Powder for laser additive manufacturing and method for producing the same

Abstract

To provide a powder for laser additive manufacturing exhibiting excellent flowability and increased laser absorption rate.SOLUTION: A powder for laser additive manufacturing comprising a Ni-based alloy powder having carbon nanoparticles with an average particle diameter of 10 to 100 nm adhered to its surface, the powder having a laser absorptivity of 70% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a powder for laser additive manufacturing and a method for producing the same. [Background technology]

[0002] Several powder materials have been proposed in the past.

[0003] For example, Patent Document 1 describes a powder material that is made of atomized powder of a Ni-based alloy containing inclusions, and is characterized in that the number of inclusion particles contained is 100 or less per 10,000 particles of the atomized powder.

[0004] For example, Patent Document 2 describes a copper alloy powder for metal additive manufacturing that has excellent laser absorptivity, containing 0.003% by mass or more and 5.0% by mass or less of B, with the remainder consisting of unavoidable impurities and Cu, having an average particle size of 20 μm or more and 80 μm or less, and having a laser absorptivity of 15% or more for a laser with a wavelength of 1064 nm.

[0005] For example, Patent Document 3 describes an aluminum-based member for laser welding, which is characterized in that a zinc-plated layer having a thickness of 0.05 to 0.30 μm is formed on the surface of an aluminum-based member body made of aluminum or an aluminum alloy.

[0006] For example, Patent Document 4 describes a metal powder in which a coating made of one or more of Gd, Ho, Lu, Mo, Nb, Os, Re, Ru, Tb, Tc, Th, Tm, U, V, W, Y, Zr, Cr, Rh, Hf, La, Ce, Pr, Nd, Pm, Sm, and Ti is formed on the surface of copper or copper alloy powder, and the thickness of the coating is 5 nm or more and 500 nm or less.

[0007] For example, Patent Document 5 describes a copper powder made of copper or a copper alloy, which has an oxide film formed on the surface, the oxide film having an average thickness of 10 nm or more and 60 nm or less, and a flowability of 30 sec or less. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2021-46584 [Patent Document 2] Patent No. 7015976 [Patent Document 3] Special Publication No. 7-65193 [Patent Document 4] Patent No. 6650531 [Patent Document 5] Japanese Patent Application Publication No. 2020-186429 Summary of the Invention [Problem to be solved by the invention]

[0009] Previously, no powder for laser additive manufacturing consisting of Ni-based alloy powder with carbon nanoparticles of a specific particle size attached to the surface had been proposed.

[0010] The present invention provides a powder for laser additive manufacturing that has excellent flowability and high laser absorptivity. [Means for solving the problem]

[0011] The present invention includes the following (1) to (5). (1) Powder for laser additive manufacturing consisting of a Ni-based alloy powder with carbon nanoparticles having an average particle size of 10 to 100 nm attached to the surface, and having a laser absorption rate of 70% or more. (2) The powder for laser layered manufacturing according to (1) above, wherein the carbon nanoparticles have a content of 0.01 to 0.02 mass %. (3) The powder for laser layered manufacturing according to (1) or (2) above, which has a carbon content of 0.01 to 0.05% by mass. (4) In mass %, 50%≦Ni≦60%, 15%≦Cr≦25%, 0% <Mo≦5%、 0.1%≦Ti≦1.5%, 0.1%≦Al≦1.5%, 0% <Nb≦6%、 Contains 0.005%≦N≦0.05%; The powder for laser layered manufacturing according to any one of (1) to (3) above, wherein the remainder consists of Fe and unavoidable impurities. (5) preparing carbon nanoparticles having an average particle size of 10 to 100 nm; preparing a Ni-based alloy powder; and mixing the Ni-based alloy powder with 0.01 to 0.02 mass % of the carbon nanoparticles, and adhering the carbon nanoparticles to the surface of the Ni-based alloy powder; A method for producing a powder for laser additive manufacturing, comprising: [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a powder for laser additive manufacturing that has excellent fluidity and high laser absorptivity. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 10 is a diagram for explaining a method for measuring an avalanche angle. [Figure 2] 1 is a graph showing the relationship between the amount of carbon nanoparticles added and laser absorptance obtained in Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will now be described. The present invention provides a powder for laser additive manufacturing, which comprises a Ni-based alloy powder having carbon nanoparticles with an average particle size of 10 to 100 nm attached to the surface thereof, and has a laser absorptivity of 70% or more. Such a powder for laser additive manufacturing will hereinafter also be referred to as "powder for manufacturing of the present invention."

[0015] The present invention also provides a method for producing powder for laser additive manufacturing, comprising the steps of preparing carbon nanoparticles having an average particle size of 10 to 100 nm, preparing Ni-based alloy powder, and mixing the Ni-based alloy powder with 0.01 to 0.02 mass % of the carbon nanoparticles to adhere the carbon nanoparticles to the surface of the Ni-based alloy powder. Such a method for producing a powder for laser layered manufacturing will be hereinafter referred to as the "production method of the present invention."

[0016] The powder for molding of the present invention is preferably produced by the production method of the present invention.

[0017] The powder for molding of the present invention will now be described. The powder for molding of the present invention has excellent fluidity and therefore high uniformity. Furthermore, it is preferable that the powder for molding of the present invention has excellent mixability, and in this case, the uniformity is further improved. The powder for molding of the present invention also has high laser absorption.

[0018] The powder for molding of the present invention has high laser absorption properties and can therefore be preferably used as a raw material in layered manufacturing, a method for producing three-dimensional objects that utilizes solidification of powder materials by irradiating them with energy rays. Examples of additive manufacturing methods using metal powder materials include powder lamination fusion and powder deposition. A specific example of powder layer melting is selective laser melting (SLM). In this method, metal powder material is supplied onto a base substrate to form a powder bed, and a laser beam is irradiated at a predetermined location on the powder bed based on three-dimensional design data. The powder material in the irradiated area then solidifies through melting and re-solidification, forming a model. A three-dimensional object can be obtained by repeatedly supplying powder material to the powder bed and irradiating it with energy beams to form the object by sequentially stacking layers. SLM, in particular, is suitable for manufacturing parts with precise and complex shapes due to its high degree of design freedom, and is expected to be applied to a variety of fields. A specific example of a powder deposition method is laser metal deposition (LMD), in which metal powder is sprayed from a nozzle onto the desired location for forming a three-dimensional object while simultaneously irradiating it with a laser beam to form a three-dimensional object of the desired shape. The additive manufacturing method described above can be carried out using Ni-based alloy powder as a raw material. Because Ni-based alloy powder has excellent heat resistance and corrosion resistance, the additive manufacturing products can be used to manufacture equipment that operates in harsh environments, such as rocket engines and turbine blades.

[0019] The powder for molding of the present invention is made by adhering carbon nanoparticles of a specific particle size to the surface of Ni-based alloy powder.

[0020] The adhesion of carbon nanoparticles to the surface of the Ni-based alloy powder can be confirmed by observation using a scanning electron microscope (SEM).

[0021] The carbon nanoparticles have an average particle size of 10 to 100 nm. Here, the average particle size of the carbon nanoparticles is a value obtained by the following measurement. First, an image (SEM image) of the powder for molding of the present invention is obtained at a magnification of 20,000 times using a scanning electron microscope (SEM). Next, 100 carbon nanoparticles are randomly selected from the obtained SEM image, and the equivalent diameter of a circle with the same area is determined for each. The value obtained by simply averaging these values ​​is set as the average particle size of the carbon nanoparticles.

[0022] The shape of the carbon nanoparticles is not particularly limited, and may be approximately spherical, polyhedral, irregular, or the like.

[0023] In the powder for molding of the present invention, the content of the carbon nanoparticles as described above is preferably 0.01 to 0.02 mass %.

[0024] The Ni-based alloy powder contains 50 mass % or more of Ni, and is not particularly limited in composition, shape, particle size, etc., as long as it can be used as the powder for laser additive manufacturing as described above.

[0025] The content (composition), shape, particle size, etc. of each component in the Ni-based alloy powder are substantially the same as the content (composition), shape, particle size, etc. of each component in the powder for shaping of the present invention.

[0026] The content of each component in the powder for molding of the present invention will be explained below. The content of each component in the powder for molding of the present invention is not particularly limited, but is preferably within the ranges shown below. (1) 50%≦Ni≦60% Ni is the main component. Ni-based alloys exhibit high heat resistance and corrosion resistance. The Ni content is more preferably 55% or less.

[0027] (2) 15%≦Cr≦25% Cr is an element that contributes to solid-solution strengthening and improved oxidation resistance of the alloy. To fully obtain these effects, the Cr content is preferably 15% or more, more preferably 17% or more. On the other hand, if too much Cr is added, the δ phase is formed, reducing the high-temperature strength and toughness of the Ni-based alloy. Therefore, the Cr content is preferably 25% or less, more preferably 21% or less.

[0028] (3) 0% <Mo≦5% Mo contributes to solid-solution strengthening of alloys and is an effective element for increasing alloy strength. Because even a small amount of Mo exhibits significant additive effects, there is no particular lower limit for the Mo content, but it is preferable for it to be 0.1% or more. On the other hand, if Mo is added in an excessive amount, it promotes the formation of μ-phase and σ-phase in Ni-based alloys, which contributes to embrittlement. Therefore, the Mo content is preferably 5% or less, and more preferably 3.5% or less.

[0029] (4) 0.1%≦Ti≦1.5% Ti is an element that forms the γ' phase in Ni-based alloys and improves creep rupture strength and oxidation resistance. To fully obtain these effects, the Ti content is preferably 0.1% or more. On the other hand, excessive Ti content can lead to high-temperature cracking, which can be a cause of cracking during additive manufacturing. To avoid this, the Ti content is preferably 1.5% or less. Furthermore, when Ti is contained in an alloy together with N, it forms inclusions such as TiN. Furthermore, when Ti is contained together with O, it forms inclusions such as TiO2. To suppress the formation of such inclusions, the Ti content is preferably 1.5% or less.

[0030] (5) 0.1%≦Al≦1.5% Like Ti, Al is an element that forms the γ' phase and improves creep rupture strength and oxidation resistance. From the viewpoint of fully obtaining these effects, the Al content is preferably 0.1% or more. On the other hand, if too much Al is added, hot cracking is likely to occur, which is one of the causes of cracking during additive manufacturing. From the viewpoint of avoiding this, the Al content is preferably 1.5% or less. Furthermore, when Al is contained in an alloy together with O, it forms inclusions such as Al2O3. From the viewpoint of suppressing the formation of such inclusions, the Al content is preferably 1.5% or less.

[0031] (6) 0% <Nb≦6% Nb forms carbonitrides and a γ' phase in Ni-based alloys, thereby improving the strength of the alloy. Since even a small amount of Nb is highly effective, there is no particular lower limit for the Nb content, but it is preferably 4.0% or more. On the other hand, if Nb is added in an excessive amount, a Laves layer is formed, which actually reduces the strength. Therefore, the Nb content is preferably 6% or less, and more preferably 5.5% or less.

[0032] (7) 0.005%≦N≦0.05% N contributes to solid solution strengthening of Ni, thereby improving the hardness of the additively manufactured product. To fully obtain this effect, the N content is preferably 0.005% or more. On the other hand, if too much N is added, the ductility of the Ni-based alloy decreases, promoting cracking. It also promotes the formation of inclusions such as metal nitrides. To suppress these phenomena, the N content is preferably 0.05% or less.

[0033] (8) 0.01≦C≦0.05% C forms inclusions such as metal carbides in Ni-based alloys. From the viewpoint of keeping the amount of inclusions formed sufficiently low, the C content is preferably 0.01 to 0.05 mass %. The powder for manufacturing of the present invention contains carbon nanoparticles attached to the surface of the Ni-based alloy powder, and further contains C as an unavoidable impurity in the Ni-based alloy powder. The C content of the powder for manufacturing of the present invention is the total amount of these.

[0034] The powder for molding of the present invention preferably contains the above-mentioned predetermined amounts of Ni, Cr, Mo, Ti, Al, Nb, N, and C, with the remainder being Fe and unavoidable impurities.

[0035] As described above, the powder for molding of the present invention contains carbon in the form of carbon nanoparticles attached to the surface of the Ni-based alloy powder, and also as an unavoidable impurity contained in the Ni-based alloy powder.

[0036] The powder for molding of the present invention may contain O and S in addition to C as unavoidable impurities. Each of the inevitable impurities is described below. The content of the inevitable impurities in the powder for molding of the present invention is not particularly limited, but the content of each component may be within the ranges shown below.

[0037] (9) O≦0.02% O may form oxides with Fe, Ti, Al, etc., which may cause a decrease in strength and toughness. From the viewpoint of suppressing the formation of oxides, the O content is preferably 0.02% or less.

[0038] (10) S≦0.03% S forms inclusions such as MnS, etc. From the viewpoint of suppressing the formation of such inclusions, the S content is preferably 0.03% or less.

[0039] The powder for molding of the present invention may optionally contain at least one element selected from the following elements in addition to the elements described above. (11)0% <Si≦0.5% (12)0% <Mn≦5% Si and Mn act as deoxidizers during melting to produce powder materials, and are elements that impart oxidation resistance at high temperatures. Even small amounts of Si and Mn exert their effects to a great extent, so there is no particular lower limit for their content. However, if too much Si or Mn is added, oxidation resistance at high temperatures will actually decrease, so the respective contents should preferably be 0.5% or less.

[0040] (13) 0.5%≦Hf≦3% Hf has the effect of improving the oxidation resistance of Ni-based alloys. To fully obtain this effect, the Hf content is preferably 0.5% or more. On the other hand, if too much Hf is added, an embrittlement phase is formed, reducing strength and toughness. To avoid these problems, the Hf content is preferably 3% or less.

[0041] (14) 0.5%≦Zr≦3% Zr segregates at grain boundaries in Ni-based alloys and is effective in increasing creep strength. To fully obtain this effect, the Zr content is preferably 0.5% or more. On the other hand, if Zr is added in an excessive amount, toughness decreases, so the Zr content is preferably 3% or less.

[0042] (15)0% <Co≦2% Co increases the solubility of the γ' phase in Ni solid solutions, thereby improving high-temperature ductility and high-temperature strength. Since even a small amount of Co can exert these effects, there is no particular lower limit for the Co content. However, since too much Co can embrittle the Ni-based alloy, the Co content is preferably 2% or less.

[0043] (16)0% <Ta≦6% Ta strengthens the γ' phase and improves the strength of Ni-based alloys. Even a small amount of Ta exerts these effects, so there is no particular lower limit for the Ta content. On the other hand, if Ta is added in an excessive amount, Laves phases are formed, which reduces the strength, so the Ta content is preferably 6% or less.

[0044] The content of each component in the powder for molding of the present invention can be measured using an ICP emission spectrometer. However, C and S are measured by the combustion-infrared absorption method, and O and N are measured by the inert gas fusion-infrared analysis method.

[0045] The particle size of the powder for molding of the present invention is not particularly limited. 90 The diameter is preferably 150 μm or less, and in this case, it can be preferably used for laser additive manufacturing. Here, D 90 The diameter refers to the particle diameter at which the cumulative undersize fraction in the mass distribution is 90%.

[0046] The shape of the powder for molding of the present invention is not particularly limited, and may be approximately spherical, polyhedral, irregular, or the like, with approximately spherical being preferred.

[0047] The powder for molding of the present invention preferably has a measured avalanche angle of less than 40 degrees, more preferably 35 degrees or less. The molding powder of the present invention having such an avalanche angle has higher flowability. In the examples below, a method for measuring the avalanche angle of Alloy 718 powder after adding and mixing nanoparticles will be explained, and the avalanche angle of the powder for molding of the present invention will also be measured in the same manner.

[0048] <Production Method of the Present Invention> The manufacturing method of the present invention will be described. The manufacturing method of the present invention includes a step of preparing carbon nanoparticles having an average particle size of 10 to 100 nm. The carbon nanoparticles here may be the same as the carbon nanoparticles in the powder for shaping of the present invention described above. The average particle size of the carbon nanoparticles prepared in this step is a value obtained by measuring the average particle size using the Kr gas adsorption method and the multipoint BET method.

[0049] The manufacturing method of the present invention includes a step of preparing a Ni-based alloy powder. The Ni-based alloy powder used here may be the same as the Ni-based alloy powder used in the powder for shaping of the present invention described above.

[0050] The Ni-based alloy powder is preferably produced by an atomization method such as gas atomization, disk atomization, or water atomization. The Ni-based alloy powder is more preferably produced by a gas atomization method using an inert gas such as a rare gas. The Ni-based alloy powder produced by gas atomization and the powder for molding of the present invention containing the Ni-based alloy powder are generally circular in shape.

[0051] The manufacturing method of the present invention includes the steps of mixing the Ni-based alloy powder with 0.01 to 0.02 mass % of the carbon nanoparticles, and adhering the carbon nanoparticles to the surface of the Ni-based alloy powder. Specifically, the carbon nanoparticles having an average particle size of 10 to 100 nm and Ni-based alloy powder are prepared and mixed as raw materials, with the carbon nanoparticles added to the raw materials in an amount of 0.01 to 0.02 mass% of the total raw material, and then mixed under conditions that allow the carbon nanoparticles to adhere to the surface of the Ni-based alloy powder.

[0052] Here, the method for mixing the carbon nanoparticles and the Ni-based alloy powder is not particularly limited. It is sufficient that the carbon nanoparticles are attached to the surface of the Ni-based alloy powder by mixing. For example, a method in which they are put into a container and mixed can be mentioned. Alternatively, an airflow dispersion device such as that disclosed in Japanese Patent Laid-Open Publication No. 4-330957 may be used. In this type of airflow dispersion device, a high-speed airflow is ejected from a ring nozzle. Carbon nanoparticles and Ni-based alloy powder supplied from a supply port are then sucked in by the negative pressure generated by the airflow, and the high-speed airflow is then collided with the sucked carbon nanoparticles and Ni-based alloy powder. The carbon nanoparticles and Ni-based alloy powder are accelerated by the airflow, and due to inter-particle collisions, collisions with the device walls, and the application of shear force, the inter-particle agglomerations are dissolved and dispersed. As a result, the carbon nanoparticles are highly dispersed, and at least a portion of them are dispersed and mixed with the Ni-based alloy powder, and the carbon nanoparticles adhere to the surface of the Ni-based alloy powder. [Example]

[0053] Alloy 718 (Ni-Cr-Nb-Mo alloy) powder was prepared by gas atomization and classified to separate only those with particle sizes between 15 and 53 μm. The specific alloy composition was evaluated by X-ray fluorescence analysis and gas analysis, revealing the following: Ni: 52.2%, Cr: 19.0%, Mo: 3.0%, Ti: 0.9%, Al: 0.4%, Nb: 5.1%, and N: 0.01%. Alloy 718 powder with these particle sizes is preferably used for laser additive manufacturing.

[0054] Then, in each of Examples 1 to 12, as shown in Table 1 below, each type of nanoparticle was added and mixed using a container rotation and shaking type mixer to obtain a sample for each of Examples 1 to 12. Table 1 shows the type of nanoparticles and the amount added.

[0055] Here, after adding the nanoparticles to the Alloy 718 powder, the presence or absence of nanoparticle aggregation during mixing was visually determined. Samples with no aggregation were evaluated as having good mixability (○), samples with one aggregation site were evaluated as having fair mixability (△), and samples with two or more aggregation sites were evaluated as having poor mixability (×). The results are shown in Table 1. The carbon content was measured using a combustion-infrared absorption method and was found to be 0.12%.

[0056] In addition, the Alloy718 powder after adding and mixing the nanoparticles was subjected to a rotating drum type powder flowability measuring device to measure the avalanche angle and evaluate the flowability. The method for measuring the avalanche angle will be explained with reference to FIG. First, a predetermined amount of powder is placed in a cylindrical container (drum). Next, the drum was rotated at 0.6 RPM. As the drum rotated, the powder layer was pulled upward. When the balance between the adhesive forces between particles and gravity was lost, an avalanche occurred. The periodic avalanche phenomenon occurring inside the rotating drum was continuously photographed with a digital camera. The images were then analyzed to measure the slope angle of the sediment layer at the time of the avalanche 128 times, and the average value was taken as the avalanche angle. The fluidity was judged to be good (◯) when the avalanche angle was less than 40 degrees, and poor (×) when the avalanche angle was 40 degrees or more. The results are shown in Table 1.

[0057] Next, each of the obtained samples was irradiated with a laser having a wavelength of 1075 nm using an ultraviolet-visible-near infrared spectrophotometer (UH4150, manufactured by Hitachi High-Tech Science) to determine the laser absorptance. The results are shown in Table 1.

[0058] [Table 1]

[0059] FIG. 2 shows the relationship between the amount of carbon nanoparticles added and the laser absorptance when carbon nanoparticles are used (Examples 1 to 4).

[0060] As shown in Table 1, in Examples 1 to 3 in which carbon nanoparticles were added, the laser absorptance increased compared to when nanoparticles other than carbon were added (Examples 5 to 12). 2, in Examples 1 to 3 in which carbon nanoparticles were added, the laser absorptance was higher than in Example 4 in which no nanoparticles were added. However, in Example 3 in which the amount of added nanoparticles was 0.03 mass %, the miscibility was deteriorated. From the above, it can be said that in Examples 1 and 2, which correspond to the present invention, fluidity and mixability are ensured, resulting in improved uniformity, and that the powders for laser additive manufacturing have high laser absorptivity.

Claims

1. A laser additive manufacturing powder consisting of a Ni-based alloy powder with carbon nanoparticles having an average particle size of 10 to 100 nm attached to its surface, and having a laser absorption rate of 70% or more.

2. The laser additive manufacturing powder according to claim 1, wherein the carbon nanoparticle content is 0.01 to 0.02% by mass.

3. In mass percent, 50% ≤ Ni ≤ 60%, 15% ≤ Cr ≤ 25%, 0% < Mo ≤ 5%, 0.1% ≤ Ti ≤ 1.5%, 0.1% ≤ Al ≤ 1.5%, 0% < Nb ≤ 6%, It contains 0.005% ≤ N ≤ 0.05%, The laser additive manufacturing powder according to claim 1 or 2, wherein the remainder consists of Fe and unavoidable impurities.

4. A process for preparing carbon nanoparticles with an average particle size of 10 to 100 nm, A process for preparing Ni-based alloy powder, and A step of mixing the Ni-based alloy powder with 0.01 to 0.02 mass% of the carbon nanoparticles, and attaching the carbon nanoparticles to the surface of the Ni-based alloy powder. A method for producing powder for laser additive manufacturing, comprising the following:

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