: 2.5–5.0%, C: 0–0.2%, and the balance: Ni and unavoidable impurities. The types and contents of the added elements and the reasons for their limitations are as follows. Furthermore, the "%" in each component indicates mass percentage.

[0032] First, let's explain Ni, which is the main component, and Cr and Al, which must be added to it.

[0033] Ni

[0034] Ni is a component that can produce materials with excellent corrosion resistance, strength, and toughness, so the alloys used in this invention are based on Ni.

[0035] Cr：30.0～45.0%

[0036] Cr is a necessary forming element for lamellar formation. When Ni-based alloys containing a specified amount of Cr are aged, the αCr phase, along with the γ and / or γ' phases, precipitates in layers, contributing to increased strength and hardness. Furthermore, Cr forms a protective film on the material surface under various corrosive environments, significantly improving resistance to high-temperature corrosion.

[0037] When the Cr content is too low, it is impossible to stably form lamellar structures throughout the entire tissue area through aging treatment, resulting in reduced hardness. Therefore, the Cr content is preferably 30.0% or more. More preferably, it is 33.0% or more, and even more preferably, it is 36.0% or more.

[0038] On the other hand, if the amount of Cr is excessive, the amount of Ni will be relatively small, resulting in insufficient precipitation of the γ' phase. Therefore, the amount of Cr is preferably 45.0% or less. More preferably, the amount of Cr is 42.0% or less, and even more preferably, it is 40.0% or less. These upper limits can be arbitrarily combined with the lower limits mentioned above.

[0039] Al：2.5～5.0%

[0040] Al is a forming element required for lamellar formation. Furthermore, Al forms Ni3Al (γ' phase) through aging treatment. In NiCrAl alloys, the αCr phase precipitates lamellarly with the γ and / or γ' phases, forming a lamellar structure and achieving high hardness. Additionally, Al contributes to improved high-temperature corrosion resistance and oxidation resistance. To achieve these effects, the Al content is preferably 2.5% or more. More preferably, it is 3.0% or more, and even more preferably 3.5% or more.

[0041] On the other hand, if the Al content is excessive, solidification cracks are likely to occur during molding. Therefore, the Al content is preferably 5.0% or less. More preferably, the Al content is 4.5% or less, and even more preferably 4.0% or less. These upper limits can be arbitrarily combined with the lower limits mentioned above.

[0042] C：0～0.2%

[0043] The Ni-based alloy used in this invention may contain carbon (C) as an additional component, in addition to Ni, Cr, and Al. The C content can be 0% or higher, but is preferably 0.2% or less. C forms carbides, which contribute to the high hardness of the material; however, excessive C content leads to coarse carbides that degrade the material's toughness. Therefore, even when C is present as an impurity, the C content is preferably 0.2% or less. More preferably, the C content is 0.1% or less, and even more preferably 0.03% or less.

[0044] The Ni-based alloys used in this invention may contain one or more elements selected from C, Si, Mn, Fe, Co, Mo, P, S, O and N as unavoidable impurities.

[0045] [The αCr phase, γ phase, and / or γ' phase precipitate in layers, and do not contain particulate precipitates with a particle size greater than 400 nm in terms of equivalent circular diameter.]

[0046] The shaped article of the present invention is characterized in that the αCr phase and the γ phase and / or the γ' phase precipitate in layers, and does not contain particulate precipitates with a particle size of 400 nm or more in terms of equivalent circumference. The layered precipitation of the αCr phase and the γ phase and / or the γ' phase, and the absence of particulate precipitates with a particle size of 400 nm or more in terms of equivalent circumference, can be confirmed by the method described in the embodiments.

[0047] When the αCr and γ phases, or the αCr and γ' phases, or the αCr, γ, and γ' phases precipitate in layers, forming a lamellar structure, high hardness can be obtained. Moreover, the smaller the lamellar spacing, the higher the hardness; therefore, fine lamellar spacing is desirable.

[0048] The molded article of the present invention is obtained by subjecting an aging treatment to a molded article (sometimes referred to in this specification as "unheat-treated molded article" or "molded article before aging treatment"). When an aging treatment is performed on an unheat-treated molded article, the αCr phase, γ phase, and / or γ' phase precipitate in layers, resulting in lamellar growth. If the molded article comes into contact with coarse granular precipitates, the growth of lamellar structure is hindered, thus preventing the granular precipitates from becoming coarse is more advantageous. Therefore, it is preferable that the unheat-treated molded article does not contain granular precipitates with a particle size of 400 nm or more in terms of equivalent circle diameter. Because solution treatment of the unheat-treated molded article causes the growth of granular precipitates, performing aging treatment on the unheat-treated molded article without solution treatment can suppress the growth of lamellar structure caused by coarse granular precipitates, achieving excellent age-hardness. As a result of the absence of granular precipitates with a particle size of 400 nm or more in the untreated molded article, the molded article of the present invention also does not contain granular precipitates with a particle size of 400 nm or more in the equivalent circumference. In the molded article of the present invention, because the αCr phase, γ phase and / or γ' phase precipitate in layers and there are no granular precipitates with a particle size of 400 nm or more in the equivalent circumference, mechanical properties such as toughness are not further impaired, and high hardness such as Rockwell hardness of 50.0 HRC or more (especially 59.5 HRC or more) and Vickers hardness of 513 HV or more (especially 700 HV or more) can be achieved.

[0049] [The original γ particle size was less than 100 μm]

[0050] Traditionally, the initial gamma particle size is around 400 μm (refer to Non-Patent Literature 1). However, metal additive manufacturing and other molding processes are suitable for obtaining molded objects with a fine initial gamma particle size before aging treatment, allowing the initial gamma particle size of the molded object before aging treatment to be 100 μm or less. If the initial gamma particle size of the molded object before aging treatment is 100 μm or less, the time required for the precipitation of lamellar structures can be accelerated during aging treatment. Therefore, it is preferable that the initial gamma particle size of the molded object before aging treatment is 100 μm or less. The initial gamma particle size of the molded object before aging treatment is also maintained after aging treatment. Therefore, when the initial gamma particle size of the molded object before aging treatment is 100 μm or less, the initial gamma particle size of the molded object after aging treatment (i.e., the molded object of the present invention) is also 100 μm or less.

[0051] [powder]

[0052] The molding process uses Ni-based alloy powder. The Ni-based alloy constituting the Ni-based alloy powder is explained above. The Ni-based alloy powder used for molding should ideally be approximately spherical, have excellent flowability, and be able to fill without gaps; therefore, gas-atomized powder is preferred. The average particle size of the Ni-based alloy powder, converted to volume average particle size (D50), is preferably 10–100 μm. D50 is the particle size at the point where the cumulative volume reaches 50% in the cumulative frequency distribution curve, which is calculated using the total volume of the powder as 100%. D50 is measured by laser diffraction scattering. A suitable device for this measurement is the "Microtrac MT3000" laser diffraction scattering particle size distribution measuring device from Nikkiso Corporation. The particle size can be detected based on the light scattering information of the particles by pouring the powder and pure water into the sample cell of the device.

[0053] [modeling]

[0054] The molded object before aging treatment is made from Ni-based alloy powder containing Cr and Al, through a process involving rapid melting and rapid solidification. The material of the molded object before aging treatment is a Ni-based alloy containing Cr and Al. By subjecting the molded object to aging heat treatment, a lamellar microstructure with αCr phase, γ phase, and / or γ' phase arranged in a layered manner can be obtained.

[0055] Methods for fabricating molded objects before aging treatment include, for example, rapid melting and solidification processes involving the melting and solidification of metal powder. Specific examples of such processes include three-dimensional additive manufacturing, thermal spraying, laser cladding, and welding. Molded objects before aging treatment (and consequently, molded objects after aging treatment, i.e., the molded objects of this invention) are preferably layered molded objects fabricated using three-dimensional additive manufacturing. Specific examples of three-dimensional additive manufacturing include powder-bed bonding and directional energy deposition (powder deposition). Specific examples of powder-bed bonding include selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM). In particular, the Ni-based alloy powder of this invention is suitable for three-dimensional additive manufacturing using the powder-bed bonding method, enabling the high-density formation of large-sized molded objects.

[0056] Three-dimensional additive manufacturing methods, such as those using 3D printers, can be employed. In powder-bed additive manufacturing, the Ni-based alloy powder of this invention is irradiated with a laser beam or electron beam.

[0057] Upon irradiation, the particles are rapidly heated and melted. The molten particles then solidify rapidly. Through this melting and solidification, the particles bond together. Irradiation is selectively applied to a portion of the laid Ni-based alloy powder. Unirradiated portions of the powder do not melt. A bonding layer forms only in the irradiated areas.

[0058] A thin layer of Ni-based alloy powder is then deposited on top of the bonding layer. A portion of this Ni-based alloy powder is irradiated with a laser beam or electron beam. Upon irradiation, the particles rapidly melt. The molten particles then rapidly solidify. Through this melting and solidification process, the particles in the powder bond together to form a new bonding layer. This new bonding layer also bonds with the existing bonding layer.

[0059] Through repeated irradiation, the resulting bonding layers gradually grow into an aggregate. This growth process yields a layered structure with a three-dimensional shape. This additive manufacturing method allows for the easy creation of layered structures with complex shapes.

[0060] [Heat Treatment]

[0061] The untreated molded object obtained by molding using Ni-based alloy powder is not used directly, but undergoes an aging process to obtain the molded object of the present invention with the desired characteristics.

[0062] When NiCrAl alloys are used in traditional processes such as forging, they are generally solution treated at temperatures above 1100°C. However, the inventors have discovered that when creating untreated molded objects using molding methods such as three-dimensional additive manufacturing as described in this invention, excellent mechanical properties can be achieved by omitting the solution treatment of the untreated molded objects and directly performing aging treatment on them.

[0063] When aging untreated molded objects, heat treatment at temperatures below 600°C reduces the lamellar spacing between the αCr phase and the γ and / or γ' phases, resulting in molded objects with high hardness. The aging temperature is preferably below 600°C, more preferably below 585°C, further preferably below 540°C, and most preferably below 500°C. The lower limit is not particularly limited; for example, it can be above 400°C or above 450°C. These lower limits can be arbitrarily combined with the aforementioned upper limits.

[0064] When aging untreated molded objects, energy costs can be reduced by shortening the aging time. The aging time is preferably 10 hours or less, more preferably 8 hours or less, further preferably 4 hours or less, and most preferably 2 hours or less. The lower limit is not particularly limited; for example, it can be 0.5 hours or more, or 1 hour or more. These lower limits can be arbitrarily combined with the aforementioned upper limits.

[0065] [Laminar morphology]

[0066] Lamellar structures of αCr, γ and / or γ' phases precipitate out by aging the untreated molded object. Figure 1 The image shows a SEM image of the microstructure of the laminated model of the present invention, obtained by air cooling after holding the unheat-treated laminated model at 700°C for 4 hours. It can be seen that when aging is performed at 700°C, lamellar layers of tens of nm in size are formed. Figure 2 The image shows a SEM image of the microstructure of the laminated model of the present invention, obtained by air cooling after holding the unheat-treated laminated model at 500°C for 8 hours. It can be seen that when aging is performed at 500°C, the lamellar spacing is much finer compared to the case where aging is performed at 700°C, resulting in a very fine microstructure.

[0067] Since the smaller the interlamellar spacing, the higher the hardness, it is preferable to perform aging treatment at low temperature to induce the precipitation of fine lamellar layers.

[0068] [Area ratio of particulate precipitates]

[0069] Figure 3 The image shows a SEM image of the microstructure of a laminated model obtained after solution treatment (held at 1150°C for 30 minutes followed by water cooling), then held at 500°C for 2 hours, and subsequently air-cooled. It can be seen that coarse granular precipitates with a particle size greater than 400 nm occur after solution treatment. EDS analysis shows that the granular precipitates are Cr-rich, presumably representing the α-Cr phase. The lamellars grow in the direction indicated by the arrows in the image, but lamellar growth is hindered at the contact points between the coarse granular precipitates and the leading edges of the growing lamellars.

[0070] Coarse granular precipitates hinder the growth of lamellar plates, increasing the time required for the precipitation reaction to complete (full lamellar precipitation), thus incurring additional energy costs from heat treatment. Therefore, it is preferable to prevent the precipitation of coarse granular precipitates. The occurrence of coarse granular precipitates can be avoided by avoiding solution treatment and / or avoiding prolonged aging treatment. In the shaped article of the present invention, the area fraction of granular precipitates with a particle size of 400 nm or more in terms of equivalent circumference diameter is preferably 0.0%. The area fraction of granular precipitates with a particle size of 400 nm or more in terms of equivalent circumference diameter can be measured by the method described in the embodiments.

[0071] [Original γ particle size]

[0072] In NiCrAl alloys, the lamellae precipitate out from the grain boundaries in a cellular manner. Therefore, the finer the structure, the faster the precipitation reaction is completed, which is preferred.

[0073] The original gamma particle size of the sculpted object before and after aging treatment (i.e., the sculpted object of the present invention) is preferably 100 μm or less, more preferably 90 μm or less, further preferably 80 μm or less, and most preferably 70 μm or less. The lower limit is not particularly limited; for example, it can be 5 μm or more, or 20 μm or more. These lower limits can be arbitrarily combined with the aforementioned upper limits. The original gamma particle size can be measured by the method described in the embodiments. The original gamma particle size is analyzed by EBSD (electron backscatter diffraction) in the microstructure of the sculpted object after aging treatment; therefore, in the embodiments, the original gamma particle size is measured using the microstructure of the sculpted object before aging treatment. The original gamma particle size of the sculpted object before aging treatment can also be maintained after aging treatment; therefore, the original gamma particle size measured using the microstructure of the sculpted object before aging treatment can be considered as the original gamma particle size of the sculpted object after aging treatment.

[0074] [hardness]

[0075] NiCrAl alloys are used in bearing parts and engine parts, so high hardness is desirable.

[0076] Therefore, the Rockwell hardness of the molded articles of the present invention is preferably 50.0 HRC or higher, more preferably 60.0 HRC or higher, even more preferably 61.0 HRC or higher, and most preferably 62.0 HRC or higher. The upper limit is not particularly limited, for example, it is 65.0 HRC or lower. The Rockwell hardness can be measured by the method described in the embodiments.

[0077] Furthermore, the Vickers hardness of the molded articles of the present invention is preferably 513 HV or higher, more preferably 700 HV or higher, even more preferably 750 HV or higher, and most preferably 790 HV or higher. There is no particular limitation on the upper limit, for example, it can be 850 HV or lower. The Vickers hardness can be measured by the method described in the embodiments.

[0078] Example

[0079] [powder]

[0080] Table 1 shows the chemical composition of the Ni-based alloy powders used in the examples and comparative examples. After the Ni-based alloy powders were prepared by vacuum melting and inert gas atomization, they were graded using a sieve with a mesh size of -63 μm. The undersize particles were used as Ni-based alloy powders for additive manufacturing. "-63 μm" indicates a mesh size of less than 63 μm. In the examples and comparative examples, argon was used as the inert gas. Furthermore, C, Si, Mn, Fe, Co, Mo, P, S, O, and N in Table 1 are unavoidable impurities; "Bal." in Table 1 indicates the balance.

[0081] Table 1

[0082]

[0083] [modeling]

[0084] Using Ni-based alloy powder for additive manufacturing as raw material, additive manufacturing was carried out using a 3D additive manufacturing apparatus (EOS-M290, manufactured by EOS Corporation) to create a 10×10×10mm cuboid as a test piece for hardness and microstructure investigation. The following conditions were used for modeling: based on the standard apparatus parameter HX (layer thickness 40μm), the output power was changed to 200W, the scanning speed was changed to 1200mm / s, and the scanning spacing was changed to 0.05mm.

[0085] [Heat Treatment]

[0086] Table 2 shows the heat treatment conditions for Examples 1 to 6, and Table 3 shows the heat treatment conditions for Comparative Examples 1 to 15.

[0087] Solution treatment and aging are carried out under the following conditions.

[0088] • Solution treatment: After maintaining the temperature shown in Table 3 for 30 minutes under atmospheric conditions, water cooling is performed. Alternatively, as shown in Table 2, solution treatment is not performed in the embodiments.

[0089] • Aging treatment: Under atmospheric conditions, maintain the temperature and time shown in Tables 2 and 3 respectively, and then air cool.

[0090] [Tissue observation: Determining the area fraction of particulate precipitates]

[0091] After cutting the heat-treated specimen (10×10×10mm) with a face parallel to the stacking direction, mechanical grinding and plasma milling were performed. The center of the ground specimen was observed using FE-SEM (Field Emission Scanning Electron Microscopy). Observation was performed at 10,000x magnification, based on... Figures 1-3Images of the area shown are captured and analyzed to determine the area fraction of particulate precipitates with a diameter greater than 400 nm. Furthermore, the particle diameter referred to here means the equivalent circle diameter, that is, the diameter of a circle whose area is equal to the area of ​​the particulate precipitates determined through image analysis.

[0092] [Tissue observation: Determining the original gamma particle size]

[0093] Following the same procedure as FE-SEM, the prepared sample before aging treatment was polished with colloidal silica and then subjected to EBSD (electron backscatter diffraction). The original γ grain size was determined based on the crystal orientation pattern obtained from the EBSD measurements. Furthermore, boundaries with an orientation difference greater than 15° were defined as grain boundaries.

[0094] Table 2

[0095]

[0096] Table 3

[0097]

[0098] Also, the "-" mark in the column for solution temperature and solution time in Tables 2 and 3 indicates that solution treatment was not performed.

[0099] [Rockwell Hardness Measurement]

[0100] Using a Rockwell hardness tester, the Rockwell hardness of the surface perpendicular to the stacking direction is measured on the heat-treated test piece. The Rockwell hardness measurement is performed according to JIS Z 2245:2016.

[0101] [Vickers Hardness Measurement]

[0102] The heat-treated test piece was embedded in resin, and after grinding the surface of the test piece, the Vickers hardness was measured using a micro Vickers hardness tester. The load was 1.96 N. The Vickers hardness measurement was performed according to JIS Z2244-1:2020.

[0103] Based on the results obtained, the characteristics of the embodiments and comparative examples were evaluated according to the following criteria.

[0104] • Delivery time: If the delivery time is within 10 hours, it is considered good and is expressed as "good". If the delivery time exceeds 10 hours, it is considered poor and is expressed as "NG (not Good)".

[0105] • Rockwell hardness: If it is above 59.5 HRC, the hardness is excellent and rated "A"; if it is between 50.0 and below 59.5 HRC, it is acceptable and rated "B"; if it is below 50.0 HRC, the hardness is poor and unacceptable and rated "C".

[0106] • Vickers hardness: If it is above 700 HV, the hardness is excellent and rated "A"; if it is between 513 and below 700 HV, it is acceptable and rated "B"; if it is below 513 HV, the hardness is poor and unacceptable and rated "C".

[0107] The results are shown in Tables 4 and 5.

[0108] Table 4

[0109]

[0110] Table 5

[0111]

[0112] As shown in Examples 1 to 6, when aging treatment is carried out at low temperatures such as 500°C and 585°C, no coarse granular precipitates occur, so it is confirmed that high hardness of Rockwell hardness above 59.5 HRC and Vickers hardness above 700 HV can be achieved.

[0113] In the embodiments of the present invention, high hardness can be achieved in a shorter time than 16 hours as in existing patent documents 1 and 2, which can significantly reduce energy costs in manufacturing.

[0114] As an example closest to the present invention, Patent Document 2 describes "Ni-38Cr-3.8Al-0.1C, aged at 600°C for 16 hours (Comparative Example 2)", but the microstructure contains Cr carbides, and the hardness after aging remains at 680 HV. The embodiments of the present invention do not contain coarse granular precipitates, have higher hardness, and have a shorter aging time, which is also superior in terms of energy cost.

[0115] Furthermore, even materials that appear to have the same hardness at first glance generally exhibit reduced toughness due to the presence of coarse granular precipitates, resulting in significantly different other mechanical properties. The embodiments of the present invention, lacking coarse granular precipitates, exhibit excellent mechanical properties, primarily toughness. On the other hand, in, for example, Non-Patent Document 1, the coarse granular precipitates are generated due to solution treatment as a smelted material, resulting in inferior mechanical properties compared to the embodiments of the present invention.

[0116] As shown in Tables 3 and 5, although Comparative Example 1 met the hardness standard, its energy cost was unsatisfactory due to the long aging process. Furthermore, after the long aging process, particulate precipitates with a particle size greater than 400 nm were generated.

[0117] In Comparative Examples 2-5, due to aging treatment at 700°C, granular precipitates with a particle size of 400 nm or larger were generated. Cr was consumed by the granular precipitates, resulting in a decrease in the strengthening of the lamellar structure and a reduction in hardness.

[0118] Comparative Examples 6-15 underwent solution treatment, resulting in the formation of particulate precipitates with a particle size of 400 nm or larger, a decrease in hardness, or, due to the reduced rate of lamellar precipitation, a longer precipitation time and lower energy costs compared to direct aging treatment.

[0119] As shown in Table 3, solution treatment reduces the original γ grain size. This is because fine grains are regenerated from the grain boundaries during solution treatment.

[0120] In the embodiments of the present invention, the original γ particle size is less than 100 μm, which is smaller than the original γ particle size (approximately 400 μm) of the smelting material described in Non-Patent Document 1. The fine original γ particle size unique to metal additive manufacturing in the embodiments of the present invention is considered effective in accelerating the precipitation completion time of lamellar structures.

[0121] Industrial availability

[0122] The shapes (especially the stacked shapes) of the present invention can be used in engine parts, bearing parts, molds and medical guide wires, etc.

Claims

1. A shape formed from a Ni-based alloy, wherein, The αCr phase, γ phase, and / or γ' phase precipitate in layers, and does not contain particulate precipitates with a particle size greater than 400 nm in terms of equivalent circular diameter.

2. The shape according to claim 1, wherein, The original γ particle size was less than 100 μm.

3. The object according to claim 1 has a Rockwell hardness of 50.0 HRC or higher.

4. The shaped object according to claim 1 has a Vickers hardness of 513 HV or higher.

5. The shaped object according to any one of claims 1 to 4, wherein, The Ni-based alloy has the following composition by mass: Cr: 30.0-45.0%, Al: 2.5-5.0%, C: 0-0.2%, and balance: Ni and unavoidable impurities.

6. The shaped object according to any one of claims 1 to 4, wherein, The object in question is a layered object.

7. The shaped object according to claim 5, wherein, The object in question is a layered object.

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