A nickel-based high-temperature alloy K447A and a preparation method thereof

Abstract

The invention discloses a nickel-based high-temperature alloy K447A and a preparation method thereof, the preparation method comprising: establishing a three-dimensional model of a SLM-formed K447A nickel-based high-temperature alloy sample, importing a slicing software, and performing layered processing; setting the sample placement position and columnar hollow support parameters to generate supports; setting forming laser process parameters, laser remelting process parameters, and remelting times; laying nickel-based high-temperature alloy powder, performing laser forming scanning, and obtaining an intermediate product of a forming layer; remelting the intermediate product of the forming layer to obtain a forming layer; and processing layer by layer to obtain a formed part. In the selective laser melting forming process, by designing the forming path and the number of scans, the temperature field in the forming process is improved, and the solidification cracks formed by the segregation of interdendritic elements and precipitated phases at the grain boundaries due to excessive temperature gradients are reduced. There are almost no cracks in the formed sample after multiple remeltings, and there are only a few pores, the forming quality is good, and it is easy to operate and the cost is low.

Description

Technical Field

[0001] The present invention relates to the field of metal additives, and in particular to a nickel-based high-temperature alloy K447A and a preparation method thereof. Background Art

[0002] Nickel-based high-temperature alloy K447A (Mar-M247) can work continuously for a long time at temperatures above 650°C and under stress conditions. It has good toughness, fatigue performance, oxidation resistance and thermal corrosion resistance under high loads and high temperatures. It is widely used in the manufacture of hot end components, turbine blades and combustion chambers of gas turbines and other aerospace fields.

[0003] K447A nickel-based high-temperature alloy was first used in directional solidification. The mechanical properties of the alloy's equiaxed crystal structure at high temperatures are also among the best in high-temperature alloys, so it is also used for equiaxed crystal castings. It has excellent casting performance, high-temperature service performance, and creep and hot corrosion resistance. During the solidification process, some boride phases will also precipitate at the grain boundaries. However, traditional casting has high casting costs, long cycles, strict process requirements, low production efficiency, poor dimensional accuracy, and is prone to defects such as sand inclusions and pores.

[0004] Selective Laser Melting (SLM) technology is a typical method of metal additive manufacturing technology. It does not require expensive molds or time-consuming post-processing to obtain parts that meet the design structure, high material utilization and high production flexibility, and the size accuracy of the formed parts is high, which has significant advantages. SLM technology first digitizes the three-dimensional model of the part to be formed, obtains the laser scanning path slice, and then uses the computer system and scanning galvanometer to control the laser beam to scan the designed path to melt the powder. After all the paths of the current slice layer are scanned, the substrate drops by one slice layer thickness, and correspondingly, the powder supply bin rises by one slice layer height. The powder laying mechanism uses a scraper to evenly cover the new metal powder on the completed forming layer. The above processing process is repeated, and the layers are stacked and added until all the slice path data are scanned, and finally the formed metal parts are obtained.

[0005] K447A nickel-based high-temperature alloy has been widely used in gas turbines due to its good high-temperature creep performance and good oxidation resistance. However, K447A was developed for casting processing, with an Al+Ti content of more than 6%, and a high content of the strengthening phase γ′ dispersed in the matrix γ phase. During the selective laser melting process, due to the excessive cooling rate and large temperature gradient, interdendritic elements and precipitated phases are segregated at the grain boundaries, which easily causes solidification cracks, reduced working performance, and reduced service life, directly affecting the reliability of the formed parts.

[0006] Patent CN115351294A discloses a method for preparing nickel-based high-temperature alloy products by selective laser melting. First, a low-power laser beam and a slow scanning speed are used to scan the powder layer for the first time to preheat the powder layer and achieve pre-connection between powder particles, while significantly reducing the temperature gradient between the powder layer and the workpiece; then a high-power laser beam is used at a faster scanning speed to melt and form a formed layer. By precisely controlling the energy input of the laser twice scanning, the problems of poor bonding and unstable molten pool caused by powder splashing under the action of high-energy laser and metal powder are avoided, and the formation of pores is suppressed. However, this method still has the problem of cracking in the prepared K447A, and the quality is not ideal.

[0007] Therefore, how to suppress the cracking of the nickel-based high-temperature casting alloy K447A formed by selective laser melting and improve the forming quality of the high-temperature casting alloy formed by selective laser melting is a technical problem that needs to be solved at present. Summary of the invention

[0008] The solution of this application is based on the above ideas. Aiming at the development needs of the selective laser melting forming of nickel-based high-temperature alloy K447A, the laser scanning path is designed for multiple remelting to improve the temperature field distribution, reduce the temperature gradient and cooling rate, and reduce solidification cracks in the forming process. A nickel-based high-temperature alloy K447A and a preparation method thereof are provided, which solves the problem that the nickel-based high-temperature casting alloy K447A is prone to cracking when formed by selective laser melting, and provides a new technical approach for the one-time forming of complex structural parts of high-temperature casting alloys.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] In one aspect, the present invention provides a method for preparing a nickel-based high-temperature alloy K447A, comprising the following steps:

[0011] Step 1: Establish a 3D model of the SLM-formed K447A nickel-based superalloy sample, import it into the slicing software, and perform layering processing;

[0012] Step 2: Place the formed substrate into the forming chamber, set the sample placement position and columnar hollow support parameters, and generate support;

[0013] Step 3: Set forming laser process parameters, laser remelting process parameters and remelting times;

[0014] Step 4: Lay the nickel-based high-temperature alloy powder on the forming substrate, and perform laser forming scanning on the nickel-based high-temperature alloy powder according to the laser process parameters set in step 3 to obtain an intermediate product of the forming layer;

[0015] Step 5: remelting the intermediate product of the forming layer according to the laser remelting process parameters and remelting times set in step 3 to obtain the forming layer;

[0016] Step 6: Repeat steps 4 and 5 to stack the obtained shaping layers layer by layer until a formed part having the shape of the three-dimensional model established in step 1 is obtained.

[0017] Furthermore, the remelting times are 3 to 5 times per layer.

[0018] Furthermore, in the process of remelting the intermediate product of the forming layer in step 5, each time the remelting is performed, the laser rotation scanning angle is 60 to 90 degrees.

[0019] Furthermore, in step 4, the thickness of the powder layer of the nickel-based high-temperature alloy powder spread on the forming substrate is 30 to 50 μm.

[0020] Furthermore, a protective gas is introduced into the forming chamber, and the oxygen content of the environment is within 50 ppm.

[0021] Furthermore, the protective gas is argon.

[0022] Furthermore, the forming laser process parameters are: forming laser power 120-160W, scanning speed 700-800mm / s, scanning spacing 0.06-0.08mm.

[0023] Furthermore, the laser remelting process parameters are: remelting laser power 120-150W, scanning speed 700-800mm / s, scanning spacing 0.07-0.08mm.

[0024] On the other hand, the present invention also provides a nickel-based high-temperature alloy K447A, which is prepared by the above-mentioned preparation method.

[0025] Furthermore, the nickel-based high-temperature alloy K447A provided by the present invention has the following components by mass: Co: 10.12%, Cr: 8.7%, Mo: 0.74%, W: 10.3%, Ta: 3.1%, Ti: 1.15%, Al: 5.6%, Hf: 1.6%, Zr: 0.055%, B: 0.017%, C: 0.14%, Fe: 0.13%, Si: 0.04%, Mn: 0.01%, S: 0.003%, O: 0.011%, N: 0.005%, and the rest is Ni.

[0026] The present invention can significantly reduce the crack density of the nickel-based high-temperature casting alloy K447A formed by selective laser melting through a laser multiple remelting strategy. By comprehensively considering process parameters such as laser power, scanning strategy, scanning speed and scanning spacing, the K447A nickel-based high-temperature alloy sample formed by the provided multiple remelting process parameters significantly reduces the crack density and improves its forming quality.

[0027] Compared with the prior art, the K447A nickel-based high-temperature alloy and the preparation method thereof provided by the present invention have the following advantages:

[0028] (1) The present invention improves the temperature field distribution, reduces the temperature gradient and cooling rate, and reduces solidification cracks during the forming process by designing a laser scanning path for multiple remelting. This is an important breakthrough in the laser rapid forming of nickel-based high-temperature casting alloy materials, reduces the defects of cracking of formed parts, and effectively improves the crack sensitivity of such high-temperature alloys. At the same time, it is easy to operate and has low cost, which is conducive to the large-scale promotion of the selective laser melting forming process of nickel-based high-temperature casting alloys.

[0029] (2) Due to the laser scanning path design, the multiple remelting under the optimized process parameters of the present invention does not cause obvious thermal deformation, and the forming quality is good, and the precision and surface quality are high.

[0030] (3) After multiple remelting tests, the K447A nickel-based high-temperature alloy sample has a crack density of less than 0.1% and a hardness value of 410.8±15.2HV 0.2 , to achieve casting performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following is a brief description of the contents expressed in the drawings of the specification:

[0032] Figure 1 A flow chart of the preparation method of the nickel-based high-temperature alloy K447A provided in this application;

[0033] Figure 2 A schematic diagram of the remelting model design in the method for preparing the nickel-based high-temperature alloy K447A provided in Example 1 of the present application;

[0034] Figure 3 A schematic diagram of a forming path and a remelting path in the method for preparing the nickel-based high-temperature alloy K447A provided in Example 1 of the present application;

[0035] Figure 4 This is a microscopic image of a longitudinal section of a nickel-based high-temperature alloy K447A formed part prepared in Example 1 of the present application;

[0036] Figure 5 This is a microscopic image of a longitudinal section of a nickel-based high-temperature alloy K447A formed part prepared in Example 2 of the present application;

[0037] Figure 6 This is a microscopic image of the longitudinal section of the nickel-based high-temperature alloy K447A formed part prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The present invention aims at the development demand of selective laser melting forming nickel-based high-temperature alloy K447A. By designing laser scanning path for multiple remelting to improve temperature field distribution, reduce temperature gradient and cooling rate, and reduce solidification cracks in the forming process, the problem of easy cracking of nickel-based high-temperature casting alloy K447A formed by selective laser melting is solved, and a new technical approach is provided for one-time forming of high-temperature casting alloy complex structure parts. The process of the remelting selective laser melting forming nickel-based high-temperature alloy K447A provided by the present invention is as follows: Figure 1 As shown, it is implemented by the following steps:

[0040] Step 1: Establish a 3D model of the SLM-formed K447A nickel-based superalloy sample, import it into the slicing software, and perform layering processing;

[0041] Step 2: Place the formed substrate into the forming chamber, set the sample placement position and columnar hollow support parameters, and generate support;

[0042] Step 3: Set forming laser process parameters, laser remelting process parameters and remelting times;

[0043] Step 4: Lay the nickel-based high-temperature alloy powder on the forming substrate, and perform laser forming scanning on the nickel-based high-temperature alloy powder according to the laser process parameters set in step 3 to obtain an intermediate product of the forming layer;

[0044] Step 5: remelting the intermediate product of the forming layer according to the laser remelting process parameters and remelting times set in step 3 to obtain the forming layer;

[0045] Step 6: Repeat steps 4 and 5 to stack the obtained shaping layers layer by layer until a formed part having the shape of the three-dimensional model established in step 1 is obtained.

[0046] Among them, the experimenters of this application found that when the number of remelting times for each layer is controlled at 3 to 5 times and the laser scanning is rotated 60 to 90° before each remelting, the best remelting effect can be obtained, that is, the quality of the prepared formation layer is uniform and the crack density is minimal.

[0047] The process of the above preparation method is described in detail below in conjunction with specific examples.

[0048] Example 1

[0049] K447A nickel-based high-temperature alloy is selected, and the components and proportions are as follows: Co is 10.12%, Cr is 8.7%, Mo is 0.74%, W is 10.3%, Ta is 3.1%, Ti is 1.15%, Al is 5.6%, Hf is 1.6%, Zr is 0.055%, B is 0.017%, C is 0.14%, Fe is 0.13%, Si is 0.04%, Mn is 0.01%, S is 0.003%, O is 0.011%, N is 0.005%, and the rest is Ni. The forming equipment model used in this embodiment is Charmray CR SLM-100.

[0050] The forming method comprises the following steps:

[0051] S100: Establish a 3D model of the SLM-formed K447A nickel-based superalloy sample, such as Figure 2 As shown, and imported into the slicing software in STL format.

[0052] S200: Set the sample placement position and columnar hollow support parameters.

[0053] S300: Set the forming laser process parameters: forming laser power 120W, scanning speed 700mm / s, scanning spacing 0.06mm, powder layer thickness 30μm, protective gas is argon, and the oxygen content in the forming chamber environment is within 50ppm.

[0054] S400: Set the laser remelting process parameters: remelting laser power 150W, scanning speed 700mm / s, scanning spacing 0.07mm, powder layer thickness 30μm, remelting 3 times, each remelting laser rotation scanning angle is 90°, remelting path is as follows Figure 3 As shown, the protective gas for each remelting is argon, and the oxygen content in the forming chamber is within 50ppm.

[0055] S500: Print samples layer by layer.

[0056] The final formed K447A sample was cut along the longitudinal line of the central axis, and after inlaying, it was polished with 240#, 400#, 600#, 800#, 1200#, 1500#, 2000#, and 3000# sandpaper respectively. After cleaning with alcohol and drying, it was observed under an optical microscope. The longitudinal section micrograph is shown in the figure. Figure 4 As shown, the magnification is 50 times, the contrast is adjusted by Image-pro software, and the statistical crack density is 0.09%.

[0057] Example 2

[0058] K447A nickel-based high-temperature alloy is selected, and the components and proportions are as follows: Co is 10.12%, Cr is 8.7%, Mo is 0.74%, W is 10.3%, Ta is 3.1%, Ti is 1.15%, Al is 5.6%, Hf is 1.6%, Zr is 0.055%, B is 0.017%, C is 0.14%, Fe is 0.13%, Si is 0.04%, Mn is 0.01%, S is 0.003%, O is 0.011%, N is 0.005%, and the rest is Ni. The forming equipment model used in this embodiment is Charmray CR SLM-100.

[0059] The forming method comprises the following steps:

[0060] S100: Establish a 3D model of the SLM-formed K447A nickel-based superalloy sample and import it into the slicing software in STL format.

[0061] S200: Set the sample placement position and columnar hollow support parameters.

[0062] S300: Set the forming laser process parameters: forming laser power 120W, scanning speed 700mm / s, scanning spacing 0.06mm, powder layer thickness 30μm, protective gas is argon, and the oxygen content in the forming chamber environment is within 50ppm.

[0063] S400: Set the laser remelting process parameters: remelting laser power 180W, scanning speed 800mm / s, scanning spacing 0.07mm, powder layer thickness 30μm, remelting 6 times, each remelting laser rotation scanning angle is 60°, protective gas is argon, and the oxygen content in the forming chamber environment is within 50ppm.

[0064] S500: Print samples layer by layer.

[0065] The final formed K447A sample was cut along the longitudinal line of the central axis, and after inlaying, it was polished with 240#, 400#, 600#, 800#, 1200#, 1500#, 2000#, and 3000# sandpaper respectively. After cleaning with alcohol and drying, it was observed under an optical microscope. The longitudinal section micrograph is shown in the figure. Figure 5 As shown, the magnification is 50 times. By adjusting the contrast with Image-pro software, it can be seen that there are no obvious cracks, only a small amount of pores, and the forming quality is good. The hardness of the tested sample is 410HV 0.2 .

[0066] Comparative Example 1

[0067] K447A nickel-based high-temperature alloy is selected, and the components and proportions are as follows: Co is 10.12%, Cr is 8.7%, Mo is 0.74%, W is 10.3%, Ta is 3.1%, Ti is 1.15%, Al is 5.6%, Hf is 1.6%, Zr is 0.055%, B is 0.017%, C is 0.14%, Fe is 0.13%, Si is 0.04%, Mn is 0.01%, S is 0.003%, O is 0.011%, N is 0.005%, and the rest is Ni. The forming equipment model used in this embodiment is Charmray CR SLM-100.

[0068] The forming method comprises the following steps:

[0069] S100: Establish a 3D model of the SLM-formed K447A nickel-based superalloy sample and import it into the slicing software in STL format.

[0070] S200: Set the sample placement position and columnar hollow support parameters.

[0071] S300: Set the forming laser process parameters: forming laser power 120W, scanning speed 700mm / s, scanning spacing 0.06mm, powder layer thickness 30μm, protective gas is argon, and the oxygen content in the forming chamber environment is within 50ppm.

[0072] S400: Print samples layer by layer.

[0073] The final formed K447A sample was cut along the longitudinal line of the central axis, and after inlaying, it was polished with 240#, 400#, 600#, 800#, 1200#, 1500#, 2000#, and 3000# sandpaper respectively. After cleaning with alcohol and drying, it was observed under an optical microscope. The longitudinal section micrograph is shown in the figure. Figure 6 As shown, the magnification is 50 times. By adjusting the contrast with Image-pro software, it can be seen that there are many obvious cracks and a small amount of pores, and the forming quality is not ideal. The hardness of the tested sample is 390HV 0.2 .

[0074] By comparing Examples 1 to 2 with Comparative Example 1, it can be seen that by designing laser scanning paths for multiple remelting to improve temperature field distribution, reduce temperature gradient and cooling rate, and reduce solidification cracks during the forming process, the crack sensitivity of the nickel-based high-temperature casting alloy K447A can be effectively improved, and the hardness of the product can also be improved. The hardness of the formed sample after remelting is increased by 5% compared with the existing process. Therefore, the present invention can improve the crack sensitivity of such nickel-based high-temperature casting alloys by designing the number of remelting times and the laser multiple remelting paths according to different nickel-based high-temperature casting alloy forming process windows, thereby effectively improving the forming quality of the nickel-based high-temperature casting alloy formed by selective laser melting.

[0075] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a nickel-based high-temperature alloy K447A, characterized in that: The steps include: Step 1: Establish a 3D model of the SLM-formed K447A nickel-based superalloy sample, import it into the slicing software, and perform layering processing; Step 2: Place the formed substrate into the forming chamber, set the sample placement position and columnar hollow support parameters, and generate support; Step 3: Setting forming laser process parameters, laser remelting process parameters and remelting times; wherein the forming laser process parameters are: forming laser power 120-160W, scanning speed 700-800mm / s, scanning spacing 0.06-0.08mm, and the laser remelting process parameters are: remelting laser power 120-150W, scanning speed 700-800mm / s, scanning spacing 0.07-0.08mm; Step 4: Lay the nickel-based high-temperature alloy powder on the forming substrate, and perform laser forming scanning on the nickel-based high-temperature alloy powder according to the laser process parameters set in step 3 to obtain an intermediate product of the forming layer; Step 5: remelting the intermediate product of the forming layer according to the laser remelting process parameters and the number of remelting times set in step 3 to obtain a forming layer; the number of remelting times is 3 to 5 times per layer; Step 6: Repeat steps 4 and 5 to stack the obtained shaping layers layer by layer until a formed part having the shape of the three-dimensional model established in step 1 is obtained.

2. The method for preparing a nickel-based high-temperature alloy K447A according to claim 1, characterized in that: In the process of remelting the intermediate product of the forming layer in step 5, the laser rotation scanning angle is 60 to 90 degrees each time the remelting is performed.

3. The method for preparing a nickel-based high-temperature alloy K447A according to claim 1, characterized in that: In step 4, the nickel-based high-temperature alloy powder is spread on the forming substrate to a powder layer thickness of 30 to 50 μm.

4. The method for preparing a nickel-based high-temperature alloy K447A according to claim 1, characterized in that: A protective gas is introduced into the forming chamber, and the oxygen content of the environment is within 50 ppm.

5. The method for preparing a nickel-based high-temperature alloy K447A according to claim 4, characterized in that: The protective gas is argon.

6. A nickel-based high-temperature alloy K447A, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. The nickel-based high-temperature alloy K447A according to claim 6, characterized in that: It has the following compositions by mass: Co: 10.12wt.%, Cr: 8.7wt.%, Mo: 0.74wt.%, W: 10.3wt.%, Ta: 3.1wt.%, Ti: 1.15wt.%, Al: 5.6wt.%, Hf: 1.6wt.%, Zr: 0.055wt.%, B: 0.017wt.%, C: 0.14wt.%, Fe: 0.13wt.%, Si: 0.04wt.%, Mn: 0.01wt.%, S: 0.003wt.%, O: 0.011wt.%, N: 0.005wt.%, and the rest is Ni.

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