Method for improving performance of nickel-based superalloy manufactured by laser additive manufacturing through C-N steady-state compound precipitation and pinning strengthening

Abstract

The invention discloses a laser additive manufacturing nickel-based superalloy performance improving method through C-N steady-state compound precipitation and pinning strengthening, which comprises the following steps: adding g-C3N4 powder into nickel-based superalloy GH4169 according to a preset proportion, uniformly mixing, and melting and forming by adopting a laser additive manufacturing process, the high-performance nickel-based high-temperature alloy material with C-N steady-state compound precipitation and pinning strengthening can be obtained; the addition amount of the g-C3N4 powder is 0.2 wt% of the composite powder composed of the nickel-based high-temperature alloy GH4169 and the g-C3N4 powder. Therefore, the nickel-based superalloy composite material with C-N steady-state compound precipitation and pinning strengthening is obtained, the strength, hardness and modulus of the nickel-based superalloy are remarkably improved, the friction coefficient is reduced, and the comprehensive mechanical property of the nickel-based superalloy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser powder bed fusion forming of metal components, and particularly relates to a method for improving the performance of laser additive manufacturing nickel-based superalloy through the precipitation and pinning strengthening of C-N stable compounds. Background Technique

[0002] Nickel-based superalloy GH4169 has excellent high-temperature mechanical properties, corrosion resistance and oxidation resistance, so it is widely used in the manufacture of aero-engine combustion devices and other high-temperature components. Nickel-based superalloy components in practical applications usually have the characteristics of complex shapes and high dimensional accuracy, so there are certain challenges in their precise forming. Laser powder bed fusion (LPBF) technology uses a high-energy laser beam with a diameter of micron level to manufacture components layer by layer according to the CAD model, which is an effective technical way to precisely form high-precision complex nickel-based components. The progress and development of science and technology have put forward higher performance requirements for LPBF-formed nickel-based superalloy components. Scholars have carried out detailed and in-depth research on this problem, including various methods such as laser process optimization, post-heat treatment, and nano-modification. Among them, the performance improvement range of laser process optimization is limited, and post-heat treatment will extend the production cycle and increase the cost of LPBF nickel-based superalloy components. The nano-modification method provides an ideal way to improve the performance of LPBF-formed nickel-based superalloy components. By regulating the microstructure of nickel-based superalloy, the mechanical properties, corrosion resistance and oxidation resistance of the alloy are significantly improved. This method will play an important role in the further wide application of LPBF-formed nickel-based superalloy, and is expected to promote the technological innovation and development in high-end manufacturing fields such as aerospace.

[0003] At present, there have been many studies on LPBF-formed nano-modified nickel-based superalloys, and the reinforcing phases are mostly ceramic particles and metal elements, such as TiC, WC, ZrB2, SiC, Y, etc. In recent years, in the research of LPBF-formed metal matrix composites, two-dimensional materials (such as graphene, hexagonal boron nitride, g-C3N4, etc.) have received more and more attention as reinforcing phases, but there are few reports on nickel-based superalloys. Summary of the Invention

[0004] The present invention aims to develop a method for improving the performance of laser additive manufacturing nickel-based superalloy through the precipitation and pinning strengthening of C-N stable compounds, so as to obtain a nickel-based superalloy composite material with the precipitation and pinning strengthening of C-N stable compounds, significantly improve the strength, hardness, modulus of the nickel-based superalloy, reduce the friction coefficient, and improve its comprehensive mechanical properties.

[0005] To achieve the above technical objectives, the present invention will adopt the following technical solutions:

[0006] A method for improving the performance of a nickel-based superalloy by laser additive manufacturing with precipitation and pinning strengthening of C-N stable compounds, characterized in that after adding g-C3N4 powder to the nickel-based superalloy according to a preset ratio and mixing evenly, the laser additive manufacturing process is used for melting and forming, and a high-performance nickel-based superalloy composite material with precipitation and pinning strengthening of C-N stable compounds can be obtained; the addition amount of g-C3N4 powder is 0.2 wt% of the composite powder composed of the nickel-based superalloy and g-C3N4 powder.

[0007] Preferably, after adding g-C3N4 powder to the nickel-based superalloy according to a preset ratio, the nickel-based superalloy and g-C3N4 powder are mixed evenly by a ball milling process.

[0008] Preferably, the parameters of the laser additive manufacturing process are: the laser energy density is 30-95 J / mm 3 , the laser power is 100-300 W, the scanning speed is 700-1100 mm / s, the scanning spacing is 80 μm, and the layer thickness is 30 μm.

[0009] Preferably, the laser power is 100-200 W and the scanning speed is 800-1000 mm / s.

[0010] Preferably, the laser power is 150 W and the scanning speed is 800 mm / s.

[0011] Preferably, during the melting and forming process of the laser additive manufacturing process, high-purity argon is used as the protective atmosphere throughout the process.

[0012] Preferably, before the melting and forming of the laser additive manufacturing process, a substrate preheating mode is adopted.

[0013] Preferably, in the composite powder, the particle size of the nickel-based superalloy powder is 40-50 μm, and the particle size of the g-C3N4 powder is 1-3 μm.

[0014] Preferably, the parameters of the ball milling process are: the ball-to-material ratio is 1:2, the ball milling time is 4 h, and the ball milling speed is 250 r / min.

[0015] Another technical object of the present invention is to provide a high-performance metal nickel-based superalloy composite material, which is prepared and formed based on the above method for improving the performance of a nickel-based superalloy by laser additive manufacturing with precipitation and pinning strengthening of C-N stable compounds.

[0016] The advantages of the present invention are:

[0017] 1. The present invention first uses g-C3N4 as the strengthening phase for LPBF forming of nickel-based superalloy. The prepared composite material has a nickel-based superalloy (such as GH4169) as the matrix, and the laser absorption rate is regulated to affect the laser forming temperature field, thereby obtaining a high-performance nickel-based superalloy composite material with the precipitation of C-N stable compounds and pinning strengthening (that is, the high-performance nickel-based superalloy composite material formed by the present invention has C-N stable compound precipitation phases on the grain boundaries, and the C-N stable compound precipitation phases are arranged on the grain boundaries in a pinning-like manner to achieve pinning strengthening of the grain boundaries, referring to the attached Figure 5 ), significantly improving the strength, hardness, modulus of the nickel-based superalloy, reducing the friction coefficient, and enhancing its comprehensive mechanical properties.

[0018] 2. A method for improving the performance of laser additive manufacturing nickel-based superalloy through the precipitation of C-N stable compounds and pinning strengthening. As can be seen from the nickel-based superalloy comparative example prepared under the same conditions, this method does not cause obvious changes in the grain morphology, stress distribution, and texture strength and type, and avoids changing other properties of the material while improving the comprehensive performance.

[0019] 3. The high-performance metal nickel-based superalloy composite material prepared by the present invention is particularly suitable for combustion chambers, engine blades, and also suitable for structural components such as radiators. Description of the Drawings

[0020] Figure 1 Powder of GH4169 used in the examples and comparative examples.

[0021] Figure 2 Powder of g-C3N4 used in the examples and comparative examples.

[0022] Figure 3 Powder of 0.2% g-C3N4 / GH4169 used in the examples and comparative examples.

[0023] Figure 4 Laser absorption rates of powders of GH4169, g-C3N4, and 0.2% g-C3N4 / GH4169 used in the examples and comparative examples.

[0024] Figure 5 Microstructure of the LPBF formed 0.2% g-C3N4 / GH4169 specimen in Example 1.

[0025] Figure 6 Grain morphology of the LPBF formed 0.2% g-C3N4 / GH4169 specimen in Example 1.

[0026] Figure 7For the grain boundary distribution of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0027] Figure 8 For the KAM map of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0028] Figure 9 For the Taylor factor map of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0029] Figure 10 For the pole figure of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0030] Figure 11 For the tensile fracture morphology of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0031] Figure 12 For the laser confocal microscope image of the wear scar of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0032] Figure 13 For the SEM image of the wear scar of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0033] Figure 14 For the microstructure of the GH4169 specimen formed by LPBF in Comparative Example 1.

[0034] Figure 15 For the grain morphology of the GH4169 specimen formed by LPBF in Comparative Example 1.

[0035] Figure 16 For the grain boundary distribution of the GH4169 specimen formed by LPBF in Comparative Example 1.

[0036] Figure 17 For the KAM map of the GH4169 specimen formed by LPBF in Comparative Example 1.

[0037] Figure 18 For the Taylor factor map of the GH4169 specimen formed by LPBF in Comparative Example 1.

[0038] Figure 19 For the pole figure of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0039] Figure 20 For the tensile fracture morphology of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0040] Figure 21 It is the laser confocal microscope image of the wear scar of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1.

[0041] Figure 22 It is the SEM image of the wear scar of the 0.2% g-C3N4 / GH4169 specimen formed by LPBF in Example 1. Detailed implementation manners

[0042] The present invention will be described in detail below in conjunction with the accompanying drawings of the specification and embodiments, but the protection scope of the present invention is not limited thereto. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention.

[0043] In order to improve the comprehensive mechanical properties of existing nickel-based superalloys (GH4169 powder is used in the embodiments of the present invention), especially in terms of strength, hardness, modulus and friction coefficient, the nano-modified reinforcing phase g-C3N4 powder is introduced.

[0044] The g-C3N4 powder has excellent chemical and optical stability and can remain stable during the high-temperature laser melting process, enabling it to withstand high energy input and rapid cooling processes in laser additive manufacturing. It has a high specific surface area, which helps to be evenly dispersed in the substrate during the additive manufacturing process, providing more interfaces and reaction sites.

[0045] At the same time, through more research, the present invention finds that when high-melting-point metals are nano-modified, the matrix (such as GH4169 powder) and the reinforcing phase (such as g-C3N4 powder) are mixed in a certain molar ratio, and the optimal composition of the material system can often be obtained. Therefore, the mass percentage of g-C3N4 powder added to the GH4169 powder in the present invention is determined to be 0.2%. After being mixed evenly by ball milling, it is melted and formed by laser additive manufacturing process (parameters: laser power is 100-300W, scanning speed is 700-1100mm / s, scanning spacing is 80μm, layer thickness is 30μm), and a high-performance nickel-based superalloy composite material with precipitation and pinning strengthening of C-N stable compounds can be obtained.

[0046] To illustrate in detail the technical solutions involved in the present invention, the present invention provides a total of 25 examples and 3 comparative examples (refer to Table 1 below).

[0047]

[0048]

[0049] Some of the examples and comparative examples recorded in Table 1 are described in more detail below.

[0050] Example 12

[0051] This example is a method for improving the properties of a nickel-based superalloy by laser additive manufacturing through the precipitation and pinning strengthening of C-N stable compounds.

[0052] The composite material involved has a composition of 0.2 wt.% g-C3N4 / GH4169. The particle size of the GH4169 powder involved is 40 - 50 μm, and the particle size of the g-C3N4 powder is 1 - 3 μm.

[0053] The preparation method of this example specifically includes the following steps:

[0054] Step (1): Place the GH4169 powder ( Figure 1 ) and the g-C3N4 powder ( Figure 2 ) in a ceramic ball milling tank in proportion for ball milling and mixing. The grinding balls used are ceramic grinding balls, and the ball-to-material ratio is 1:2. High-purity argon gas is filled in the ball milling tank as a protective atmosphere. The ball milling time is 6 h, and the rotation speed is 250 r / min to obtain a composite powder ( Figure 3 ). The laser absorption rate of this composite powder is increased by 9.46 compared with the GH4169 powder ( Figure 4 . For the measurement of the laser absorption rate, a UV3600 UV–Vis-NIR spectrophotometer is used for testing at 1064 nm).

[0055] Step (2): Use the obtained composite powder for laser powder bed fusion forming. The laser power used is 150 W, the scanning speed is 800 mm / s, the scanning spacing is 80 μm, and the layer thickness is 30 μm. High-purity argon gas is used as a protective atmosphere throughout the forming process.

[0056] To improve the forming density and properties, in this invention, a substrate preheating mode is adopted before the laser powder bed fusion forming process to reduce stress.

[0057] After the laser forming is completed and cooled, the specimen is separated from the substrate by electrical discharge machining to obtain the 0.2 wt.% g-C3N4 / GH4169 composite material.

[0058] The microstructure of the obtained composite material is as shown in Figure 5 . It can be seen that there are uniformly distributed precipitation phases of C-N stable compounds in the specimen. The grain morphology, grain boundary distribution, dislocation distribution, texture strength, and texture type of the specimen are respectively as shown in Figures 6 - 10 .

[0059] The obtained composite material specimens were subjected to tensile tests using a CMT5250 universal testing machine. The tensile rate was 2 mm / min. The tensile strength at room temperature was 1422.36 MPa, and the elongation rate was 18.56%. Obvious dimples were observed on the tensile fracture surface by a ZEISS Sigma 360 scanning electron microscope ( Figure 11 ).

[0060] The obtained composite material specimens were subjected to Vickers hardness tests using an HXS-1000AY hardness tester. The load was 5 kg, and the holding time was 10 s. After testing, the Vickers hardness at room temperature was 347.36 HV5, the nano-hardness was 240.21 GPa, and the modulus was 4.64 GPa.

[0061] The obtained composite material specimens were subjected to wear tests using a CFT-I friction and wear testing machine. The friction pair was a silicon nitride ceramic ball. The friction speed was 50 mm / s, and the friction time was 30 min. The wear scar morphology was observed using a VK-150K laser microscope. After testing, the friction coefficient of the obtained composite material specimens at room temperature was 0.52, and the wear volume was 0.05 mm 3 ( Figure 12 ), and there were no obvious spalling or cracks on the wear scar ( Figure 13 ).

[0062] The above performance improvement can be attributed to the precipitation and pinning strengthening of C-N stable compounds, which can be attributed to the addition of 0.2 wt.% g-C3N4 improving the laser absorption rate, thereby increasing the molten pool temperature, increasing the liquid phase existence time of the molten pool, promoting the precipitation of C-N stable compounds, pinning them at grain boundaries / sub-grain boundaries, and then forming a strengthening effect and improving the comprehensive mechanical properties of the specimens.

[0063] Example 16

[0064] Refer to the implementation steps of Example 1. The difference between this example and Example 1 is only that the laser power and scanning speed used in laser powder bed fusion forming in step (2) are changed. In this example, the laser power is 200 W and the scanning speed is 700 mm / s. The tensile strength at room temperature of the finally prepared composite material is 1111.26 MPa, and the elongation rate is 13.95%.

[0065] Example 3

[0066] Refer to the implementation steps of Example 1. The difference between this example and Example 1 is only that the laser power and scanning speed used in the laser powder bed fusion forming in step (2) are changed. In this example, the laser power is 50 W and the scanning speed is 900 mm / s. The room temperature tensile strength of the finally prepared composite material is 781.22 MPa, and the elongation is 5.11%. It can be seen that the elongation of Example 3 is lower, and the tensile performance is also lower than that of Example 1. This process is not an optimized process.

[0067] Comparative Example 1

[0068] Refer to the implementation operation of Example 1. The difference between Comparative Example 1 and Example 1 is only that: the GH4169 material involved in Comparative Example 1 does not contain g-C3N4 and is only the pure GH4169 material formed by laser powder bed fusion. The microstructure of the obtained GH4169 material is as Figure 14 shown. It can be seen that there is no obvious precipitation phase in the specimen. The grain morphology, grain boundary distribution, dislocation distribution, texture strength, and texture type of the specimen are respectively as Figures 15 - 19 shown. The room temperature tensile strength is 1045.74 MPa, the elongation is 19.49%, and there are obvious cleavage steps on the fracture surface ( Figure 20 ). The room temperature Vickers hardness is 316.34 HV5, the nano-hardness is 241.47 GPa, and the modulus is 4.30 GPa. The room temperature friction coefficient is 0.58, and the wear amount is 0.07 mm 3 ( Figure 21 ), and there is obvious spalling on the wear scar ( Figure 22 ).

[0069] According to Table 1, when the laser energy density is small (below 30 J / mm 3 ), for the specimens made of the composite material with a composition of 0.2 wt.% g-C3N4 / GH4169, both the room temperature tensile strength and elongation have a significant decrease compared with Comparative Examples 1-3. When the laser energy density is moderate (below 30 - 95 J / mm 3 ), for the specimens made of the composite material with a composition of 0.2 wt.% g-C3N4 / GH4169, the room temperature tensile strength has a large increase compared with Comparative Examples 1-3. When the laser energy density is too large (above 95 J / mm 3 ), for the specimens made of the composite material with a composition of 0.2 wt.% g-C3N4 / GH4169, the improvement in tensile performance is not significant compared with Comparative Examples 1-3.

[0070] In summary, g-C3N4 has excellent chemical and optical stability. By regulating the laser absorption rate, it affects the laser forming temperature field, and then obtains a nickel-based superalloy composite with the precipitation of C-N stable compounds and pinning strengthening, significantly improving the strength, hardness, and modulus of the nickel-based superalloy, reducing the friction coefficient, and enhancing its comprehensive mechanical properties. It is worth noting that compared with the GH4169 samples prepared under the same conditions, there are no obvious changes in the grain morphology, stress distribution, and texture strength and type of this composite material, further proving that the strengthening mechanism of this nickel-based superalloy composite is the precipitation of C-N stable compounds and pinning strengthening guided by g-C3N4.

Claims

1. A method for improving the performance of a nickel-based high-temperature alloy manufactured by laser additive manufacturing through precipitation and pinning strengthening of CN stable compounds, characterized in that: After adding g-C3N4 powder into the nickel-based superalloy according to a preset ratio and mixing evenly, the high-performance nickel-based superalloy material with the precipitation and pinning strengthening of C-N stable compounds can be obtained by melting and forming using the laser additive manufacturing process; the addition amount of g-C3N4 powder is 0.2 wt% of the composite powder composed of the nickel-based superalloy and g-C3N4 powder.

2. The method for improving the properties of a nickel-based superalloy by laser additive manufacturing through precipitation and pinning strengthening of C-N stable compounds according to claim 1, characterized in that After adding g-C3N4 powder into the nickel-based superalloy according to a preset ratio, the nickel-based superalloy and g-C3N4 powder are mixed evenly by using the ball milling process.

3. The method for improving the performance of nickel-based high-temperature alloys manufactured by laser additive manufacturing through precipitation and pinning strengthening of CN stable compounds according to claim 2, characterized in that: The parameters of the laser additive manufacturing process are as follows: the laser energy density is 30 - 95 J / mm 3 , the laser power is 100 - 300 W, the scanning speed is 700 - 1100 mm / s, the scanning pitch is 80 μm, and the layer thickness is 30 μm.

4. The method for improving the properties of nickel-based superalloys by laser additive manufacturing through the precipitation and pinning strengthening of C-N stable compounds according to claim 3, characterized in that, The laser power is 100 - 200 W, and the scanning speed is 800 - 1000 mm / s.

5. The method for improving the properties of a nickel-based superalloy by laser additive manufacturing through precipitation and pinning strengthening of C-N stable compounds according to claim 4, characterized in that The laser power is 150 W, and the scanning speed is 800 mm / s.

6. The method for improving the properties of a nickel-based superalloy by laser additive manufacturing through precipitation and pinning strengthening of C-N stable compounds according to claim 3, characterized in that, During the melting and forming process of the laser additive manufacturing process, high-purity argon gas is used as the protective atmosphere throughout the process.

7. The method for improving the performance of nickel-based high-temperature alloys manufactured by laser additive manufacturing through precipitation and pinning strengthening of CN stable compounds according to claim 3, characterized in that: Before the melting and forming of the laser additive manufacturing process, a substrate preheating mode is adopted.

8. The method for improving the properties of a nickel-based superalloy by laser additive manufacturing through precipitation and pinning strengthening of C-N stable compounds according to claim 1, characterized in that, In the composite powder, the particle size of the nickel-based superalloy powder is 40 - 50 μm, and the particle size of the g-C3N4 powder is 1 - 3 μm.

9. The method for improving the properties of a nickel-based superalloy by laser additive manufacturing through precipitation and pinning strengthening of C-N steady-state compounds according to claim 1, characterized in that, The ball milling process parameters are: the ball-to-material ratio is 1:2, the ball milling time is 4 h, and the ball milling rotation speed is 250 r / min.

10. A high-performance metal nickel-based superalloy composite material, characterized in that, It is formed by the method for improving the performance of the laser additive manufacturing nickel-based superalloy through the precipitation and pinning strengthening of C-N stable compounds according to any one of claims 1 to 5.

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