KR102585060B1 - Manufacturing method for Inconel 718 alloy multilayer shaped structure with excellent high-temperature tensile properties and Inconel 718 alloy multilayer shaped structure thereof - Google Patents

Abstract

The present invention relates to a method of manufacturing an Inconel 718 alloy laminated sculpture that has excellent high-temperature tensile properties by controlling the processing direction and process variables. It can have excellent high-temperature properties by evaluating the tensile properties according to the microstructure by controlling the processing direction and process variables. It relates to a method of manufacturing an Inconel 718 alloy laminated sculpture and an Inconel 718 alloy laminated sculpture using the same.
The method of manufacturing an Inconel 718 alloy laminated sculpture with excellent high-temperature tensile properties according to the present invention is a first method of providing Inconel 718 alloy powder manufactured by a gas injection method in an additive manufacturing method using a laser powder sintering method (L-PBF). step; A second step of setting process parameters for laser powder sintering (L-PBF); A third step of supplying the Inconel 718 alloy powder; A fourth step of melting the Inconel 718 alloy powder by selectively irradiating a modeling light source; A fifth step of forming one layer of Inconel 718 material while cooling and solidifying the molten Inconel 718 alloy powder; A sixth step of repeatedly stacking the third to fifth steps until a three-dimensional sculpture made of the Inconel 718 material is completed; and a seventh step of heat treating the laminated three-dimensional sculpture; It includes, and the process variable of the second step is set to a laser power of 260 to 295 (W).

Description

Manufacturing method for Inconel 718 alloy multilayer shaped structure with excellent high-temperature tensile properties and Inconel 718 alloy multilayer shaped structure using the same

The present invention relates to a method of manufacturing an Inconel 718 alloy laminated sculpture that has excellent high-temperature tensile properties by controlling the processing direction and process variables. It can have excellent high-temperature properties by evaluating the tensile properties according to the microstructure by controlling the processing direction and process variables. It relates to a method of manufacturing an Inconel 718 alloy laminated sculpture and an Inconel 718 alloy laminated sculpture using the same.

The turbine part of aircraft engines and gas turbine engines used for energy generation is exposed to high temperature environments of over 1000°C, so materials with excellent high-temperature characteristics are used. A representative material is Inconel 718 alloy. The method of improving high-temperature characteristics by growing the material into a single crystal in the existing casting process is widely used in the production of turbine parts, but the manufacturing process is complicated and parts with complex shapes, such as microchannels for cooling inside the engine, have a high raw material loss rate. There are limitations to casting-based production. To overcome these manufacturing limitations, there is increasing interest in developing Inconel 718 alloy additive manufacturing process technology with excellent high-temperature characteristics by using an additive manufacturing method that is close to the design shape and can manufacture complex shapes.

Additive manufacturing process technology has the characteristic of showing a unidirectional solidification microstructure depending on the laser scanning direction, so the stacking direction and optimal shape design are important aspects when stacking. In addition, it is possible to predict the microstructure after lamination by controlling the process conditions according to the laser power and scanning speed, making it possible to control the microstructure, unlike the existing casting process where microstructure control is difficult at the process stage.

In the present invention, the specimen is manufactured so that the processing direction is vertical and horizontal, the process conditions are controlled to manufacture the Inconel 718 alloy by layering, and the specimen is processed at room temperature (24 to 26 ° C). and high-temperature tensile testing to develop Inconel 718 alloy additive manufacturing process technology with excellent high-temperature characteristics. By using this, process steps through additive manufacturing can be minimized, and it is expected that it can be used in the gas turbine engine parts manufacturing process by reducing parts manufacturing costs.

Korean Patent No. 10-2241876

The present invention was developed to solve the above problems, and the purpose of the present invention is to provide a method for manufacturing Inconel 718 alloy with excellent high temperature characteristics in a additive manufacturing method.

In addition, the purpose of the present invention is to provide an Inconel 718 alloy manufacturing method that can reduce part manufacturing costs by minimizing process steps in the additive manufacturing method.

The technical problems to be solved by the invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

The method for manufacturing an Inconel 718 alloy laminated sculpture with excellent high-temperature tensile properties according to the present invention,

In the additive manufacturing method using laser powder sintering (L-PBF),

A first step of providing Inconel 718 alloy powder manufactured by gas injection;

A second step of setting process parameters for laser powder sintering (L-PBF);

A third step of supplying the Inconel 718 alloy powder;

A fourth step of melting the Inconel 718 alloy powder by selectively irradiating a modeling light source;

A fifth step of forming one layer of Inconel 718 material while cooling and solidifying the molten Inconel 718 alloy powder;

A sixth step of repeatedly stacking the third to fifth steps until a three-dimensional sculpture made of the Inconel 718 material is completed; and

A seventh step of heat treating the laminated three-dimensional sculpture; It is made including,

The process variable of the second step is set to a laser power of 260 to 295 (W).

By solving the above problem, the present invention provides an effective Inconel 718 alloy additive manufacturing process technology by controlling the processing direction and process conditions of the specimen, and can manufacture an Inconel 718 alloy laminated sculpture with excellent high-temperature characteristics.

Additionally, the present invention can reduce part manufacturing costs by minimizing process steps in the additive manufacturing method.

Figure 1 is a flow chart showing the method of manufacturing an Inconel 718 alloy laminated sculpture with excellent high temperature characteristics according to the present invention.
Figure 2 is a schematic diagram of an Inconel 718 alloy laminated sculpture manufacturing apparatus with excellent high temperature characteristics according to an embodiment of the present invention.
Figure 3 is a schematic diagram of a method for manufacturing an Inconel 718 alloy laminated sculpture manufactured with different processing directions horizontally (a) and vertically (b) according to an embodiment of the present invention.
Figure 4 is a graph showing heat treatment conditions for the method of manufacturing an Inconel 718 alloy laminated sculpture with excellent high temperature characteristics according to an embodiment of the present invention.
Figure 5 is a graph showing the measured tensile strength of various Inconel 718 alloy laminated sculpture specimens manufactured according to an embodiment of the present invention and comparative example specimens.

The terms used in this specification will be briefly explained, and the present invention will be described in detail.

The terms used in the present invention are general terms that are currently widely used as much as possible while considering the function in the present invention, but this may vary depending on the intention or precedent of a person working in the art, the emergence of new technology, etc. Therefore, the terms used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, rather than simply the name of the term.

When a part in the entire specification is said to “include” a certain element, this means that it does not exclude other elements but may further include other elements, unless specifically stated to the contrary.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

Specific details, including the problem to be solved by the present invention, the means for solving the problem, and the effect of the invention, are included in the examples and drawings described below. The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings.

Hereinafter, the present invention will be described in more detail with reference to the attached drawings.

As shown in Figure 1, the method of manufacturing an Inconel 718 alloy laminated sculpture with excellent high-temperature tensile properties is performed by the following steps.

First, the first step (S10) provides Inconel 718 alloy powder. The present invention is performed according to additive manufacturing using laser powder sintering (L-PBF), and uses Inconel 718 alloy powder with a particle size of 20 to 45 ㎛ manufactured by gas injection in step 1 (S10).

Next, the second step (S20) sets the process variables. The second step (S20) sets process parameters for laser powder sintering (L-PBF). The process variables are controlled by setting the laser power, scanning speed, hatching space, layer thickness, and creation direction of the laminated sculpture.

The laser power is preferably set to 260 to 295 (W). When the laser power is less than 260 (W), the energy density is so low that the powder cannot be completely melted, and tensile properties may be deteriorated due to unmelted powder. This can be solved by lowering the scan speed to a low speed and stacking, but this takes too long to create a stack, and when the laser power exceeds 295 (W), the energy density is high due to the influence of thermal stress that cannot be sufficiently resolved. There is a risk that the laminated sculpture may be physically deformed. Similarly, this can be solved by setting the scan speed quickly, but there is a risk of lowering the tensile properties due to the formation of micropores due to the fast scan speed, so it is preferable to perform the problem under the above conditions.

When the size of the laser power during additive manufacturing is outside the range of these conditions, the scanning speed must be set to a low speed to completely melt the powder, so the laminated production time takes a long time, which does not meet the problem that the present invention aims to solve. You will see the results. On the other hand, if the laser power is too high, the scan speed is set quickly, which may result in a fast cooling rate, which may result in the laminated product being deformed or unable to be laminated.

Additionally, the scan speed is preferably set to 860 to 1,260 (mm/s). If the scan speed is less than 860 (mm/s), there is a problem that the stacking time takes too long, and if the scan speed is more than 1,260 (mm/s), micropores and unmelted powder are created inside. There is a risk that the resulting laminated sculpture may be physically deformed or its tensile strength may be reduced, so it is preferable to perform the process under the above conditions.

In addition, the hatching space is the distance from the center of one laser beam to the center of the next laser beam when the laser scan path along which the laser moves is referred to as the scan space, and is preferably set to 70 to 130 ㎛. If the hatching space is too narrow, micropores may be resolved, but the section where the laser beam overlaps may not be able to resolve thermal stress, causing deformation. If the hatching space is too wide, micropores that appear between spaces may cause damage. Tensile properties may deteriorate. If the hatching space is less than 70 ㎛, there is a problem of deformation due to unresolved thermal stress due to excessive energy load in the section where the laser beam overlaps, and if the hatching space is more than 130 ㎛, fine fusion occurs in the unmelted space. Since pores (micro pores) are created and the tensile properties are deteriorated, it is preferable to perform the process under the above conditions.

Additionally, it is preferable to set the layer thickness to 30 to 60 ㎛. The layer thickness is affected by the advanced laser power and scan speed. If the layer thickness is too thin, the lamination creation time becomes longer, and there is a risk of deformation due to unresolved thermal stress. If the layer thickness is less than 30 ㎛, the lamination time takes a long time and the laminated sculpture may be deformed, and if the layer thickness exceeds 60 ㎛, unfused layers occur, resulting in delamination in which the unbonded layers crack and separate. Since the phenomenon occurs, it is desirable to carry out the problem under the above conditions.

In addition, it is desirable to set the processing direction of the Inconel 718 alloy laminated sculpture to be vertical and horizontal. As a result of performing a tensile test on the Inconel 718 alloy laminated sculpture manufactured according to the present invention at room temperature (24 to 26 ℃) and high temperature, when compared with the Inconel 718 alloy laminated sculpture manufactured by the conventional method, the processing direction of the laminated sculpture was It was confirmed that better tensile properties were obtained when manufactured in the horizontal direction, as shown in 3(a).

To increase productivity, energy density must be increased by using higher laser power and scan speed. Since the 1980s, laser power and scan speed have generally been limited to less than 200 (W) and 1200 (mm/s), respectively, due to operational stability and equipment specification limitations. As shown in Figure 2, efforts were made to obtain appropriate mechanical properties by controlling various process variables under the laser output and scan speed conditions of the present invention.

Build rate (VB), a representative indicator of the productivity of the L-PBF process, is determined by the following equation (1).

VB = VS

(where VS is the scan speed, Δy is the increase in hatch space, and Δz is the increase in layer height)

The productivity of L-PBF parts is volumetrically affected by the control of process parameters, and scan speed is the most important parameter for improving productivity.

Next, in the third step (S30), the Inconel 718 alloy powder is supplied. The third step (S30) supplies the Inconel 718 alloy powder.

Next, in the fourth step (S40), the Inconel 718 alloy powder is melted. In the fourth step (S40), the Inconel 718 alloy powder is melted by selectively irradiating the modeling light source. In the fourth step (S40), irradiation of the formative light source is performed in an inert gas atmosphere (Ar Gas) and while maintaining the oxygen concentration below 100 ppm. When carried out at an oxygen concentration higher than 100 PPM, a problem occurs in which the molten powder and oxygen react to form an oxide, so it is preferable to carry out the above conditions.

Next, the fifth step (S50) forms one layer of Inconel 718 material. The fifth step (S50) cools and solidifies the molten material to form one layer of Inconel 718 material.

Next, the sixth step (S60) is stacked by repeating the third step (S30) to the fifth step (S50). In the sixth step (S60), the third step (S30) to the fifth step (S50) are repeated and stacked until the three-dimensional sculpture made of the Inconel 718 material is completed.

Next, in the seventh step (S70), heat treatment is performed through steps 7-1 (S71) to 7-6 (S76) below. By performing the above heat treatment, we intend to manufacture Inconel 718 alloy, which has excellent high-temperature tensile strength.

Step 7-1 (S71) involves homogenization. In the 7-1 step (S71), after performing the 6th step (S60), homogenization is performed at 975 to 985 ° C. for 50 to 70 minutes. The homogenization treatment in step 7-1 (S71) is performed for the purpose of single-phase homogenization treatment by recrystallizing it into γ phase. During the homogenization treatment in step 7-1 (S71), if treated at less than 975 ℃, the γ phase is not sufficiently heated to the recrystallization temperature, resulting in a problem of not being homogenized into a single phase. If the temperature exceeds 985 ℃, the γ phase recrystallization temperature Problems arise due to high melting temperatures exceeding the above, so it is preferable to carry out the process under the above conditions. In addition, during the homogenization treatment in step 7-1 (S71), if the treatment is performed for less than 50 minutes, a problem occurs in which the precipitated phase is not solidified inside the recrystallized γ phase and cannot be homogenized into a single phase, and if the treatment is performed for less than 70 minutes, Since the effect compared to the processing time is minimal due to unnecessary homogenization processing time, it is preferable to carry out the treatment under the above conditions.

Step 7-2 (S72) is annealing. In the 7-2 step (S72), after the homogenization treatment in the 7-1 step (S71), the product is cooled to room temperature (24 to 26° C.) and annealed. When annealing in step 7-2 (S72), it is rapidly cooled to room temperature (24 to 26°C). If the cooling end temperature exceeds room temperature (24 to 26°C), a problem occurs in which dissolved precipitates precipitate during solution treatment, so it is preferable to perform the treatment under the above conditions. In addition, when the cooling rate is controlled slowly, the γ phase may grow excessively or precipitate nuclei may be generated and precipitated, so it is desirable to rapidly cool the cooling rate.

Step 7-3 (S73) is heat treatment. In the 7-3 step (S73), after annealing in the 7-2 step (S72), heat treatment is performed at 755 to 765 ° C. for 50 to 70 minutes. During the heat treatment in step 7-3 (S73), a certain amount of δ-phase nuclei are created at the γ-phase grain boundaries, thereby hindering grain boundary growth at high temperatures and improving tensile properties. If treated at less than 755 ℃, the nuclei of the δ phase are not sufficiently generated, and if the temperature exceeds 765 ℃, the δ phase changes into a needle-like shape rather than a spherical shape. The needle-shaped δ phase shows lower ductility than the spherical shape, which has the problem of lowering the tensile properties. Since this occurs, it is desirable to carry out the above conditions. In addition, during the heat treatment in step 7-3 (S73), if the treatment is performed for less than 50 minutes, the nuclei of the δ phase are not generated and are dissolved back into the base, or a very small amount of nuclei are generated, making it difficult to confirm their characteristics. If it exceeds 70 minutes, the δ phase nuclei are excessively generated or grow, creating new crystal grains and causing a problem of lowering the tensile properties, so it is preferable to carry out the procedure under the above conditions.

Step 7-4 (S74) is cooling. In the 7-4 step (S74), after the heat treatment in the 7-3 step (S73), cooling is performed to 620 ° C. for 50 to 70 minutes, and the nucleation and growth of the δ phase are affected depending on the temperature conditions and cooling time. gives. During the cooling treatment in the 7-4 step (S74), if the temperature exceeds 620°C, the nuclei of the δ phase generated at the grain boundary may not grow and may be dissolved back into the matrix, and if the temperature is less than 620°C, the generated nuclei may Since it is unevenly distributed or excessively produced, a problem of lowering the tensile strength occurs, so it is preferable to carry out the above-mentioned conditions. In addition, the cooling time is closely related to the above temperature conditions. If the cooling treatment exceeds 70 minutes, the nuclei growth time may be prolonged and coarse precipitates may appear, and if the cooling time is less than 50 minutes, the nuclei may appear. Since there is a problem of failure to grow and re-employment within the base, it is desirable to carry out the above conditions.

Step 7-5 (S75) is aging. In the 7-5 step (S75), after cooling in the 7-4 step (S74), aging is performed for 7.5 to 8.5 hours, and the γ'' phase precipitates are uniformly deposited inside the γ phase matrix to improve high temperature tensile strength. It is implemented for the purpose. When aging in the 7-5 step (S75), if the aging process is performed for less than 7.5 hours, a problem occurs in which the γ'' phase is not sufficiently uniformly precipitated within the γ phase matrix, and if the aging process exceeds 8.5 hours, the γ'' phase Since the problem of coarsening of the and γ bases occurs, it is preferable to carry out the above conditions.

In step 7-6 (S76), cool to room temperature (24 to 26°C). In the 7-6 step (S76), after aging in the 7-5 step (S75), it is cooled to room temperature (24 to 26°C) and rapidly cooled with room temperature (24 to 26°C) as the cooling end temperature. When cooling in the 7-6 step (S76), if the room temperature (24 to 26°C) is exceeded, the cooling end temperature is high and the tensile properties are deteriorated due to coarsening of the precipitate formed inside, so the above conditions occur. It is desirable to carry out this. In addition, when the cooling rate is controlled slowly, the problem of coarsening of the precipitated phase generated inside occurs as if the cooling end temperature exceeds room temperature (24 to 26° C.), so it is preferable to perform the process under the above conditions.

The Inconel 718 alloy laminated sculpture of the present invention is characterized in that it is manufactured by the Inconel 718 alloy laminated sculpture manufacturing method described above.

The Inconel 718 alloy laminated sculpture is characterized in that the laser power is controlled to 260 to 295 (W) during manufacturing. If the laser power is less than 260 (W), the energy is too low, so the lamination creation time takes too long, and the tensile strength of the generated lamination sculpture is too low, and if the laser power exceeds 295 (W), the Since there is a risk that the laminated sculpture may be physically deformed, it is preferable to perform under the above conditions.

In addition, the Inconel 718 alloy laminated sculpture is characterized in that the scan speed is controlled to 860 to 1,260 (mm/s) during manufacturing. If the scan speed is less than 860 (mm/s), the scan speed is too low and a problem occurs that the laminated production time takes too long, and if the scan speed exceeds 1,260 (mm/s), the created laminated sculpture is physically damaged. Since there is a risk of deformation, it is preferable to perform under the above conditions.

In addition, the Inconel 718 alloy laminated sculpture is characterized in that it is manufactured by controlling the hatching space, which is the gap between the laser scan paths along which the laser moves, to 70 to 130 ㎛ during manufacturing. If the hatching space is less than 70 ㎛, there is a problem of deformation due to unresolved thermal stress due to excessive energy load in the section where the laser beam overlaps, and if the hatching space is more than 130 ㎛, fine fusion occurs in the unmelted space. Since pores (micro pores) appear and the tensile properties are lowered, it is preferable to perform the process under the above conditions.

In addition, the Inconel 718 alloy laminated sculpture is characterized in that one layer thickness is 30 to 60 ㎛ when laminated with a laser. If the layer thickness is less than 30 ㎛, it takes a long time to create the lamination and shape deformation may occur, and if the layer thickness exceeds 60 ㎛, a layer that is not melted may occur, causing cracks and separation in the unbonded layer. Since problems occur, it is desirable to perform the procedure under the above conditions.

In addition, it is desirable to set the processing direction of the Inconel 718 alloy laminated sculpture to be vertical and horizontal. That is, as shown in FIG. 3(a), the longitudinal direction of the laminated sculpture is horizontal or parallel to the powder bed of the L-PBF, or as shown in FIG. 3(b), the laminated sculpture is manufactured. It can be manufactured in a direction in which the longitudinal direction is perpendicular to the powder bed of the L-PBF. As a result of performing a tensile test on the Inconel 718 alloy laminated sculpture manufactured according to the present invention at room temperature (24 to 26 ℃) and high temperature, when compared with the Inconel 718 alloy laminated sculpture manufactured by the conventional method, the processing direction of the laminated sculpture was It was confirmed that better tensile properties were obtained when manufactured in the horizontal direction, as shown in 3(a).

In addition, the Inconel 718 alloy laminated sculpture is characterized by a tensile strength of 1,460 to 1,600 MPa at room temperature (25 ℃) and 1,180 to 1,270 MPa at high temperature (649 ℃). The Inconel 718 alloy laminated sculpture manufactured by the present invention has increased tensile strength even at high temperatures by controlling the process variables of laser power, scan speed, hatching space, and laser thickness. In particular, by controlling the creation direction of the laminated sculpture, the tensile strength is further increased even at high temperatures compared to room temperature. In the past, a heat treatment process was performed to control the microstructure and precipitation phase to increase the tensile strength of Ti alloy at high temperatures, but the tensile strength was confirmed to be only about 800 to 1000 MPa.

In addition, the Inconel 718 alloy laminated sculpture is characterized in that the yield strength is 1,240 to 1,330 MPa at room temperature (25 ℃) and 1,060 to 1,140 MPa at high temperature (649 ℃). The Inconel 718 alloy laminated sculpture manufactured by the present invention has increased yield strength even at high temperatures by controlling the process variables of laser power, scan speed, hatching space, and laser thickness. In particular, by controlling the creation direction of the laminated sculpture, the yield strength is further increased even at high temperatures compared to room temperature.

In addition, the Inconel 718 alloy laminated sculpture was confirmed to have an elongation of 17.5% or more at room temperature (24 to 26 °C) and 9% or more at high temperature (649 °C).

Below, tensile strength, yield strength, and elongation were measured using the Inconel 718 alloy laminated sculpture manufactured by the method described above. Hereinafter, the present invention will be described in detail through examples to aid understanding. However, the following examples only illustrate the content of the present invention and the scope of the present invention is not limited to the following examples. Examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Inconel 718 alloy powder manufactured through gas injection was laminated using the L-PBF (Laser-Powder Bed Fusion) method using EOS-M290 equipment. As shown in Table 1, it was performed with various process parameters (laser power: 260-295 W, scanning speed: 860-1,260 (mm/s), hatch space: 70-130 μm, layer thickness: 30-60 μm. Specimens with a horizontal processing direction were named H, and specimens with a vertical processing direction were named V.

According to ASM standards, each specimen was homogenized at 980°C for 1 h and annealed by cooling to room temperature (24 to 26°C) in a heating furnace. Each annealed specimen was heat treated at 760°C for 1h, cooled to 620°C in a heating furnace, and then aged for 8h. Afterwards, it was cooled to room temperature (24 to 26°C) in a heating furnace.

sample Laser power
(W) Scanning speed (mm/s) Hatch space (㎛) Layer thickness (㎛) powder-bed direction H1160 285 1,160 110 40 horizontal V960 285 960 110 40 vertical

Comparative example

The comparative example was molded using the L-PBF (Laser-Powder Bed Fusion) method in the same way as the previously described example. However, as shown in the process conditions in Table 2 below, the laser power, scanning speed, hatch space, and layer thickness were controlled differently from the examples to manufacture the laminated sculpture.

sample Laser power
(W) Scanning speed (mm/s) Hatch space (㎛) Layer thickness (㎛) powder-bed direction H1 285 960 110 40 horizontal H2 285 1,060 110 40 horizontal V1 285 1,060 110 40 vertical V2 285 1,160 110 40 vertical C 285 960 - - horizontal

Experiment example

(1) Tensile test

Tensile specimens with a gauge length of 36 mm and a diameter of 5 mm were produced in different directions (horizontal and vertical) according to ASTM standards E8/E8M. The uniaxial tensile test was performed at room temperature (25 ℃) and high temperature (649 ℃) using a universal testing machine (MINOS-300S, MTDI, Korea) at a test speed of 1 × 10 ^-3 /s. The data obtained after the test was expressed as a stress-strain curve, and the maximum tensile strength was measured by analyzing the data at the point where the maximum load was applied in the plastic deformation section after the yield strength.

(2) Yield strength measurement

A tensile test was conducted under the conditions of Experimental Example (1), and the yield strength was measured by expressing the results as a stress-strain curve. Yield strength is measured at the point where the material leaves the elastic zone and undergoes plastic deformation. However, because it is difficult to confirm the exact point where deformation occurs, the slope of the elastic zone is offset by 0.2% in the stress-strain curve and the stress-strain curve is measured at the point where plastic deformation occurs. The strength at the intersection of the strain curve is called yield strength, and the yield strength was measured using the above method.

(3) Elongation measurement

A tensile test was conducted under the conditions of Experimental Example (1), and the results were expressed as a stress-strain curve to measure elongation. The measurement of elongation in the stress-strain curve measures the increase in gauge distance according to the applied load, and the value excluding the strain in the elastic section at the point of fracture was measured as elongation.

sample Yield Strength (MPa) Tensile Strength (MPa) Elongation (%) Testing temperature (℃) H1160 1,328 1,551 20.4 25 V960 1,180 1,375 21.3 25 H1 1,244 1,467 17.6 25 H2 1,270 1,494 17.5 25 V1 1,194 1,389 19.9 25 V2 1,232 1,430 19.5 25 C - 1417 15.6 25 H1160 1,138 1,261 9 649 V960 989 1,133 22 649 H1 1,064 1,187 10 649 H2 1,062 1,194 9 649 V1 1,015 1,115 17 649 V2 1,034 1,178 17 649

In the conventional case, in order to increase the high-temperature tensile properties during additive manufacturing of Inconel 718 alloy, the laser power, scan speed, layer thickness, hatching space, and direction of the powder bed were adjusted to achieve successful additive manufacturing and at the same time have excellent high-temperature tensile strength. There are no cases of inventing a material. As a result of checking the tensile strength according to the comparative example, a heat treatment process was performed to control the microstructure and precipitation phase to increase the high temperature tensile strength. However, as shown in Table 3, the tensile strength is only about 1,494 MPa at the maximum. , the elongation rate was 5-9% lower.

In the present invention, tensile strength, yield strength, and elongation were confirmed by controlling various process variables. As shown in Table 3, higher tensile strength and yield strength values were observed when the fabrication direction was horizontal.

In addition, as shown in Figure 5, it was confirmed that specimen H1160 manufactured according to the present invention had a tensile strength of 134 MPa higher and an elongation of 4.8% higher than that of the comparative example at room temperature (24 to 26 °C). In addition, in terms of high temperature tensile properties, H1160 had the highest tensile strength at 1,261 MPa. However, it was confirmed that V960 had the highest elongation rate of 21.6%.

By solving the above problem, the present invention provides an effective Inconel 718 alloy additive manufacturing process technology by controlling the processing direction and process conditions of the specimen and can manufacture an Inconel 718 alloy laminated sculpture with excellent high-temperature characteristics.

Additionally, the present invention can reduce part manufacturing costs by minimizing process steps in the additive manufacturing method.

As such, a person skilled in the art will understand that the technical configuration of the present invention described above can be implemented in other specific forms without changing the technical idea or essential features of the present invention.

Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive, and the scope of the present invention is indicated by the claims described later rather than the detailed description above, and the meaning and scope of the claims and their All changes or modified forms derived from the equivalent concept should be construed as falling within the scope of the present invention.

S10. The first step to providing Inconel 718 alloy powder
S20. The second step of setting process variables
S30. Third step of supplying the Inconel 718 alloy powder
S40. The fourth step of melting the Inconel 718 alloy powder
S50. Fifth step to form one layer of Inconel 718 material
S60. 6th step of stacking by repeating the 3rd to 5th steps
S70. A seventh step of heat treatment in steps 7-1 to 7-6;
S71. Step 7-1 of homogenization treatment
S72. Annealing Step 7-2
S73. Step 7-3 of heat treatment
S74. Cooling step 7-4
S75. Stage 7-5 of Aging
S76. Step 7-6 of cooling to room temperature (24 to 26 ℃)

Claims (14)

In the additive manufacturing method using laser powder sintering (L-PBF),
A first step of providing Inconel 718 alloy powder manufactured by gas injection;
A second step of setting process parameters for laser powder sintering (L-PBF);
A third step of supplying the Inconel 718 alloy powder;
A fourth step of melting the Inconel 718 alloy powder by selectively irradiating a modeling light source;
A fifth step of cooling and solidifying the molten Inconel 718 alloy powder to form one layer of Inconel 718 material;
A sixth step of repeatedly stacking the third to fifth steps until a three-dimensional sculpture made of the Inconel 718 material is completed; and
A seventh step of heat treating the laminated three-dimensional sculpture; It is made including,
In the first step, Inconel 718 alloy powder is manufactured with a particle size of 20 to 45 ㎛,
The process variables of the second step are,
The laser power is 260 to 295 (W),
A scan speed of 860 to 1,260 (mm/s),
The hatching space, which is the interval between the laser scan paths along which the laser moves, is 70 to 130 ㎛,
The layer thickness is 30 to 60 ㎛,
Set the processing direction to be horizontal,
The formative light source in the fourth step is operated in argon (Ar) gas, which is an inert gas atmosphere, with the oxygen concentration maintained at 100 ppm or less,
The seventh step is,
Step 7-1 of homogenizing at 975 to 985°C for 50 to 70 minutes, recrystallizing into γ phase and performing single-phase homogenization;
A 7-2 step of annealing by cooling to room temperature (24 to 26° C.) after the homogenization treatment;
After the annealing, a 7-3 step of heat treatment at 755 to 765 ° C. for 50 to 70 minutes to generate a certain amount of δ phase nuclei at the γ phase grain boundaries to prevent grain boundary growth at high temperature to improve tensile properties;
Step 7-4 of cooling to 620° C. for 50 to 70 minutes after the heat treatment;
Step 7-5 of aging for 7.5 to 8.5 hours after cooling; and
After the aging, step 7-6 of cooling to room temperature (24 to 26 ℃) is sequentially performed.
A method of manufacturing an Inconel 718 alloy laminated sculpture with excellent high-temperature tensile properties.
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