Selective laser melting forming method for ZrTi alloy powder

Abstract

The invention provides a selective laser melting forming method for ZrTi alloy powder. The ZrTi alloy powder is prepared through a gas atomization method, and the ZrTi alloy powder comprises, by mass, one of 40 wt.% of Zr and 60 wt.% of Ti, 50 wt.% of Zr and 50 wt.% of Ti, and 60 wt.% of Zr and 40 wt.% of Ti. The ZrTi binary alloy is prepared and proportioned, multi-element alloy integration is achieved, the hardness and tensile strength are improved, and meanwhile the corrosion resistance of an original titanium-based alloy is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal additive manufacturing, and in particular relates to a laser selective melting molding method for titanium-based alloy composite powder. Background Art

[0002] Additive manufacturing (AM) is a technique that forms three-dimensional objects by selectively melting and resolidifying metal powders layer by layer. This method has gained tremendous popularity in recent years, especially in the biomedical field, as it enables the rapid and economical production of patient-specific orthopedic devices without the complexity and tooling costs of traditional multi-step manufacturing (e.g., casting, milling, etc.). Therefore, additive manufacturing (AM) is expected to become a key technology in the context of the rapid growth of the orthopedic device market, such as knee prostheses, porous orthopedic screws, screw-port dental implants, and acetabular cups for total hip replacement.

[0003] With the development of science and technology, especially in the fields of biomedicine and other fields, higher requirements are placed on the performance of alloys. On the basis of titanium alloys, it is imperative to explore new alloy systems with better performance. Zirconium (Zr) alloy, as an important nuclear material, has the potential to resist space radiation and atomic oxygen corrosion. At the same time, Zr also has excellent corrosion resistance and low expansion coefficient. In addition, Zr and Ti belong to the same element subgroup (IVB) and can be dissolved in titanium alloys indefinitely. Therefore, ZrTi binary alloy is one of the ideal alloys to improve the performance of titanium-based alloys. Summary of the invention

[0004] The purpose of the present invention is to provide a laser selective melting forming method for ZrTi binary alloy powder.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A laser selective melting molding method for ZrTi binary alloy powder, wherein the components of the ZrTi binary alloy powder are one of 40wt.% Zr-60wt.% Ti, 50wt.% Zr-50wt.% Ti, and 60wt.% Zr-40wt.% Ti in mass percentage.

[0006] The molding method comprises the following steps: (1) Preparing ZrTi binary alloy powders with corresponding mass fraction ratios by gas atomization method; (2) placing the ZrTi alloy powder obtained in step (1) into a drying oven for drying; (3) The ZrTi alloy powder dried in step (2) is placed in a metal additive manufacturing device for molding to obtain a sample.

[0007] Furthermore, the ZrTi binary alloy powder is a solid sphere with a particle size of 15 to 53 μm; Furthermore, the gas atomization powdering process of the alloy in step (1) includes: melting the small metal particles into liquid metal by medium frequency induction heating in a vacuum, and then filling it with argon gas to protect it. The liquid metal is allowed to enter the atomization area by regulating the gas pressure. Finally, the high-pressure gas is turned on for atomization, and a separation device is used to allow the atomized powder to fall into a powder collecting tank and wait for cooling.

[0008] Furthermore, in step (1), the atomizing gas used in the process of preparing the alloy powder by gas atomization is high-purity argon, the maximum medium-frequency induction heating power is 350 kW, the infrared temperature measurement molten pool temperature is 1350 °C, the pressure difference between the melting chamber and the atomizing chamber is less than 0.3 MPa, and the pressure of the high-pressure atomizing gas is 4 MPa.

[0009] Furthermore, in step (2), the vacuum drying oven is evacuated, the drying temperature of the vacuum drying oven is 60° C. to 80° C., and the drying time is 3 to 6 hours.

[0010] Furthermore, in step (3), the process parameters of the laser selective melting molding are as follows: laser power is 150-350 W, scanning speed is 550-1350 mm / s, scanning spacing is 0.10-0.12 mm, powder thickness is 0.02-0.03 mm, the substrate is a titanium alloy substrate, the substrate preheating temperature is 180-200° C., the scanning angle of adjacent powder layers is rotated 67°, and the molding chamber uses argon gas with an oxygen content of less than 100 ppm.

[0011] Compared with the prior art, the present invention has the following effects: the present invention is reasonably designed and uses gas atomization to prepare ZrTi binary alloy powder. By using multi-alloy fusion on the basis of selective laser melting to form titanium-based alloy powder, the hardness, tensile strength, corrosion resistance and other properties of the formed alloy sample are improved through the characteristics of each alloy in the multi-alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a scanning electron microscope image of the shape of the powder used in Example 1 of the present invention; Figure 2 This is a microstructure diagram of corrosion of a sample formed by selective laser melting in Example 1 of the present invention; Figure 3 This is a microstructure diagram of corrosion of a sample formed by selective laser melting in Example 2 of the present invention; Figure 4 This is a microstructure diagram of the corrosion of the sample formed by selective laser melting in Example 3 of the present invention; Figure 5 This is the microstructure diagram of the corrosion of the sample formed by selected laser melting in comparative example 1 of the present invention. DETAILED DESCRIPTION

[0013] In order to make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0014] Example 1 S1. Weigh out two metals in the ratio of 40wt.% Zr and 60wt.% Ti for use; S2. Perform gas atomization powder making treatment on the alloy: melt the small metal particles into liquid metal by medium frequency induction heating in a vacuum, and then fill it with argon gas to protect it. Allow the molten metal to enter the atomization area by adjusting the air pressure. Finally, turn on the high-pressure gas for atomization, and use a separation device to let the atomized powder fall into the powder collecting tank and wait for cooling. Among them, the maximum power of medium frequency induction heating is 350 kW, the temperature of the infrared temperature measurement molten pool is 1350 ℃, the pressure difference between the smelting chamber and the atomization chamber is less than 0.3 MPa, and the pressure of the high-pressure atomizing gas is 4 MPa; then carry out drying treatment, the drying box is evacuated, the drying temperature is 70 ℃, and the drying time is 6 hours.

[0015] S3, laser selective melting molding of the dried composite powder of S2: molding process parameters: laser power is 300W, scanning speed is 900mm / s, scanning spacing is 0.12mm, powder thickness is 0.03mm, substrate is titanium alloy substrate, substrate preheating temperature is 200℃, adjacent powder layer scanning angle is rotated 67°, molding chamber uses argon gas, oxygen content is less than 100ppm. Mechanical properties of the molded sample: tensile strength is 1311.2Mpa, elongation is 8.6%, hardness is 441HV, corrosion potential is -0.403V, ​​corrosion current density is 3.540×10 -7 A / cm 2 .

[0016] Example 2 S1. Weigh out two metals in a ratio of 50wt.% Zr and 50wt.% Ti for later use; S2. Perform gas atomization powder making treatment on the alloy: melt the small metal particles into liquid metal by medium frequency induction heating in a vacuum, and then fill it with argon gas to protect it. Allow the molten metal to enter the atomization area by adjusting the air pressure. Finally, turn on the high-pressure gas for atomization, and use a separation device to let the atomized powder fall into the powder collecting tank and wait for cooling. Among them, the maximum power of medium frequency induction heating is 350 kW, the temperature of the infrared temperature measurement molten pool is 1350 ℃, the pressure difference between the smelting chamber and the atomization chamber is less than 0.3 MPa, and the pressure of the high-pressure atomizing gas is 4 MPa; then carry out drying treatment, the drying box is evacuated, the drying temperature is 70 ℃, and the drying time is 6 hours.

[0017] S3, laser selective melting molding of the dried composite powder of S2: molding process parameters: laser power is 300W, scanning speed is 900mm / s, scanning spacing is 0.12mm, powder thickness is 0.03mm, substrate is titanium alloy substrate, substrate preheating temperature is 200℃, adjacent powder layer scanning angle is rotated 67°, molding chamber uses argon gas, oxygen content is less than 100ppm. Mechanical properties of the molded sample: tensile strength is 1495.95Mpa, elongation is 10.5%, hardness is 468HV, corrosion potential is -0.336V, corrosion current density is 2.929×10 -7 A / cm 2 .

[0018] Example 3 S1. Weigh out two metals in a ratio of 60wt.% Zr and 40wt.% Ti for later use; S2. Perform gas atomization powder making treatment on the alloy: melt the small metal particles into liquid metal by medium frequency induction heating in a vacuum, and then fill it with argon gas to protect it. Allow the molten metal to enter the atomization area by adjusting the air pressure. Finally, turn on the high-pressure gas for atomization, and use a separation device to let the atomized powder fall into the powder collecting tank and wait for cooling. Among them, the maximum power of medium frequency induction heating is 350 kW, the temperature of the infrared temperature measurement molten pool is 1350 ℃, the pressure difference between the smelting chamber and the atomization chamber is less than 0.3 MPa, and the pressure of the high-pressure atomizing gas is 4 MPa; then carry out drying treatment, the drying box is evacuated, the drying temperature is 70 ℃, and the drying time is 6 hours.

[0019] S3, laser selective melting molding of the dried composite powder of S2: molding process parameters: laser power is 300W, scanning speed is 900mm / s, scanning spacing is 0.12mm, powder thickness is 0.03mm, substrate is titanium alloy substrate, substrate preheating temperature is 200℃, adjacent powder layer scanning angle is rotated 67°, molding chamber uses argon gas, oxygen content is less than 100ppm. Mechanical properties of the molded sample: tensile strength is 1523.11Mpa, elongation is 12.6%, hardness is 493HV, corrosion potential is -0.225V, corrosion current density is 1.384×10 -7 A / cm 2 .

[0020] Comparative Example 1 S1. Weigh a certain amount of pure titanium metal powder for later use; S2. Dry the titanium metal powder weighed in S1, evacuate the drying box, set the drying temperature to 70°C, and dry for 6 hours. Then perform laser selective melting molding: molding process parameters: laser power is 300W, scanning speed is 900mm / s, scanning spacing is 0.12mm, powder thickness is 0.03mm, substrate is aluminum alloy substrate, substrate preheating temperature is 200°C, adjacent powder layer scanning angle is rotated 67°, and the molding chamber uses argon gas with an oxygen content of less than 100ppm. Mechanical properties of the molded sample: tensile strength is 1078.95Mpa, elongation is 7.9%, hardness is 357HV, corrosion potential is -0.466V, corrosion current density is 6.241×10 -7 A / cm 2 .

[0021] The electron microscope image of the ZrTi binary alloy powder in Example 1 is as follows: Figure 1 The density of the sample prepared by selective laser melting in Example 1 is 98.71%. The image of the surface corrosion of the sample was obtained by electron microscopy, as shown in FIG. Figure 2 As shown in the figure, it can be seen that a basket-net structure is formed inside the surface of the sample. Figure 3 From the sample prepared by laser selective melting in Example 2, it can be found that the basket mesh structure in Example 1 is more compact, which is also the reason for the improvement of hardness and tensile strength. Figure 4 As shown in the figure, with the increase of Zr content, the fine needle-like structure becomes more and more obvious, and ends at the original β grain boundary, which is consistent with the structural characteristics of the martensite α΄ phase. It can be determined that with the addition of Zr, a transformation from β phase to α΄ phase occurs in the microstructure. This transformation improves the hardness and strength of the metal.

[0022] Figure 4 As shown in the figure, due to the absence of Zr element, the phases inside the sample are mostly primary (α+β) phases and are not dense.

[0023] In NaCl solution, a stable passivation film is formed on the surface of ZrTi binary alloy, which acts as a protective layer and inhibits corrosion of the alloy in NaCl solution.

[0024] The samples of Example 1, Example 2, Example 3 and Comparative Example 1 were subjected to tensile test, hardness test and corrosion test as shown in Table 1.

[0025] Table 1 Comprehensive performance table of samples The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A laser selective melting method for ZrTi alloy powder, characterized in that: The composition of the ZrTi alloy powder is one of 40wt.% Zr-60wt.% Ti, 50wt.% Zr-50wt.% Ti, and 60wt.% Zr-40wt.% Ti in mass percentage.

2. The method according to claim 1, characterized in that: The ZrTi alloy powder is solid spherical and has a particle size of 15 to 53 μm.

3. The method according to claim 1 or 2, characterized in that: The following steps are involved: (1) Preparing ZrTi alloy powders with corresponding mass fraction ratios by gas atomization method; (2) placing the ZrTi alloy powder obtained in step (1) into a drying oven for drying; (3) The ZrTi alloy powder dried in step (2) is placed in a metal additive manufacturing device for molding to obtain a sample.

4. The method according to claim 3, characterized in that: The operation of gas atomization powdering of the alloy in step (1) includes: melting small raw metal particles into liquid metal by medium frequency induction heating in a vacuum, and then filling it with argon gas to protect it; allowing the molten metal to enter the atomization area by adjusting the gas pressure; finally, turning on the high-pressure argon gas for atomization, and using a separation device to let the atomized powder fall into a powder collecting tank and wait for cooling; wherein, the maximum power of the medium frequency induction heating is 350 kW, the temperature of the molten pool measured by infrared temperature measurement is 1350 ° C, the pressure difference between the smelting chamber and the atomization chamber is less than 0.3 MPa, and the pressure of the high-pressure atomizing gas is 4 MPa.

5. The method according to claim 3, characterized in that: In step (2), the drying box is evacuated.

6. The method according to claim 3, characterized in that: In step (2), the drying temperature is 60° C. to 80° C., and the drying time is 3 to 6 hours.

7. The method according to claim 3, characterized in that: The laser selective melting forming process parameters in step (3) are as follows: laser power is 150-350 W, scanning speed is 550-1350 mm / s, scanning spacing is 0.10-0.12 mm, powder thickness is 0.02-0.03 mm, the substrate is a titanium alloy substrate, the substrate preheating temperature is 180-200 ° C, the scanning angle of adjacent powder layers is rotated 67 °, and the forming chamber uses argon gas with an oxygen content of less than 100 ppm.

8. The method according to claim 3, characterized in that: The element content of the sample in step (3) is 40wt.%Zr-60wt.%Ti.

9. The method according to claim 3, characterized in that: The element content of the sample in step (3) is 50wt.%Zr-50wt.%Ti.

10. The method according to claim 3, characterized in that: The element content of the sample in step (3) is 60wt.%Zr-40wt.%Ti.

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