Follow-up rolling-assisted nickel-based alloy thin-wall part additive forming method

Abstract

The invention provides a follow-up rolling-assisted nickel-based alloy thin-wall part additive forming method, and belongs to the technical field of additive manufacturing and machining. According to the method, the nickel alloy layer is deposited on the substrate through the L-DED technology, the nickel alloy layer is subjected to instant rolling treatment through the mechanical rolling device while L-DED deposition is conducted, and deposition and rolling are conducted synchronously by controlling technological parameters. Through rolling treatment, grains can be obviously refined, the dislocation density can be improved, and the strengthening effect can be enhanced, so that the mechanical property of the material can be improved. The influence of different rolling process parameters on the performance of the formed part and how to further improve the material performance by optimizing the process parameters can be further explored through future research. In addition, the method has wide application prospects in the field of manufacturing of parts with complex shapes and high performance requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing and mechanical processing, and in particular to a method for additive forming of nickel-based alloy thin-walled parts assisted by follower rolling. Background Art

[0002] As an important method of laser additive manufacturing, L-DED technology has significant advantages in manufacturing complex parts. However, due to the influence of heat input and cooling rate, pores, cracks and surface morphology defects are easily generated during the L-DED forming process. In addition, the anisotropy of the mechanical properties of the formed parts in different directions also limits the further application of L-DED technology. How to overcome these defects and obtain a method for preparing IN625 nickel-based high-temperature alloy by rolling-assisted L-DED is a technical problem that needs to be solved at present. Summary of the invention

[0003] The object of the present invention is to provide a method for additive forming of nickel-based alloy thin-walled parts assisted by follow-up rolling, which is used to solve the technical problem of anisotropy of mechanical properties of parts formed by L-DED technology in different directions.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for additive forming of nickel-based alloy thin-walled parts assisted by follow-up rolling, comprising the following steps:

[0006] A nickel alloy layer is deposited on the substrate by the L-DED process. During the L-DED deposition, a mechanical rolling device is used to perform instant rolling treatment on the nickel alloy layer. By controlling the process parameters, the deposition and rolling are carried out simultaneously.

[0007] In the L-DED process, the laser power is 1200-1300W;

[0008] In the rolling process, the rolling pressure is 7000-9000N.

[0009] Furthermore, in the L-DED process, the scanning rate is 5 to 15 mm / s, the powder feeding rate is 5 to 10 g / min, the spot diameter is 2 to 3 mm, the layer height is 0.1 to 0.3 mm, and the number of deposition layers is 50 to 80 layers.

[0010] Furthermore, the mechanical rolling device is provided with a rolling head with a cooling function to ensure that the nickel alloy layer will not be thermally affected during the rolling process.

[0011] Furthermore, the raw material used in the L-DED process is spherical IN625 powder, and the size of the spherical IN625 powder ranges from 53 to 150 μm.

[0012] Beneficial effects of the present invention:

[0013] (1) The rolling treatment in the present invention significantly refines the grain structure of the IN625 alloy. Compared with the unrolled samples, the grain size of the rolled samples is significantly reduced, from hundreds of microns to several microns to tens of microns. This grain refinement phenomenon directly enhances the yield strength of the material through the Hall-Petch relationship. In addition, the rolling treatment also introduces a large number of dislocations, further enhancing the dislocation strengthening effect of the material. Through in-situ EBSD analysis, it was observed that during the deformation process of the rolled samples, the dislocation density increased significantly, and low-angle grain boundaries (LAGBs) were formed and increased, indicating that dislocations are continuously activated and moved during the deformation process to coordinate the macroscopic strain.

[0014] (2) In terms of mechanical properties, the rolled IN625 alloy exhibited significantly improved tensile strength and yield strength, while the hardness also increased. However, the elongation after fracture decreased, which may be due to the increased brittleness of the material caused by grain refinement and increased dislocation density. Nevertheless, the rolled sample still exhibited good toughness and plastic deformation ability, and its fracture morphology showed ductile fracture characteristics.

[0015] (3) Through quantitative calculation of different strengthening mechanisms, it was found that dislocation strengthening played a dominant role in the rolled samples, while the grain boundary strengthening effect was also significantly improved. The rolling process not only changed the microstructure of the material, but also affected its texture direction and strength, further eliminated organizational segregation and internal stress, and improved the mechanical properties of the material in a specific direction.

[0016] In summary, rolling-assisted laser powder directed energy deposition technology provides an effective method for manufacturing high-performance IN625 alloy formed parts. Through rolling treatment, the grains can be significantly refined, the dislocation density can be increased, and the strengthening effect can be enhanced, thereby improving the mechanical properties of the material. Future research can further explore the effects of different rolling process parameters on the performance of formed parts, and how to further improve material performance by optimizing process parameters. In addition, the present invention has broad application prospects in the field of manufacturing parts with complex shapes and high performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the rolling-assisted laser powder directed energy deposition technology of the present invention;

[0018] Figure 2 IPF coloring diagram of the formed parts prepared in Example 1 of the present invention and Comparative Example 1 after EBSD testing;

[0019] Figure 3KAM diagrams of the molded parts prepared in Example 1 of the present invention and Comparative Example 1;

[0020] Figure 4 The pole figures of the formed parts prepared in Example 1 of the present invention and Comparative Example 1;

[0021] Figure 5 The tensile stress-strain curves of the formed parts prepared in Example 1 of the present invention and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0022] The present invention provides a method for additive forming of nickel-based alloy thin-walled parts assisted by follow-up rolling, comprising the following steps:

[0023] A nickel alloy layer is deposited on the substrate by the L-DED process. During the L-DED deposition, a mechanical rolling device is used to perform instant rolling treatment on the nickel alloy layer. By controlling the process parameters, the deposition and rolling are carried out simultaneously.

[0024] In the L-DED process, the laser power is 1200-1300W;

[0025] In the rolling process, the rolling pressure is 7000-9000N.

[0026] In the present invention, in the L-DED process, the laser power is preferably 1250W;

[0027] In the rolling process, the rolling pressure is preferably 8000N.

[0028] In the present invention, in the L-DED process, the scanning rate is 5 to 15 mm / s, preferably 10 mm / s; the powder feeding rate is 5 to 10 g / min, preferably 6 to 9 g / min, and further preferably 6.6 g / min; the spot diameter is 2 to 3 mm, preferably 2 mm; the layer height is 0.1 to 0.3 mm, preferably 0.18 to 0.2 mm; the number of deposition layers is 50 to 80 layers, preferably 60 layers.

[0029] In the present invention, a rolling head with a cooling function is provided in the mechanical rolling device to ensure that the nickel alloy layer will not be thermally affected during the rolling process.

[0030] In the present invention, the design of the rolling head should be adapted to the manufacturing requirements of parts of different shapes and sizes to ensure the uniformity and effectiveness of the rolling process.

[0031] In the present invention, the raw material used in the L-DED process is spherical IN625 powder, and the size of the spherical IN625 powder ranges from 53 to 150 μm, preferably from 60 to 130 μm.

[0032] In the present invention, the spherical IN625 powder used is a spherical IN625 powder prepared by rotary atomization and provided by Ningbo Zhongyuan New Material Technology Co., Ltd.

[0033] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0034] Example 1

[0035] High-purity IN625 nickel-based high-temperature alloy powder (size range of 60-120μm) is selected as the raw material, and L-DED technology is used to perform layer-by-layer deposition on the substrate. At the same time, a mechanical rolling device is used to perform instant rolling on the deposited layer. During the rolling process, cooling water is passed through the rolling head for real-time cooling to reduce the temperature during the rolling process and avoid thermal effects on the deposited layer. By precisely controlling the laser energy input, cooling speed, rolling pressure, rolling speed and other parameters of the rolling device, the simultaneous deposition and rolling is achieved.

[0036] The process parameters are set as shown in Table 1.

[0037] Comparative Example 1

[0038] The same as Example 1, except that only the L-DED deposition process is used to prepare the molded part, and the specific parameters are set as shown in Table 1 below.

[0039] Table 1 Process parameters of formed parts

[0040]

[0041] Performance Testing:

[0042] EBSD test: horizontal and vertical samples were taken from the deposited parts for EBSD test. The IPF coloring diagram is as follows: Figure 2 As shown, it can be clearly seen that in the 0# horizontal direction, larger columnar crystals and equiaxed crystals can be seen, such as Figure 2 (a), while the vertical direction is mainly composed of larger columnar crystals, such as Figure 2 As shown in (b), the equivalent grain diameter is mainly distributed between 400-800 μm. Compared with the unrolled 0# sample, the grains of the 8# sample are obviously refined. Figure 2 (c)(d) It can be seen that the horizontal direction presents fine equiaxed crystals, and the equivalent diameter of the grains is mainly distributed between 3-20μm, while the vertical direction is divided into obvious equiaxed crystal areas and fine columnar crystal areas. The equivalent diameter of the grains in the equiaxed crystal area is mainly distributed between 3-45μm, while the equivalent diameter of the columnar crystal area is about 60-200μm. Figure 3The KAM diagram is given, where the black lines represent small-angle grain boundaries and the red lines represent large-angle grain boundaries. It can be clearly seen that compared with the 0# sample, the 8# sample has a large number of dislocations in the grains. The GND of the 0# sample is measured to be 3.54×10 14 m -1 , while the 8# sample is 13.41×10 14 m -1 The dislocation density of the 8# sample is about 4 times that of the 0# sample, which plays a key role in the overall strengthening. Figure 4 The corresponding pole figures are given, and it can be seen that the orientation of the 0# sample is mainly in the 001 direction, while the 8# sample after rolling is transferred to the 011 direction.

[0043] Mechanical properties test: The mechanical properties of 0# and 8# samples were tested using a universal testing machine. Figure 5 The stress-strain curves of 0# and 8# samples parallel and perpendicular to the deposition direction were plotted, and the specific values ​​of UTS, YS and EL are given in Table 2. It can be seen that the UTS and YS of the two samples in the horizontal and vertical directions are not much different, and there is no obvious anisotropy in strength. In terms of plasticity, the elongation in the horizontal direction is about half of that in the vertical direction, and there is obvious toughness anisotropy. After rolling, the tensile strength and yield strength of the formed parts are significantly improved, about 47% and 95% in the horizontal and vertical directions respectively, but the elongation after fracture decreases, and the elongation in the horizontal and vertical directions decreases by about 60% after rolling. In terms of microhardness, there is an improvement in both directions after rolling, 13% in the horizontal direction and 41% in the vertical direction. The results are shown in Table 2.

[0044] Table 2 Mechanical properties of two formed parts in different directions

[0045]

[0046] It can be seen from the above embodiments that the present invention provides a method for additive forming of nickel-based alloy thin-walled parts assisted by follow-up rolling. The rolling process of the present invention significantly refines the grain structure of the IN625 alloy. Compared with the unrolled samples, the grain size of the rolled samples is significantly reduced, from hundreds of microns to a few microns to tens of microns. The present invention conducts comprehensive mechanical property tests on the formed parts. The test results show that the mechanical properties of the IN625 nickel-based high-temperature alloy formed parts after rolling are significantly improved, and the tensile strength, yield strength, elongation and hardness are all improved. At the same time, the anisotropy of the mechanical properties of the formed parts in different directions is significantly improved, and the overall performance is more uniform and stable.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for additive forming of nickel-based alloy thin-walled parts assisted by follow-up rolling, characterized in that: The following steps are involved: A nickel alloy layer is deposited on the substrate by the L-DED process. During the L-DED deposition, a mechanical rolling device is used to perform instant rolling treatment on the nickel alloy layer. By controlling the process parameters, the deposition and rolling are carried out simultaneously. In the L-DED process, the laser power is 1200-1300W; In the rolling process, the rolling pressure is 7000-9000N.

2. The method for additive forming of nickel-based alloy thin-walled parts assisted by follower rolling according to claim 1, characterized in that: In the L-DED process, the scanning rate is 5 to 15 mm / s, the powder feeding rate is 5 to 10 g / min, the spot diameter is 2 to 3 mm, the layer height is 0.1 to 0.3 mm, and the number of deposited layers is 50 to 80 layers.

3. The method for additive forming of nickel-based alloy thin-walled parts assisted by follower rolling according to claim 1 or 2, characterized in that: The mechanical rolling device is provided with a rolling head with a cooling function to ensure that the nickel alloy layer will not be thermally affected during the rolling process.

4. The method for additive forming of nickel-based alloy thin-walled parts assisted by follower rolling according to claim 3, characterized in that: The raw material used in the L-DED process is spherical IN625 powder, and the size of the spherical IN625 powder ranges from 53 to 150 μm.

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