Method for printing titanium alloy with binder

Abstract

The present invention discloses a method for printing titanium alloy with a binder, which includes: preparing raw materials, using near-spherical Ti6Al4V powder produced by gas atomization, with a powder particle size of 15-53 μm and a bimodal distribution, and a powder purity of 99.9%; vacuum drying the prepared Ti6Al4V powder at 80 °C for 4 hours, and spreading it on a substrate after drying; according to the completed three-dimensional model, importing the three-dimensional model data into a printing device to complete model recognition and slicing work; setting printing parameters, and the nozzle of the printing device sprays the binder onto the Ti6Al4V powder bed to wet the powder and start printing; after printing, thermally curing the product in the printing device until the binder dries; degreasing and sintering the cured product; completing sintering and taking out the product. The method of the present invention uses an aqueous binder for printing and a method of adding a small amount of PVP, which inhibits the void nucleation phenomenon of PEG and PMMA, improves the quality while ensuring cleanliness.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional forming manufacturing, and particularly relates to a method for printing titanium alloy with binder. Background Art

[0002] After more than seventy years of development, titanium alloy has now become one of the three major light metal structural materials. Titanium and its alloys have properties such as low density, high specific strength, excellent corrosion resistance, and biocompatibility, and are forming materials for important parts in fields such as aerospace, ocean engineering, and biomedical.

[0003] Currently, commonly used technologies for titanium alloy in additive manufacturing include selective laser melting (SLM), electron beam melting (EBM), metal injection molding (MIM), and binder jet additive manufacturing (BJAM), etc. Selective laser melting and electron beam melting can be collectively referred to as powder bed fusion (PBF). PBF usually uses a high-energy beam heat source to melt materials in an inert atmosphere or vacuum. This process can print high-performance metal parts, but there are problems such as low printing efficiency, high cost, and prominent residual stress. The metal injection molding technology (MIM) is different from traditional processing technologies and manufactures precision metal parts by combining injection molding with metal powder. It allows for more flexible structural design while ensuring the structural strength of the parts. At the same time, the application of MIM in titanium alloy has achieved the low-cost production of complex geometric components of titanium alloy.

[0004] The BJAM technology is also known as 3DP (3D printing), which refers to an additive manufacturing process of spraying binder onto a powder bed, where the binder bonds and solidifies the powder and forms layers one by one. The process includes two stages: spraying binder in a selective area layer by layer through an inkjet print head onto the powder bed to bond and print the initial blank of a three-dimensional solid part; placing the printed initial blank in a uniform thermal environment for debinding and sintering to make it densify and obtain a part with good mechanical properties. Compared with PBF and DED technologies, the BJAM technology has unique advantages: low cost, a wide range of material systems, good surface quality, and no need for support structures, etc. However, currently, the BJAM technology for forming titanium alloy parts faces a series of problems such as difficult debinding, large shrinkage rate during the sintering process, poor shape control accuracy, and low density of the final formed parts resulting in poor performance.

[0005] Based on the above technical problems existing in the prior art, the present invention proposes a method for printing titanium alloy with binder. Summary of the Invention

[0006] The present invention provides a method for printing titanium alloy with binder.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for printing titanium alloy with binder, comprising:

[0009] Step 1: Prepare raw materials. Use near-spherical Ti6Al4V powder produced by gas atomization. The powder particle size is 15 - 53 μm and has a bimodal distribution. The powder purity is 99.9%. Make a three-dimensional model.

[0010] Step 2: Vacuum-dry the prepared Ti6Al4V powder at 80 °C for 4 hours. After drying, spread it on the substrate.

[0011] Step 3: According to the completed three-dimensional model, import the three-dimensional model data into the printing device to complete model recognition and slicing.

[0012] Step 4: Set the printing parameters. The nozzle of the printing device sprays the binder onto the Ti6Al4V powder bed to wet the powder and start printing.

[0013] Step 5: After printing, thermally cure the product in the printing device until the binder dries.

[0014] Step 6: Debind and sinter the cured product.

[0015] Step 7: Complete sintering and take out the product.

[0016] Further, in Step 4, the binder is a water-based binder, including 65 - 78 parts by mass of polyethylene glycol (PEG), 20 - 27 parts by mass of polymethyl methacrylate (PMMA), 2 - 10 parts by mass of polyvinylpyrrolidone (PVP), and 2 - 5 parts by mass of stearic acid (SA).

[0017] Further, in Step 4, the optional powder layer thickness is 50 μm / 80 μm / 120 μm / 150 μm, the binder saturation is 60% - 90%, the powder spreading roller speed is 50 mm / s, the roller rotation speed is 75 rpm, and the powder bed temperature is 15 - 30 °C. Among them, a low powder spreading speed and roller rotation speed can ensure a small surface roughness of the powder bed and improve the surface quality of the printed parts.

[0018] Further, in Step 5, the curing temperature is 100 - 220 °C and the time is 2 - 3 h.

[0019] Further, in Step 6, the sintering atmosphere is vacuum and the vacuum degree is 10⁻³ Pa.

[0020] Further, in step 6, the debinding and sintering are divided into seven temperature stages, with the heating temperatures being 300°C, 400°C, 450°C, 550°C, 800°C, 1100°C, and 1300°C respectively, and the heating-up times being 60 min, 20 - 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; the holding times are 90 - 300 min, 90 - 300 min, 60 min, 180 - 300 min, 60 min, 0 min, and 120 min respectively.

[0021] Compared with the prior art, the superior effects of the present invention are as follows:

[0022] 1. For the method for printing titanium alloy with binder of the present invention, water-based binder is used for printing and a small amount of PVP is added, which inhibits the void nucleation phenomenon of PEG and PMMA. While improving the quality, it also ensures cleanliness.

[0023] 2. For the method for printing titanium alloy with binder of the present invention, in the debinding and sintering stage, a multi-stage heating and sintering process is adopted. The slow heating enables the debinding process to proceed step by step, reducing the shrinkage rate of the product and ensuring the dimensional accuracy of the product.

[0024] 3. For the method for printing titanium alloy with binder of the present invention, near-spherical Ti6Al4V powder with a particle size of 15 - 53 μm and a bimodal distribution and a powder purity of 99.9% is used, enabling the binder to fully wet the powder particles and the green body to have relatively high strength. The coarse powder ensures fluidity, and the fine powder fills the pores between large particles to increase the packing density and reduce the shrinkage rate. Description of the Drawings

[0025] Figure 1 is the thermogravimetric curve of the binder in Example 3 of the present invention;

[0026] Figure 2 is the thermogravimetric curve of the printed green body in Example 3 of the present invention;

[0027] Figure 3 is the metallographic diagram of the sample in Example 3 of the present invention. Detailed Embodiments

[0028] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0029] Example 1

[0030] S1. Prepare raw materials, using near-spherical Ti6Al4V powder produced by gas atomization, with a powder particle size of 15 - 53 μm and a purity of 99.4%, and make a three-dimensional model;

[0031] S2. Vacuum-dry the prepared Ti6Al4V powder at 80 °C for 4 hours and spread it on the substrate;

[0032] S3. According to the provided drawings, complete the three-dimensional modeling of the product to be produced in advance, import the model into the printing device, and complete the identification and slicing work;

[0033] S4. Set the printing parameters. The optional powder layer thickness is 50 μm, the binder saturation is 60%, the laying speed of the roller is 50 mm / s, and the roller rotation speed is 75 rpm; the powder bed temperature is 15 °C. The equipment nozzle sprays the binder onto the powder bed to wet the powder and start printing;

[0034] S5. After printing, thermally cure the product until the binder dries. The curing temperature is 200 and the time is 2 h;

[0035] S6. Debind and sinter the cured product. The sintering atmosphere is vacuum and the vacuum degree is 10 -3 Pa; The debinding and sintering are divided into seven temperature stages. The heating temperatures are 300, 400, 450, 550, 800, 1100, and 1300 respectively, and the heating times are 60 min, 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; the holding times are 90 min, 90 min, 60 min, 180 min, 60 min, 0 min, and 120 min respectively.

[0036] S7. Complete sintering and take out the product.

[0037] In step S4 of the above embodiment, the binder is a water-based binder, including 78 parts of polyethylene glycol (PEG), 27 parts of polymethyl methacrylate (PMMA), 3 parts of polyvinylpyrrolidone (PVP), and 2 parts of stearic acid (SA).

[0038] Example 2

[0039] S1. Prepare raw materials, using near-spherical Ti6Al4V powder produced by gas atomization, with a powder particle size of 15 - 53 μm and a purity of 99.4%;

[0040] S2. Vacuum-dry the prepared Ti6Al4V powder at 80 °C for 4 hours and spread it on the substrate;

[0041] S3. According to the provided drawings, complete the three-dimensional modeling of the product to be produced in advance, import the model into the printing device, and complete the identification and slicing work;

[0042] S4. Set the printing parameters. The optional powder spreading layer thickness is 80 μm, the binder saturation is 70%, the roller laying speed is 50 mm / s, and the roller rotation speed is 75 rpm; the powder bed temperature is 20 °C, and the equipment sprays the binder onto the powder to start printing.

[0043] S5. After printing is completed, thermally cure the product until the binder is dry. The curing temperature is 150 °C and the time is 3 h.

[0044] S6. Debind and sinter the cured product. The sintering atmosphere is vacuum and the vacuum degree is 10 -3 Pa; the debinding and sintering are divided into seven temperature stages in total. The heating temperatures are 300, 400, 450, 550, 800, 1100, and 1300 respectively, and the heating-up times are 60 min, 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; the heat preservation times are 90 min, 180 min, 60 min, 180 min, 60 min, 0 min, and 120 min respectively.

[0045] S7. Complete sintering and take out the product.

[0046] In the above step S4, the binder is a water-based binder, and its mass ratio is 70% polyethylene glycol (PEG), 24% polymethyl methacrylate (PMMA), 2% polyvinylpyrrolidone (PVP), and 4% stearic acid (SA).

[0047] Example 3

[0048] S1. Prepare the raw materials. Use near-spherical Ti6Al4V powder produced by gas atomization. The powder particle size is 15 - 53 μm and the purity is 99.4%.

[0049] S2. Vacuum dry the prepared Ti6Al4V powder at 80 °C for 4 hours and spread it on the substrate.

[0050] S3. According to the provided drawings, complete the three-dimensional modeling of the product to be produced in advance, import the model into the printing equipment, and complete the identification and slicing work.

[0051] S4. Set the printing parameters. The optional powder spreading layer thickness is 120 μm, the binder saturation is 80%, the roller laying speed is 50 mm / s, and the roller rotation speed is 75 rpm; the powder bed temperature is 30 °C, and the equipment sprays the binder onto the powder to start printing.

[0052] S5. After printing is completed, thermally cure the product until the binder is dry. The curing temperature is 200 and the time is 2 h.

[0053] S6. Debind and sinter the cured product. The sintering atmosphere is vacuum and the vacuum degree is 10-3 Pa; The debinding and sintering are divided into seven temperature stages, with the heating temperatures being 300, 400, 450, 550, 800, 1100, and 1300 respectively, and the heating-up times being 60 min, 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; the holding times are 180 min, 180 min, 60 min, 180 min, 60 min, 0 min, and 120 min respectively.

[0054] S7. Complete sintering and take out the product.

[0055] During debinding and sintering, thermogravimetric curve analysis is performed on the distribution of the binder and the printed green body, and the results are as Figure 1 、 Figure 2 shown. These results all indicate that when the heating temperature reaches 300 °C, the binder begins to decompose, and by 430 °C, the decomposition is basically completed. The binder is relatively thoroughly debound during this debinding and sintering process, and the residual binder is less than one-thousandth of the green body, with excellent debinding effect.

[0056] The metallographic structure of the sample is as Figure 3 shown. The titanium alloy powder particles have been interconnected and densified. The metallographic structure of the sample is mainly α-phase, and the β-phase is distributed in a network structure. In the above step S4, the binder is a water-based binder, and its mass ratio is 78% polyethylene glycol (PEG), 27% polymethyl methacrylate (PMMA), 3% polyvinylpyrrolidone (PVP), and 2% stearic acid (SA).

[0057] Example 4

[0058] S1. Prepare raw materials, use near-spherical Ti6Al4V powder produced by gas atomization, with a powder particle size of 15 - 53 μm and a purity of 99.4%;

[0059] S2. Vacuum-dry the prepared Ti6Al4V powder at 80 °C for 4 hours and spread it on the substrate;

[0060] S3. According to the provided drawings, complete the 3D modeling of the product in advance, import the model into the printing device, and complete the recognition and slicing work;

[0061] S4. Set the printing parameters. The optional powder layer thickness is 150 μm, the binder saturation is 90%, the roller laying speed is 50 mm / s, and the roller rotation speed is 75 rpm; the powder bed temperature is 15 °C, and the device sprays the binder to start printing;

[0062] S5. After printing, thermally cure the product until the binder is dry, with a curing temperature of 200 and a time of 2 h;

[0063] S6. Degrease and sinter the cured product. The sintering atmosphere is vacuum, and the vacuum degree is 10 -3 Pa; The degreasing and sintering are divided into seven temperature stages. The heating temperatures are 300, 400, 450, 550, 800, 1100, and 1300 respectively, and the heating-up times are 60 min, 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; The holding times are 300 min, 300 min, 60 min, 300 min, 60 min, 0 min, and 120 min respectively.

[0064] S7. Complete sintering and take out the product.

[0065] In the above step S4, the binder is a water-based binder, and its mass ratio is 70% polyethylene glycol (PEG), 24% polymethyl methacrylate (PMMA), 2% polyvinylpyrrolidone (PVP), and 4% stearic acid (SA).

[0066] Comparative Example 1

[0067] S1. Prepare raw materials. Use near-spherical Ti6Al4V powder produced by gas atomization. The powder particle size is 15 - 53 μm, and the purity is 99.4%;

[0068] S2. Vacuum-dry the prepared Ti6Al4V powder at 80°C for 4 hours and spread it on the substrate;

[0069] S3. According to the provided drawings, complete the three-dimensional modeling of the product in advance, import the model into the printing device, and complete the identification and slicing work;

[0070] S4. Set the printing parameters. The optional powder layer thickness is 50 μm, the binder saturation is 70%, the roller laying speed is 50 mm / s, and the roller rotation speed is 75 rpm; The powder bed temperature is 30°C, and the device sprays the binder to start printing;

[0071] S5. After printing is completed, thermally cure the product until the binder is dry. The curing temperature is 200 and the time is 2 h;

[0072] S6. Degrease and sinter the cured product. The sintering atmosphere is vacuum, and the vacuum degree is 10 -3 Pa; The degreasing and sintering are divided into seven temperature stages. The heating temperatures are 300, 400, 450, 550, 800, 1100, and 1300 respectively, and the heating-up times are 60 min, 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; The holding times are 90 min, 90 min, 60 min, 180 min, 60 min, 0 min, and 120 min respectively.

[0073] S7. Complete sintering and take out the product.

[0074] In the above step S4, the binder is a water-based binder, and its mass ratio is 79% polyethylene glycol (PEG), 28% polymethyl methacrylate (PMMA), and 3% stearic acid (SA).

[0075] Comparative Example 2

[0076] S1. Prepare raw materials, use near-spherical Ti6Al4V powder produced by gas atomization, the powder particle size is 15 - 53 μm, and the purity is 99.4%;

[0077] S2. Vacuum dry the prepared Ti6Al4V powder at 80 °C for 4 hours and spread it on the substrate;

[0078] S3. According to the provided drawings, complete the 3D modeling of the product to be produced in advance, import the model into the printing device, and complete the identification and slicing work;

[0079] S4. Set the printing parameters. The optional powder layer thickness is 150 μm, the binder saturation is 70%, the roller laying speed is 50 mm / s, and the roller rotation speed is 75 rpm; the powder bed temperature is 15 °C, and the device sprays the binder onto the powder to start printing;

[0080] S5. After printing, thermally cure the product until the binder is dry. The curing temperature is 200 and the time is 2 h;

[0081] S6. Debind and sinter the cured product. The sintering atmosphere is vacuum, and the vacuum degree is 10 -3 Pa; The debinding and sintering are divided into seven temperature stages. The heating temperatures are 300, 400, 450, 550, 800, 1100, and 1300 respectively, and the heating times are 60 min, 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; the holding times are 300 min, 300 min, 60 min, 180 min, 60 min, 0 min, and 120 min respectively.

[0082] S7. Complete sintering and take out the product.

[0083] In the above step S4, the binder is a water-based binder, and its mass ratio is 78% polyethylene glycol (PEG), 27% polymethyl methacrylate (PMMA), 3% polyvinylpyrrolidone (PVP), and 2% stearic acid (SA).

[0084] Table 1 Printing and sintering parameters and product performance tests

[0085] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Layer thickness (μm) 50 80 120 150 50 150 Binder saturation (%) 60 70 80 90 70 70 Powder bed temperature (°C) 15 20 30 15 30 15 Sintering time at 300°C (min) 90 90 180 300 90 300 Sintering time at 400°C (min) 90 180 180 300 90 300 Sintering time at 550°C (min) 180 180 180 300 180 180 Shrinkage rate (%) 17.3 18.7 16.5 18.6 19.0 15.2 Relative density (%) 95.6 95.8 96.3 94.9 88.9 97.6 Yield strength (Mpa) 380 370 385 373 360 400 Tensile strength (Mpa) 726 681 766 639 532 780

[0086] In the above embodiments, the water-based binder in this embodiment is adopted. Due to multi-stage heating sintering, the debinding during the sintering process is relatively successful, obtaining a high density as well as very good yield strength and tensile strength. In all the embodiments and Comparative Example 2, there is a small amount of PVP in the binder, which inhibits the void nucleation phenomenon of PEG and PMMA and improves the overall quality.

[0087] In Comparative Example 1, PVP was not added to the binder, and there was a void nucleation phenomenon in PEG and PMMA, resulting in uneven distribution of the binder. Larger voids appeared in the titanium alloy sample, the density of the sample was poor, and both the yield strength and tensile strength were lower than those in Comparative Example 2. Moreover, due to the relatively short overall sintering time in Comparative Example 1, the debinding was almost unsuccessful; while the sintering time in Comparative Example 2 was controlled more reasonably and the debinding effect was good.

[0088] The present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims.

Claims

1. A method for printing titanium alloy with a binder, characterized in that, comprising: Step 1, prepare raw materials, use near-spherical Ti6Al4V powder produced by gas atomization, the powder particle size is 15 - 53μm and has a bimodal distribution, the powder purity is 99.9%, and make a three-dimensional model; Step 2, vacuum dry the prepared Ti6Al4V powder at 80°C for 4 hours, and spread it on the substrate after drying; Step 3, according to the completed three-dimensional model, import the three-dimensional model data into the printing device to complete model recognition and slicing work; Step 4, set the printing parameters, the printing device nozzle sprays the binder onto the Ti6Al4V powder bed to wet the powder, and start printing. Among them, the binder is a water-based binder, including 65 - 78 parts of polyethylene glycol, 20 - 27 parts of polymethyl methacrylate, 2 - 10 parts of polyvinylpyrrolidone and 2 - 5 parts of stearic acid. The above components are by mass. The optional powder layer thickness is 50μm / 80μm / 120μm / 150μm, the binder saturation is 60% - 90%, the powder spreading roller speed is 50mm / s, the roller rotation speed is 75rpm, and the powder bed temperature is 15 - 30°C; Step 5, after printing, thermally cure the product in the printing device until the binder dries; Step 6, degreasing and sintering the solidified product, the sintering atmosphere is vacuum, and the vacuum degree is 10 -3 Pa. The degreasing and sintering are divided into seven temperature stages, and the heating temperatures are 300°C, 400°C, 450°C, 550°C, 800°C, 1100°C, and 1300°C respectively. The heating-up times are 60 min, 20 - 50 min, 50 min, 50 min, 30 min, 150 min, and 100 min respectively; the holding times are 90 - 300 min, 90 - 300 min, 60 min, 180 - 300 min, 60 min, 0 min, and 120 min respectively; Step 7, complete sintering and take out the product.

2. The method for printing titanium alloy with a binder according to claim 1, characterized in that, in Step 5, the thermal curing temperature is 100 - 220°C and the time is 2 - 3h.

Images