A plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces and its preparation and application

Abstract

The present invention relates to a plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces and its preparation and application, belonging to the technical field of metal surface treatment. A plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces, characterized in that: the plasma polishing liquid used is an aqueous solution, composed of the following components: 500-750ml / L of methanesulfonic acid, 1-3g / L of NH2SO4, 1-7ml / L of sulfosalicylic acid, and 5-10g / L of sodium chloride. The plasma polishing liquid of the present invention is green and environmentally friendly, the raw materials are easy to obtain, and there is no pollution to the processing environment; the voltage required for plasma polishing is lower, which effectively reduces the energy consumption of production, adapts to the development direction of green manufacturing, and is therefore conducive to promotion. The plasma polishing liquid is used to polish the laser additive manufacturing special-shaped titanium alloy workpiece, the weight loss rate of the sample is small, the surface roughness of the titanium alloy can be effectively reduced, the overall glossiness can be improved, and a high-quality titanium alloy workpiece surface can be obtained.

Description

Technical Field

[0001] The invention relates to a plasma polishing liquid for laser additive manufacturing of a titanium alloy workpiece and a preparation method and application thereof, belonging to the technical field of metal surface treatment. Background Art

[0002] Laser additive manufacturing technology has the advantages of fast molding speed, high material utilization rate, and the ability to form complex parts in one piece. It is currently widely used to manufacture metal workpieces that are difficult to manufacture using traditional methods or that are expensive to manufacture using traditional manufacturing methods. The metals used in additive manufacturing technology mainly include titanium, nickel, aluminum, etc. Among them, titanium alloys have attracted widespread attention due to their advantages such as light weight, high strength, good toughness, corrosion resistance, and high heat resistance. Additive manufacturing of titanium alloys has also been increasingly widely used in aerospace, navigation, petrochemicals, human implants, biomedical engineering and other fields. However, in these fields, the requirements for the surface quality of titanium alloy parts are also constantly increasing, and it is particularly important to improve the surface treatment technology of titanium alloys for additive manufacturing.

[0003] However, due to the poor cutting performance of titanium alloy, an oxide film is easily formed on the surface of the substrate. Therefore, mechanical polishing, chemical polishing and other methods are generally used to perform surface finishing treatment.

[0004] Mechanical polishing is a method of removing a very thin layer of metal from the grinding surface of the sample by grinding and rolling with very fine polishing powder. The mechanical polishing method is simple but labor-intensive and cannot achieve uniform leveling of all parts for special-shaped titanium alloy workpieces with complex structures or with curved surfaces, corners, grids and other polishing dead corners, so its scope of use is greatly limited. Chemical polishing is a method of eliminating wear marks, erosion and leveling samples by selectively dissolving the uneven areas on the surface of the sample through the chemical etching of chemical reagents. The chemical polishing equipment is simple and can handle thin tubes, parts with deep holes and complex shapes. It has high production efficiency and is an effective way to improve the surface quality of titanium alloys and improve processing efficiency. However, the polishing liquid of chemical polishing is mostly a highly corrosive acidic solution, which will react violently during the operation, which is dangerous to the operator and the toxic substances or irritating gases produced are easily volatilized into the air, which will harm the environment.

[0005] Based on this, plasma polishing has received more and more attention. The main technical point of plasma polishing is that when the solute in the polishing liquid is under high temperature and high pressure, the electrons will escape from the nucleus and the nucleus will form a positively charged ion. When these ions reach a certain number, they can become a plasma state. The plasma state has great energy. When these plasmas rub against the object to be polished, the object will instantly achieve a bright surface effect. No scratches are produced during plasma polishing, and the polishing effect is good. The surface of the processed workpiece is bright and beautiful, with bright colors and dazzling luster. It can also prevent the rust of the workpiece, maintain and improve the gloss of the workpiece surface, and play a role in cleaning the workpiece and the abrasive. At the same time, plasma polishing is simple to operate and has a high degree of automation. It is a polishing method that can effectively improve the surface quality of titanium alloys.

[0006] Several plasma polishing liquids disclosed in the prior art mainly use low-concentration inorganic salt aqueous solutions such as sodium sulfate, ammonium sulfate, sodium citrate, and hydrofluoric acid salts, and the polishing process is green and environmentally friendly. However, the active components in this type of plasma polishing liquid will be continuously consumed during the polishing process, and gas and some insoluble precipitation will be generated at the same time, and the newly configured polishing liquid needs to be replaced regularly; and the voltage applied during plasma polishing is usually above 300V, which greatly increases the production cost. Therefore, it is urgent to develop a plasma polishing liquid that has good polishing effect, easy-to-obtain raw materials, low energy consumption, and renewable solution on the basis of green environmental protection, which can meet the processing needs. Summary of the invention

[0007] The purpose of the present invention is to address the shortcomings of existing laser additive manufacturing titanium alloy plasma polishing liquid and polishing process, and to provide a plasma polishing liquid and polishing method suitable for laser additive manufacturing of special-shaped titanium alloy workpieces with curved surfaces, corners, grids and other processing dead corners, which has low configuration cost, strong stability, green energy saving and environmental protection, regenerative solution, and can effectively protect the titanium alloy matrix, and has an ideal surface flatness and smoothness.

[0008] A plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces, wherein the plasma polishing liquid used is an aqueous solution and is composed of the following components:

[0009]

[0010] Preferably, a plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces, the plasma polishing liquid used is composed of the following components:

[0011]

[0012] Preferably, a plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces, the plasma polishing liquid used is composed of the following components:

[0013]

[0014] Another object of the present invention is to provide a method for preparing the plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces.

[0015] A method for preparing a plasma polishing liquid for laser additive manufacturing of a titanium alloy workpiece comprises the following steps: placing methanesulfonic acid, NH2SO4, sulfosalicylic acid and sodium chloride in deionized water and mixing them evenly according to a certain proportion to obtain a polishing liquid.

[0016] Another object of the present invention is to provide a method for plasma polishing of a titanium alloy workpiece using the plasma polishing liquid for laser additive manufacturing.

[0017] A plasma polishing method for a laser additively manufactured titanium alloy workpiece comprises the following steps: ultrasonically cleaning and degreasing the laser additively manufactured titanium alloy workpiece in acetone, and then cleaning and drying the workpiece with deionized water; firstly, the polishing liquid is placed in an electrolytic cell, and the electrolytic cell is heated to make the solution temperature reach 95°C; then, the titanium alloy workpiece is used as a positive electrode and graphite is used as a negative electrode, and is immersed in the polishing liquid together for polishing, cleaning, and drying.

[0018] Preferably, the polishing temperature is 95°C.

[0019] Preferably, the polishing time is 120 s.

[0020] Preferably, the polishing voltage is 270V to 300V, and more preferably, the polishing voltage is 280V.

[0021] Preferably, the method includes a polishing liquid regeneration step, specifically: adding 25-50 g / L of NaOH to the polishing liquid containing titanium ions, filtering to remove titanium precipitates, and adding 70-200 ml / L of 38% hydrochloric acid.

[0022] Preferably, the polishing liquid is a prepared new polishing liquid or a regenerated polishing liquid.

[0023] The beneficial effects of the present invention are:

[0024] The plasma polishing liquid of the present invention is green and environmentally friendly, the raw materials are easily available, and there is no pollution to the processing environment; the voltage required for plasma polishing is lower, which effectively reduces the energy consumption of production, adapts to the development direction of green manufacturing, and is therefore conducive to promotion. The plasma polishing process for the surface of additively manufactured titanium alloys described in the present invention is simple to implement and has a wide range of applications. It is not only suitable for additively manufactured titanium alloy products with regular shapes, but also for complex titanium alloy products with pipes, inner holes or internal flow channels of different diameters. The plasma polishing liquid for additively manufactured titanium alloys described in the present invention can be recycled multiple times on the premise of replenishing the mother liquor, and is highly efficient. When this plasma polishing liquid is used to polish laser additively manufactured special-shaped titanium alloy workpieces, the weight loss rate of the sample is small, the surface roughness of the titanium alloy can be effectively reduced, the overall glossiness can be improved, and a high-quality titanium alloy workpiece surface can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 SEM image of the surface morphology of the laser additively manufactured titanium alloy workpiece after simple pretreatment.

[0026] Figure 2 This is a SEM image of the surface morphology of the laser additively manufactured titanium alloy workpiece in Example 5 after being treated with the plasma polishing liquid and polishing method described in the present invention.

[0027] Figure 3 This is the relationship between the polishing time and the surface roughness and thinning rate of the titanium alloy workpiece in Example 3.

[0028] Figure 4 This is the relationship between the polishing voltage and the surface roughness and thinning rate of the titanium alloy workpiece in Example 4. DETAILED DESCRIPTION

[0029] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0030] The test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0031] The components and their content percentages in a plasma polishing liquid for laser additive manufacturing of special-shaped titanium alloy workpieces are:

[0032]

[0033] Preferably, the components and contents of the plasma polishing liquid suitable for laser additive manufacturing of special-shaped titanium alloy workpieces described in the present invention are:

[0034]

[0035] Further preferably, the components and contents of the plasma polishing liquid suitable for laser additive manufacturing of special-shaped titanium alloy workpieces described in the present invention are:

[0036]

[0037] A plasma polishing liquid and a polishing method for laser additive manufacturing of special-shaped titanium alloy workpieces, further comprising the following process steps:

[0038] (1) Pretreatment: The laser additively manufactured titanium alloy workpiece was ultrasonically cleaned and degreased in an acetone solution, and then the workpiece was cleaned and dried with deionized water.

[0039] (2) Prepare plasma polishing liquid: The polishing liquid used for plasma polishing is the polishing liquid described in claim 1: 610-640 ml / L methylsulfonic acid (analytical grade), 1.7-2.3 g / L NH2SO4 (analytical grade), 3.1-4.9 ml / L sulfosalicylic acid (analytical grade), and 6.6-8.4 g / L sodium chloride are added in proportion and mixed evenly to prepare 1 L of solution.

[0040] (3) Plasma polishing: First, put the evenly mixed polishing liquid into the electrolytic cell and heat the electrolytic cell to make the solution temperature reach 95°C. Then, immerse the titanium alloy workpiece as the positive electrode and graphite as the negative electrode in the solution, polish at 95°C for 120s, and control the voltage to 270-300V.

[0041] (4) Post-processing: Take out the treated titanium alloy sample and clean and dry it.

[0042] Example 1

[0043] Plasma polishing was performed on an additively manufactured TC4 titanium alloy workpiece with a length and width of 8 mm, 20 mm, and a height of 3 mm.

[0044] (1) Pretreatment: The laser additively manufactured titanium alloy workpiece was ultrasonically cleaned and degreased in an acetone solution, and then the parts were cleaned and dried with deionized water.

[0045] (2) Preparation of plasma polishing liquid: According to the polishing liquid provided by the present invention, preferably, 610 ml of methanesulfonic acid (analytical grade), 1.7 g of NH2SO4 (analytical grade), 3.1 ml of sulfosalicylic acid (analytical grade), and 6.6 g of sodium chloride are added in proportion and mixed evenly to prepare a 1 L solution.

[0046] (3) Plasma polishing: First, put the mixed polishing liquid into the electrolytic cell and heat the electrolytic cell to make the solution temperature reach 95°C. Then, immerse the titanium alloy workpiece as the positive electrode and graphite as the negative electrode in the solution, and polish at 95°C for 110s, with the control voltage at 270V.

[0047] (4) Post-treatment: The special-shaped titanium alloy workpiece after plasma polishing was ultrasonically cleaned with anhydrous ethanol for 5 minutes, then taken out, blown dry, and the surface of the sample was observed.

[0048] The surface roughness of the laser additively manufactured special-shaped titanium alloy workpiece was significantly reduced and the weight loss was less before and after plasma polishing. The roughness dropped from 10.385um to 1.943um, and the weight loss rate of the sample was 5.173%.

[0049] Example 2

[0050] Plasma polishing was performed on an additively manufactured TC4 titanium alloy workpiece with a length and width of 8 mm, 20 mm, and a height of 3 mm.

[0051] (1) Pretreatment: The laser additively manufactured titanium alloy workpiece was ultrasonically cleaned and degreased in an acetone solution, and then the parts were cleaned and dried with deionized water.

[0052] (2) Preparation of plasma polishing liquid: According to the polishing liquid provided by the present invention, preferably, 620 ml of methanesulfonic acid (analytical grade), 1.9 g of NH2SO4 (analytical grade), 3.7 ml of sulfosalicylic acid (analytical grade), and 7.2 g of sodium chloride are added in proportion and mixed evenly to prepare a 1 L solution.

[0053] (3) Plasma polishing: First, put the mixed polishing liquid into the electrolytic cell and heat the electrolytic cell to make the solution temperature reach 95°C. Then, immerse the titanium alloy workpiece as the positive electrode and graphite as the negative electrode in the solution, and polish for 120s at 95°C with a control voltage of 280V.

[0054] (4) Post-treatment: The special-shaped titanium alloy workpiece after plasma polishing was ultrasonically cleaned with anhydrous ethanol for 5 minutes, then taken out, blown dry, and the surface of the sample was observed.

[0055] The surface roughness of the laser additively manufactured special-shaped titanium alloy workpiece was significantly reduced before and after plasma polishing, and the weight loss was less. The roughness dropped from 9.745um to 1.328um, and the weight loss rate of the sample was 5.253%.

[0056] Example 3

[0057] Plasma polishing was performed on an additively manufactured TC4 titanium alloy workpiece with a length and width of 8 mm, 20 mm, and a height of 3 mm.

[0058] (1) Pretreatment: The laser additively manufactured titanium alloy workpiece was ultrasonically cleaned and degreased in an acetone solution, and then the parts were cleaned and dried with deionized water.

[0059] (2) Preparation of plasma polishing liquid: According to the polishing liquid provided by the present invention, preferably, 630 ml of methanesulfonic acid (analytical grade), 2.1 g of NH2SO4 (analytical grade), 4.3 ml of sulfosalicylic acid (analytical grade), and 7.8 g of sodium chloride are added in proportion and mixed evenly to prepare a 1 L solution.

[0060] (3) Plasma polishing: First, put the evenly mixed polishing liquid into the electrolytic cell and heat the electrolytic cell to make the solution temperature reach 95°C. Then, the titanium alloy workpiece is used as the positive electrode and the graphite is used as the negative electrode and immersed in the solution together. Polishing is performed at a temperature of 95°C for 110s, 120s, 130s, and 140s, and the control voltage is 290V.

[0061] (4) Post-treatment: The special-shaped titanium alloy workpiece after plasma polishing was ultrasonically cleaned with anhydrous ethanol for 5 minutes, then taken out, blown dry, and the surface of the sample was observed.

[0062] The surface roughness and weight loss rate of laser additively manufactured special-shaped titanium alloy workpieces were measured before and after plasma polishing. The polishing time was 110s-140s, and the roughness dropped from 10.115um to 2.012um, 1.633um, 1.481um, and 1.572um, respectively, and the weight loss rate of the samples was 4.093%, 5.227%, 5.981%, and 6.327%.

[0063] Example 4

[0064] Plasma polishing was performed on an additively manufactured TC4 titanium alloy workpiece with a length and width of 8 mm, 20 mm, and a height of 3 mm.

[0065] (1) Pretreatment: The laser additively manufactured titanium alloy workpiece was ultrasonically cleaned and degreased in an acetone solution, and then the parts were cleaned and dried with deionized water.

[0066] (2) Preparation of plasma polishing liquid: According to the polishing liquid provided by the present invention, preferably, 630 ml of methanesulfonic acid (analytical grade), 2.1 g of NH2SO4 (analytical grade), 4.3 ml of sulfosalicylic acid (analytical grade), and 7.8 g of sodium chloride are added in proportion and mixed evenly to prepare a 1 L solution.

[0067] (3) Plasma polishing: First, put the mixed polishing liquid into the electrolytic cell and heat the electrolytic cell to make the solution temperature reach 95°C. Then, the titanium alloy workpiece is used as the positive electrode and the graphite is used as the negative electrode and immersed in the solution together. Polishing is carried out at a temperature of 95°C for 130s, and the control voltages are 270V, 280V, 290V, and 300V respectively.

[0068] (4) Post-treatment: The special-shaped titanium alloy workpiece after plasma polishing was ultrasonically cleaned with anhydrous ethanol for 5 minutes, then taken out, blown dry, and the surface of the sample was observed.

[0069] The surface roughness and weight loss rate of laser additively manufactured special-shaped titanium alloy workpieces before and after plasma polishing were measured to change with polishing voltage. When the polishing voltage was 270V, 280V, 290V, and 300V, the roughness dropped from 9.984um to 1.971um, 1.239um, 1.636um, and 1.929um, respectively, and the weight loss rate of the samples was 5.643%, 5.579%, 6.342%, and 7.314%.

[0070] Example 5

[0071] Plasma polishing was performed on an additively manufactured TC4 titanium alloy workpiece with a length and width of 8 mm, 20 mm, and a height of 3 mm.

[0072] (1) Pretreatment: The laser additively manufactured titanium alloy workpiece was ultrasonically cleaned and degreased in an acetone solution, and then the parts were cleaned and dried with deionized water.

[0073] (2) Regenerating the polishing liquid obtained in Example 1: According to the polishing liquid regeneration method provided by the present invention, 40 g of NaOH (analytical grade) was added to the titanium-loaded polishing liquid and stirred, the titanium precipitate was removed by suction, and 100 ml of 38% hydrochloric acid was added and stirred evenly.

[0074] (3) Plasma polishing: First, regenerate the polishing liquid and put it into the electrolytic cell, and heat the electrolytic cell to make the solution temperature reach 95°C. Then, the titanium alloy workpiece is used as the positive electrode and the graphite is used as the negative electrode and immersed in the solution together, and polished at a temperature of 95°C for 110s, with a control voltage of 270V.

[0075] (4) Post-treatment: The special-shaped titanium alloy workpiece after plasma polishing was ultrasonically cleaned with anhydrous ethanol for 5 minutes, then taken out, blown dry, and the surface of the sample was observed.

[0076] The surface roughness of the laser additively manufactured special-shaped titanium alloy workpiece was significantly reduced and the weight loss was less before and after plasma polishing. The roughness dropped from 10.125um to 1.436um, and the weight loss rate of the sample was 5.427%.

[0077] The surface roughness of the laser additively manufactured special-shaped titanium alloy workpiece treated with the plasma polishing liquid and polishing method described in the present invention was measured, and the scanning electron microscope morphology analysis was performed. It was found that the surface roughness of the special-shaped titanium alloy obtained after the plasma polishing liquid and polishing treatment described in the present invention was significantly reduced, the glossiness was improved, the sample weight loss rate was small, there was no polishing lines, and the surface was as smooth as a mirror.

Claims

1. A plasma polishing liquid for laser additive manufacturing of titanium alloy workpieces, characterized in that: The plasma polishing liquid used is an aqueous solution composed of the following components:

2. The polishing liquid according to claim 1, characterized in that: The plasma polishing liquid used is composed of the following components:

3. The polishing liquid according to claim 1, characterized in that: The plasma polishing liquid used is composed of the following components:

4. The method for preparing the polishing liquid according to claim 1, characterized in that: According to the proportion, methanesulfonic acid, NH2SO4, sulfosalicylic acid and sodium chloride are placed in deionized water and mixed evenly to obtain a polishing solution.

5. A plasma polishing method for laser additive manufacturing of titanium alloy workpieces, characterized in that: The laser additively manufactured titanium alloy workpiece is ultrasonically cleaned and degreased in acetone, and then the workpiece is cleaned and dried with deionized water; the polishing liquid described in any one of claims 1 to 3 is first placed in an electrolytic cell, the electrolytic cell is heated to make the solution temperature reach 95°C, and then the titanium alloy workpiece is used as a positive electrode and graphite is used as a negative electrode. It is immersed in the polishing liquid for polishing, cleaning, and drying.

6. The method according to claim 5, characterized in that: The polishing temperature is 95°C; the polishing time is 120s; and the polishing voltage is 270-300V.

7. The method according to claim 5, characterized in that: The method comprises a polishing liquid regeneration step, specifically, adding 25-50 g / L of NaOH to the polishing liquid containing titanium ions, filtering to remove titanium precipitates, and adding 70-200 ml / L of 38% hydrochloric acid.

8. The method according to claim 5, characterized in that: The polishing liquid is a prepared new polishing liquid or a regenerated polishing liquid.

Images