Method for eliminating residual stress in additive manufacturing of nickel-based superalloy

Abstract

The invention relates to a method for eliminating residual stress in additive manufacturing of nickel-based superalloy, and relates to the technical field of additive manufacturing materials. According to the main technical scheme, stress relief treatment is carried out in the mode that continuous pulse current treatment is applied to the additive manufacturing nickel-based superalloy, so that at least part of residual stress in the additive manufacturing nickel-based superalloy is eliminated, and the additive manufacturing nickel-based superalloy subjected to stress relief treatment is obtained. According to the method, the residual stress in the additive manufacturing nickel-based superalloy can be effectively reduced. According to the method, the internal structure state of the original alloy is not changed, meanwhile, the method is low in treatment temperature, short in treatment time, more efficient and more energy-saving, and the requirement for green and sustainable development of the current industry is met.

Description

Technical Field

[0001] The invention relates to the technical field of additive manufacturing materials, and in particular to a method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys. Background Art

[0002] Additive Manufacturing (AM) is a digital manufacturing method that is conducive to the realization of automated, intelligent and networked manufacturing. Compared with traditional manufacturing methods, the additive manufacturing process is simple and efficient, with high material utilization, and has been widely used in industrial fields such as automobiles, aerospace, energy and medical equipment. Metal additive manufacturing technology can be divided into direct energy deposition (DED) and powder bed fusion (PBF). Among them, DED includes laser metal deposition (LMD) and wire arc additive manufacturing (WAAM). Among them, PBF includes electron beam selective melting (EBSM) and laser selective melting (SLM).

[0003] The unique thermal cycle characteristics of metal additive manufacturing are: (1) high energy intensity, steep temperature gradient, and fast heating rate; (2) small molten pool volume, fast cooling rate, and fast solidification rate; (3) melt remelting, which involves melting the top powder layer and remelting the previously solidified bottom layer at the same time. Here, the residual stress caused by the unique thermal cycle in additive manufacturing is a key issue in the manufacture of metal parts. Large residual stress can cause part deformation, thereby reducing the dimensional accuracy of the part. In addition, it is easy to cause part cracking during long-term service, greatly reducing the ultimate service life of the part. Therefore, additive manufacturing technology still faces great challenges in part quality control.

[0004] At present, the research on eliminating residual stress of additively manufactured alloys mainly focuses on two methods: adjusting printing process parameters and traditional heat treatment. The effect of eliminating residual stress by adjusting the additive manufacturing printing process parameters is very limited, and it will also bring about significant changes in the mechanical properties of the parts, affecting their strength and plasticity. Another method is traditional heat treatment or hot isostatic pressing. The prior art proposes a method for reducing residual stress of additively manufactured high-temperature alloys based on hot isostatic pressing. Hot isostatic pressing is performed on an additively manufactured high-temperature alloy. Although this method effectively eliminates the residual stress inside the sample, the processing temperature of this method is high, the processing time is long, and the internal organization state of the original sample is changed.

[0005] In summary, in response to the bottleneck problems encountered in the existing technology, it is urgent to develop a new method to eliminate residual stress in additively manufactured nickel-based high-temperature alloys, which can effectively reduce the residual stress in additively manufactured nickel-based high-temperature alloys and play an important role in promoting the industrial application of additively manufactured nickel-based high-temperature alloys. Summary of the invention

[0006] In view of this, the present invention provides a method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys, the main purpose of which is to effectively reduce the residual stress in additively manufactured nickel-based high-temperature alloys.

[0007] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0008] On the one hand, an embodiment of the present invention provides a method for eliminating residual stress in an additively manufactured nickel-based high-temperature alloy, wherein stress elimination treatment is performed by applying continuous pulse current treatment to the additively manufactured nickel-based high-temperature alloy to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy, thereby obtaining the additively manufactured nickel-based high-temperature alloy after stress elimination treatment.

[0009] Preferably, the chemical composition of the additively manufactured nickel-based high-temperature alloy is as follows, in terms of weight percentage: Fe: 1-35wt%, Cr: 2-35wt%, Mo: 0-10wt%, Al: 0.1-5wt%, Ti: 0-5wt%, Nb: 2-10wt%, Ta: 0-5wt%, W: 0.5-5wt%, Co: 1-20wt%, Zr: 0-1wt%, Hf: 0-1wt%, C: 0-0.5wt%, B: 0-0.05wt%, Si: 0-0.05wt%, Ni: balance.

[0010] Preferably, the additively manufactured nickel-based high-temperature alloy is a laser additively manufactured deposited nickel-based high-temperature alloy. Preferably, the additively manufactured nickel-based high-temperature alloy is a laser direct energy deposition additively manufactured deposited nickel-based high-temperature alloy.

[0011] Preferably, the parameters of the continuous pulse current treatment are as follows: the continuous pulse current density is 10-400A / mm 2 , the continuous pulse current width is 1us-5ms, the continuous pulse current frequency is 1-50Hz, the duty cycle is 10-99%, the temperature of the continuous pulse current treatment is 900-1100℃, and the time of the continuous pulse current treatment is 1-20min.

[0012] Preferably, the parameters of the continuous pulse current treatment are as follows: the continuous pulse current density is 200-300A / mm 2, the continuous pulse current width is 0.05-1ms, the continuous pulse current frequency is 10-30Hz, the duty cycle is 20-80%, the temperature of the continuous pulse current treatment is 1000℃±2℃, and the time of the continuous pulse current treatment is 6min±2min.

[0013] Preferably, the dislocation density in the laser additively manufactured deposited nickel-based high-temperature alloy is 8×10 14 m 2 -10×10 14 m 2 ; and / or the dislocation density in the additively manufactured nickel-based high-temperature alloy after the stress relief treatment is 1×10 13 m 2 -2×10 14 m 2 .

[0014] Preferably, the additively manufactured nickel-based high-temperature alloy is an arc additively manufactured deposited nickel-based high-temperature alloy.

[0015] Preferably, the parameters of the continuous pulse current treatment are as follows: the continuous pulse current density is 300-400A / mm 2 , the continuous pulse current width is 0.2-0.8ms, the continuous pulse current frequency is 30-50Hz, the duty cycle is 30-60%, the temperature of the continuous pulse current treatment is 1100℃±2℃, and the time of the continuous pulse current treatment is 10min±2min.

[0016] Preferably, the GND density in the arc additively manufactured deposited nickel-based high-temperature alloy is 8×10 14 m 2 -10×10 14 m 2 ; and the GND density of the additively manufactured nickel-based high-temperature alloy after the stress relief treatment is 1×10 13 m 2 -2×10 14 m 2 .

[0017] Preferably, the method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys comprises the following steps:

[0018] Step 1), processing the additively manufactured nickel-based high-temperature alloy into a workpiece for continuous pulse current processing;

[0019] Step 2), connecting the workpiece to a pulse power supply, turning on the pulse power supply, and applying a continuous pulse current treatment to the workpiece;

[0020] Step 3), cooling the workpiece after continuous pulse current treatment to obtain a treated additively manufactured nickel-based high-temperature alloy;

[0021] Preferably, in the step 1), the additively manufactured nickel-based high-temperature alloy is cut, polished and cleaned to obtain a workpiece of a set size.

[0022] Compared with the prior art, the method of eliminating residual stress in additively manufactured nickel-based high-temperature alloys of the present invention has at least the following beneficial effects:

[0023] The embodiment of the present invention provides a method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys, by applying continuous pulse current treatment to the additively manufactured nickel-based high-temperature alloy to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy, and obtain the additively manufactured nickel-based high-temperature alloy after stress elimination treatment. Here, the present invention applies continuous pulse current to the additively manufactured nickel-based high-temperature alloy, so that the combination of electrical effect (electron wind force) and thermal effect (Joule heat) drives the movement of dislocations in the alloy, wherein the electron wind force drives electrons to continuously impact dislocations to increase the movement and speed of dislocation slip and climbing; Joule heat provides a driving force for dislocation migration, increases the vibration frequency of dislocations, and provides energy for the accelerated movement of dislocations; the above two effects ultimately lead to the rearrangement and annihilation of dislocations, and the dislocation density is reduced, thereby effectively eliminating the residual stress in the additively manufactured nickel-based high-temperature alloy.

[0024] Furthermore, an embodiment of the present invention provides a method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys. When applying continuous pulse current treatment to additively manufactured nickel-based high-temperature alloys, the selection of pulse current parameters is crucial. By selecting appropriate parameters for continuous pulse current treatment, the residual stress in the alloy can be eliminated to a great extent while ensuring that the original alloy structure state is unchanged. When the pulse current parameters are not selected reasonably, the residual stress in the alloy will not be sufficiently eliminated or the alloy structure state will be changed.

[0025] In summary, compared with the traditional heat treatment process, the method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys provided by the embodiment of the present invention does not change the internal structure of the original alloy; at the same time, the method of the present invention has a low processing temperature, a short processing time, and is more efficient and energy-saving, which meets the requirements of current industrial green and sustainable development. Therefore, the present invention provides a new method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys such as lasers and arcs.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a comparison chart of GND density of laser additive manufacturing samples that have not been treated with continuous pulse current, and samples after stress removal treatment in different embodiments and comparative examples.

[0028] Figure 2 These are the EBSD results of laser additively manufactured samples without continuous pulse current treatment; (a) is the IPF map, and (b) is the GND density map.

[0029] Figure 3 These are the EBSD results of the laser additive manufacturing sample after continuous pulse current treatment in Example 1; wherein (a) is the IPF map, and (b) is the GND density map.

[0030] Figure 4 These are the EBSD results of the laser additive manufacturing sample after continuous pulse current treatment in Example 2; wherein (a) is the IPF map, and (b) is the GND density map.

[0031] Figure 5 These are the EBSD results of the laser additive manufacturing sample after continuous pulse current treatment in Example 3; wherein (a) is the IPF map, and (b) is the GND density map.

[0032] Figure 6 This is a comparison diagram of the GND density of the arc additively manufactured sample that has not been treated with continuous pulse current and the arc additively manufactured sample that has been treated with stress removal in the embodiment.

[0033] Figure 7 These are the EBSD results of arc additive manufacturing samples without continuous pulse current treatment; (a) is the IPF map, and (b) is the GND density map.

[0034] Figure 8 These are the EBSD results of the arc additively manufactured sample after continuous pulse current treatment in Example 4; wherein (a) is the IPF map, and (b) is the GND density map.

[0035] Fig. 9 These are the EBSD results of the laser additive manufacturing sample after traditional heat treatment in Comparative Example 1; wherein (a) is the IPF map, and (b) is the GND density map.

[0036] Fig.10 These are the EBSD results of the laser additive manufacturing sample after traditional heat treatment in Comparative Example 2; wherein (a) is the IPF map, and (b) is the GND density map.

[0037] Fig.11These are the EBSD results of the laser additive manufacturing sample after continuous pulse current treatment in Comparative Example 3; wherein (a) is the IPF map, and (b) is the GND density map. DETAILED DESCRIPTION

[0038] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0039] In order to overcome the difficulties of the prior art, the present invention provides a method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys, which can quickly achieve the purpose of reducing or eliminating the residual stress inside the sample by applying continuous pulse current treatment to the additively manufactured nickel-based high-temperature alloy. The specific solution of the present invention is as follows:

[0040] An embodiment of the present invention provides a method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys, comprising the following steps:

[0041] Step 1), processing the additively manufactured nickel-based high-temperature alloy into a workpiece for continuous pulse current processing.

[0042] Preferably, the additively manufactured nickel-based high-temperature alloy is cut, polished and cleaned to obtain a workpiece of a set size.

[0043] Step 2), connecting the workpiece to a pulse power supply, turning on the pulse power supply, and applying continuous pulse current treatment to the workpiece.

[0044] Step 3), cooling the workpiece after continuous pulse current treatment to obtain the treated additively manufactured nickel-based high-temperature alloy.

[0045] Here, regarding the above-mentioned solution of the present invention, the chemical composition of the additively manufactured nickel-based high-temperature alloy is as follows, in terms of weight percentage:

[0046] Fe: 1-35wt%, Cr: 2-35wt%, Mo: 0-10wt%, Al: 0.1-5wt%, Ti: 0-5wt%, Nb: 2-10wt%, Ta: 0-5wt%, W: 0.5-5wt%, Co: 1-20wt%, Zr: 0-1wt%, Hf: 0-1wt%, C: 0-0.5wt%, B: 0-0.05wt%, Si: 0-0.05wt%, Ni: balance.

[0047] Here, regarding the above-mentioned solution of the present invention, the additively manufactured high-temperature nickel-based high-temperature alloy is a laser additively manufactured deposited nickel-based high-temperature alloy or an arc additively manufactured deposited nickel-based high-temperature alloy.

[0048] Wherein, the additively manufactured high-temperature nickel-based high-temperature alloy is a laser additively manufactured deposited nickel-based high-temperature alloy, and the parameters of the continuous pulse current treatment are as follows:

[0049] Continuous pulse current density is 10-400A / mm 2 , the continuous pulse current width is 1us-5ms, the continuous pulse current frequency is 1-50Hz, the duty cycle is 10-99%, the temperature of the continuous pulse current treatment is 900-1100℃, and the time of the continuous pulse current treatment is 1-20min.

[0050] Preferably, the continuous pulse current density is 200-300A / mm 2 , the continuous pulse current width is 0.05-1ms, the continuous pulse current frequency is 10-30Hz, the duty cycle is 20-80%, the temperature of the continuous pulse current treatment is 1000℃±2℃, and the time of the continuous pulse current treatment is 6min±2min.

[0051] Wherein, the additively manufactured high-temperature nickel-based high-temperature alloy is an arc additively manufactured deposited nickel-based high-temperature alloy, and the parameters of the continuous pulse current treatment are as follows:

[0052] Continuous pulse current density is 300-400A / mm 2 , the continuous pulse current width is 0.2-0.8ms, the continuous pulse current frequency is 30-50Hz, the duty cycle is 30-60%, the temperature of the continuous pulse current treatment is 1100℃±2℃, and the time of the continuous pulse current treatment is 10min±2min.

[0053] In addition, the above-mentioned solution of the present invention needs to be explained as follows:

[0054] 1) The present invention applies continuous pulse current to the additively manufactured nickel-based high-temperature alloy, and the combination of electrical effect (electron wind force) and thermal effect (Joule heat) promotes the movement of dislocations. Among them, the electron wind force drives electrons to continuously impact dislocations to increase the movement and speed of dislocation slip and climbing; Joule heat provides a driving force for dislocation migration, increases the vibration frequency of dislocations, and provides energy for the accelerated movement of dislocations. Ultimately, it leads to the rearrangement and annihilation of dislocations, and the dislocation density is reduced, thereby effectively eliminating the residual stress in the additively manufactured nickel-based high-temperature alloy.

[0055] 2) The present invention applies continuous pulse current treatment to the additively manufactured nickel-based high-temperature alloy, which can effectively eliminate the residual stress in the alloy at a lower temperature. Since the continuous pulse current treatment time is short, the organizational state of the original alloy is not changed.

[0056] In summary, compared with the traditional solution heat treatment technology, the present invention utilizes the continuous pulse current treatment technology, which can effectively reduce or eliminate the residual stress in the additively manufactured nickel-based high-temperature alloy at a lower temperature and in a shorter time, and has many advantages such as high efficiency, energy saving and environmental protection.

[0057] The present invention is further described below by specific experimental examples:

[0058] In the following embodiments and comparative examples, the laser additive manufacturing samples were printed by a coaxial powder feeding device, and the alloy powder used for printing was prepared by a plasma rotating electrode (PREP) method, wherein the printing process parameters were: laser power of 900w; laser scanning speed of 8mm / s; powder feeding amount of 7g / min, and Z-axis lifting height of 0.7mm.

[0059] The arc additive manufacturing sample was printed by an ABB industrial robot. The wire diameter used for printing was 1.0 mm. The printing process parameters were: wire feeding speed of 7 m / min, printing speed of 5 mm / s, airflow protection of 25 L / min, and Z-axis lifting height of 3 mm.

[0060] It should be noted here that the solution of the present invention is mainly proposed for additively manufactured nickel-based high-temperature alloys to eliminate residual stress in the alloy. It is not limited to the above-mentioned printing process parameters. As long as it is an additively manufactured nickel-based high-temperature alloy with residual stress, it can be processed using the solution of the present invention.

[0061] In addition, the temperature of the laser additively manufactured nickel-based high-temperature alloy is recorded in real time by an infrared thermometer, and the temperature rise caused by the Joule heating effect of the continuous pulse current is considered to be uniform on the cross section.

[0062] In addition, the compositions of nickel-based high-temperature alloys manufactured by laser additive manufacturing and arc additive manufacturing in the following embodiments and comparative examples are shown in Table 1. At the same time, in order to intuitively reflect the superiority of the continuous pulse current treatment of the present invention, the alloys with the compositions shown in Table 1 were subjected to traditional solution treatment in a box-type resistance furnace for comparison and analysis of the advantages of the continuous pulse current treatment method.

[0063] In addition, the residual stresses in the nickel-based high-temperature alloys manufactured by laser additive manufacturing and arc additive manufacturing in the following embodiments and comparative examples are observed and analyzed using EBSD technology, and the changes in the density of geometric necessary dislocations (GND) are used to approximately reflect the level of residual stress in the samples.

[0064] Table 1 shows the alloy composition (wt%) used in the examples of the present invention.

[0065] element Al Ti Nb W Mo Cr Co Fe C Ni wt% 1.5 0.9 5.4 1.1 2.5 18.1 9.2 9.5 0.02 margin

[0066] Example 1

[0067] In this embodiment, a stress relief treatment is performed by subjecting the laser additively manufactured nickel-based high-temperature alloy to continuous pulse current treatment to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy. The main steps are as follows:

[0068] 1) Laser additively manufactured nickel-based high-temperature alloys were processed into workpiece specimens for continuous pulse current processing.

[0069] Strip-shaped workpiece specimens were cut from the deposited samples of nickel-based high-temperature alloy manufactured by laser additive manufacturing, and the surfaces were polished with 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpapers in sequence to eliminate wire cutting marks while ensuring that there were no obvious macroscopic defects, so as to ensure good contact between the workpiece specimen and the electrode.

[0070] 2) Connect the sample to the pulse power supply, turn on the pulse power supply, and apply continuous pulse current treatment to the workpiece sample.

[0071] Fix the workpiece sample with a clamp at the output end of the power supply (connect the two poles of the pulse power supply to the two ends of the sample to form a loop).

[0072] The power supply is turned on to apply continuous pulse current to the laser additively manufactured nickel-based high-temperature alloy workpiece, wherein the continuous pulse current density is 280A / mm 2 ; Continuous pulse current width is 0.5ms; Continuous pulse current frequency is 28Hz; Duty cycle is 20%. Continuous pulse current treatment is carried out at 1000℃ for 5min.

[0073] The central part of the sample after continuous pulse current treatment in this embodiment was taken, and the residual stress elimination and grain morphology in the sample were observed using EBSD characterization technology, such as Figure 3 In addition, the EBSD results of the sample that has not been treated with continuous pulse current are shown in Figure 2 The GND density comparison of the laser additive manufacturing sample without continuous pulse current treatment, the sample obtained in the embodiment and the comparative example is shown in FIG. Figure 1 It is obvious that the GND density (9.51×10 14 m 2 ) is higher, which means that there is a higher residual stress. The GND density (1.98×10 14 m 2) is significantly reduced, which means that the residual stress in the sample has been effectively eliminated. At the same time, the grain orientation, grain size and grain morphology of the sample have basically not changed after continuous pulse current treatment.

[0074] Example 2

[0075] In this embodiment, a stress relief treatment is performed by subjecting the laser additively manufactured nickel-based high-temperature alloy to continuous pulse current treatment to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy. The main steps are as follows:

[0076] 1) Laser additively manufactured nickel-based high-temperature alloys were processed into workpiece specimens for continuous pulse current processing.

[0077] Strip-shaped workpiece specimens were cut from the deposited samples of nickel-based high-temperature alloy manufactured by laser additive manufacturing, and the surfaces were polished with 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpapers in sequence to eliminate wire cutting marks while ensuring that there were no obvious macroscopic defects, so as to ensure good contact between the workpiece specimen and the electrode.

[0078] 2) Connect the sample to the pulse power supply, turn on the pulse power supply, and apply continuous pulse current treatment to the workpiece sample.

[0079] Fix the workpiece sample with a clamp at the output end of the power supply (connect the two poles of the pulse power supply to the two ends of the sample to form a loop).

[0080] The power supply is turned on to apply continuous pulse current to the laser additively manufactured nickel-based high-temperature alloy workpiece, wherein the continuous pulse current density is 280A / mm 2 ; Continuous pulse current width is 0.5ms; Continuous pulse current frequency is 25Hz; Duty cycle is 20%. Continuous pulse current treatment is carried out at 1000℃ for 6min.

[0081] The central part of the sample after continuous pulse current treatment in this embodiment was taken, and the residual stress elimination and grain morphology were observed using EBSD characterization technology, such as Figure 4 shown.

[0082] It is obvious that the sample after continuous pulse current treatment in this embodiment has a lower GND density (1.95×10 14 m 2 ), which means that the residual stress in the sample is low. Compared with the deposited sample, the residual stress of the sample after continuous pulse current treatment has been effectively eliminated. At the same time, the grain orientation, grain size and grain morphology of the sample after continuous pulse current treatment have basically not changed.

[0083] Example 3

[0084] In this embodiment, a stress relief treatment is performed by subjecting the laser additively manufactured nickel-based high-temperature alloy to continuous pulse current treatment to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy. The main steps are as follows:

[0085] 1) Laser additively manufactured nickel-based high-temperature alloys were processed into workpiece specimens for continuous pulse current processing.

[0086] Strip-shaped workpiece specimens were cut from the deposited samples of nickel-based high-temperature alloy manufactured by laser additive manufacturing, and the surfaces were polished with 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpapers in sequence to eliminate wire cutting marks while ensuring that there were no obvious macroscopic defects, so as to ensure good contact between the workpiece specimen and the electrode.

[0087] 2) Connect the sample to the pulse power supply, turn on the pulse power supply, and apply continuous pulse current treatment to the workpiece sample.

[0088] Fix the workpiece sample with a clamp at the output end of the power supply (connect the two poles of the pulse power supply to the two ends of the sample to form a loop).

[0089] Among them, the power supply is turned on to apply continuous pulse current treatment to the laser additively manufactured nickel-based high-temperature alloy workpiece, and the continuous pulse current density is 180A / mm 2 ; Continuous pulse current width is 0.8ms; Continuous pulse current frequency is 10Hz; Duty cycle is 50%. Continuous pulse current treatment is performed for 5min at 900℃.

[0090] The central part of the sample after continuous pulse current treatment in this embodiment was taken, and the residual stress elimination and grain morphology were observed using EBSD characterization technology, such as Figure 5 shown.

[0091] It is obvious that compared with the deposited sample, the dislocation density in the sample treated with continuous pulse current is reduced. However, the sample still has a high GND density (5.68×10 14 m 2 ), which means that the residual stress in the sample is still high. This shows that without selecting the optimal pulse current parameters for treatment, the residual stress in the sample is difficult to be effectively eliminated.

[0092] Example 4

[0093] In this embodiment, a stress relief treatment is performed by subjecting the arc additively manufactured nickel-based high-temperature alloy to continuous pulse current treatment to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy. The main steps are as follows:

[0094] 1) Arc additively manufactured nickel-based high-temperature alloys are processed into workpiece specimens for continuous pulse current processing.

[0095] Strip-shaped workpiece specimens were cut from the deposited samples of nickel-based high-temperature alloy manufactured by arc additive manufacturing, and the surfaces were polished with 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpapers in sequence to eliminate wire cutting marks while ensuring that there were no obvious macroscopic defects, so as to ensure good contact between the workpiece specimen and the electrode.

[0096] 2) Connect the sample to the pulse power supply, turn on the pulse power supply, and apply continuous pulse current treatment to the workpiece sample.

[0097] Fix the workpiece sample with a clamp at the output end of the power supply (connect the two poles of the pulse power supply to the two ends of the sample to form a loop).

[0098] The power supply is turned on to apply continuous pulse current to the laser additively manufactured nickel-based high-temperature alloy workpiece, wherein the continuous pulse current density is 350A / mm 2 ; Continuous pulse current width is 0.6ms; Continuous pulse current frequency is 40Hz; Duty cycle is 50%. Continuous pulse current treatment is carried out at 1100℃ for 10min.

[0099] The central part of the sample after continuous pulse current treatment in this embodiment was taken, and the residual stress elimination and grain morphology in the sample were observed using EBSD characterization technology, such as Figure 8 In addition, the EBSD results of the sample that has not been treated with continuous pulse current are shown in Figure 7 The GND density comparison between the sample without continuous pulse current treatment and the sample obtained in the embodiment is shown in FIG. Figure 6 It is obvious that the GND density (8.31×10 14 m 2 ) is higher, which means that there is a higher residual stress. The GND density (1.52×10 14 m 2 ) is significantly reduced, which means that the residual stress in the sample has been effectively eliminated. At the same time, the grain orientation, grain size and grain morphology of the sample have basically not changed after continuous pulse current treatment.

[0100] Comparative Example 1

[0101] Comparative Example 1: The laser additively manufactured nickel-based high-temperature alloy workpiece is subjected to conventional heat treatment, specifically as follows: heating at 1000° C. for 30 minutes for conventional heat treatment.

[0102] EBSD characterization technology was used to observe the residual stress relief and grain morphology of the samples after traditional heat treatment, such as Fig. 9 shown.

[0103] It was found that after the laser additive manufacturing nickel-based high-temperature alloy of comparative example 1 was heated at 1000°C for 50 min for conventional heat treatment, a relatively high GND density (5.15×10 14 m 2 ), the elimination effect is quite different from that of the sample treated with continuous pulse current at 1000°C for 5 minutes as described in the above embodiment. It can be seen that the traditional heat treatment at low temperature and for a short time cannot effectively eliminate the residual stress in the sample.

[0104] Comparative Example 2

[0105] Comparative Example 2: The laser additively manufactured nickel-based high-temperature alloy workpiece was subjected to conventional solution treatment, specifically as follows: heating at 1150° C. for 60 minutes for conventional heat treatment.

[0106] EBSD characterization technology was used to observe the residual stress relief and grain morphology of the samples after traditional heat treatment, such as Fig.10 shown.

[0107] It was found that the GND density of the laser additively manufactured nickel-based high-temperature alloy in comparative example 2 was significantly reduced (1.48×10 14 m 2 ), which means that the residual stress in the sample is basically eliminated, and the elimination effect is basically the same as that of the sample after continuous pulse current treatment in the above embodiment. However, the grain size of the sample after conventional heat treatment in comparative example 2 has grown significantly. It can be seen that continuous pulse current treatment can reduce the treatment temperature and time while maintaining the original alloy structure state.

[0108] Comparative Example 3

[0109] Comparative Example 3: A stress relief treatment is performed by subjecting the laser additively manufactured nickel-based high-temperature alloy to continuous pulse current treatment to eliminate at least part of the residual stress in the additively manufactured nickel-based high-temperature alloy. The main steps are as follows:

[0110] 1) Laser additively manufactured nickel-based high-temperature alloys were processed into workpiece specimens for continuous pulse current processing.

[0111] Strip-shaped workpiece specimens were cut from the deposited samples of nickel-based high-temperature alloy manufactured by laser additive manufacturing, and the surfaces were polished with 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpapers in sequence to eliminate wire cutting marks while ensuring that there were no obvious macroscopic defects, so as to ensure good contact between the workpiece specimen and the electrode.

[0112] 2) Connect the sample to the pulse power supply, turn on the pulse power supply, and apply continuous pulse current treatment to the workpiece sample.

[0113] Fix the workpiece sample with a clamp at the output end of the power supply (connect the two poles of the pulse power supply to the two ends of the sample to form a loop).

[0114] The power supply is turned on to apply continuous pulse current to the laser additively manufactured nickel-based high-temperature alloy workpiece, wherein the continuous pulse current density is 9A / mm 2 ; Continuous pulse current width is 0.8ms; Continuous pulse current frequency is 60Hz; Duty cycle is 9%. At 100℃, continuous pulse current treatment lasts for 6min.

[0115] The central part of the pulse current treated sample of Comparative Example 3 was taken, and the residual stress relief and grain morphology of the sample after pulse treatment were observed using EBSD characterization technology. Fig.11 shown.

[0116] The results show that: (1) the sample of comparative example 3 after continuous pulse current treatment still has a high GND density (8.66×10 14 m 2 ), which means that the residual stress in the sample is still high. (2) Compared with the deposited sample, the grain orientation, grain size and grain morphology of the sample after continuous pulse current treatment have not changed significantly, and the residual stress has not been effectively eliminated. This is mainly due to the low density of pulse current treatment, which leads to low treatment temperature, and the relatively small electron wind force makes it difficult to promote dislocation movement and annihilation, so the residual stress elimination effect of the sample is not significant. Compared with the embodiment, when the parameters of continuous pulse current treatment are not selected reasonably, the ideal effect of residual stress elimination cannot be achieved.

[0117] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys, characterized in that: A stress relief treatment is performed by applying a continuous pulse current treatment to the additively manufactured nickel-based high-temperature alloy to eliminate at least a portion of the residual stress in the additively manufactured nickel-based high-temperature alloy, thereby obtaining the additively manufactured nickel-based high-temperature alloy after the stress relief treatment.

2. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 1, characterized in that: The chemical composition of the additively manufactured nickel-based high-temperature alloy is as follows, in terms of weight percentage: Fe: 1-35wt%, Cr: 2-35wt%, Mo: 0-10wt%, Al: 0.1-5wt%, Ti: 0-5wt%, Nb: 2-10wt%, Ta: 0-5wt%, W: 0.5-5wt%, Co: 1-20wt%, Zr: 0-1wt%, Hf: 0-1wt%, C: 0-0.5wt%, B: 0-0.05wt%, Si: 0-0.05wt%, Ni: balance.

3. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 2, characterized in that: The additively manufactured nickel-based high-temperature alloy is a laser additively manufactured deposited nickel-based high-temperature alloy; Preferably, the additively manufactured nickel-based high-temperature alloy is a laser direct energy deposition additively manufactured deposited nickel-based high-temperature alloy.

4. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 3, characterized in that: The parameters of the continuous pulse current treatment are as follows: Continuous pulse current density is 10-400A / mm 2 , the continuous pulse current width is 1us-5ms, the continuous pulse current frequency is 1-50Hz, the duty cycle is 10-99%, the temperature of the continuous pulse current treatment is 900-1100℃, and the time of the continuous pulse current treatment is 1-20min.

5. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 4, characterized in that: The parameters of the continuous pulse current treatment are as follows: Continuous pulse current density is 200-300A / mm 2 , the continuous pulse current width is 0.05-1ms, the continuous pulse current frequency is 10-30Hz, the duty cycle is 20-80%, the temperature of the continuous pulse current treatment is 1000℃±2℃, and the time of the continuous pulse current treatment is 6min±2min.

6. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to any one of claims 3 to 5, characterized in that: The GND density in the laser additively manufactured deposited nickel-based high-temperature alloy is 8×10 14 m 2 -10×10 14 m 2 . ; and / or The GND density in the additively manufactured nickel-based high-temperature alloy after the stress relief treatment is 1×10 13 m 2 -2×10 14 m 2 .

7. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 2, characterized in that: The additively manufactured nickel-based high-temperature alloy is an arc additively manufactured deposited nickel-based high-temperature alloy.

8. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 7, characterized in that: The parameters of the continuous pulse current treatment are as follows: Continuous pulse current density is 300-400A / mm 2 , the continuous pulse current width is 0.2-0.8ms, the continuous pulse current frequency is 30-50Hz, the duty cycle is 30-60%, the temperature of the continuous pulse current treatment is 1100℃±2℃, and the time of the continuous pulse current treatment is 10min±2min.

9. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to claim 7 or 8, wherein the GND density in the arc additively manufactured deposited nickel-based high-temperature alloy is 8×10 14 m 2 -10×10 14 m 2 ; and / or The stress in the additively manufactured nickel-based high-temperature alloy after the stress relief treatment is GND density 1×10 13 m 2 -2×10 14 m 2 .

10. The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloy according to any one of claims 1 to 9, characterized in that: The method for eliminating residual stress in additively manufactured nickel-based high-temperature alloys comprises the following steps: Step 1), processing the additively manufactured nickel-based high-temperature alloy into a workpiece for continuous pulse current processing; Step 2), connecting the workpiece to a pulse power supply, turning on the pulse power supply, and applying a continuous pulse current treatment to the workpiece; Step 3), cooling the workpiece after continuous pulse current treatment to obtain a treated additively manufactured nickel-based high-temperature alloy; Preferably, in the step 1), the additively manufactured nickel-based high-temperature alloy is cut, polished and cleaned to obtain a workpiece of a set size.

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