Method for preparing nickel-based alloy additive body with gradient hardness based on electric arc additive manufacturing technology

Abstract

The invention discloses a method for preparing a nickel-based alloy additive body with gradient hardness based on an electric arc additive manufacturing technology, which changes a block structure obtained by a traditional deposition strategy by changing a printing path, adopting an interval printing mode and adjusting a cooling condition during printing. The hardness of the additive body in the construction direction and the direction perpendicular to the moving direction of the welding gun is changed in a gradient mode, and the material performance is more uniform at all positions. The hardness of the prepared block-shaped additive body at different positions is different, the whole block-shaped additive body is in gradient hardness change similar to a trigonometric function, the problem that in the process of preparing the Inconel 625 alloy additive body through an additive manufacturing method, the hardness of all areas is not uniform, and failure is prone to occurring is effectively solved, and the method is high in efficiency, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to an arc additive manufacturing method for an Inconel 625 alloy additive body with gradient hardness, belonging to the technical field of additive manufacturing. Background Art

[0002] Nickel-based 625 alloy is widely used in aerospace, marine, petrochemical, nuclear reactors and other fields. It is a nickel-based high-temperature alloy with high strength, corrosion resistance, fatigue strength and thermal fatigue resistance under high temperature conditions. It can withstand large stresses and has good surface stability. These properties are necessary for aircraft engines, pipelines, nuclear reactors and nuclear power equipment. Arc additive manufacturing is an additive manufacturing process that uses an electric arc as a heat source to melt metal welding wire, and then deposits it layer by layer on a metal substrate according to a set path. Arc additive manufacturing has a short manufacturing cycle and a high level of automation, which can achieve digital, intelligent and flexible manufacturing. It has a high utilization rate of raw materials and can quickly produce parts with relatively complex shapes and structures, while also having fewer size restrictions on parts.

[0003] In the arc additive manufacturing process, the mechanical properties of Inconel 625 alloy are generally different at different positions of the block structure, which results in the strength and plasticity of each part not being well adapted. The gradient change in the material is a structure that increases the stability of the material performance. Materials with a gradient structure generally have better overall performance, better stability, and are less prone to sudden failure. The microstructure of the additive body under the conventional printing strategy is shown in Figure 5, which is generally coarse columnar crystals. It is precisely because the crystal structure of the present invention is different from that under the conventional printing strategy that the mechanical properties are different. Therefore, introducing a gradient structure into the material is a key and difficult point in the research. Summary of the Invention

[0004] The purpose of the present invention is to propose an additive manufacturing method for an Inconel 625 alloy additive body with gradient hardness. Through this method, a sample with gradient hardness can be obtained in the building direction and the direction perpendicular to the travel of the welding gun, which effectively improves the problem of large differences in mechanical properties at different positions of the Inconel 625 alloy additive body and is suitable for industrial production.

[0005] To solve the above technical problems, the technical solution of the present invention is: a method for preparing a nickel-based alloy additive body with gradient hardness based on arc additive manufacturing technology, wherein the nickel-based alloy additive body is Inconel 625, and the specific steps are as follows: (1) Place a clean carbon steel alloy plate as a substrate on the operating table; (2) Arc additive manufacturing technology is used, and the printing path of each layer is set to interval printing. The specific process is: the welds are divided into odd welds and even welds, and Inconel 625 is used as the wire. The odd welds are first printed on the substrate. After the printing is completed, it is cooled to room temperature. Then the even welds are printed. After the printing is completed, it is cooled to room temperature again. Then the second layer is printed in a cycle until an Inconel 625 nickel-based alloy additive body with gradient hardness is obtained.

[0006] Furthermore, in step (1), the carbon steel alloy plate is a Q235 steel plate having a size of 500 mm × 300 mm × 20 mm (length × width × height).

[0007] Furthermore, in step (2), during the deposition process, the layers are rotated 180 degrees. o Alternate reverse deposition.

[0008] Furthermore, in step (2), the welding speed is 10 mm / s and the wire feeding speed is 6 m / min.

[0009] Furthermore, in step (2), pure argon is used as a protective gas during the printing process to prevent the deposited layer from being oxidized during the manufacturing process.

[0010] Furthermore, in step (2), air cooling is used to cool to room temperature. Furthermore, in step (2), Inconel 625 is used as the wire material, and its diameter is 1.2 mm.

[0011] Furthermore, in step (2), the widths of the odd-numbered weld beads and the even-numbered weld beads are the same.

[0012] Compared with the prior art, the present invention has the following significant advantages: Based on cold metal transfer arc additive manufacturing, this invention proposes an Inconel 625 alloy additive body with a gradient hardness structure in the build direction and perpendicular to the direction of the welding torch, simply by adjusting the printing path (interval printing method) and cooling conditions. This invention primarily changes the bulk structure obtained by traditional deposition strategies by changing the printing path, adopting an interval printing method, and adjusting the cooling conditions during printing. This results in a gradient hardness variation in the additive body in the build direction and perpendicular to the welding torch movement, making the material properties more uniform across all locations.

[0013] (2) The present invention can obtain Inconel 625 alloy with a gradient hardness structure by simply adjusting the printing strategy. It has high deposition efficiency and simple equipment, which greatly reduces the manufacturing cycle and manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The images show the hardness change perpendicular to the printing direction of the arc-added Inconel 625 alloy body in Example 1 when the layers are cooled to 25°C. (a) The top of the printed part, (b) The bottom of the printed part.

[0015] Figure 2 These are images of the hardness change perpendicular to the printing direction of the arc-added Inconel 625 alloy body in Example 2 when the layer is cooled to 100°C. (a): top of the printed part, (b): bottom of the printed part.

[0016] Figure 3 This is an electron backscatter diffraction electron microscopy image of the arc-added Inconel 625 alloy additive body in Example 1 under the condition of layer cooling to 25°C.

[0017] Figure 4 This is an electron backscatter diffraction electron microscopy image of the arc-added Inconel 625 alloy additive body in Example 2 under the condition of layer cooling to 100°C.

[0018] Figure 5 This is an electron backscatter diffraction electron microscope image of a nickel-based alloy additive body under conventional printing strategy.

[0019] Figure 6 This is a schematic diagram of the interval printing method. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] Example 1: (1) First, place the Q235 substrate on the operating table, and perform laser polishing on the deposited side of the substrate. After polishing, wash it with clean water, then with anhydrous ethanol, then with anhydrous acetone, and finally with clean water to make the surface of the substrate free of oil and other impurities.

[0022] (2) Arc additive manufacturing based on cold metal transition was performed on a Q235 substrate, and the printing path of each layer was set to interval printing (e.g. Figure 6 The specific process is as follows: the welds are divided into odd welds and even welds. Inconel 625 is used as the wire material. The odd welds are printed on the substrate first. After the printing is completed, it is cooled to room temperature (25°C). Then the even welds are printed. After the printing is completed, it is cooled to room temperature (25°C). Then the welding gun is rotated 180 degrees. o The deposition direction is changed, and the second layer is printed cyclically and intermittently according to the printing method of the first layer until a nickel-based alloy additive body with gradient hardness is obtained.

[0023] During the deposition process, the layers are rotated 180 degrees.o Alternating reverse deposition is to improve the quality of the deposited thin wall and reduce the porosity.

[0024] The present invention adopts interval printing and cooling conditions mainly to make fine grain structure appear between layers and welds, which is different from the internal structure of the deposited layer, and then the mechanical properties appear different, thereby effectively improving the problem of large differences in mechanical properties at different positions of the Inconel 625 alloy additive body.

[0025] The hardness values ​​measured at different positions of the layer after cooling to room temperature are as follows Figure 1 As shown, Figure 1 Figures a and b show the trend of the microhardness of the top and bottom of the block additive body with the number of passes. It can be seen that the hardness changes gradiently within the range of 30 mm, and the hardness value fluctuates between 30-40 HV. The average hardness is around 260 HV. It can be clearly seen from the figure that the hardness value shows a gradient change.

[0026] The electron backscatter diffraction electron microscope image of the nickel-based alloy additive body in this embodiment is as follows: Figure 3 As shown, Figure 3 It can be seen from the figure that when the layers are cooled to room temperature, there are more fine grains in the interlayer and inter-weld areas, and the interlayer area is more obvious.

[0027] Example 2: The difference from Example 1 is that the interlayer cooling temperature of arc additive manufacturing is 100 °C, the interval printing strategy is still adopted, and the other parameters in the arc welding process remain unchanged.

[0028] like Figure 2 The a and b in the figure show the hardness values ​​measured at different positions of the Inconel 625 alloy additive body when the layer is cooled to 100 °C. Figure 2 It can be seen that under this condition, the change in hardness with distance no longer has a gradient trend, but is roughly within a horizontal range. There is no large fluctuation between the average values ​​of two adjacent rows of hardness points, and the overall average hardness is around 260 HV.

[0029] The electron backscatter diffraction electron microscope image of the nickel-based alloy additive body in this example is as follows Figure 4 As shown, Figure 4 It can be seen from the figure that when the layers are cooled to 100 ℃, the interlayer area is more blurred than the former, and is roughly a columnar crystal growing along the BD direction. The difference in structure may be the main reason for the difference in hardness change of the samples.

Claims

1. A method for preparing a nickel-based alloy additive body with gradient hardness based on arc additive manufacturing technology, characterized in that: The specific steps are as follows: (1) Place a clean carbon steel alloy plate as a substrate on the operating table; (2) Arc additive manufacturing technology is used, and the printing path of each layer is set to interval printing. The specific process is: the welds are divided into odd welds and even welds, the odd welds are printed on the substrate first, and after the printing is completed, they are cooled to room temperature, and then the even welds are printed, and after the printing is completed, they are cooled to room temperature again, and then the second layer is printed in a cycle until a nickel-based alloy additive body with gradient hardness is obtained.

2. The method according to claim 1, wherein In step (1), the carbon steel alloy plate is a Q235 steel plate with a size of 500 mm × 300 mm × 20 mm.

3. The method according to claim 1, wherein In step (2), during the deposition process, the layers are rotated 180 degrees. o Alternate reverse deposition.

4. The method according to claim 1, wherein In step (2), the welding speed is 10 mm / s and the wire feeding speed is 6 m / min.

5. The method according to claim 1, wherein In step (2), pure argon is used as the shielding gas during the printing process, and the shielding gas flow rate is 20 L / min.

6. The method according to claim 1, wherein In step (2), Inconel 625 is used as the wire material, and its diameter is 1.2 mm.

7. The method according to claim 1, wherein In step (2), the widths of odd-numbered welds and even-numbered welds are the same.

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