A method for binder jet printing high-strength and tough β-titanium alloy

Abstract

The present invention discloses a method for printing high-strength and tough β-titanium alloy by binder jetting, and relates to the technical field of material forming. The method comprises the following steps: (1) making a high-strength and tough β-titanium alloy three-dimensional model, importing the three-dimensional data model into a printing device, and completing model recognition and slicing; (2) setting printing parameters, spraying a water-based binder to wet the near-β-titanium alloy powder, and printing: first laying #1 near-β-titanium alloy powder, and then laying #2 near-β-titanium alloy powder on the surface of the obtained #1 near-β-titanium alloy powder layer; (3) after printing, thermally curing the printed product until the water-based binder is dry; (4) degreasing and sintering the product cured in step (3) to obtain a high-strength and tough β-titanium alloy; the present invention uses high-strength and tough near-β-titanium alloy powders of different scales for printing, matches a water-based binder, and adopts a solid solution + aging heat treatment method to prepare a high-strength and tough β-titanium alloy.

Description

Technical Field

[0001] The invention relates to the technical field of material forming, and in particular to a method for printing a high-strength and tough beta titanium alloy by binder jetting. Background Art

[0002] Titanium and titanium alloys have the advantages of low density, high specific strength, high corrosion resistance, and biocompatibility, and are widely used in aerospace, automotive, medical, navigation, precision instruments and other fields. Among them, high-strength and tough β-titanium alloys are widely used in the aerospace field due to their excellent corrosion resistance, high strength and low modulus. Among them, near-β titanium alloys have higher strength and fracture toughness than traditional β-titanium alloys, and they have β-stabilizing elements slightly higher than the critical concentration.

[0003] With the development of the aerospace field, higher requirements are placed on the performance and dimensional accuracy of materials. The excellent hardenability of near-β titanium alloys makes it easier to obtain excellent mechanical properties after heat treatment. However, the high-strength and tough β titanium alloys processed by traditional melting and casting methods have coarse structures, and further heat treatment requires hot processing to coordinate the scale of the organization. The traditional melting and casting method is time-consuming and labor-intensive. In addition, if you want to prepare complex structural parts, machining is also required, and the chemical properties of titanium alloys are active and hard, which easily wears the tools. The additive manufacturing method for preparing high-strength and tough β titanium alloy parts can achieve integrated net forming and reduce subsequent processing steps. In addition, the materials of additive manufacturing have a fine structure due to rapid cooling, so the hot processing steps in the traditional processing method can be eliminated, and the heat treatment process can be directly carried out.

[0004] At present, the methods for additive manufacturing of near-β titanium alloys include powder bed fusion (PBF) technology, powder injection molding (MIM) technology, and binder jetting (BJAM) technology. Among them, PBF technology requires the three-dimensional part slices to be imported into the computer first, and the powder bed is melted layer by layer using high-energy heat sources such as lasers and electron beams to achieve layer-by-layer deposition. This technology can achieve high-density forming, and the performance of the formed parts can be comparable to that of forgings. At present, many near-β titanium alloy powder bed fusion technologies have been reported, but this technology has problems such as high powder requirements, low production efficiency, and severe residual stress. MIM and BJAM technologies have low residual stress while ensuring the strength performance of the parts, and the requirements for powder are not high, which can reduce production costs.

[0005] Binder jetting (BJAM) technology also imports two-dimensional data into the computer through slicing of three-dimensional part models, uses a powder roller to spread powder layer by layer, and then uses an inkjet print head to selectively spray a specific binder layer by layer on the powder bed according to the two-dimensional structure. After curing, the binder and powder are bonded together to obtain a part blank, and then the powder on the surface of the blank is removed, and then the binder is removed by degreasing, and finally sintered into the final densified part. Compared with PBF technology, BJAM technology has the advantages of low cost, a wide range of powder types, low operating difficulty, and no need for support structures. However, BJAM forming of near-β titanium alloys faces problems such as difficult to control sintering shrinkage, low density, and poor mechanical properties.

[0006] Based on the above existing problems, the present invention proposes a method for binder jet printing of high-strength and toughness β-titanium alloy. Summary of the invention

[0007] The purpose of the present invention is to provide a method for printing high-strength and toughness β-titanium alloy by binder jetting to solve the problems existing in the above-mentioned prior art.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] The present invention provides a method for binder jet printing of high-strength and toughness β-titanium alloy, comprising the following steps:

[0010] (1) Produce a three-dimensional model of high-strength and tough β-titanium alloy, import the three-dimensional data model into the printing equipment, and complete the model recognition and slicing work;

[0011] (2) Setting printing parameters, spraying a water-based binder until the near-β titanium alloy powder is moistened, and then printing: first laying #1 near-β titanium alloy powder, and then laying #2 near-β titanium alloy powder on the surface of the obtained #1 near-β titanium alloy powder layer;

[0012] (3) After printing is completed, the printed product is thermally cured until the water-based adhesive is dry;

[0013] (4) degreasing, sintering, solutionizing and aging the product after solidification in step (3) to obtain the high-strength and toughness β titanium alloy;

[0014] The #1 near-β titanium alloy powder is a near-β titanium alloy mixed powder with 90% of the particle size of 15-35 μm and 10% of the particle size of 60-70 μm; the #2 near-β titanium alloy powder is a near-β titanium alloy powder with 100% of the particle size of 15-35 μm;

[0015] The raw materials of the water-based adhesive are as follows: 55-75% polyethylene glycol, 15-25% polymethyl methacrylate, 7-15% ethylene glycol methyl ether, 3-10% zinc stearate, and 5-10% polyvinyl pyrrolidone in percentage by weight.

[0016] Furthermore, the composition of the near-β titanium alloy powder is 3% Al, 8% Mo, 3% V, 2% Cr, 2% Zr, and the balance is Ti.

[0017] Furthermore, the thickness of the #1 near-β titanium alloy powder layer is 80-120 μm; and the laying thickness of the #2 near-β titanium alloy powder is 10-20 μm.

[0018] Furthermore, during the printing process, the temperature of the powder bed is 20-50°C.

[0019] Furthermore, the saturation (mass percentage of water content) of the water-based adhesive is 70-90%.

[0020] Furthermore, the thermal curing temperature is 100-200° C. and the time is 2-3 hours.

[0021] Furthermore, the degreasing temperature is 400-600° C., and the time is 3-5 hours; and the degreasing gas environment is an argon environment.

[0022] Furthermore, the sintering is vacuum micro-pressure sintering, and the sintering vacuum degree is 10 -3 Pa;

[0023] The sintering temperature is 1000-1200° C., and the time is 3-4 hours; the solution temperature is 750° C., and the time is 2-3 hours; the aging temperature is 400° C., and the time is 5-8 hours.

[0024] The present invention also provides a high-strength and toughness β titanium alloy prepared by the above preparation method.

[0025] The present invention discloses the following technical effects:

[0026] The present invention adopts a water-based binder to print high-strength and tough β-titanium alloy, which is green, environmentally friendly and pollution-free. In addition, ethylene glycol methyl ether is added to the binder to promote the penetration of the binder into the powder bed, ensure the uniformity of the binder, and improve the bonding effect.

[0027] The present invention uses high-strength and toughness near-β titanium alloy powders of different scales for printing, and lays the #2 powder layer after laying the #1 powder, thereby avoiding uneven bonding of the sample, reducing binder residue, and reducing powder porosity and product shrinkage.

[0028] The present invention adopts a solid solution + aging treatment method, solid solution of near-β titanium alloy in a dual-phase region to precipitate a micron-sized primary α phase, and aging to precipitate a nanometer-sized secondary α phase, thereby forming a multi-scale microstructure and improving the performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 The temperature-time curve during the preparation of the high-strength and tough β-titanium alloy of the present invention;

[0031] Figure 2 In the figure, (a) is the OM image of the printed sample of Example 1 (sample after sintering treatment), (b) is the SEM image of the sample after solution treatment in Example 1, (c) is the SEM image of the sample after solution and aging treatment in Example 1, and (d) is the SEM image of Comparative Example 1. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] (1) Spherical near-β titanium alloy powders (composition: 3% Al, 8% Mo, 3% V, 2% Cr, 2% Zr, balance Ti) with a particle size of 20 μm and 65 μm were prepared by gas atomization method, and the powder purity was 99.9%; 90% of the near-β titanium alloy powders with a particle size of 20 μm and 10% of the near-β titanium alloy powders with a particle size of 65 μm were set as #1 powder, and 100% of the near-β titanium alloy powders with a particle size of 20 μm were set as #2 powder;

[0039] (2) placing the nearly β titanium alloy powder in a vacuum oven at 70° C. and drying it thoroughly for 24 hours, and then spreading it evenly on a substrate after drying;

[0040] (3) making a three-dimensional model, and then importing the three-dimensional data model into a printing device according to the made three-dimensional model to complete the model recognition and slicing work;

[0041] (4) Setting printing parameters, the nozzle of the printing equipment sprays the binder to the near-β titanium alloy powder bed to wet the powder, and printing begins. The binder saturation is 75%, the powder spreading roller speed is 50 mm / s, the roller speed is 75 rpm, the powder bed temperature is 25°C, and the binder is a water-based binder with the following ingredients: 60% polyethylene glycol, 20% polymethyl methacrylate, 8% ethylene glycol methyl ether, 7% zinc stearate, and 5% polyvinyl pyrrolidone. When spreading the powder, first spread the #1 powder with a thickness of 100 μm, and then spread the #2 powder with a thickness of 20 μm;

[0042] (5) After printing is completed, the product is thermally cured in a printing device until the binder is dry, the curing temperature is 180° C., the time is 3 h, and the loose sand on the surface of the preform is cleaned to obtain a preform;

[0043] (6) Degreasing the solidified preform by keeping it at 440° C. for 4 h in an argon atmosphere;

[0044] (7) The degreased samples were sintered at 10 -3 The sample was placed on a corundum ball with a diameter of 0.5 cm, and then cooled to room temperature by passing inert gas. The sample was then placed in a 750°C holding furnace for 2 hours, and then air-cooled to room temperature. The sample was then placed in a 400°C furnace for 8 hours and then air-cooled.

[0045] (8) After preparation, take out the sample.

[0046] The near-β titanium alloy printed sample prepared in this embodiment has a phase composition of equiaxed β grains, micron-sized primary α phase and nanometer-sized secondary α phase dispersed inside the β phase, with fewer micropores and void defects.

[0047] Example 2

[0048] (1) Spherical near-β titanium alloy powders (composition: 3% Al, 8% Mo, 3% V, 2% Cr, 2% Zr, balance Ti) with a particle size of 20 μm and 65 μm were prepared by gas atomization method, and the powder purity was 99.9%; 90% of the near-β titanium alloy powders with a particle size of 20 μm and 10% of the near-β titanium alloy powders with a particle size of 65 μm were set as #1 powder, and 100% of the near-β titanium alloy powders with a particle size of 20 μm were set as #2 powder;

[0049] (2) placing the nearly β titanium alloy powder in a vacuum oven at 70° C. and drying it thoroughly for 24 hours, and then spreading it evenly on a substrate after drying;

[0050] (3) making a three-dimensional model, and then importing the three-dimensional data model into a printing device according to the made three-dimensional model to complete the model recognition and slicing work;

[0051] (4) Setting printing parameters: binder saturation is 80%, powder spreading roller speed is 50 mm / s, roller speed is 75 rpm, powder bed temperature is 30°C, binder is water-based binder, composition is: 60% polyethylene glycol, 18% polymethyl methacrylate, 10% ethylene glycol methyl ether, 8% zinc stearate, 4% polyvinyl pyrrolidone, first spread the powder layer thickness of 100 μm #1 powder, then spread 20 μm #2 powder, and start printing;

[0052] (5) After printing is completed, the product is thermally cured in a printing device until the binder is dry, the curing temperature is 180° C., the time is 3 h, and the loose sand on the surface of the preform is cleaned to obtain a preform;

[0053] (6) Degreasing the solidified preform by keeping it at 440° C. for 5 h in an argon atmosphere;

[0054] (7) The degreased samples were sintered at 10 -3 The sample was placed on a corundum ball with a diameter of 0.5 cm, and then cooled to room temperature by passing inert gas. The sample was then placed in a 750°C holding furnace for 2 hours, and then cooled to room temperature. The sample was then placed in a 400°C holding furnace for 8 hours and then air-cooled.

[0055] (8) After preparation, take out the sample.

[0056] The near-β titanium alloy printed sample prepared in this embodiment has a phase composition of equiaxed β grains, micron-sized primary α phase and nanometer-sized secondary α phase dispersed inside the β phase, with fewer micropores and void defects.

[0057] Example 3

[0058] (1) Spherical near-β titanium alloy powders (composition: 3% Al, 8% Mo, 3% V, 2% Cr, 2% Zr, balance Ti) with a particle size of 20 μm and 65 μm were prepared by gas atomization method, and the powder purity was 99.9%; 90% of the near-β titanium alloy powders with a particle size of 20 μm and 10% of the near-β titanium alloy powders with a particle size of 65 μm were set as #1 powder, and 100% of the near-β titanium alloy powders with a particle size of 20 μm were set as #2 powder;

[0059] (2) placing the nearly β titanium alloy powder in a vacuum oven at 70° C. and drying it thoroughly for 24 hours, and then spreading it evenly on a substrate after drying;

[0060] (3) making a three-dimensional model, and then importing the three-dimensional data model into a printing device according to the made three-dimensional model to complete the model recognition and slicing work;

[0061] (4) Setting printing parameters: binder saturation is 80%, powder spreading roller speed is 50 mm / s, roller speed is 75 rpm, powder bed temperature is 30°C, binder is water-based binder, composition is: 60% polyethylene glycol, 18% polymethyl methacrylate, 10% ethylene glycol methyl ether, 8% zinc stearate, 4% polyvinyl pyrrolidone, first spread the powder layer thickness of 100 μm #1 powder, then spread 20 μm #2 powder, and start printing;

[0062] (5) After printing is completed, the product is thermally cured in a printing device until the binder is dry, the curing temperature is 180° C., the time is 3 h, and the loose sand on the surface of the preform is cleaned to obtain a preform;

[0063] (6) Degreasing the solidified preform by keeping it at 440° C. for 5 h in an argon atmosphere;

[0064] (7) The degreased samples were sintered at 10 -3 The sample was placed on a corundum ball with a diameter of 0.5 cm, and then cooled to room temperature by passing inert gas. The sample was then placed in a 750°C holding furnace for 2 hours, and then cooled to room temperature. The sample was then placed in a 400°C holding furnace for 8 hours and then air-cooled.

[0065] (8) After preparation, take out the sample.

[0066] The near-β titanium alloy printed sample prepared in this embodiment has a phase composition of equiaxed β grains, micron-sized primary α phase and nanometer-sized secondary α phase dispersed inside the β phase, with fewer micropores and void defects.

[0067] Comparative Example 1

[0068] The only difference from Example 1 is that the laying of #2 powder is not performed.

[0069] The near-β titanium alloy printed sample prepared in this comparative example has a phase composition of equiaxed β grains, micron-sized primary α phase and nanometer-sized secondary α phase dispersed inside the β phase, and there are many micropores and voids in the matrix.

[0070] Comparative Example 2

[0071] The only difference from Example 1 is that the binder composition is: 60% polyethylene glycol, 20% polymethyl methacrylate, 8% ether, 7% zinc stearate, and 5% polyvinyl pyrrolidone.

[0072] The near-β titanium alloy printed sample prepared in this comparative example has a phase composition of equiaxed β grains, micron-sized primary α phase and nanometer-sized secondary α phase dispersed inside the β phase, and there are many micropores and voids in the matrix.

[0073] Comparative Example 3

[0074] The only difference from Example 1 is that no solution treatment and aging treatment steps are performed.

[0075] The near-β titanium alloy printed sample prepared in this comparative example has a phase composition of equiaxed β grains and a small amount of small-sized α phase, with fewer micropores and void defects.

[0076] Comparative Example 4

[0077] The only difference from Example 1 is that the sintering temperature is 1380°C.

[0078] The near-β titanium alloy printed samples prepared in this comparative example have obvious pores and microcracks.

[0079] Product performance characterization:

[0080] The density, yield strength, tensile strength, elongation and shrinkage of the high-strength and tough β-titanium alloy prints prepared in Examples 1-3 and Comparative Examples 1-4 were tested, and the test method was as follows:

[0081] Density test method: Use BSA124S electronic balance to measure mass and calculate according to Archimedes principle;

[0082] Strength and elongation test method: The tensile test was carried out in accordance with GB / T 228.1 2010 standard, and the room temperature performance was tested on an Instron-5969 universal testing machine. The room temperature tensile specimen is a non-standard specimen with a gauge length of 18×4×2mm. During the test, an extensometer with a length of 12.5mm was used to record the change in displacement during the stretching process, and the stretching speed was 0.5mm / min. Before conducting the performance test, it is necessary to polish the surface with different types of sandpaper to eliminate the influence of wire cutting marks on the performance. The ordinate value of the highest point in the obtained engineering stress-strain curve is the tensile strength value, and the abscissa is 0.2%. The ordinate of the intersection of the straight line with the elastic modulus as the slope and the curve is the yield strength value, and the value of the point on the abscissa axis where the intersection line with the elastic modulus as the slope and the end point of the stress-strain curve intersects is the elongation;

[0083] Shrinkage measurement method: Use a standard ruler to measure the size. The shrinkage is equal to the ratio of the linear shrinkage of the material size to the initial size. Calculate the linear shrinkage in three directions respectively.

[0084] The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087] From the comparison between Example 1 and Comparative Example 1, it can be seen that the porosity has a great influence on the mechanical properties of the sample. The present invention improves the density of the powder bed and the printed part by regulating the powder layering method, and the combination of ethylene glycol methyl ether can reduce the use of binder, resulting in less shrinkage in the final sintering process.

[0088] By comparing Example 1 with Comparative Example 2, it can be seen that adding ethylene glycol methyl ether to the binder can increase the penetration effect of the binder, improve the uniformity of the binder, ensure uniform shrinkage of the sintered parts, show good mechanical properties and forming properties, and the sintered products are clean and pollution-free.

[0089] It can be seen from Example 1 and Comparative Example 3 that adding solid solution and aging treatments helps to coordinate multi-scale microstructures and improve the strength of the material while ensuring the elongation.

[0090] It can be seen from Example 1 and Comparative Example 4 that the sintering temperature has a great influence on the performance of the experimental samples, and a suitable sintering temperature can better alloy the samples without generating macroscopic defects.

[0091] The dual-scale powder spreading method of the present invention, the use of a water-based binder, and the introduction of a solid solution + aging treatment can effectively improve the density and mechanical properties of printed parts. At the same time, the sintering shrinkage of the sample is more uniform, which is conducive to the preparation of printed parts with precise dimensions and that meet the requirements. Compared with traditional processing methods, the steps of thermal processing can be reduced, the processing cycle can be reduced, and costs can be saved.

[0092] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for binder jet printing of high-strength and tough β-titanium alloy, characterized in that: The following steps are involved: (1) Produce a high-strength and tough β-titanium alloy three-dimensional model, import the three-dimensional data model into the printing equipment, and complete the model recognition and slicing work; (2) Setting printing parameters, spraying a water-based binder until the near-β titanium alloy powder is moistened, and then printing: first laying #1 near-β titanium alloy powder, and then laying #2 near-β titanium alloy powder on the surface of the obtained #1 near-β titanium alloy powder layer; (3) After printing is completed, the printed product is thermally cured until the water-based adhesive is dry; (4) degreasing, sintering, solutionizing and aging the product after solidification in step (3) to obtain the high-strength and toughness β titanium alloy; The #1 near-β titanium alloy powder is a near-β titanium alloy mixed powder with 90% of the particle size of 15-35 μm and 10% of the particle size of 60-70 μm; the #2 near-β titanium alloy powder is a near-β titanium alloy powder with 100% of the particle size of 15-35 μm; The raw materials of the water-based adhesive are as follows: 55-75% polyethylene glycol, 15-25% polymethyl methacrylate, 7-15% ethylene glycol methyl ether, 3-10% zinc stearate, and 5-10% polyvinyl pyrrolidone by mass percentage; Calculated by mass percentage, the composition of the near-β titanium alloy powder is 3% Al, 8% Mo, 3% V, 2% Cr, 2% Zr, and the balance is Ti; The thickness of the #1 near-β titanium alloy powder layer is 80-120 μm; the laying thickness of the #2 near-β titanium alloy powder is 10-20 μm; During printing, the temperature of the powder bed is 20-50°C; The thermal curing temperature is 100-200°C and the time is 2-3h; The degreasing temperature is 400-600°C, and the time is 3-5h; the degreasing gas environment is an argon environment; The sintering is vacuum micro-pressure sintering, and the sintering vacuum degree is 10 -3 Pa; the sintering temperature is 1000-1200°C, and the time is 3-4h; the solution temperature is 750°C, and the time is 2-3h; the aging temperature is 400°C, and the time is 5-8h.

2. The method according to claim 1, characterized in that The water content of the water-based adhesive is 70%-90% by mass.

3. A high-strength and tough β-titanium alloy prepared by the method according to any one of claims 1 to 2.

Images