Process method for inhibiting selective laser melting cracks of WMoTaNbV refractory high-entropy alloy

Abstract

The invention provides a selective laser melting crack inhibition process method for a WMoTaNbV refractory high-entropy alloy, and relates to the technical field of selective laser melting refractory high-entropy alloys. According to the selective laser melting forming technology, the characteristic that in the micro-oxygen atmosphere, nano-graphite powder is prone to being oxidized in a molten pool to form gaseous CO, and consequently a finally-formed sample is a dispersion micropore is utilized, so that stress release of the WMoTaNbV refractory high-entropy alloy in the forming process is achieved, and the cracking problem caused by stress concentration is avoided. The method is simple in process, high in controllability, good in operability, low in energy consumption, controllable in cost, environmentally friendly, free of pollution and beneficial to industrial large-scale production and popularization. Compared with the directly formed WMoTaNbV refractory high-entropy alloy, the crack characteristics of the formed dispersion micropore WMoTaNbV refractory high-entropy alloy sample are obviously reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory high-entropy alloy selective laser melting forming, in particular to a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression processing technology. TECHNICAL BACKGROUND

[0002] With the development of new generation aerospace field, the traditional nickel-based high-temperature alloy material has been unable to meet the high-temperature resistance demand of new generation high-temperature hot end components, and it is urgent to develop new high-temperature resistant materials. Refractory high-entropy alloy, due to its good high-temperature strength at high temperature, is expected to become a new generation of high-temperature structural material of aero-engine. However, refractory high-entropy alloy is subject to room temperature brittleness, and the existing preparation method has great limitations. It is excessively dependent on vacuum environment, the sample shape is simple, and the processing performance is poor, etc. These shortcomings have delayed the application process of refractory high-entropy alloy and restricted the play of its excellent high-temperature performance in aerospace field. As a rapid melting-solidification method, selective laser melting technology can realize direct forming and personalized customization of complex shape, which will effectively solve the problem of room temperature brittleness deteriorating the processing performance of most refractory high-entropy alloy systems.

[0003] Taking WMoTaNbV refractory high-entropy alloy as a representative, the ductility is usually extremely poor, which leads to a large number of cracks and other defects in the selective laser melting forming process, becoming a key bottleneck restricting its personalized forming and application. Therefore, it is urgent to develop new technologies to solve the technical problems of cracking of refractory high-entropy alloy. SUMMARY

[0004] A WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method, the WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method comprises the following steps:

[0005] S1, preparation of WMoTaNbV composite powder dispersed with nano-graphite powder: the nano-graphite powder is added to the WMoTaNbV refractory high-entropy alloy pre-alloy powder by ball milling, and the ball milling is prepared in an argon protective atmosphere;

[0006] S2, preparation of WMoTaNbV refractory high-entropy alloy selective laser melting sample dispersed with nano-gap: using selective laser melting technology, according to a specific scanning strategy, the WMoTaNbV composite powder dispersed with nano-graphite powder is formed on a Ti6Al4V round base;

[0007] S3, heat treatment of selective laser melting high-entropy alloy.

[0008] Preferably, the mass ratio of each element in the WMoTaNbV high-entropy alloy in S1 is: W-30.41%, Mo-15.87%, Ta-29.93%, Nb-15.37%, and V-8.43%.

[0009] Preferably, the purity of the graphite powder in S1 is above 99.9%.

[0010] Preferably, the spherical pre-alloyed powder of the WMoTaNbV high-entropy alloy in S1 is prepared by a multi-process of suspension melting alloying + ball milling and crushing + plasma spheroidization and is obtained by screening.

[0011] The suspension melting process: the prepared raw materials are placed in a water-cooled copper crucible, vacuumized to 5.0x10 -3 Pa, and then high-purity argon is filled to 0.05-0.06 MPa as a protective atmosphere. Melting is performed by a high-frequency induction coil, and the melting temperature is controlled at 2500-3200°C. Each melting lasts for 3-8 minutes, and the process of melting-turning is repeated 5-8 times to ensure that the alloy elements are fully diffused and homogenized, thereby obtaining a WMoTaNbV high-entropy alloy ingot with uniform composition and no macrosegregation.

[0012] The ball milling and crushing process: first, the ingot is crushed to coarse particles with a particle size of less than 3 mm by using a hydraulic crusher. Then, the coarse particles and high-hardness tungsten carbide balls are placed in a high-energy planetary ball mill, the rotation speed of the ball mill is set to 250-400 rpm, the ball-to-material ratio is 10:1-20:1, and the ball milling time is 5-20 hours. Before ball milling, argon is introduced into the ball mill tank for protection to prevent powder oxidation.

[0013] The plasma spheroidization process: irregular powder is used as raw material, and a radio frequency plasma spheroidization device is used to send the raw material into the center of the plasma torch at a rate of 5-20 g / min, and the powder is spheroidized at a plasma power of 40-100 kW. Finally, 15-53 μm spherical powder is obtained by screening.

[0014] Preferably, the nano-graphite powder dispersion strengthened WMoTaNbV composite powder in S1 is prepared by mixing 15-53 μm spherical WMoTaNbV refractory high-entropy alloy powder with 50-100 nm flaky graphite powder at a mass ratio of 99:1, and the ball milling is carried out in an argon protective atmosphere.

[0015] Preferably, the ball milling process has a rotation speed of 200-300 rpm, an intermittent ratio of 10:1, a ball-to-material ratio of 5:1, and the ball mill tank and the grinding balls are made of tungsten steel.

[0016] Preferably, in the selective laser melting technology forming process in S2, first introduce 1000-2000ppm of oxygen into the chamber, and the nanometer graphite powder will react in the molten pool as follows: C+½O2→CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high-entropy alloy sample containing a certain amount of nanosheet-shaped pore characteristics is obtained;

[0017] Preferably, the specific scanning strategy in S2 is to form a regular-shaped small molten pool feature by scanning 2-3mm single channel length at an angle of 120° or 60°, with an overlap rate of 50%, and parallel scanning 100-120 channels, and the formed sample is printed by combining each layer of such small molten pool features;

[0018] The preferred laser line speed of the selective laser melting process is in the range of 800-1500mm / min, and the laser power is in the range of 600-900kW.

[0019] Preferably, the high-temperature strength of the dispersed microporous WMoTaNbV refractory high-entropy alloy selective laser melting sample before heat treatment is 50MPa at 1200℃, and the Vickers hardness is 700HV.

[0020] Preferably, the heat treatment process in S3 is to place the prepared dispersed microporous WMoTaNbV refractory high-entropy alloy selective laser melting sample in a muffle furnace, and take it out after heating from room temperature to 1200℃ and holding for 5-8h and air cooling treatment.

[0021] Preferably, the high-temperature strength of the dispersed microporous WMoTaNbV refractory high-entropy alloy selective laser melting sample after heat treatment is 300MPa at 1200℃, and the Vickers hardness is 960HV.

[0022] The technical principle of the present application is that during the selective laser melting process, a small amount of oxygen in the chamber reacts with graphite in the molten pool to form CO gas, resulting in a dispersed porous structure of the formed WMoTaNbV, so as to realize stress release of the WMoTaNbV during the forming process and avoid the occurrence of cracks.

[0023] Compared with the prior art, the above technical solution has at least the following beneficial effects: the above scheme, the present application proposes a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method, which can solve the problem of cracking of the WMoTaNbV refractory high-entropy alloy directly formed by selective laser melting in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0025] Figure 1 is a local optical microscope image of a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method formed sample according to Embodiment 1 of the present application;

[0026] Figure 2 is a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method formed sample image according to Embodiment 1 of the present application;

[0027] Figure 3 is a local area optical microscope image of a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method formed sample according to Comparative Example 1 of the present application;

[0028] Figure 4 is a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method formed sample image according to Embodiment 2 of the present application;

[0029] Figure 5 is a WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method formed sample image according to Embodiment 3 of the present application; DETAILED DESCRIPTION

[0030] A WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method, the WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method comprises the following steps:

[0031] S1, preparation of a nanographite powder dispersion strengthened WMoTaNbV composite powder;

[0032] S2, preparation of a WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed nanometer gaps;

[0033] S3, heat treatment of the selective laser melting high-entropy alloy.

[0034] Preferably, the mass percentage of each element of the WMoTaNbV high-entropy alloy in S1 is: W-30.41%, Mo-15.87%, Ta-29.93%, Nb-15.37%, and V-8.43%;

[0035] Preferably, the purity of the graphite powder in S1 is more than 99.9%;

[0036] Preferably, the WMoTaNbV high-entropy alloy spherical pre-alloyed powder in S1 is prepared and sieved through a multi-process process of suspension melting alloying + ball milling and crushing + plasma spheroidization.

[0037] The suspension smelting process involves placing the prepared raw materials in a water-cooled copper crucible and evacuating it to a vacuum level of 5.0 × 10⁻⁶. -3 The pressure is below 0.05 MPa, and then high-purity argon gas is introduced to 0.05~0.06 MPa as a protective atmosphere. Melting is carried out by a high-frequency induction coil, and the melting temperature is controlled at 2500~3200℃. Each melting lasts for 3~8 minutes, and the melting-turning is repeated 5~8 times to ensure that the alloying elements are fully diffused and homogenized, so as to obtain a WMoTaNbV high-entropy alloy ingot with uniform composition and no macrosegregation.

[0038] The ball milling and crushing process is as follows: First, a hydraulic crusher is used to crush the ingot into coarse particles with a particle size of less than 3 mm. Then, the coarse particles are placed together with high-hardness tungsten carbide grinding balls in a high-energy planetary ball mill. The ball mill speed is set to 250~400 rpm, the ball-to-material ratio is 10:1~20:1, and the ball milling time is 5~20 hours. Before ball milling, argon gas is introduced into the grinding jar for protection to prevent powder oxidation.

[0039] The plasma spheroidization process involves using irregular powder as raw material and employing a radio frequency plasma spheroidization device. The raw material is fed into the center of the plasma torch at a rate of 5-20 g / min, and the powder is spheroidized with a plasma power of 40-100 kW. Finally, the powder is sieved to obtain 15-53 μm spherical powder.

[0040] In the preferred embodiment S1, the WMoTaNbV composite powder with nano-graphite powder dispersion reinforcement is mainly prepared by mixing 15-53μm spherical WMoTaNbV refractory high entropy alloy powder with 50-100nm flake graphite powder at a mass ratio of 99:1 and then ball milling the powder.

[0041] Preferably, the ball milling mixing process has a rotation speed of 200-300 rpm, an intermittent ratio of 10:1, and a ball-to-material ratio of 5:1. During mixing, the ball mill jar is filled with argon gas as a protective gas, and both the ball mill jar and the grinding balls are made of tungsten steel.

[0042] Preferably, in the selective laser melting process of S2, 1000-2000 ppm of oxygen is first introduced into the chamber, and the nano-graphite powder will undergo the following reaction in the molten pool: C + ½O2 → CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high entropy alloy sample containing a certain amount of lamellar pore characteristics is obtained;

[0043] Preferably, the specific scanning strategy described in S2 is to perform 90-120 parallel scans with a single pass length of 2-3 mm at an angle of 120° or 60°, an overlap rate of 50-70%, to form a small molten pool feature of a regular shape for forming. Each layer of the formed sample is printed by combining such small molten pool features.

[0044] The preferred selective laser melting process uses a laser linear velocity in the range of 800-1500 mm / min and a laser power in the range of 600-900 W.

[0045] Preferably, the high-temperature strength of the dispersed microporous WMoTaNbV refractory high-entropy alloy selective laser melting sample before heat treatment at 1200℃ is 40-80MPa and the Vickers hardness is 600-750HV.

[0046] Preferably, the heat treatment process in S3 is as follows: the prepared dispersed microporous WMoTaNbV refractory high entropy alloy selective laser melting sample is placed in a muffle furnace, heated from room temperature to 1200℃ and held for 5-8 hours, and then taken out and air-cooled.

[0047] Preferably, the heat-treated dispersed microporous WMoTaNbV refractory high-entropy alloy selective laser melting sample has a high-temperature strength of 200-300 MPa and a Vickers hardness of 860-960 HV at 1200℃.

[0048] Example 1

[0049] This embodiment presents a selective laser melting crack suppression process for WMoTaNbV refractory high-entropy alloys, comprising the following steps:

[0050] S1, Preparation of WMoTaNbV composite powder with dispersion reinforcement of nano-graphite powder;

[0051] S2. Preparation of WMoTaNbV refractory high-entropy alloy samples with dispersed nano-interstic gaps by selective laser melting;

[0052] S3, Selective laser melting heat treatment of high-entropy alloys;

[0053] Preferably, the mass percentages of each element in the WMoTaNbV high-entropy alloy in S1 are: W - 30.41%, Mo - 15.87%, Ta - 29.93%, Nb - 15.37%, and V - 8.43%.

[0054] Preferably, the graphite powder in S1 has a purity of 99.9% or higher;

[0055] Preferably, the WMoTaNbV high-entropy alloy spherical pre-alloyed powder in S1 is prepared and sieved through a multi-process process of suspension melting alloying + ball milling and crushing + plasma spheroidization.

[0056] The suspension smelting process involves placing the prepared raw materials in a water-cooled copper crucible and evacuating it to a vacuum level of 5.0 × 10⁻⁶. -3 The pressure is below 0.05 MPa, and then high-purity argon gas is introduced to 0.05 MPa as a protective atmosphere. Melting is carried out by a high-frequency induction coil, with the melting temperature controlled at 2500℃. Each melting lasts for 8 minutes, and the melting-turning process is repeated 8 times to ensure that the alloying elements are fully diffused and homogenized, resulting in a WMoTaNbV high-entropy alloy ingot with uniform composition and no macroscopic segregation.

[0057] The ball milling and crushing process is as follows: First, a hydraulic crusher is used to crush the ingot into coarse particles with a particle size of less than 3 mm. Then, the coarse particles are placed together with high-hardness tungsten carbide grinding balls in a high-energy planetary ball mill. The ball mill speed is set to 250 rpm, the ball-to-material ratio is 10:1, and the milling time is 20 hours. Before milling, argon gas is introduced into the milling jar for protection to prevent powder oxidation.

[0058] The plasma spheroidization process involves using irregular powder as raw material and employing a radio frequency plasma spheroidization device. The raw material is fed into the center of the plasma torch at a rate of 20 g / min, and the powder is spheroidized with a plasma power of 100 kW. Finally, the powder is sieved to obtain 15-53 μm spherical powder.

[0059] In the preferred embodiment S1, the WMoTaNbV composite powder with nano-graphite powder dispersion reinforcement is mainly prepared by mixing 15-53μm spherical WMoTaNbV refractory high entropy alloy powder with 50-100nm flake graphite powder at a mass ratio of 99:1 and then ball milling the powder.

[0060] Preferably, the ball milling mixing process ranges as follows: rotation speed of 200 rpm, intermittent ratio of 10:1, ball-to-material ratio of 5:1, the ball mill jar is filled with argon gas as a protective gas during mixing, the ball mill jar and grinding balls are both made of tungsten steel, and the mixing time is 24 hours.

[0061] Preferably, during the selective laser melting process in S2, 1000 ppm of oxygen is introduced into the chamber, and the nano-graphite powder will undergo the following reaction in the molten pool: C + ½O₂ → CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high entropy alloy sample containing a certain amount of lamellar pore characteristics is obtained;

[0062] Preferably, the specific scanning strategy described in S2 is to perform 90 parallel scans with a single length of 3mm at an angle of 120° or 60°, an overlap rate of 50%, to form a small molten pool feature with a regular shape. Each layer of the formed sample is printed by combining such small molten pool features.

[0063] The preferred selective laser melting process uses a laser linear velocity in the range of 800 mm / min and a laser power in the range of 600 W. The resulting sample exhibits local optical microscopic features such as... Figure 1 As shown, the shaped sample is as follows Figure 2 As shown.

[0064] Preferably, the high-temperature strength of the WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed micropores is 40 MPa and the Vickers hardness is 600 HV at 1200℃ before heat treatment.

[0065] Preferably, the heat treatment process in S3 is as follows: the prepared dispersed microporous WMoTaNbV refractory high entropy alloy selective laser melting sample is placed in a muffle furnace, heated from room temperature to 1200℃ and held for 5 hours, and then taken out and air-cooled.

[0066] Preferably, the heat-treated WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed microporous structure has a high-temperature strength of 200 MPa and a Vickers hardness of 860 HV at 1200℃.

[0067] Comparative Example 1

[0068] This embodiment presents a selective laser melting crack suppression process for WMoTaNbV refractory high-entropy alloys, comprising the following steps:

[0069] S1, Preparation of WMoTaNbV composite powder with dispersion reinforcement of nano-graphite powder;

[0070] S2. Preparation of WMoTaNbV refractory high-entropy alloy samples with dispersed nano-interstic gaps by selective laser melting;

[0071] S3, Selective laser melting heat treatment of high-entropy alloys;

[0072] Preferably, the mass percentages of each element in the WMoTaNbV high-entropy alloy in S1 are: W - 30.41%, Mo - 15.87%, Ta - 29.93%, Nb - 15.37%, and V - 8.43%.

[0073] Preferably, the graphite powder in S1 has a purity of 99.9% or higher;

[0074] Preferably, the WMoTaNbV high-entropy alloy spherical pre-alloyed powder in S1 is prepared and sieved through a multi-process process of suspension melting alloying + ball milling and crushing + plasma spheroidization.

[0075] The suspension smelting process involves placing the prepared raw materials in a water-cooled copper crucible and evacuating it to a vacuum level of 5.0 × 10⁻⁶. -3 The pressure is below 0.05 MPa, and then high-purity argon gas is introduced to 0.05 MPa as a protective atmosphere. Melting is carried out by a high-frequency induction coil, with the melting temperature controlled at 2500℃. Each melting lasts for 8 minutes, and the melting-turning process is repeated 8 times to ensure that the alloying elements are fully diffused and homogenized, resulting in a WMoTaNbV high-entropy alloy ingot with uniform composition and no macroscopic segregation.

[0076] The ball milling and crushing process is as follows: First, a hydraulic crusher is used to crush the ingot into coarse particles with a particle size of less than 3 mm. Then, the coarse particles are placed together with high-hardness tungsten carbide grinding balls in a high-energy planetary ball mill. The ball mill speed is set to 250 rpm, the ball-to-material ratio is 10:1, and the milling time is 20 hours. Before milling, argon gas is introduced into the milling jar for protection to prevent powder oxidation.

[0077] The plasma spheroidization process involves using irregular powder as raw material and employing a radio frequency plasma spheroidization device. The raw material is fed into the center of the plasma torch at a rate of 20 g / min, and the powder is spheroidized with a plasma power of 100 kW. Finally, the powder is sieved to obtain 15-53 μm spherical powder.

[0078] In the preferred embodiment S1, the WMoTaNbV composite powder with nano-graphite powder dispersion reinforcement is mainly prepared by mixing 15-53μm spherical WMoTaNbV refractory high entropy alloy powder with 50-100nm flake graphite powder at a mass ratio of 99:1 and then ball milling the powder.

[0079] Preferably, the ball milling mixing process ranges as follows: rotation speed of 200 rpm, intermittent ratio of 10:1, ball-to-material ratio of 5:1, the ball mill jar is filled with argon gas as a protective gas during mixing, the ball mill jar and grinding balls are both made of tungsten steel, and the mixing time is 24 hours.

[0080] Preferably, during the selective laser melting process in S2, 1000 ppm of oxygen is introduced into the chamber, and the nano-graphite powder will undergo the following reaction in the molten pool: C + ½O₂ → CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high entropy alloy sample containing a certain amount of lamellar pore characteristics is obtained;

[0081] Preferably, the specific scanning strategy described in S2 is to perform 90 parallel scans with a single length of 3mm at an angle of 120° or 60°, an overlap rate of 50%, to form a small molten pool feature with a regular shape. Each layer of the formed sample is printed by combining such small molten pool features.

[0082] The preferred selective laser melting process uses a laser linear velocity in the range of 800 mm / min and a laser power in the range of 600 W. The resulting sample exhibits local optical microscopic features as follows: Figure 3 As shown.

[0083] Preferably, the high-temperature strength of the WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed micropores is 40 MPa and the Vickers hardness is 600 HV at 1200℃ before heat treatment.

[0084] Preferably, the heat treatment process in S3 is as follows: the prepared dispersed microporous WMoTaNbV refractory high entropy alloy selective laser melting sample is placed in a muffle furnace, heated from room temperature to 1200℃ and held for 5 hours, and then taken out and air-cooled.

[0085] Preferably, the heat-treated WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed microporous structure has a high-temperature strength of 200 MPa and a Vickers hardness of 860 HV at 1200℃.

[0086] Example 2

[0087] A selective laser melting crack suppression process for WMoTaNbV refractory high-entropy alloys, comprising the following steps:

[0088] S1, Preparation of WMoTaNbV composite powder with dispersion reinforcement of nano-graphite powder;

[0089] S2. Preparation of WMoTaNbV refractory high-entropy alloy samples with dispersed nano-interstic gaps by selective laser melting;

[0090] S3, Selective laser melting heat treatment of high-entropy alloys;

[0091] Preferably, the mass percentages of each element in the WMoTaNbV high-entropy alloy in S1 are: W - 30.41%, Mo - 15.87%, Ta - 29.93%, Nb - 15.37%, and V - 8.43%.

[0092] Preferably, the graphite powder in S1 has a purity of 99.9% or higher;

[0093] Preferably, the WMoTaNbV high-entropy alloy spherical pre-alloyed powder in S1 is prepared and sieved through a multi-process process of suspension melting alloying + ball milling and crushing + plasma spheroidization.

[0094] The suspension smelting process involves placing the prepared raw materials in a water-cooled copper crucible and evacuating it to a vacuum level of 5.0 × 10⁻⁶. -3 The pressure is below 0.06 MPa, and then high-purity argon gas is introduced to 0.06 MPa as a protective atmosphere. Melting is carried out by a high-frequency induction coil, and the melting temperature is controlled at 3200℃. Each melting lasts for 3 minutes, and the melting and flipping are repeated 5 times to ensure that the alloying elements are fully diffused and homogenized, so as to obtain a WMoTaNbV high-entropy alloy ingot with uniform composition and no macrosegregation.

[0095] The ball milling and crushing process is as follows: First, a hydraulic crusher is used to crush the ingot into coarse particles with a particle size of less than 3 mm. Then, the coarse particles are placed together with high-hardness tungsten carbide grinding balls in a high-energy planetary ball mill. The ball mill speed is set to 400 rpm, the ball-to-material ratio is 20:1, and the milling time is 5 hours. Before milling, argon gas is introduced into the milling jar for protection to prevent powder oxidation.

[0096] The plasma spheroidization process involves using irregular powder as raw material and employing radio frequency plasma spheroidization equipment. The raw material is fed into the center of the plasma torch at a rate of 5 g / min, and the powder is spheroidized with a plasma power of 40 kW. Finally, the powder is sieved to obtain 15-53 μm spherical powder.

[0097] In the preferred embodiment S1, the WMoTaNbV composite powder with nano-graphite powder dispersion reinforcement is mainly prepared by mixing 15-53μm spherical WMoTaNbV refractory high entropy alloy powder with 50-100nm flake graphite powder at a mass ratio of 99:1 and then ball milling the powder.

[0098] Preferably, the ball milling mixing process ranges as follows: rotation speed of 300 rpm, intermittent ratio of 10:1, ball-to-material ratio of 5:1, the ball mill jar is filled with argon gas as a protective gas during mixing, the ball mill jar and grinding balls are both made of tungsten steel, and the mixing time is 18 hours.

[0099] Preferably, in the selective laser melting forming process in S2, 2000 ppm of oxygen is first introduced into the chamber, and the nano-graphite powder will undergo the following reaction in the molten pool: C + ½O₂ → CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high entropy alloy sample containing a certain amount of lamellar pore characteristics is obtained;

[0100] Preferably, the specific scanning strategy described in S2 is to perform 120 parallel scans with a single length of 2mm at an angle of 120° or 60°, an overlap rate of 70%, to form a small molten pool feature with a regular shape for forming. Each layer of the formed sample is printed by combining such small molten pool features.

[0101] The preferred selective laser melting process uses a laser linear velocity in the range of 1500 mm / min and a laser power in the range of 900 W. The resulting sample exhibits the following characteristics: Figure 4 As shown.

[0102] Preferably, the high-temperature strength of the WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed micropores is 80 MPa and the Vickers hardness is 750 HV at 1200℃ before heat treatment.

[0103] Preferably, the heat treatment process in S3 is as follows: the prepared dispersed microporous WMoTaNbV refractory high entropy alloy selective laser melting sample is placed in a muffle furnace, heated from room temperature to 1200℃ and held for 8 hours, and then taken out and air-cooled.

[0104] Preferably, the heat-treated dispersed microporous WMoTaNbV refractory high-entropy alloy selective laser melting sample has a high-temperature strength of 300 MPa and a Vickers hardness of 960 HV at 1200℃.

[0105] Example 3

[0106] A selective laser melting crack suppression process for WMoTaNbV refractory high-entropy alloys, comprising the following steps:

[0107] S1, Preparation of WMoTaNbV composite powder with dispersion reinforcement of nano-graphite powder;

[0108] S2. Preparation of WMoTaNbV refractory high-entropy alloy samples with dispersed nano-interstic gaps by selective laser melting;

[0109] S3, Selective laser melting heat treatment of high-entropy alloys;

[0110] Preferably, the mass percentages of each element in the WMoTaNbV high-entropy alloy in S1 are: W - 30.41%, Mo - 15.87%, Ta - 29.93%, Nb - 15.37%, and V - 8.43%.

[0111] Preferably, the graphite powder in S1 has a purity of 99.9% or higher;

[0112] Preferably, the WMoTaNbV high-entropy alloy spherical pre-alloyed powder in S1 is prepared and sieved through a multi-process process of suspension melting alloying + ball milling and crushing + plasma spheroidization.

[0113] The suspension smelting process involves placing the prepared raw materials in a water-cooled copper crucible and evacuating it to a vacuum level of 5.0 × 10⁻⁶. -3The pressure is below 0.055 MPa, and then high-purity argon gas is introduced to 0.055 MPa as a protective atmosphere. Melting is carried out by a high-frequency induction coil, with the melting temperature controlled at 3000℃. Each melting lasts for 5 minutes, and the melting and flipping are repeated 6 times to ensure that the alloying elements are fully diffused and homogenized, so as to obtain a WMoTaNbV high-entropy alloy ingot with uniform composition and no macrosegregation.

[0114] The ball milling and crushing process is as follows: First, a hydraulic crusher is used to crush the ingot into coarse particles with a particle size of less than 3 mm. Then, the coarse particles are placed together with high-hardness tungsten carbide grinding balls in a high-energy planetary ball mill. The ball mill speed is set to 300 rpm, the ball-to-material ratio is 15:1, and the milling time is 15 hours. Before milling, argon gas is introduced into the milling jar for protection to prevent powder oxidation.

[0115] The plasma spheroidization process involves using irregular powder as raw material and employing a radio frequency plasma spheroidization device. The raw material is fed into the center of the plasma torch at a rate of 15 g / min, and the powder is spheroidized with a plasma power of 80 kW. Finally, the powder is sieved to obtain 15-53 μm spherical powder.

[0116] In the preferred embodiment S1, the WMoTaNbV composite powder with nano-graphite powder dispersion reinforcement is mainly prepared by mixing 15-53μm spherical WMoTaNbV refractory high entropy alloy powder with 50-100nm flake graphite powder at a mass ratio of 99:1 and then ball milling the powder.

[0117] Preferably, the ball milling mixing process ranges from a rotation speed of 250 rpm to an intermittent ratio of 10:1 and a ball-to-material ratio of 5:1. During mixing, the ball mill jar is filled with argon gas as a protective gas, and both the ball mill jar and the grinding balls are made of tungsten steel.

[0118] Preferably, in the selective laser melting forming process in S2, 1500 ppm of oxygen is first introduced into the chamber, and the nano-graphite powder will undergo the following reaction in the molten pool: C + ½O₂ → CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high entropy alloy sample containing a certain amount of lamellar pore characteristics is obtained;

[0119] Preferably, the specific scanning strategy described in S2 is to perform 100 parallel scans with a single length of 2.5 mm at an angle of 120° or 60°, an overlap rate of 60%, to form a small molten pool feature with a regular shape. Each layer of the formed sample is printed by combining such small molten pool features.

[0120] The preferred selective laser melting process uses a laser linear velocity in the range of 1000 mm / min and a laser power in the range of 750 W. The resulting sample will resemble... Figure 5As shown.

[0121] Preferably, the high-temperature strength of the WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed micropores is 60 MPa and the Vickers hardness is 650 HV at 1200℃ before heat treatment.

[0122] Preferably, the heat treatment process in S3 is as follows: the prepared dispersed microporous WMoTaNbV refractory high entropy alloy selective laser melting sample is placed in a muffle furnace, heated from room temperature to 1200℃ and held for 6.5h, and then taken out and air-cooled.

[0123] Preferably, the heat-treated WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed microporous structure has a high-temperature strength of 250 MPa and a Vickers hardness of 900 HV at 1200℃.

Claims

1. A WMoTaNbV refractory high-entropy alloy selective laser melting crack inhibition process method, the WMoTaNbV refractory high-entropy alloy selective laser melting crack inhibition process method comprising the following steps: S1, preparation of nano-graphite powder dispersion strengthened WMoTaNbV composite powder: adding nano-graphite powder to WMoTaNbV refractory high-entropy alloy pre-alloy powder by ball milling, and preparing in an argon atmosphere; S2, preparation of a WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed nano-gaps: using selective laser melting technology, forming nano-graphite powder dispersion strengthened WMoTaNbV composite powder on a Ti6Al4V round base according to a specific scanning strategy; S3, high-entropy alloy heat treatment: placing the prepared WMoTaNbV refractory high-entropy alloy selective laser melting sample with dispersed micro-holes in a muffle furnace, heating from room temperature to 1200 DEG C at a constant rate, and taking out after heat preservation for 5-8 h for air cooling treatment.

2. The WMoTaNbV refractory high-entropy alloy selective laser melting crack suppression process method of claim 1, wherein, In S1, the preparation of nano-graphite powder dispersion strengthened WMoTaNbV composite powder is performed by mixing 15-53 μm spherical WMoTaNbV refractory high-entropy alloy powder and 50-100 nm flaky graphite powder at a mass ratio of 99:1, ball milling in an argon atmosphere, using a rotation speed of 200-300 rpm, an intermittent ratio of 10:1, and a ball-to-powder ratio of 5:

1.

3. A process for suppressing cracks in a WMoTaNbV refractory high-entropy alloy by selective laser melting according to claim 1, characterized in that, In the selective laser melting technology forming process in S2, first, 1000-2000ppm of oxygen is introduced into the chamber, so that the nano-graphite powder will react in the molten pool as follows: C+½O2→CO, ΔG ○ =-275kJ / mol (T=1600℃), a certain amount of gaseous CO is formed, and a WMoTaNbV refractory high-entropy alloy sample containing a certain amount of nanosheet-shaped pore characteristics is obtained; the specific scanning strategy is to scan 100-120 parallel lines according to 2-3mm single line length at an angle of 120° or 60°, the overlap rate is 50%, a regular-shaped small molten pool feature is formed for forming, and each layer of the formed sample is formed by combining and printing such small molten pool features; the preferred process laser line speed is in the range of 800-1500mm / min, and the laser power is in the range of 600-900W.

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