Preparation method of powder material for improving toughness of metal additive part

Abstract

The invention discloses a preparation method of a powder material for improving the toughness of a metal additive part, which is characterized by comprising the following steps: mixing Y2O3 nano powder and titanium alloy powder through high-energy ball milling under the protection of argon, ball-milling for 2-4 hours to obtain mixed powder, preparing the mixed powder into an electrode through cold isostatic pressing under the protection of argon, and performing vacuum sintering to obtain a compact blank, the preparation method comprises the following steps: processing the raw materials into a bar, carrying out homogenizing annealing, cooling in an air cooling manner, carrying out multi-pass temperature control drawing on the bar to prepare a wire material, carrying out electrolytic polishing on the wire material in an electrolyte, preheating the wire material in an argon atmosphere protection furnace, and preparing the wire material into micron powder by adopting an axial wire feeding type plasma atomizer. And performing screening and vacuum annealing on the powder to obtain spherical powder, and processing the powder into a titanium alloy workpiece through SLM (selective laser melting) equipment. The method has the beneficial effects that the toughness of the titanium alloy additive part is improved, and the use safety and reliability of the part can be improved conveniently under the working conditions that the part bears complex loads such as impact and vibration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal additive manufacturing, more particularly, it relates to a powder material preparation method for improving the toughness of metal additive manufactured parts, which is particularly suitable for the preparation of titanium alloy powder. BACKGROUND

[0002] Metal additive manufacturing refers to a process of manufacturing metal parts by using metal powder, metal wire and other raw materials through 3D printing technology. It is the application of 3D printing in the field of metal materials. Metal additive manufacturing technology (such as selective laser melting (SLM)) has the advantages of no need for molds, direct manufacturing of complex structures, high material utilization rate, and short production cycle, and has been increasingly widely used in the fields of aerospace, medical devices, automobile manufacturing, and high-end equipment. In the field of aerospace, it can be used to manufacture key components such as engine blades and fuel nozzles with complex internal cavities and special-shaped structures; in the field of medical devices, it can accurately prepare implant bodies that match the shape of human bones, greatly improving the treatment effect and patient comfort.

[0003] Titanium alloy, as a high-performance metal material, has high specific strength, excellent corrosion resistance, and good biocompatibility, and is an important raw material in the field of metal additive manufacturing. The commonly used powder for titanium alloy additive manufacturing is titanium alloy spherical powder, such as TC4 (Ti-6Al-4V), TA15, Ti-6Al-4V ELI, etc. In the traditional technology for preparing titanium alloy additive manufactured parts, the preparation process mainly includes three core stages: preparation, additive manufacturing, and post-processing. The preparation stage covers three-dimensional model design and slicing, preparation and pretreatment of titanium alloy powder (such as drying and screening), and equipment debugging and substrate preparation; the additive manufacturing stage is the process of layer-by-layer powder laying, high-energy beam (laser or electron beam) melting / sintering powder, and layer-by-layer accumulation to form the final part.

[0004] However, in the traditional technology for preparing titanium alloy additive manufactured parts, the toughness of the parts needs to be improved. Therefore, a powder material preparation method for improving the toughness of metal additive manufactured parts is needed to improve the toughness of titanium alloy additive manufactured parts, so as to improve the safety and reliability of the parts under complex load conditions such as impact and vibration. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a powder material preparation method for improving the toughness of metal additive manufactured parts.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A powder material preparation method for improving the toughness of metal additive manufactured parts, comprising the following steps:

[0008] S1, Y2O3 nanopowder (particle size 50-100 nm) and titanium alloy powder are mixed by high-energy ball milling under argon protection, the addition amount of Y2O3 nanopowder is 0.1-0.5wt% of the mass of titanium alloy powder, ball milling for 2-4 hours, rotation speed 300-400 rpm, ball-to-material ratio 10:1, to obtain mixed powder;

[0009] S2, the mixed powder is cold isostatic pressed (200-300 MPa, pressure maintaining for 5 min) under argon protection to prepare an electrode, and then vacuum sintering (1200℃±10℃ / 4h, vacuum degree ≤10 -3 Pa) is adopted to obtain a dense blank, the blank is processed into a rod with a diameter of Φ10-20 mm by hot forging / hot rolling / extrusion, and then homogenization annealing is carried out at 950℃ / 2h, followed by air cooling cooling;

[0010] S3, the rod obtained in S2 is prepared into a homogeneous wire with a diameter of 1.5-2.5 mm by multi-pass temperature-controlled drawing, and the distribution deviation of Y2O3 is confirmed to be less than 5% by SEM-EDS detection;

[0011] S4, the wire obtained in S3 is electrolytic polished in an electrolyte (volume ratio HNO3:HF:H2O=3:1:6), current density 20A / cm 2 , time 30s;

[0012] S5, the wire is preheated to 450-550℃ in an argon atmosphere protection furnace, the heating rate is controlled to be 5-10℃ / min, after reaching the target temperature, the temperature is maintained for 30min (wire diameter ≤2mm) or 45min (diameter >2mm), argon purity ≥99.999%, flow rate 20-30L / min;

[0013] S6, the preheated wire of S5 is prepared into micron powder by using an axial wire feeding type plasma atomizer, the process parameters of this step are: plasma power 100-120kW, melting temperature 3000-4000℃, cooling rate ≥10 6 K / s (helium pressure ≥1.8MPa), wire feeding speed 3-5m / min, to obtain powder with a melting drop size D50=15-25μm, the plasma gas is Ar / He mixed gas (volume ratio 7:3);

[0014] S7, the powder obtained in S6 is sieved (particle size range 15-53μm) and vacuum annealed (800℃ / 2h, oxygen content <400ppm in Ar atmosphere) to obtain spherical powder, satellite powder ratio <5%;

[0015] S8, the powder obtained in S7 is processed into a titanium alloy part by SLM equipment.

[0016] Further arrangement, the titanium alloy powder has a particle size range of 15-45 mu m, a sphericity of > 0.9, and an oxygen content of < 800 ppm.

[0017] Further arrangement, the multi-pass temperature control drawing in S3 is divided into three stages.

[0018] The first stage: 1-3 passes, temperature 750-800 DEG C, single pass deformation amount 15-18%, annealing between passes 800 DEG C / 15 min.

[0019] The second stage: 4-6 passes, temperature 650-700 DEG C, single pass deformation amount 12-15%, annealing between passes 700 DEG C / 10 min.

[0020] The third stage: 7-9 passes, temperature 450-550 DEG C, single pass deformation amount 8-10%, final annealing 600 DEG C / 1 h.

[0021] Further arrangement, the plasma power in S6 is dynamically adjusted according to the wire diameter:

[0022] When the wire diameter is 1.5 mm, the plasma power is 100 kW;

[0023] The plasma power is increased by 5 kW for each 0.5 mm increase in wire diameter, and the maximum is not more than 120 kW.

[0024] Further arrangement, the atomization process in S6 needs to be controlled:

[0025] The distance between the plasma gun and the cooling surface is 300-400 mm, the helium flow rate is 50-60 L / min, and the powder collection bin temperature is <= 50 DEG C.

[0026] Further arrangement, the process parameters in S8 are: laser power 370 W, scanning speed 1000 mm / s, layer thickness 30 mu m, hatch spacing 100 mu m, protective gas Ar, oxygen content < 100 ppm, substrate preheating temperature 200+ / -10 DEG C, and the formed product needs to be subjected to hot isostatic pressing treatment.

[0027] Further arrangement, the hot isostatic pressing treatment is divided into two stages, the first stage: 850 DEG C / 150 MPa / 1 h; the second stage: 900 DEG C / 50 MPa / 1 h.

[0028] By adopting the above technical scheme, the application has the beneficial effects of improving the toughness of the titanium alloy additive manufacturing part, and facilitating the improvement of the use safety and reliability of the part under complex load conditions such as impact and vibration. BRIEF DESCRIPTION OF DRAWINGS

[0029] The application has no drawings. DETAILED DESCRIPTION

[0030] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0031] The materials, reagents, etc. used in the following examples can be obtained commercially unless otherwise specified.

[0032] Example 1: A powder material preparation method for improving the toughness of metal additive manufacturing parts, comprising the following steps:

[0033] S1, Y2O3 nano powder (particle size 50-100 nm) and titanium alloy powder (taking Ti-6Al-4V as an example) are mixed by high-energy ball milling under argon protection, the addition amount of Y2O3 nano powder is 0.1-0.5wt% of the mass of titanium alloy powder, the ball milling time is 2-4 hours, the rotation speed is 300-400 rpm, the ball-to-material ratio is 10:1, the mixed powder is obtained, the particle size of the titanium alloy powder is 15-45 μm, the sphericity is >0.9, the oxygen content is <800 ppm, the purity of the Y2O3 nano powder is ≥99.9%, and the Y2O3 nano powder is pre-vacuum dried at 120℃ for 2h to remove adsorbed water;

[0034] The Y2O3 nano powder is dispersed in the titanium alloy powder and on the surface of the titanium alloy powder particles by high-energy ball milling. Since the melting point of Y2O3 is 2410℃, the temperature during the subsequent plasma melting in S6 is 3000-4000℃, which is beneficial to uniformly dispersing Y2O3 in the titanium alloy melt and facilitating more uniform dispersion in the final titanium alloy part.

[0035] S2, the mixed powder is cold isostatic pressed (200-300 MPa, pressure holding for 5 min) under argon protection to form an electrode, and then vacuum sintered (1200℃±10℃ / 4h, vacuum degree ≤10 -3 Pa) to obtain a dense blank, the blank is processed into a rod with a diameter of Φ10-20 mm by hot forging / hot rolling / extrusion, and then homogenized annealed at 950℃ / 2h, followed by air cooling cooling;

[0036] S3, the rod obtained in S2 is prepared into a homogeneous wire with a diameter of 1.5-2.5 mm by multi-pass temperature-controlled drawing, and the Y2O3 distribution deviation is confirmed to be <5% by SEM-EDS detection, wherein the multi-pass temperature-controlled drawing is divided into three stages:

[0037] First stage: 1-3 passes, temperature 750-800℃, single-pass deformation 15-18%, inter-pass annealing 800℃ / 15min;

[0038] Second stage: 4-6 passes, temperature 650-700℃, single-pass deformation 12-15%, inter-pass annealing 700℃ / 10min;

[0039] Third stage: 7-9 passes, temperature 450-550℃, single pass deformation 8-10%, final annealing 600℃ / 1h.

[0040] S4, electrolytic polishing the wire material obtained in S3 in electrolyte (volume ratio HNO3:HF:H2O=3:1:6), current density 20A / cm 2 , time 30s;

[0041] S5, preheating the wire material in an argon atmosphere protection furnace to 450-550℃, controlling the heating rate 5-10℃ / min, holding for 30min (wire diameter≤2mm) or 45min (diameter>2mm) after reaching the target temperature, argon purity≥99.999%, flow rate 20-30L / min, after preheating, directly transmitting to the plasma atomizer through a sealed wire feeding channel (oxygen content<50ppm);

[0042] S6, preparing micron powder from the preheated wire material of S5 by using an axial wire feeding type plasma atomizer, the process parameters of this step: plasma power 100-120kW, melting temperature 3000-4000℃, cooling rate≥10 6 K / s (helium pressure≥1.8MPa), wire feeding speed 3-5m / min, obtaining powder with droplet size D50=15-25μm, plasma gas is Ar / He mixed gas (volume ratio 7:3),

[0043] wherein the plasma power is dynamically adjusted according to the wire diameter: when the wire diameter is 1.5mm, the plasma power is 100kW, for each 0.5mm increase in wire diameter, the plasma power is increased by 5kW, the highest does not exceed 120kW,

[0044] wherein the atomization process needs to be controlled: the distance between the plasma gun and the cooling surface is 300-400mm, helium flow rate is 50-60L / min, powder collection bin temperature≤50℃;

[0045] S7, obtaining spherical powder after screening (15-53μm particle size range) and vacuum annealing (800℃ / 2h, rate 5℃ / min, oxygen content in Ar atmosphere<400ppm) of the powder obtained in S6, satellite powder ratio<5%, and then treating by inert gas fluidized bed (tumbling in Ar gas flow for 10min).

[0046] S8, the powder obtained in S7 is processed into a titanium alloy part by an SLM device, the SLM device model: SLM Solutions SLM 280 2.0 (Germany SLM Solutions), process parameters: laser power 370 W, scanning speed 1000 mm / s, layer thickness 30 μm, hatch spacing 100 μm, protective gas Ar, oxygen content <100 ppm, substrate preheating temperature 200±10℃, atomization chamber vacuum degree, after forming, hot isostatic pressing treatment is needed, the hot isostatic pressing treatment is divided into two stages, the first stage: 850℃ / 150MPa / 1h; the second stage: 900℃ / 50MPa / 1h.

[0047] Example 1 titanium alloy part A prepared by the method S1-S8 of the present application; Comparative Example 1 titanium alloy part B prepared by a traditional titanium alloy part preparation method.

[0048] The properties tested for titanium alloy part A and titanium alloy part B are tensile strength, yield strength and elongation. The test samples of titanium alloy part A and the test samples of titanium alloy part B are 15 groups respectively, each group has 5 samples, and the data of each group is the arithmetic mean of the effective data of the samples in the group;

[0049] The test sample groups of titanium alloy part A are numbered as A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15 respectively; the test sample groups of titanium alloy part B are numbered as B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15 respectively.

[0050] The experimental data of tensile strength (MPa) at 25℃ of test sample groups A1, A2, A3, A4, A5 and test sample groups B1, B2, B3, B4, B5 are measured according to ISO 6892-1:2019 as follows:

[0051] Table A-1

[0052] Table B-1

[0053] The experimental data of yield strength (MPa) at 25℃ of test sample groups A6, A7, A8, A9, A10 and test sample groups B6, B7, B8, B9, B10 are measured according to ISO 6892-1:2019 as follows:

[0054] Table A-2

[0055] Table B-2

[0056] The experimental data of elongation (%) of the test sample groups A11, A12, A13, A14, A15 and the test sample groups B11, B12, B13, B14, B15 measured at 25 DEG C according to ISO 6892-1:2019 are as follows:

[0057] Table A-3

[0058] Table B-3

[0059] According to Table A1, Table A2, Table A3 and Table B1, Table B2, Table B3, Table 4 is obtained:

[0060] The elongation of the titanium alloy part A of Example 1 is 16.3±0.7%, and the elongation of the titanium alloy part B of the conventional process is 12.8±1.0%, the toughness of the titanium alloy part prepared by the present application is significantly improved, and the tensile strength is improved by 11.7% and the yield strength is improved by 6.3%, which ensures the strength and effectively reduces the cracking risk of the part under impact and vibration load, realizes the improvement of the toughness of the titanium alloy additive manufacturing part, and facilitates the improvement of the safety and reliability of the part under complex load conditions such as impact and vibration.

[0061] In the present application, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection", "fixation" and the like should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrated; can be mechanically connected, can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0062] The control mode of the present application is automatically controlled by the controller, and the control circuit of the controller can be realized by simple programming of those skilled in the art. The power supply also belongs to the common knowledge in the art, and the present application is mainly used to protect mechanical devices, so the control mode and circuit connection of the present application will not be explained in detail.

[0063] The above only describes the preferred embodiments of the present application, and does not limit the present application. Those skilled in the art can make usual changes and replacements within the technical solution range of the present application, which should be included in the protection scope of the present application.

Claims

1. A method for preparing powder materials to improve the toughness of metal additive parts, characterized in that, The method comprises the following steps: S1, mixing Y2O3 nano powder (particle size 50-100 nm) and titanium alloy powder under argon protection by high-energy ball milling, the addition amount of Y2O3 nano powder being 0.1-0.5 wt% of the mass of the titanium alloy powder, ball milling for 2-4 hours at a rotation speed of 300-400 rpm, and the ball-to-material ratio being 10:1 to obtain mixed powder; S2, the mixed powder is cold isostatic pressed (200-300 MPa, pressure maintaining for 5 min) under the protection of argon to form an electrode, and then vacuum sintered (1200℃±10℃ / 4h, vacuum degree≤10 -3 Pa) to obtain a dense blank, the blank is processed into a rod with a diameter of Φ10-20mm through hot forging / hot rolling / extrusion, and then homogenized annealed at 950℃ / 2h, and then cooled by air cooling; S3, preparing homogeneous wire with a diameter of 1.5-2.5 mm from the rod obtained in S2 by multi-pass temperature-controlled drawing, and confirming that the Y2O3 distribution deviation is less than 5% by SEM-EDS detection; S4, electrolytic polishing the wire material obtained in S3 in an electrolyte (volume ratio HNO3:HF:H2O = 3:1:6) at a current density of 20 A / cm2for 30 s 2 ; S5, preheating the wire in an argon atmosphere protection furnace to 450-550 DEG C, controlling the heating rate to be 5-10 DEG C / min, maintaining the temperature for 30 min (when the wire diameter is less than or equal to 2 mm) or 45 min (when the wire diameter is greater than 2 mm) after reaching the target temperature, the argon purity being greater than or equal to 99.999%, and the flow rate being 20-30 L / min; S6, preparing micron powder from the preheated wire in S5 by using an axial wire feeding type plasma atomizer, and the process parameters in this step being: plasma power 100-120 kW and melting temperature 3000-4000 DEG C; Cooling rate > 10 6 K / s (helium pressure > 1.8 MPa), wire feed speed 3-5 m / min, powder with a droplet size D50 = 15-25 pm was obtained, the plasma gas being Ar / He mixed gas (volume ratio 7:3); S7, obtaining spherical powder after screening (15-53 mu m particle size range) and vacuum annealing (800 DEG C / 2 h, oxygen content in Ar atmosphere < 400 ppm) of the powder obtained in S6, and the satellite powder ratio being less than 5%; S8, processing the powder obtained in S7 into a titanium alloy part by an SLM device.

2. The method of claim 1, wherein the powder material is prepared by a process comprising: The titanium alloy powder has a particle size range of 15-45 mu m, a sphericity greater than 0.9, and an oxygen content less than 800 ppm. ​ 3. The method of claim 1, wherein the powder material is prepared by a process comprising: The multi-pass temperature-controlled drawing in S3 is divided into three stages: ​ The first stage: 1-3 passes, temperature 750-800 DEG C, single pass deformation 15-18%, and annealing between passes at 800 DEG C for 15 min; The second stage: 4-6 passes, temperature 650-700 DEG C, single pass deformation 12-15%, and annealing between passes at 700 DEG C for 10 min; The third stage: 7-9 passes, temperature 450-550 DEG C, single pass deformation 8-10%, and final annealing at 600 DEG C for 1 h.

4. The method of claim 1, wherein the powder material is prepared by a process comprising: The plasma power in S6 is dynamically adjusted according to the wire diameter: ​ When the wire diameter is 1.5 mm, the plasma power is 100 kW; For every 0.5 mm increase in the wire diameter, the plasma power is increased by 5 kW, and the maximum is not more than 120 kW.

5. The method of claim 1, wherein the powder material is prepared by a process comprising: The atomization process in S6 needs to be controlled: ​ The distance between the plasma gun and the cooling surface is 300-400 mm, the helium flow rate is 50-60 L / min, and the powder collection bin temperature is less than or equal to 50 DEG C.

6. The method of claim 1, wherein the powder material is prepared by a process comprising: The process parameters in S8 are: laser power 370 W, scanning speed 1000 mm / s, layer thickness 30 mu m, hatch spacing 100 mu m, protective gas Ar, oxygen content < 100 ppm, substrate preheating temperature 200 ± 10 DEG C, and hot isostatic pressing treatment is required after forming. ​ 7. The method of claim 6, wherein the powder material is prepared by a process comprising: The hot isostatic pressing treatment is divided into two stages: ​ The first stage: 850 DEG C / 150 MPa / 1 h; The second stage: 900 DEG C / 50 MPa / 1 h.

Images