WO2022177035A1 - Method for manufacturing oxide dispersion strengthened niobium-containing nickel-based superalloy by using additive manufacturing and oxide dispersion strengthened niobium-containing nickel-based superalloy manufactured thereby - Google Patents

Abstract

The present invention relates to a method for manufacturing an oxide dispersion strengthened niobium (Nb)-containing nickel-based superalloy and an oxide dispersion strengthened niobium-containing nickel-based superalloy manufactured thereby, wherein a metal oxide is introduced into an alloy matrix by performing additive manufacturing (AM) using, as a raw material, a niobium-containing nickel-based superalloy powder containing 0.005-0.015 wt% of oxygen. According to the present invention, an alloy with improved high-temperature mechanical properties can be easily and economically manufactured, compared with the conventional art, wherein the alloy has high resistance against the formation of cracks inside grains due to creep, fatigue, or the like by maintaining a minute size without a phase change or size growth even in a long-term exposure environment at a high temperature of 700°C or higher through an oxide dispersion strengthening effect, which is given by the introduction of an oxide with a size of approximately 10-100 nm into grains while fundamental properties of the niobium-containing nickel-based superalloy manufactured through additive manufacturing are maintained as they are.

Description

Manufacturing method of oxide dispersion-strengthened niobium-containing nickel-based superalloy using additive manufacturing method and oxide dispersion-strengthened niobium-containing nickel-based superalloy prepared thereby

The present invention is, (i) National R&D project implemented by the Ministry of Science and ICT (Project Unique No.: 1711113639, Institutional Detailed Project No.: 2020-0122, Project Name: Leading Research Center (ERC) Mechatronics Convergence Part Material, Research Project Name: Mechatronics Convergence parts and materials research center, research management institution: National Research Foundation of Korea, host institution: Changwon University Industry-University Cooperation Foundation, research period: 2018.09.01 ~ 2021.08.31) and (ii) National R&D project implemented by the Ministry of Science and ICT (task-specific) No.:1711115494, Detailed Institutional Project No.:2020-0100, Project Name: Linked to Shinjin Middle School, Research Project Name: 3D Printing Customized Super Heat Resistant Alloy Design and Grain Boundary Control Package Technology Development, Research Management Specialized Institution: National Research Foundation of Korea, Hosted by: Changwon As a result of Changwon University under the R&D support of the University-Industry-University Cooperation Foundation, research period: March 1, 2020 ~ February 28, 2020), it is about a method for manufacturing a nickel-based superalloy containing niobium, and more specifically, the additive manufacturing method. It is about a method of manufacturing an oxide dispersion strengthened (ODS) niobium-containing nickel-based superalloy containing fine oxides that increase the breakage resistance against the generation of internal cracks such as tension and creep at high temperatures by using it.

Nickel-based superalloy has excellent weldability, corrosion resistance, and high-temperature mechanical properties, and thus is used as a material for high-temperature components such as aircraft and gas turbine power assemblies for power generation. Alloy 625, which is a niobium-containing nickel-based superalloy considered in the present invention, is a wrought product in most cases, and parts having a relatively simple shape are manufactured by rolling, forging, welding and machining. Although parts can be manufactured by investment casting, the manufacturing cost is high, and quality problems such as coarse grains, casting defects, and segregation occur frequently. Alloy625 tempered products obtained through the tempering process, welding and machining are of excellent quality, but have disadvantages in that the machining cost is high and the design freedom is not high because it is difficult to manufacture parts with more complex shapes.

Recently, a three-dimensional additive manufacturing method that can overcome these shortcomings and reduce process costs including material reduction has been in the spotlight. R&D for application to combustors of turbines for aviation engines over 700°C or blade/vane parts of steam turbines is being actively conducted through process simplification and the advantage of being able to manufacture more complex structures with fewer materials. However, since the material is used for a long time at 700° C. or higher in the combustor and steam turbine blade for an aircraft engine, there is a concern that the material may break unexpectedly due to damage such as creep and fatigue as well as oxidation and corrosion by impurity gas. Therefore, improving the resistance of these materials, such as creep, fatigue, oxidation and corrosion, which are the main causes of damage, is becoming an important challenge for manufacturers, component processors and operators alike.

Research on Alloy 625 alloy using the additive manufacturing method has been rapidly progressing around the world in recent years, but the instructions for the microstructure and its properties that vary depending on the manufacturing equipment and manufacturing conditions have not been generally confirmed yet. Currently, parameter conditions are provided for several representative alloys by each equipment manufacturer, but they also satisfy only the minimum mechanical property values to represent the properties of the alloy, but there are limits to be considered as optimized conditions. bar

Meanwhile, efforts have been made to improve high-temperature mechanical properties by uniformly dispersing nano-sized fine oxides (such as Y ₂ O ₃ ) in a nickel-based superheat-resistant alloy to effectively prevent the movement of dislocations.

In order to manufacture such a fine oxide dispersion strengthened (ODS) superalloy, it is manufactured using a powder metallurgy method according to the current technology. That is, the powder of the superalloy and the oxide powder are uniformly mechanically alloyed at a cryogenic temperature using a ball milling method, and then placed in a metal container and sealed. After heating at a high temperature, it is processed into an annealed tissue using extrusion or rolling, etc., and then finished into a product through post-heat treatment. This process has a very high manufacturing cost and is limited in application because it is limited to small parts.

Accordingly, recent efforts have been made to manufacture such an oxide dispersion-strengthened superalloy using an additive manufacturing method. Powder for additive manufacturing is manufactured by gas atomization, which is a method of dissolving a material and then spraying a high-pressure gas through a nozzle while flowing a liquid through a narrow passage to form a powder through rapid solidification. It is impossible to manufacture an integrated oxide dispersion type superalloy powder by this gas spraying method. This is because oxides have a much higher melting point than metals. Therefore, all the latest technologies for manufacturing oxide dispersion-strengthened superalloys are additive manufacturing by mixing superalloy powder with oxide powder or by mechano-chemical bonding. . However, the production of the mixed powder has disadvantages in that it is difficult to produce a uniform oxide-dispersed superalloy at an appropriate level because the unit cost is very high and the technical difficulty is high.

The technical problem to be solved by the present invention is to enhance the dispersion of oxides by uniformly introducing stable and fine-sized oxides that do not undergo phase change and size growth even when exposed to high temperature heat through additive manufacturing, which is more economical and easier than the prior art. To provide a method for manufacturing a nickel-type nickel-based superalloy and an oxide dispersion-strengthened nickel-based superalloy prepared by the manufacturing method.

In order to achieve the above technical object, the present invention performs additive manufacturing (AM) using a nickel-based superalloy powder containing niobium (Nb) containing 0.005 to 0.015 wt% of oxygen as a raw material to form a metal oxide on an alloy matrix. We propose a method for producing an oxide dispersion-strengthened niobium-containing nickel-based superalloy, characterized in that it is introduced.

In addition, argon shield gas flow rate 0.02 ~ 0.05 l / s; laser power 250 to 300 W; laser scan speed 650 to 850 mm/s; and niobium (Nb)-containing nickel-based superalloy powder with an oxygen content of 0.005 to 0.015 wt% in the powder by selective laser melting (SLM) according to process conditions with a powder lamination thickness of 40 to 60 μm A method for producing an oxide dispersion strengthening type niobium-containing nickel-based superalloy, characterized in that the oxide dispersion strengthening type niobium-containing nickel-based superalloy is prepared.

In addition, the niobium-containing nickel-based superalloy is Alloy 625 (Ni-21.5Cr-2.5Fe-9Mo-3.5Nb-0.2Ti-0.2A1-0.06C), characterized in that the oxide dispersion strengthening type niobium-containing nickel group A method for manufacturing a superalloy is proposed.

In addition, after completing the additive manufacturing, (a) the oxide dispersion strengthening type niobium-containing nickel-based superalloy prepared by the additive manufacturing method solution treatment at 1250 ~ 1300 ℃ for 5 minutes or more; (b) slowly cooling at a cooling rate of 1 to 10° C./min to 800 to 900° C. for aging immediately after the solution treatment; (c) aging treatment by maintaining at 800 to 900° C. for 5 minutes to 10 hours after the step of slow cooling; And (d) proposes a method for producing an oxide dispersion-strengthened niobium-containing nickel-based superalloy, characterized in that performing a heat treatment comprising the step of air cooling after the aging treatment.

In another aspect of the present invention, an oxide dispersion-strengthened niobium-containing nickel-based superalloy prepared according to the above method is proposed.

In addition, an oxide dispersion strengthening type niobium-containing nickel-based superalloy is proposed, characterized in that metal oxide particles having a particle diameter of 10 to 100 nm are dispersed in an alloy matrix.

According to the present invention, while maintaining the basic characteristics of the niobium-containing nickel-based superalloy produced through additive manufacturing as it is, an oxide having a size of about 10 to 100 nm is introduced into the crystal grains to impart an oxide dispersion strengthening effect. It is possible to easily and economically manufacture an alloy with improved high-temperature mechanical properties that has high resistance to the generation of internal cracks such as creep and fatigue by maintaining a fine size without phase change or size growth even in an environment exposed to for a long time in the prior art. .

1 is a scanning electron microscope (SEM) photograph of an Oxide Dispersion Strengthened (ODS) Alloy 625 alloy specimen manufactured by a selective laser melting method (SLM) in an embodiment of the present application.

In describing the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Since the embodiment according to the concept of the present invention may have various changes and may have various forms, specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiment according to the concept of the present invention with respect to a specific disclosed form, and should be understood to include all changes, equivalents or substitutes included in the spirit and scope of the present invention.

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, and includes one or more other features or numbers. , it is to be understood that it does not preclude the possibility of the presence or addition of steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in detail.

Nickel-based superalloy containing niobium has low solubility and relatively large niobium appears as a significant amount of fine segregation during additive manufacturing. At this time, such niobium is the main element in the formation of NbC and γ″ phases, which have a major effect on alloy strengthening, and the formation of these two phases greatly affects the strength of the alloy. However, these two phases are also precipitated after a long time heat treatment at a specific temperature suitable for precipitation conditions, and also melt or grow when exposed to high temperatures for a long time, thereby losing the mechanical properties of the alloy.

To compensate for this phenomenon, an oxide dispersion-strengthened alloy has been developed to maintain mechanical properties for a long time by uniformly distributing fine-sized oxides with little phase change and size growth at high temperatures.

In the present invention, an oxide dispersion strengthening alloy is manufactured using an additive manufacturing method, but unlike the prior art of manufacturing an alloy by mixing an oxide powder with an alloy powder and performing additive manufacturing, additive manufacturing using an alloy powder having an oxygen content in a specific numerical range It is characterized in that by controlling the main process parameters of the oxide dispersion-strengthened nickel-based superalloy in which stable and fine-sized oxides that do not undergo phase change and size growth even when exposed to high temperature heat are uniformly distributed.

Specifically, the present invention performs additive manufacturing (AM) using a nickel-based superalloy powder containing niobium (Nb) containing 0.005 to 0.015 wt% of oxygen as a raw material to introduce a metal oxide into an alloy matrix to strengthen oxide dispersion. It is characterized in that the type niobium-containing nickel-based superalloy is manufactured.

The additive manufacturing is preferably made by a powder bed fusion (PBF) method that selectively dissolves a shape by using a high thermal energy source (laser or electron beam) in a powder chamber among various known additive manufacturing methods. and, more preferably, a selective laser melting method (SLM) among the PBF methods may be used.

When implementing the method for producing an oxide dispersion-enhanced niobium-containing nickel-based superalloy according to the present invention using a selective laser melting method (SLM), an argon shield gas flow rate of 0.02 to 0.05 l/s; laser power 250 to 300 W; laser scan speed 650 to 850 mm/s; and a nickel-based superalloy powder containing niobium (Nb) containing 0.005 to 0.015 wt% of oxygen in the powder under process conditions of a powder lamination thickness of 40 to 60 μm to produce an oxide dispersion strengthening type niobium-containing nickel-based superalloy. It is preferable to manufacture

When the oxygen present in the alloy powder is melted by a laser, it reacts with a melt pool to generate an oxide. When the oxygen content in the powder is less than 0.005 wt%, the fine oxide is not sufficiently formed, 0.015 When it exceeds wt%, coarse oxides having a size of 1 μm or more are generated and some of them are dissolved and have a detrimental effect on fracture toughness. is limited to 0.005 to 0.015 wt%.

Also, argon gas is commonly used to protect a melt pool from the atmosphere when melting powders by a laser. If argon shielding gas is not used, not only coarse oxides, nitrides, and hydrides are generated when oxygen, nitrogen, hydrogen, etc. from the atmosphere enter the molten pool in large amounts and solidify, but also large pores due to the shrinkage caused by these formation. Occurs. Therefore, the flow rate of the argon shielding gas is usually in the range of 0.02 ~ 0.05 l/s during additive manufacturing using the selective laser melting (SLM) method. In the present invention, it was confirmed that the fine oxide was formed when the flow rate of argon gas was present within the range of 0.02 ~ 0.05 l/s. When the flow rate is less than 0.02 l/s, a large amount of pores are generated and a sound laminated object cannot be obtained. When oxygen from the atmosphere penetrates into the molten pool in a large amount and solidifies, coarse oxides with a size of 1 μm or more are generated, which has a detrimental effect on fracture toughness. . On the other hand, when the flow rate exceeds 0.05 l/s, the argon gas's ability to protect the molten pool is strong, so it is difficult for oxygen to penetrate, so fine oxides are not sufficiently generated. Therefore, in the present invention, the flow rate of the argon shielding gas among the process parameters of the selective laser melting method (SLM) is limited to 0.02 to 0.05 l/s as described above.

In the oxide dispersion strengthening type niobium-containing nickel-based superalloy prepared by the manufacturing method according to the present invention, the oxide introduced into the alloy through additive manufacturing interacts with dislocations inside the alloy to maximize the oxide dispersion strengthening effect. It is preferable to include two or more metal oxide particles having a size of 10 to 100 nm per alloy unit area (㎛ ² ) so as to be able to do so.

On the other hand, selective laser melting (SLM) uses a high-density laser probe in the solid state to melt a thin layer of metal powder on a bed in an inert atmosphere, and a steep temperature gradient is typically formed by rapid cooling. Inhomogeneous microstructure is injured. Therefore, if necessary, in order to remove the residual stress of the oxide dispersion-strengthened niobium-containing nickel-based superalloy prepared according to the above manufacturing method, a post-process heat treatment may be additionally performed.

As an example of the post-process heat treatment, (a) subjecting the oxide dispersion-strengthened niobium-containing nickel-based superalloy prepared through the above-described additive manufacturing to a solution treatment at 1250 to 1300° C. for 5 minutes or more; (b) slowly cooling at a cooling rate of 1 to 10° C./min to 800 to 900° C. for aging immediately after the solution treatment; (c) aging treatment by maintaining at 800 to 900° C. for 5 minutes to 10 hours after the step of slow cooling; and (d) a heat treatment comprising the step of air cooling after the aging treatment, but is not necessarily limited thereto.

According to the method for manufacturing the oxide dispersion-strengthened niobium-containing nickel-based superalloy according to the present invention described above, the basic properties of the niobium-containing nickel-based superalloy produced through additive manufacturing are maintained as they are, and about 10 to 100 By introducing an oxide with a size of nm to impart an oxide dispersion strengthening effect, it maintains a fine size without phase change or size growth even in an environment exposed to high temperatures of 700°C or higher for a long time, and has high resistance to internal cracks such as creep and fatigue An alloy having improved high-temperature mechanical properties can be easily and economically manufactured compared to the prior art.

Hereinafter, the present invention will be described in more detail by way of examples.

Embodiments according to the present specification may be modified in various other forms, and the scope of the present specification is not to be construed as being limited to the embodiments described in detail below. The embodiments of the present specification are provided to more completely explain the present specification to those of ordinary skill in the art.

<Example>

For Alloy 625 (Ni-21.5Cr-2.5Fe-9Mo-3.5Nb-0.2Ti-0.2A1-0.06C) powder with an oxygen content of 0.013 wt% in the powder, argon shield gas flow rate 0.03 l/s; An oxide dispersion-strengthened nickel-based superalloy specimen was prepared by performing selective laser melting (SLM) with a laser power of 275 W, a laser scan speed of 760 mm/s, and a powder stacking thickness of 50 μm.

Then, for the solution treatment of the oxide dispersion-strengthened nickel-based superalloy specimen, the solution treatment time (5 minutes or more) was maintained in a high temperature range of 1250 to 1300°C. Thereafter, it was slowly cooled at a rate of 1 to 10° C./min to the intermediate temperature region of the aging treatment temperature (800 to 900° C.). Next, after maintaining the aging treatment time (5 minutes or more) at the aging treatment temperature of 800 to 900°C, the heat treatment was completed by air cooling.

1 is a scanning electron microscope (SEM) photograph of an Oxide Dispersion Strengthened (ODS) Alloy 625 alloy specimen manufactured by selective laser melting (SLM) in an embodiment of the present application. It was confirmed that the oxide having a size of about 50 nm was uniformly dispersed in the dispersion-strengthened nickel-based superalloy.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

According to the present invention, an oxide having a size of about 10 to 100 nm is introduced into the crystal grains of the niobium-containing nickel-based superalloy produced through additive manufacturing to give an oxide dispersion strengthening effect, thereby preventing the generation of internal cracks such as creep and fatigue. It is possible to easily and economically manufacture an alloy having high temperature resistance and improved mechanical properties compared to the prior art.

Claims (6)

Oxide dispersion strengthening type, characterized in that a metal oxide is introduced into an alloy matrix by performing additive manufacturing (AM) with a nickel-based superalloy powder containing niobium (Nb) containing 0.005 to 0.015 wt% of oxygen as a raw material A method for producing a nickel-based superalloy containing niobium. According to claim 1, Argon shield gas flow rate 0.02 to 0.05 l/s; laser power 250 to 300 W; laser scan speed 650 to 850 mm/s; and a selective laser melting method (Selective Lasef Melting, SLM) performed according to process conditions of a powder lamination thickness of 40 to 60 μm, By processing a nickel-based superalloy powder containing niobium (Nb) with an oxygen content of 0.005-0.015 wt% in the powder, Characterized in manufacturing an oxide dispersion-strengthened niobium-containing nickel-based superalloy, A method for producing an oxide dispersion-strengthened nickel-based superalloy containing niobium. According to claim 1, The niobium-containing nickel-based superalloy is Alloy 625 (Ni-21.5Cr-2.5Fe-9Mo-3.5Nb-0.2Ti-0.2A1-0.06C), characterized in that the oxide dispersion reinforced nickel-based superalloy containing niobium is superheat resistant. A method of manufacturing an alloy. According to claim 1, After completing the additive manufacturing, a method for producing an oxide dispersion-strengthened niobium-containing nickel-based superalloy, characterized in that a heat treatment including the following steps (a) to (d) is performed: (a) subjecting the oxide dispersion-strengthened niobium-containing nickel-based superalloy prepared by the additive manufacturing method to a solution treatment at 1250 to 1300° C. for 5 minutes or more; (b) slowly cooling at a cooling rate of 1 to 10° C./min to 800 to 900° C. for aging immediately after the solution treatment; (c) aging treatment by maintaining at 800 to 900° C. for 5 minutes to 10 hours after the step of slow cooling; and (d) air cooling after the aging treatment. An oxide dispersion strengthening type niobium-containing nickel-based superalloy prepared according to the method according to any one of claims 1 to 4. 6. The method of claim 5, An oxide dispersion strengthening type niobium-containing nickel-based superalloy, characterized in that metal oxide particles having a particle diameter of 10 to 100 nm are dispersed in an alloy matrix.

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