MOLDED OBJECT MADE FROM A Ni-BASED ALLOY

Abstract

An object of the present invention is to provide a molded article with high hardness achieved with a short heat treatment time, and the present invention provides a molded article consisting of a Ni-based alloy wherein an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form and wherein the molded article does not contain granular deposits with a particle size of 400 nm or more than the equivalent circle diameter.

Description

AREA OF INVENTION

[0001] The present invention relates to a shaped object made of a nickel-based alloy and formed by a shaping process, such as a three-dimensional additive manufacturing process. STATE OF THE ART

[0002] Traditionally, a NiCrAl alloy was used as a nickel-based alloy exhibiting wear and corrosion resistance for engine components or the like. Examples of such a NiCrAl alloy include a high-strength, heat-resistant nickel-based alloy with an alloy composition containing, in wt%, C: 0.1% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr: 30 to 45%, and Al: 3.1 to 5%, with the remainder consisting of unavoidable impurities and Ni, wherein the alloy is made stronger by a combined deposition of a y'-phase and an α-phase (see patent document 1).

[0003] This alloy material is an attempt to obtain hardness by depositing a lamellar structure from an α-Cr phase and a γ' phase.

[0004] In recent years, a NiCrAl alloy has also been applied to additive manufacturing with metal. Examples of additively manufactured metal components obtained using a NiCrAl alloy include a Ni-based alloy product obtained using a Ni-based alloy powder containing C: 0.3 to 1.0%, Cr: 36.0 to 50.0%, and Al: 3.0 to 7.0%, with Ni and unavoidable impurities as the remainder (see patent document 2).

[0005] This alloy is an attempt to achieve hardness by forming carbide through the addition of carbon to a NiCrAl alloy. DOCUMENT LISTPATENT DOCUMENTS Patent Document 1: JP 2002-69557 A Patent Document 2: JP 2021-188069 A Non-patent document 1: Electric furnace steel, Volume 77, No. 2, p. 134, Fig. 1(a) SUMMARY OF THE INVENTIONAL PROBLEM

[0006] Although the NiCrAl alloys described in these documents are intended to achieve hardness and corrosion resistance, they require a long time for the deposition of a lamellar structure. For example, patent document 2 requires an aging treatment of approximately 16 to 20 hours. Therefore, a manufacturing disadvantage was the significant time expenditure associated with the heat treatment.

[0007] Accordingly, a problem to be solved by the present invention is the provision of a molded item made of a Ni-based alloy, such as a NiCrAl alloy, which has a high hardness achieved with a short heat treatment time. SOLUTION TO THE PROBLEM

[0008] As a result of intensive investigations, the present inventors have found that by directly subjecting a molded article obtained by molding using a Ni-based alloy powder, such as a NiCrAl alloy powder, to an aging treatment without solution treatment, a molded article consisting of a Ni-based alloy can be obtained, wherein the molded article contains no granular deposits with a particle size of 400 nm or more than the equivalent circle diameter and has a lamellar structure consisting of a γ-phase and / or a y'-phase and an α-Cr-phase, and have thus made the present invention.

[0009] In particular, the present invention provides the following molded items.

[0010] [1] Molded article consisting of a Ni-based alloy wherein an α-Cr phase and a γ-phase and / or a y'-phase are deposited in a lamellar shape and wherein the molded article does not contain granular deposits with a particle size of 400 nm or more than the equivalent circle diameter.

[0011] [2] Molded item according to [1], wherein the molded item has a prior γ-grain size of 100 µm or less.

[0012] [3] Molded item according to [1] or [2], wherein the molded item has a Rockwell hardness of 50.0 HRC or more.

[0013] [4] Molded item according to one of [1] to [3], wherein the molded item has a Vickers hardness of 513 HV or more.

[0014] [5] Molded article according to one of [1] to [4], wherein the Ni-based alloy has a composition consisting of, in wt%, Cr: 30.0 to 45.0%, Al: 2.5 to 5.0%, C: 0 to 0.2%, and as the remainder Ni and unavoidable impurities.

[0015] [6] Molded item according to one of [1] to [5], wherein the molded item is an additively manufactured molded item. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0016] A molded part made of a nickel-based alloy (for example, a NiCrAl alloy) exhibiting high hardness, such as a Rockwell hardness of 50.0 HRC or more (in particular 59.5 HRC or more) and a Vickers hardness of 513 HV or more (in particular 700 HV or more), can be obtained by performing an aging treatment for a short period (for example, within 10 hours) without a solution treatment, using a molded part produced by molding with a nickel-based alloy powder (for example, a NiCrAl alloy powder). Accordingly, the present invention can provide a molded part that not only exhibits high hardness but also low energy costs during production.

[0017] According to the molded part of the present invention, in which an α-Cr phase and a γ-phase and / or a y'-phase are deposited in a lamellar form and wherein the molded part does not contain granular deposits with a particle size of 400 nm or more than the equivalent circle diameter, a high hardness, such as a Rockwell hardness of 50.0 HRC or more (in particular 59.5 HRC or more) and a Vickers hardness of 513 HV or more (in particular 700 HV or more), can be obtained without significant loss in mechanical properties, such as toughness. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a SEM image of the microstructure of an additively manufactured molded item of the present invention, which was obtained by holding an unheated additively manufactured molded item at 700 °C for 4 hours, followed by air cooling. Fig.Figure 2 shows a SEM image of the microstructure of an additively manufactured molded item of the present invention, which was obtained by holding an unheated additively manufactured molded item at 500 °C for 8 hours, followed by air cooling. Fig. Figure 3 shows a SEM image of the microstructure of an additively manufactured part obtained by performing a solution treatment (holding at 1150 °C for 30 minutes, followed by water cooling) and then holding at 500 °C for 2 hours, followed by air cooling, using an unheated additively manufactured part. The arrows indicate the growth direction of a lamellar structure and show how the growth of the lamellar structure is stopped by granular deposits. DETAILED DESCRIPTION OF THE INVENTION

[0018] The subject matter of the present invention is described below. [Components]

[0019] The molded part of the present invention consists of a nickel-based alloy. It is preferred that the nickel-based alloy used in the present invention has a composition consisting of Cr: 30.0 to 45.0%, Al: 2.5 to 5.0%, C: 0 to 0.2%, and the remainder being nickel and unavoidable impurities. The types and amounts of the additive elements, as well as the reasons for their limitations, are as follows. Here, "%" represents the mass percentage of each component.

[0020] First, Ni, which is the main component, and Cr and Al, which are essential additives for it, are described. Ni

[0021] Ni is a component that can provide a material with excellent corrosion resistance, strength and toughness, and therefore the alloy of the present invention is based on Ni. Cr: 30.0 to 45.0%

[0022] Cr is an element required for the formation of a lamellar structure. When a nickel-based alloy containing a specified amount of Cr undergoes an aging treatment, an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form, thereby increasing strength and hardness. Furthermore, Cr forms a protective film on a material surface in various corrosive environments, significantly improving high-temperature corrosion resistance.

[0023] If the chromium content is too low, a stable lamellar structure cannot be formed in all areas of the microstructure during the aging treatment, leading to a reduction in hardness. Therefore, the chromium content is preferably 30.0% or more. More preferably, the chromium content is 33.0% or more, and even more preferably, 36.0% or more.

[0024] Conversely, if the Cr content is excessive, the Ni content is relatively reduced, leading to insufficient deposition of a y'-phase. Therefore, the Cr content is preferably 45.0% or less. More preferably, the Cr content is 42.0% or less, and even more preferably, 40.0% or less. Any of these upper limits can be combined with any of the aforementioned lower limits. Al: 2.5 to 5.0%

[0025] Aluminum is an element required for the formation of a lamellar structure. Through aging treatment, aluminum forms Ni3Al (γ'-phase). In a NiCrAl alloy, an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form, thereby creating a lamellar structure and achieving high hardness. Aluminum also contributes to improvements in high-temperature corrosion resistance and oxidation resistance. To achieve these effects, the aluminum content is preferably 2.5% or more. More preferably, the aluminum content is 3.0% or more, and even more preferably, 3.5% or more.

[0026] On the other hand, if the Al content is excessive, solidification cracking is 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. Any of these upper limits can be combined with any of the aforementioned lower limits. C: 0 to 0.2%

[0027] The nickel-based alloy used in the present invention may contain carbon (C) as an additional component, in addition to nickel, chromium (Cr), and aluminum (Al). The carbon content may be 0% or greater than 0%, and is preferably 0.2% or less. Carbon is a component that forms a carbide and contributes to an increase in the hardness of a material. However, if the carbon content is excessive, coarse carbides cause a deterioration in the toughness of a material. Therefore, even when carbon is included as an impurity, the carbon content is preferably 0.2% or less. More preferably, the carbon content is 0.1% or less, and even more preferably, 0.03% or less.

[0028] The nickel-based alloy used in the present invention may contain one or more elements selected from C, Si, Mn, Fe, Co, Mo, P, S, O and N as unavoidable impurities.

[0029] [Features in which an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form and do not contain granular deposits with a particle size of 400 nm or more than the equivalent circle diameter]

[0030] The molded object of the present invention is characterized in that an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form and that the molded object does not contain any granular deposits with a particle size of 400 nm or more than the equivalent circular diameter. The fact that an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form and that the molded object does not contain any granular deposits with a particle size of 400 nm or more than the equivalent circular diameter can be confirmed by the methods described in the examples.

[0031] When an α-Cr phase and a γ-phase, or an α-Cr phase and a γ-phase, or an α-Cr phase, a γ-phase, and a γ'-phase are deposited in a lamellar form, i.e., grown into a layered lamellar structure, high hardness is obtained. Since a finer lamellar spacing leads to greater hardness, a fine lamellar spacing is preferable.

[0032] The molded part of the present invention is obtained by performing an aging treatment on a molded part obtained by molding (which may be referred to in this description as the "unheated molded part" or "molded part before aging treatment"). When an aging treatment is performed on the unheated molded part, an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar mold, and a lamellar structure is allowed to grow. Since the growth of the lamellar structure is inhibited when it comes into contact with coarse granular deposits, it is advantageous that the granular deposits are not coarse. Therefore, it is preferred that the unheated molded part does not contain granular deposits with a particle size of 400 nm or more than the equivalent circular diameter.Granular deposits are allowed to grow by performing a solution treatment on the unheated molded part. Therefore, by performing an aging treatment without performing a solution treatment on the unheated molded part, inhibition of the lamellar structure growth caused by coarse granular deposits can be prevented, and excellent aging hardness can be achieved. As a result of the unheated molded part not containing granular deposits with a particle size of 400 nm or more than the equivalent circle diameter, the molded part of the present invention also does not contain granular deposits with a particle size of 400 nm or more than the equivalent circle diameter.In the molded part of the present invention, an α-Cr phase and a γ-phase and / or a γ'-phase are deposited in a lamellar form and no granular deposits with a particle size of 400 nm or more than the equivalent circle diameter are included; therefore, a high hardness, such as a Rockwell hardness of 50.0 HRC or more (in particular 59.5 HRC or more) and a Vickers hardness of 513 HV or more (in particular 700 HV or more), can be achieved without significant impairment of mechanical properties, such as toughness. [Characteristic where the previous γ grain size is 100 µm or less]

[0033] A conventional pre-aging γ-grain size was approximately 400 µm (see non-patent document 1). A molding process, such as metal additive manufacturing, is suitable for providing a pre-aging item with a fine pre-aging γ-grain size, and the pre-aging γ-grain size of the pre-aging item can be 100 µm or less. If the pre-aging γ-grain size of the pre-aging item is 100 µm or less, the time required for complete deposition of a lamellar structure during aging can be reduced. Therefore, it is preferred that the pre-aging γ-grain size of the pre-aging item be 100 µm or less. The pre-aging γ-grain size of the pre-aging item is maintained after the aging treatment.Therefore, if the previous γ-grain size of the molded item before the aging treatment is 100 µm or less, the previous γ-grain size of the molded item after the aging treatment (namely, the molded item of the present invention) is also 100 µm or less. [Powder]

[0034] A shaping process is carried out using a nickel-based alloy powder. The explanation regarding the nickel-based alloy that forms the nickel-based alloy powder is as described above. It is preferred that the nickel-based alloy powder used for shaping has a shape approximating a sphere, exhibits excellent flowability, and can be packed without gaps; therefore, it is preferably a gas-atomized powder. The average particle size of the nickel-based alloy powder is preferably 10 to 100 µm based on the volume-averaged particle diameter (D50). D50 refers to the particle diameter at which the cumulative volume reaches 50% on a volume-based cumulative frequency distribution curve, determined under the assumption that the total volume of the powder is 100%.D50 is measured using a laser diffraction-scattering method. Examples of suitable equipment for this measurement include a Microtrac MT3000 laser diffraction-scattering particle size distribution analyzer manufactured by NIKKISO CO., LTD. In this device, the powder is introduced into the cell along with pure water, and the particle diameter is determined based on light scattering information from the particles. [Forms]

[0035] The pre-aging item is manufactured using a nickel-based alloy powder containing chromium and aluminum as the material and by performing a process involving rapid melting and rapid solidification. The pre-aging item is then subjected to an aging heat treatment to provide a lamellar structure in which an α-Cr phase and a γ-phase and / or a γ'-phase are aligned in a lamellar configuration.

[0036] Specific examples of the method for producing the molded part prior to aging treatment include a rapid melting and rapid solidification process that comprises a step of melting and solidifying a metal powder. Specific examples of this method include a three-dimensional additive manufacturing process, a thermal spraying process, a laser coating process, and a plating process. The molded part prior to aging treatment (and consequently the molded part after aging treatment, namely the molded part of the present invention) is preferably an additively manufactured molded part produced by a three-dimensional additive manufacturing process. Specific examples of the three-dimensional additive manufacturing process include a powder bed fusion system (powder bed system) and a directed energy deposition system (powder deposition system).Specific examples of the powder bed fusion system (powder bed system) include a selective laser sintering (SLS) system, a selective laser melting (SLM) system, and an electron beam melting (EBM) system. In particular, the nickel-based alloy powder of the present invention is suitable for the three-dimensional additive manufacturing process of the powder bed fusion system, which enables the formation of a large, high-density object.

[0037] The three-dimensional additive manufacturing process can be carried out, for example, using a 3D printer. In the additive manufacturing process of the powder bed fusion system (powder bed system), the nickel-based alloy powder of the present invention is arranged as a bed and irradiated with a laser beam or an electron beam.

[0038] Irradiation enables rapid heating and melting of the particles. The molten particles are then rapidly solidified. This melting and solidification process allows the particles to bond together. Irradiation is selectively applied to a section of the nickel-based alloy powder bed. A section of the powder bed that is not irradiated remains unmelted. A bonding layer is formed only in the irradiated section.

[0039] The nickel-based alloy powder is then thinly layered on the compound layer. A section of this nickel-based alloy powder is irradiated with a laser or electron beam. This irradiation causes the particles to melt rapidly. The molten particles are then allowed to solidify rapidly. This melting and solidification process allows the particles in the powder to bond together, forming a new compound layer. This new compound layer is also bonded to the existing compound layer.

[0040] Through repeated bonding via irradiation, an aggregate of compound layers gradually grows. This growth enables the creation of a molded object with a three-dimensional shape. This additive manufacturing process allows for the simple production of molded objects with complex shapes. [Heat treatment]

[0041] The unheated molded item obtained by molding using the Ni-based alloy powder is not used as such; rather, the molded item of the present invention, which has the desired properties, can be obtained by subjecting the unheated molded item to an aging treatment step.

[0042] When a NiCrAl alloy is used in conventional processes, such as forging, it is generally subjected to a solution treatment at a temperature of 1100 °C or higher. However, the present inventors have found that when an unheated component is produced by a forming process, such as a three-dimensional additive manufacturing process as in the present invention, the solution treatment for the unheated component can be omitted, and the unheated component can be directly subjected to an aging treatment, thereby obtaining excellent mechanical properties.

[0043] If the unheated molded part is subjected to an aging treatment, it is subjected to heat treatment at 600 °C or less, such that the flake spacing of an α-Cr phase and a γ-phase and / or a γ'-phase can be reduced, thereby providing a molded part with high hardness. The aging treatment temperature is preferably 600 °C or less, more preferably 585 °C or less, even more preferably 540 °C or less, and particularly 500 °C or less. The lower limit is not specifically restricted and may, for example, be 400 °C or more or 450 °C or more. Any of these lower limits can be combined with any of the aforementioned upper limits.

[0044] If the unheated molded part undergoes an aging treatment, the aging treatment time can be shortened to save energy costs. The aging treatment time is preferably 10 hours or less, more preferably 8 hours or less, even more preferably 4 hours or less, and particularly 2 hours or less. The lower limit is not specifically restricted and may, for example, be 0.5 hours or more or 1 hour or more. Any of these lower limits can be combined with any of the aforementioned upper limits. [Lamellar morphology]

[0045] A lamellar structure consisting of an α-Cr phase and a γ-phase and / or a y'-phase is deposited by performing an aging treatment on the unheated molded part. Fig.Figure 1 shows a SEM image of the microstructure of an additively manufactured molded part according to the present invention, obtained by holding an unheated additively manufactured molded part at 700 °C for 4 hours, followed by air cooling. It can be seen that a lamellar structure on the order of several tens of nanometers is formed when the aging treatment is carried out at 700 °C. Fig. Figure 2 shows a SEM image of the microstructure of an additively manufactured molded item according to the present invention, obtained by holding an unheated additively manufactured molded item at 500 °C for 8 hours, followed by air cooling. It is evident that the aging treatment carried out at 500 °C provides a very fine microstructure with a fine lamella spacing compared to the aging treatment carried out at 700 °C.

[0046] Since the hardness increases with the finer the lamellar spacing, it is preferable to carry out the aging treatment at a low temperature so that a fine lamellar structure is deposited. [Area fraction of granular deposits]

[0047] The Fig.Figure 3 shows a SEM image of the microstructure of an additively manufactured part obtained by performing a solution treatment (holding at 1150 °C for 30 minutes, followed by water cooling) and then holding at 500 °C for 2 hours, followed by air cooling, using an unheated additively manufactured part. It is evident that the solution treatment produces coarse granular deposits with a particle diameter of 400 nm or more. As a result of EDS analysis, the granular deposits are rich in chromium and are therefore assumed to be an α-Cr phase. It is evident that while a lamellar structure is allowed to grow in the direction indicated by the arrow in the figure, the growth of the lamellar structure is inhibited at a point where the coarse granular deposits contact the tip of the grown lamellar structure.

[0048] Coarse granular deposits inhibit the growth of a lamellar structure and increase the time required to complete the deposition reaction (i.e., to deposit a lamellar structure throughout the microstructure), thereby unnecessarily increasing the energy costs of the heat treatment. Therefore, it is preferred that no coarse granular deposits be formed. The formation of coarse granular deposits can be prevented by omitting a solution treatment and / or avoiding a prolonged aging treatment. The surface area fraction of granular deposits with a particle diameter of 400 nm or more than the equivalent circle diameter in the molded part of the present invention is preferably 0.0%.The area fraction of granular deposits with a particle diameter of 400 nm or more as equivalent circle diameter can be measured by the method described in the examples. [Previous γ grain size]

[0049] Since a lamellar structure of a NiCrAl alloy is deposited in a cellular manner from a grain boundary, a finer microstructure is more preferred because the deposition reaction can be completed faster.

[0050] Each of the molded item before and after aging treatment (namely, the molded item of the present invention) has a prior γ-grain size of preferably 100 µm or less, more preferably 90 µm or less, more preferably 80 µm or less, and particularly 70 µm or less. The lower limit is not specifically restricted and may, for example, be 5 µm or more or 20 µm or more. Each of these lower limits can be combined with any of the aforementioned upper limits. The prior γ-grain size can be measured by the method described in the examples. In the examples, the microstructure of the molded item before aging treatment is used to measure the prior γ-grain size, since the prior γ-grain size in the microstructure of the molded item after aging treatment is difficult to analyze by EBSD (electron backscatter diffraction).The previous γ-grain size of the molded item before aging treatment is maintained after aging treatment; therefore, the previous γ-grain size measured using the microstructure of the molded item before aging treatment can be considered as the previous γ-grain size of the molded item after aging treatment. [Hardness]

[0051] It is preferred that the NiCrAl alloy has a high hardness, as it is used for bearing components or engine components.

[0052] Accordingly, the molded part of the present invention has a Rockwell hardness of preferably 50.0 HRC or more, more preferably 60.0 HRC or more, even more preferably 61.0 HRC or more, and particularly 62.0 HRC or more. The upper limit is not specifically restricted and is, for example, 65.0 HRC or less. The Rockwell hardness can be measured by the method described in the examples.

[0053] The molded part of the present invention has a Vickers hardness of preferably 513 HV or more, more preferably 700 HV or more, even more preferably 750 HV or more, and particularly 790 HV or more. The upper limit is not specifically restricted and is, for example, 850 HV or less. The Vickers hardness can be measured by the method described in the examples. EXAMPLES [Powder]

[0054] Table 1 shows the chemical composition of each nickel-based alloy powder used in the examples and comparison examples. After each nickel-based alloy powder was produced by a vacuum melt inert gas atomization process, the fraction that passed through a sieve with an aperture of -63 µm was used as the nickel-based alloy powder for additive manufacturing. The term "-63 µm" represents a sieve aperture of less than 63 µm. Argon was used as the inert gas in the examples and comparison examples. Here, C, Si, Mn, Fe, Co, Mo, P, S, O, and N in Table 1 are unavoidable impurities, and "Remainder" in Table 1 represents the residual. [Forms]

[0055] The nickel-based alloy powder for additive manufacturing was used as the starting material, and an additive manufacturing process was carried out using a 3D additive manufacturing device (EOS-M290, manufactured by EOS GmbH) to produce a 10 × 10 × 10 mm cube, which served as a test specimen for hardness and microstructure investigations. The mold conditions were based on the device's standard parameters HX (layer thickness: 40 µm) with modifications to the output power, scanning speed, and outlet aperture width to 200 W, 1200 mm / s, and 0.05 mm, respectively. [Heat treatment]

[0056] Table 2 shows heat treatment conditions in examples 1 to 6 and Table 3 shows heat treatment conditions in comparison examples 1 to 15.

[0057] Solution treatment and aging treatment were performed under the following conditions.

[0058] Solution treatment: Solution treatment was performed by holding the solution at each temperature shown in Table 3 for 30 minutes in an air atmosphere, followed by water cooling. However, in the examples, solution treatment was not performed as shown in Table 2.

[0059] Aging treatment: The aging treatment was carried out by holding at each temperature and time shown in Table 2 and Table 3 in an air atmosphere, followed by air cooling. [Microstructure analysis: Determination of the area fraction of granular deposits]

[0060] The molded part (10 × 10 × 10 mm) after heat treatment was cut along a plane parallel to the stacking direction, mechanically polished, and subjected to ion beam etching. The central section of the polished sample was examined using a FE-SEM (field emission scanning electron microscope). The examination was performed at 10,000x magnification, and the image analysis was carried out using images taken of areas containing the Fig. The areas shown in Figures 1 to 3 were analyzed to determine the area fraction of granular deposits with a particle size of 400 nm or more. Here, the particle size refers to the equivalent circle diameter, namely the diameter of a circle assumed to have an area identical to that of a granular deposit determined by image analysis. [Microstructure analysis: Determination of the previous γ grain size]

[0061] A sample prepared before aging treatment, using the same procedure as for FE-SEM, was finished by polishing with colloidal silicon dioxide and then subjected to EBSD (electron backscatter diffraction). The previous γ-grain size was determined from a crystal orientation map obtained by the EBSD measurement. A boundary with an orientation difference of 15° or more was defined as the crystal grain boundary. [Table 2] Solution temperature (°C) Solution time (hours) Aging temperature (°C) Aging time (hours) Previous γ grain size (µm) Area fraction of granular deposits (%) Example 1 - - 500 4 67 0,0 % Example 2 - - 500 8 67 0,0 % Example 3 - - 585 1 67 0,0 % Example 4 - - 585 2 67 0,0 % Example 5 - - 585 4 67 0,0 % Example 6 - - 585 8 67 0,0 % * The symbol “-” in the columns for solution temperature and solution time indicates that no solution treatment was performed. [Table 3] Solution temperature (°C) Solution time (hours) Aging temperature (°C) Aging time (hours) Previous γ grain size (µm) Area fraction of granular deposits (%) Comparative example 1 - - 585 16 67 0,6 % Comparative example 2 - - 700 4 67 4,0 % Comparative example 3 - - 700 8 67 5,2 % Comparative example 4 - - 700 16 67 15,7 % Comparative example 5 - - 700 32 67 5,0 % Comparative example 6 1150 0,5 500 2 44 3,5 % Comparative example 7 1150 0,5 500 4 44 6,2 % Comparative example 8 1150 0,5 500 8 44 4,6 % Comparative example 9 1150 0,5 500 16 44 3,1 % Comparative example 10 1150 0,5 500 32 44 1,3 % Comparative example 11 1150 0,5 700 2 44 3,0 % Comparative example 12 1150 0,5 700 4 44 2,9 % Comparative example 13 1150 0,5 700 8 44 3,9 % Comparison 1150 0,5 700 16 44 5,9 % example 14 Comparative example 15 1150 0,5 700 32 44 9,6 % * The symbol “-” in the columns for solution temperature and solution time indicates that no solution treatment was performed.

[0062] In Tables 2 and 3, the symbol “-” in the columns for solution temperature and solution time indicates that no solution treatment was performed. [Rockwell hardness measurement]

[0063] A Rockwell hardness tester was used to measure the Rockwell hardness of a surface perpendicular to the stacking direction of the test specimen after heat treatment. The Rockwell hardness was measured according to JIS Z 2245:2016. [Vickers hardness test]

[0064] After heat treatment, the test specimen was embedded in a resin and its surface was polished. The Vickers hardness was then measured using a micro-Vickers hardness tester. The applied load was set to 1.96 N. The Vickers hardness was measured according to JIS Z2244-1:2020.

[0065] The results obtained were used to evaluate the properties in the examples and the comparison examples according to the following criteria: Aging time: An aging time of 10 hours or less was rated as good and labelled "Good", and an aging time of more than 10 hours was rated as poor and labelled "NG (not good)". Rockwell hardness: A hardness of 59.5 HRC or higher was rated "A" as excellent, a hardness of 50.0 HRC to less than 59.5 HRC was rated "B" as acceptable, and a hardness of less than 50.0 HRC was rated "C" as poor and unacceptable. Vickers hardness: A value of 700 HV or more was considered excellent hardness and rated "A", a value of 513 HV to less than 700 HV was considered acceptable and rated "B", and a value of less than 513 HV was considered poor hardness and rated "C".

[0066] The results are shown in Tables 4 and 5. [Table 4] Hardness (HRC) Hardness (HV) Aging period Rockwell hardness Vickers hardness Example 1 60,9 796 Good A A Example 2 62,7 809 Good A A Example 3 60,2 759 Good A A Example 4 59,9 755 Good A A Example 5 61,0 743 Good A A Example 6 59,9 754 Good A A [Table 5] Hardness (HRC) Hardness (HV) Aging period Rockwell hardness Vickers hardness Comparative example 1 60,5 751 NG A A Comparative example 2 57,4 675 Good B B Comparative example 3 56,5 658 Good B B Comparative example 4 55,7 647 NG B B Comparative example 5 54,5 617 NG B B Comparative example 6 26,5 332 Good C C Comparative example 7 40,6 434 Good C C Comparative example 8 55,1 772 Good B B Comparative example 9 60,5 773 NG A A Comparative example 10 60,6 766 NG A A Comparative example 11 55,0 689 Good B B Comparative example 12 53,7 650 Good B B Comparative example 13 53,2 631 Good B B Comparative example 14 52,6 629 NG B B Comparative example 15 50,8 602 NG B B

[0067] As shown in Examples 1 to 6, no coarse granular deposits were produced in the case of aging treatment at low temperatures of 500 °C and 585 °C. Accordingly, it was confirmed that high hardness values, such as a Rockwell hardness of 59.5 HRC or more and a Vickers hardness of 700 HV or more, can be achieved.

[0068] In the examples of the present invention, a high degree of hardness can be achieved in a shorter time than the conventional time of 16 hours described in patent documents 1 and 2, and the energy costs in the manufacture can be significantly reduced.

[0069] As the closest example relating to the examples of the present invention, patent document 2 describes “Ni-38Cr-3.8Al-0.1C, aged at 600 °C for 16 hours (Comparative Example 2)”. However, the microstructure contains Cr carbides, and the hardness after aging remains at 680 HV. In contrast, the examples of the present invention, which do not contain coarse granular deposits, exhibit greater hardness, achieve a shorter aging time, and are superior in terms of energy costs.

[0070] A material containing coarse granular deposits, even if it appears to have comparable hardness, generally exhibits reduced toughness and consequently differs significantly with respect to other mechanical properties. In contrast, the examples of the present invention do not contain coarse granular deposits and therefore provide excellent results with respect to mechanical properties, including toughness. On the other hand, for example, non-patent document 1 discloses a block or ingot material in which coarse granular deposits are produced by solution treatment, and consequently its mechanical properties are inferior compared to those of the examples of the present invention.

[0071] As shown in Tables 3 and 5, comparison example 1 meets the hardness criteria; however, it requires a long aging treatment and is therefore less energy-efficient. Furthermore, such a long aging treatment causes the formation of granular deposits with a particle size of 400 nm or more.

[0072] In comparative examples 2 to 5, granular deposits with a particle size of 400 nm or more were produced as a result of an aging treatment at 700 °C. Since Cr was consumed by the granular deposits, the extent of reinforcement of a lamellar structure decreased, leading to a reduction in hardness.

[0073] The comparative examples 6 to 15 produced granular deposits with a particle size of 400 nm or more due to a solution treatment, which led to a reduction in hardness or a reduction in the lamellar deposition rate, thus requiring more time to complete the deposition compared to the case of direct aging treatment, and consequently being worse in terms of energy costs.

[0074] As shown in Table 3, the solution treatment reduces the previous γ-grain size. This is because a fine crystalline grain is newly generated from a grain boundary during the solution treatment.

[0075] The prior γ-grain size in the examples of the present invention is 100 µm or less, which is smaller than the prior γ-grain size (about 400 µm) of the block or ingot material described in non-patent document 1. It is assumed that the fine prior γ-grain size, which is characteristic of additive manufacturing with metal in the examples of the present invention, is effective in reducing the time required to complete the deposition of a lamellar structure. COMMERCIAL APPLICABILITY

[0076] The molded object of the present invention (in particular the additively manufactured molded object) can be used for engine components, bearing components, dies or nozzles, medical wires and the like. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2002-69557 A

[0005] JP 2021-188069 A

[0005]

Claims

[1] Molded article consisting of a Ni-based alloy wherein an α-Cr phase and a γ-phase and / or a y'-phase are deposited in a lamellar shape and wherein the molded article does not contain granular deposits with a particle size of 400 nm or more than the equivalent circle diameter. [2] Molded article according to claim 1, wherein the molded article has a prior γ-grain size of 100 µm or less. [3] Molded item according to claim 1, wherein the molded item has a Rockwell hardness of 50.0 HRC or more. [4] Molded item according to claim 1, wherein the molded item has a Vickers hardness of 513 HV or more. [5] Molded article according to any one of claims 1 to 4, wherein the Ni-based alloy has a composition consisting of, in mass %, Cr: 30.0 to 45.0 %, Al: 2.5 to 5.0 %, C: 0 to 0.2 %, and as the remainder Ni and unavoidable impurities. [6] Molded item according to any one of claims 1 to 4, wherein the molded item is an additively manufactured molded item. [7] Molded item according to claim 5, wherein the molded item is an additively manufactured molded item.

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