A chemical treatment method for improving the surface smoothness of laser 3D printed titanium alloy

Abstract

The present application relates to a kind of chemical treatment methods for improving the surface finish of laser 3D printing titanium alloy, belong to titanium alloy surface treatment technical field.Chemical treatment method includes: preparation multiple surface treatment solutions, including first surface treatment solution, second surface treatment solution and third surface treatment solution;Titanium alloy workpiece is placed in first surface treatment solution and is carried out first stage's immersion treatment, until the surface roughness of titanium alloy workpiece is reduced to 15~18 μm;Titanium alloy workpiece is placed in second surface treatment solution and is carried out second stage's immersion treatment, until the surface roughness of titanium alloy workpiece is reduced to 8~10 μm;Titanium alloy workpiece is placed in third surface treatment solution and is carried out third stage's immersion treatment, until the surface roughness of titanium alloy workpiece is reduced to 5 μm below;Wherein, the viscosity of first surface treatment solution, second surface treatment solution and third surface treatment solution is reduced in turn, the adsorption amount of surface active agent is increased in turn.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy surface treatment technology, and in particular to a chemical treatment method for improving the surface finish of laser 3D printed titanium alloys. Background Technology

[0002] Laser 3D printing is an advanced additive manufacturing technology characterized by high precision, speed, and efficiency, and is widely used in aerospace, automotive manufacturing, medical, and construction industries. Utilizing laser 3D printing technology for integrated structural design allows for the production of lightweight, high-strength parts and components.

[0003] Titanium alloys are widely used in aerospace, marine, and automotive fields due to their high specific strength and excellent corrosion resistance. However, the surface roughness of laser-printed titanium alloy components is generally high, typically around R30–40 μm or even higher. To reduce the surface roughness to below a few micrometers using conventional chemical milling processes, a reduction of several millimeters is generally required, which is impossible to pre-determine for the processing allowance of laser-printed parts. Furthermore, because titanium alloys are difficult to machine, grinding presents challenges such as high friction coefficient, high grinding temperature, and severe wheel adhesion. Even if high-quality surface grinding is achieved through certain methods, it remains difficult to implement when dealing with complex structures printed by laser 3D, such as blind holes. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a chemical treatment method to improve the surface finish of laser 3D printed titanium alloys, thereby solving the problem that existing methods are difficult to polish the high-roughness surface of laser 3D printed titanium alloys.

[0005] This invention provides a chemical treatment method for improving the surface finish of laser-printed titanium alloys, comprising:

[0006] Step S1: Prepare multiple surface treatment solutions, including a first surface treatment solution, a second surface treatment solution, and a third surface treatment solution; each surface treatment solution includes a passivating agent, a solvent, a viscosity modifier, a surfactant, and a solvent; the passivating agent is nitric acid, and the solvent is hydrofluoric acid;

[0007] Step S2: Immerse the titanium alloy workpiece in the first surface treatment solution for the first stage of immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to 15-18 μm.

[0008] Step S3: Immerse the titanium alloy workpiece in the second surface treatment solution for the second stage of immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to 8-10 μm.

[0009] Step S4: Immerse the titanium alloy workpiece in the third surface treatment solution for the third stage of immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to below 5 μm.

[0010] Among them, the viscosity of the first surface treatment solution, the second surface treatment solution and the third surface treatment solution decreases in sequence, and the adsorption amount of surfactant on the titanium alloy surface increases in sequence.

[0011] Furthermore, in the first surface treatment solution, the viscosity modifier includes ethylene glycol and disodium hydrogen phosphate, and the surfactant is polyethylene glycol;

[0012] In the second surface treatment solution, the viscosity modifiers include ethylene glycol and disodium hydrogen phosphate, and the surfactants include polyethylene glycol and polyoxyethylene laurate.

[0013] In the third surface treatment solution, the viscosity modifier is ethylene glycol, and the surfactants include polyethylene glycol and dodecylphenol polyoxyethylene ether.

[0014] Preferably, the second and third surface treatment solutions further include hexamethylenetetramine.

[0015] Furthermore, in the first surface treatment solution, the concentration of nitric acid is 150–200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid is 1:2–1:2.5, the concentration of ethylene glycol is 100–150 mL / L, the concentration of disodium hydrogen phosphate is 20–25 g / L, the concentration of polyethylene glycol is 1–2 g / L, and the molecular weight is ≥6000.

[0016] Furthermore, in the second surface treatment solution, the concentration of nitric acid is 150–200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid is 1:1.5–1:2, the concentration of ethylene glycol is 80–100 mL / L, the concentration of disodium hydrogen phosphate is 15–20 g / L, the concentration of polyethylene glycol is 0.5–1 g / L, and the molecular weight is 1000 ≤ molecular weight ≤ 2000, the concentration of polyoxyethylene laurate is 0.2–0.4 g / L, and the concentration of hexamethylenetetramine is 0.1–0.3 g / L.

[0017] Furthermore, in the third surface treatment solution, the concentration of nitric acid is 150–200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid is 1:1–1:1.5, the concentration of disodium hydrogen phosphate is 10–15 g / L, the concentration of ethylene glycol is 20–50 mL / L, the concentration of polyethylene glycol is 0.2–0.5 g / L and 200 ≤ molecular weight ≤ 400, the concentration of dodecylphenol polyoxyethylene ether is 0.1–0.2 g / L, and the concentration of hexamethylenetetramine is 0.1–0.3 g / L.

[0018] Furthermore, in steps S3 and S4, ultrasonic stirring is performed simultaneously with the soaking treatment, and the ultrasonic power is 800-2000W.

[0019] Furthermore, in step S2, when the surface roughness of the titanium alloy workpiece reaches the range of 15 to 18 μm, the thinning amount of the titanium alloy workpiece is controlled to be within 150 μm.

[0020] Furthermore, in step S3, when the surface roughness of the titanium alloy workpiece reaches the range of 8 to 10 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 200 μm.

[0021] Furthermore, in step S4, when the surface roughness of the titanium alloy workpiece reaches below 5 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 300 μm.

[0022] Furthermore, in the three-stage immersion treatment, if the total thinning amount of the titanium alloy workpiece reaches the maximum thinning amount requirement of the current stage, but the surface roughness still does not meet the target requirement of the current stage, then the ultrasonic power of the ultrasonic stirring is adjusted, and / or the concentration of at least one of the passivating agent, viscosity modifier and surfactant in the surface treatment solution is adjusted.

[0023] Furthermore, the concentration of at least one of the passivating agent, viscosity modifier, and surfactant is increased by 15-20%.

[0024] Furthermore, in step S2, if the surface roughness is still not reduced to below 18 μm when the thinning amount of the titanium alloy workpiece reaches 150 μm, the concentration of at least one of nitric acid, ethylene glycol and polyethylene glycol in the first surface treatment solution is increased by 15-20%, and the immersion treatment is repeated.

[0025] Furthermore, in step S3, when the surface roughness of the titanium alloy workpiece reaches the range of 8 to 10 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 200 μm.

[0026] If the surface roughness of the titanium alloy workpiece is still not reduced to below 10μm when the thinning amount reaches 200μm, reduce the ultrasonic power and continue the soaking process.

[0027] If the surface roughness is not reduced to below 10 μm when the ultrasonic power is reduced to 0, the concentration of at least one of nitric acid, ethylene glycol, polyethylene glycol and polyoxyethylene laurate in the second surface treatment solution is increased by 15-20%, and the soaking treatment is repeated.

[0028] Furthermore, in step S4, when the surface roughness of the titanium alloy workpiece reaches below 5 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 300 μm.

[0029] If the surface roughness of the titanium alloy workpiece is still not reduced to below 5μm when the thinning amount reaches 300μm, reduce the ultrasonic power and continue the soaking process.

[0030] If the surface roughness is still not reduced to below 5 μm when the ultrasonic power is reduced to 0, the concentration of at least one of nitric acid, ethylene glycol, polyethylene glycol and dodecylphenol polyoxyethylene ether in the third surface treatment solution is increased by 15-20%, and the soaking treatment is repeated.

[0031] Compared with the prior art, the chemical treatment method of the present invention can achieve at least one of the following beneficial effects:

[0032] 1. This invention reduces the surface roughness of laser 3D printed titanium alloy workpieces in three stages by preparing surface treatment solutions with different viscosities, surfactant adsorption amounts on titanium alloy surfaces, and dissolution / passivation properties. This can achieve maximum reduction in surface roughness with relatively small thinning amounts, making it more suitable for high-roughness titanium alloy workpieces with a surface roughness of more than 30μm obtained by laser 3D printing, a near-net-shape forming technology.

[0033] 2. The present invention uses a chemical treatment method, which can reduce surface roughness simply by soaking and ultrasonic stirring. Compared with mechanical polishing methods, it is more adaptable to complex surface structures, especially internal or blind hole structures.

[0034] 3. In the three-stage immersion treatment, when the total thinning amount of the titanium alloy workpiece reaches the maximum thinning amount requirement of the current stage, but the surface roughness still does not meet the target requirement of the current stage, the present invention can continue immersion by adjusting the process parameters of the immersion treatment (e.g., ultrasonic power and the concentration of some components in the surface treatment solution) to avoid excessive thinning and achieve a reduction in surface roughness while ensuring that the thinning amount meets the requirements.

[0035] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the details specifically pointed out in the description and drawings. Attached Figure Description

[0036] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0037] Figure 1 This is a surface morphology diagram of the titanium alloy workpiece in Embodiment 1 of the present invention before chemical surface treatment.

[0038] Figure 2 This is a surface morphology image of the titanium alloy workpiece after chemical surface treatment according to Embodiment 1 of the present invention. Detailed Implementation

[0039] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0040] Embodiments of the present invention provide a chemical treatment method for improving the surface finish of laser 3D printed titanium alloys, the method comprising:

[0041] Step S1: Prepare multiple surface treatment solutions, including a first surface treatment solution, a second surface treatment solution, and a third surface treatment solution. Each surface treatment solution includes a passivating agent, a solvent, a viscosity modifier, a surfactant, and a solvent. The passivating agent is nitric acid, and the solvent is hydrofluoric acid.

[0042] Step S2: Immerse the titanium alloy workpiece in the first surface treatment solution for the first stage of immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to 15-18 μm.

[0043] Step S3: Immerse the titanium alloy workpiece in the second surface treatment solution for the second stage of immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to 8-10 μm.

[0044] Step S4: Immerse the titanium alloy workpiece in the third surface treatment solution for the third stage of immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to below 5 μm.

[0045] The viscosities of the first, second, and third surface treatment solutions decrease sequentially, while the adsorption amount of surfactant on the titanium alloy surface increases sequentially.

[0046] This invention reduces the surface roughness of laser-printed titanium alloy workpieces in three stages by preparing surface treatment solutions with different viscosities, surfactant adsorption amounts on titanium alloy surfaces, and dissolution / passivation properties. This achieves maximum reduction in surface roughness with relatively small thinning amounts.

[0047] Specifically, this invention uses surface treatment solutions of different viscosities to soak titanium alloys with different roughness, so that titanium alloys with different roughness are adapted to surface treatment solutions of different viscosities. Since the higher the dissolution viscosity, the stronger the surface leveling ability, the viscosity of the surface treatment solution used is relatively high when the surface roughness of the titanium alloy is large.

[0048] At the same time, titanium alloys with different roughnesses need to be matched with surface treatment solutions with different adsorption capacities on the titanium alloy surface, so that the surfactant can be fully adsorbed in the depressions, thereby reducing the dissolution rate of the depressions and thus gradually smoothing the surface.

[0049] Furthermore, the present invention employs a chemical treatment method, which can reduce surface roughness simply by soaking. Compared with mechanical polishing methods, it is more adaptable to complex surface structures, especially internal or blind hole structures.

[0050] In some embodiments, the viscosity modifier in the first surface treatment solution includes ethylene glycol and disodium hydrogen phosphate, and the surfactant is polyethylene glycol. That is, the first surface treatment solution includes nitric acid (passivating agent), hydrofluoric acid (solvent), ethylene glycol (viscosity modifier), disodium hydrogen phosphate (viscosity modifier), and polyethylene glycol (surfactant).

[0051] In the second surface treatment solution, the viscosity modifier includes ethylene glycol and disodium hydrogen phosphate, and the surfactant includes polyethylene glycol and polyoxyethylene laurate. That is, the second surface treatment solution includes nitric acid (passivating agent), hydrofluoric acid (solvent), ethylene glycol (viscosity modifier), disodium hydrogen phosphate (viscosity modifier), polyethylene glycol (surfactant), and polyoxyethylene laurate (surfactant).

[0052] In the third surface treatment solution, the viscosity modifier is ethylene glycol, and the surfactants include polyethylene glycol and dodecylphenol polyoxyethylene ether. That is, the third surface treatment solution includes nitric acid (passivating agent), hydrofluoric acid (solvent), ethylene glycol (viscosity modifier), polyethylene glycol (surfactant), and dodecylphenol polyoxyethylene ether (surfactant).

[0053] In this invention, titanium alloys with different roughnesses are adapted to surfactants of different types and molecular sizes, so that the surfactants can be fully adsorbed at the depressions on the surface of titanium alloys with different roughnesses, thereby reducing the dissolution rate at the depressions and thus gradually smoothing the surface.

[0054] In some embodiments, the second and third surface treatment solutions further include hexamethylenetetramine. In embodiments of the present invention, hexamethylenetetramine acts as a complexing agent. This complexing agent effectively dissolves the titanium alloy surface by forming stable complexes with metal ions, while simultaneously preventing the redeposition of dissolved metal ions, thereby maintaining the smoothness of the titanium alloy surface.

[0055] In some embodiments, the solvent for each surface treatment solution is preferably deionized water.

[0056] In some embodiments, the concentration of nitric acid in the first surface treatment solution is 150–200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid is 1:2–1:2.5, the concentration of ethylene glycol is 100–150 mL / L, the concentration of disodium hydrogen phosphate is 20–25 g / L, the concentration of polyethylene glycol is 1–2 g / L, and the molecular weight is ≥6000.

[0057] For example, the concentration of nitric acid can be 150 mL / L, 155 mL / L, 160 mL / L, 165 mL / L, 170 mL / L, 175 mL / L, 180 mL / L, 185 mL / L, 190 mL / L, 195 mL / L, or 200 mL / L. The concentration ratio of hydrofluoric acid to nitric acid can be 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, or 1:2.5. The concentration of ethylene glycol can be 100 mL / L, 110 mL / L, 120 mL / L, 130 mL / L, 140 mL / L, or 150 mL / L. The concentration of disodium hydrogen phosphate can be 20 g / L, 21 g / L, 22 g / L, 23 g / L, 24 g / L, or 25 g / L. The concentrations of polyethylene glycol are 1 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L, and 2 g / L, and the molecular weights can be 6000, 7000, 8000, 9000, 10000, etc.

[0058] In the second surface treatment solution, the concentration of nitric acid is 150–200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid is 1:1.5–1:2, the concentration of ethylene glycol is 80–100 mL / L, the concentration of disodium hydrogen phosphate is 15–20 g / L, the concentration of polyethylene glycol is 0.5–1 g / L, and the molecular weight is 1000 ≤ molecular weight ≤ 2000, the concentration of polyoxyethylene laurate is 0.2–0.4 g / L, and the concentration of hexamethylenetetramine is 0.1–0.3 g / L.

[0059] For example, the concentration of nitric acid can be 150 mL / L, 155 mL / L, 160 mL / L, 165 mL / L, 170 mL / L, 175 mL / L, 180 mL / L, 185 mL / L, 190 mL / L, 195 mL / L, or 200 mL / L. The concentration ratio of hydrofluoric acid to nitric acid can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. The concentration of ethylene glycol can be 80 mL / L, 85 mL / L, 90 mL / L, 95 mL / L, or 100 mL / L. The concentration of disodium hydrogen phosphate can be 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, or 20 g / L. The concentrations of polyethylene glycol are 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, and 1 g / L, and the molecular weights can be 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, and 2000. The concentrations of polyoxyethylene laurate are 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, and 0.4 g / L, and the concentrations of hexamethylenetetramine are 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, and 0.3 g / L.

[0060] In the third surface treatment solution, the concentration of nitric acid is 150–200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid is 1:1–1:1.5, the concentration of disodium hydrogen phosphate is 10–15 g / L, the concentration of ethylene glycol is 20–50 mL / L, the concentration of polyethylene glycol is 0.2–0.5 g / L and the molecular weight is 200 ≤ molecular weight ≤ 400, the concentration of dodecylphenol polyoxyethylene ether is 0.1–0.2 g / L, and the concentration of hexamethylenetetramine is 0.1–0.3 g / L.

[0061] For example, the concentration of nitric acid can be 150 mL / L, 155 mL / L, 160 mL / L, 165 mL / L, 170 mL / L, 175 mL / L, 180 mL / L, 185 mL / L, 190 mL / L, 195 mL / L, or 200 mL / L. The concentration ratio of hydrofluoric acid to nitric acid can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5. The concentration of ethylene glycol can be 20 mL / L, 25 mL / L, 30 mL / L, 35 mL / L, 40 mL / L, 45 mL / L, or 50 mL / L. The concentration of disodium hydrogen phosphate can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, or 15 g / L. The concentrations of polyethylene glycol are 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, and 0.5 g / L, with molecular weights of 200, 250, 300, 350, and 400. The concentrations of dodecylphenol polyoxyethylene ether are 0.1 g / L, 0.11 g / L, 0.12 g / L, 0.13 g / L, 0.14 g / L, 0.15 g / L, 0.16 g / L, 0.17 g / L, 0.18 g / L, 0.19 g / L, and 0.2 g / L, and the concentrations of hexamethylenetetramine are 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, and 0.3 g / L.

[0062] This invention adjusts the concentrations of solvent, passivator, viscosity modifier, surfactant, and complexing agent in each surface treatment solution to make each surface treatment solution suitable for treating titanium alloy surfaces with different roughness levels. This achieves an optimal balance between the viscosity of dissolution, the amount of surfactant adsorbed, and the ratio of surface passivation to dissolution, allowing titanium alloy surfaces with different roughness to gradually become smooth during the dissolution process, while avoiding difficulties in dissolving the titanium alloy surface.

[0063] Increasing the concentration of the passivating agent (i.e., nitric acid) slows down the dissolution of the titanium alloy surface, making the surface smoother; however, excessively high concentrations result in slow dissolution. Increasing the concentration of the viscosity modifier increases viscosity, and increasing the concentration of the surfactant enhances the adsorption of the surfactant on the surface, gradually smoothing the surface during dissolution; however, excessively high concentrations of either the viscosity modifier or the surfactant make dissolution difficult. Therefore, this invention controls each component within a suitable range, ensuring that the titanium alloy surface can gradually dissolve and become smooth, while avoiding slow dissolution leading to low processing efficiency or difficulty in dissolution resulting in an uneven titanium alloy surface.

[0064] In some embodiments, ultrasonic stirring is performed simultaneously with the immersion treatment in steps S3 and S4. By ultrasonically stirring the surface treatment solution, this invention enables rapid diffusion of dissolved substances on the titanium alloy surface, promoting uniform dissolution and gradually smoothing the titanium alloy surface.

[0065] In some embodiments, the ultrasonic power is 800–2000 W, for example, 800 W, 900 W, 1000 W, 1200 W, 1400 W, 1500 W, 1600 W, 1800 W, and 2000 W. Lower ultrasonic power slows down the transport of surface substances and enhances their adsorption, thereby increasing the viscosity of the surface liquid layer, which helps to smooth the surface. However, if the ultrasonic power is too low or ultrasonic stirring is not performed, the dissolved substances may accumulate excessively, resulting in excessive viscosity or excessive adsorption, making dissolution difficult. Therefore, this invention, by controlling the ultrasonic power, not only helps to smooth the surface of titanium alloys but also avoids dissolution difficulties caused by the dosage of surface dissolved substances.

[0066] In some embodiments, in steps S2 to S4, the temperature of each surface treatment solution is controlled between 25 and 30°C, for example, 25±2°C, 26±2°C, 27±2°C, 28±2°C, 29±2°C, 30±2°C, etc., and then an immersion treatment is performed. Here, ±2°C refers to the allowable temperature fluctuation range during the immersion process.

[0067] Furthermore, in steps S3 and S4, the solution temperature of the surface treatment solution can be slightly higher than the solution temperature of the first surface treatment solution in step S2, so that the viscosity of the surface treatment solution is lower and can be adapted to the titanium alloy with reduced surface roughness.

[0068] In some embodiments, in step S2, when the surface roughness of the titanium alloy workpiece reaches the range of 15 to 18 μm, for example, when it reaches roughness of 15 μm, 16 μm, 17 μm, 18 μm, etc., the thinning amount of the titanium alloy workpiece is controlled to be within 150 μm, that is, the maximum thinning amount is controlled to be 150 μm.

[0069] In some embodiments, in step S3, when the surface roughness of the titanium alloy workpiece reaches the range of 8 to 10 μm, for example, when it reaches roughness of 8 μm, 9 μm, 10 μm, etc., the total thinning amount of the titanium alloy workpiece is controlled to be within 200 μm, that is, the maximum thinning amount is controlled to be 200 μm.

[0070] In some embodiments, in step S4, when the surface roughness of the titanium alloy workpiece reaches below 5 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 300 μm, that is, the maximum thinning amount is controlled to be 300 μm.

[0071] This invention controls the thinning amount of titanium alloy after immersion in various surface treatment solutions. Compared with conventional titanium alloy chemical milling technology, it avoids excessive thinning, which is detrimental to maintaining the shape and structure of 3D printed titanium alloy workpieces. It is more suitable for improving the surface finish of near-net-shape titanium alloy workpieces in 3D printing technology.

[0072] In some embodiments, in order to control the thinning amount of the titanium alloy workpiece, after the titanium alloy workpiece is immersed in each surface treatment solution, it is necessary to take the titanium alloy workpiece out at certain intervals to measure the surface roughness and total thinning amount of the titanium alloy workpiece.

[0073] Specifically, in steps S2, S3, and S4, after immersing the titanium alloy workpiece in each surface treatment solution for 3-5 minutes, the workpiece is removed for surface roughness and total thinning amount measurement to determine whether the surface roughness meets the target requirements of the current treatment stage and whether the total thinning amount is within the predetermined range. If the measured surface roughness does not meet the target requirements, immersion continues, and the workpiece is removed for measurement every 1-1.5 minutes to avoid over-treatment that could cause the titanium alloy thinning amount to exceed the predetermined range, and also to avoid frequent removal for measurement that could affect processing efficiency.

[0074] In some embodiments, if the total thinning amount of the titanium alloy workpiece reaches the maximum thinning amount requirement of the current stage in the three-stage immersion treatment, but the surface roughness still does not meet the target requirement of the current stage, then the process parameters of the immersion treatment need to be adjusted and immersion continued to control the thinning amount and avoid excessive thinning.

[0075] The process parameters for adjusting the immersion treatment include adjusting the ultrasonic power of the ultrasonic stirring and / or adjusting the concentration of at least one of the passivating agent, viscosity modifier and surfactant in the surface treatment solution.

[0076] Specifically, the ultrasonic power can be reduced; and / or the concentration of at least one of the passivating agent, viscosity modifier, and surfactant can be increased by 15-20%. For example, the concentrations of the above components can be increased by 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0077] In some embodiments, in step S2, if the surface roughness is still not reduced to below 18 μm when the thinning amount of the titanium alloy workpiece reaches 150 μm, the concentration of at least one of nitric acid, ethylene glycol and polyethylene glycol in the first surface treatment solution is increased by 15-20%, and the immersion treatment is repeated.

[0078] In step S3, if the surface roughness is still not reduced to below 10 μm when the thinning amount of the titanium alloy workpiece reaches 200 μm, the ultrasonic power is reduced and the immersion process continues. If the surface roughness is still not reduced to below 10 μm when the ultrasonic power is reduced to 0, the concentration of at least one of nitric acid, ethylene glycol, polyethylene glycol, and polyoxyethylene laurate in the second surface treatment solution is increased by 15-20%, and the immersion treatment is repeated.

[0079] In step S4, if the surface roughness is still not reduced to below 5 μm when the thinning amount of the titanium alloy workpiece reaches 300 μm, the ultrasonic power is reduced and the immersion process continues. If the surface roughness is still not reduced to below 5 μm when the ultrasonic power is reduced to 0, the concentration of at least one of nitric acid, ethylene glycol, polyethylene glycol, and dodecylphenol polyoxyethylene ether in the third surface treatment solution is increased by 15-20%, and the immersion treatment is repeated.

[0080] In surface treatment solutions, nitric acid acts as a passivating agent. Increasing its concentration slows down dissolution, resulting in a smoother surface. Increasing its concentration by 15-20% can slow the dissolution rate and prevent excessive surface thinning, while avoiding excessively high concentrations that would cause slow dissolution. Appropriately increasing the concentration of ethylene glycol increases viscosity, and appropriately increasing the concentration of surfactants such as polyethylene glycol enhances surfactant adsorption on the surface. All of these factors contribute to the gradual smoothing of the titanium alloy surface during dissolution, while also preventing dissolution difficulties caused by excessively high concentrations of either agent.

[0081] In steps S3 and S4, reducing the ultrasonic power slows down the transport of substances on the titanium alloy surface, enhances substance adsorption, and increases the viscosity of the surface liquid layer, which helps to smooth the surface and slows down the thinning of the titanium alloy. Furthermore, in steps S3 and S4, adjusting the ultrasonic power of the ultrasonic stirring can be tried first. If adjusting the ultrasonic power can control the thinning amount while reducing surface roughness, the cumbersome operation of adjusting the concentration of the surface treatment solution is avoided, making the operation simpler.

[0082] The following examples further illustrate the chemical treatment method for improving the surface finish of laser 3D printed titanium alloys according to the present invention.

[0083] Example 1

[0084] This embodiment describes the chemical surface treatment of a laser-3D printed Ti6Al4V bearing. The original surface roughness is approximately 37.6 μm (average of three points). Figure 1 As shown, its surface is relatively rough. The requirement is to reduce the surface roughness to 5 μm or less with a thinning amount not exceeding 300 μm. The specific steps of the chemical surface treatment are as follows.

[0085] 1. Prepare three surface treatment solutions:

[0086] (1) A first surface treatment solution was prepared using deionized water, ethylene glycol, polyethylene glycol, nitric acid, hydrofluoric acid and disodium hydrogen phosphate; wherein the concentration of ethylene glycol was 150 mL / L, the concentration of polyethylene glycol was 2 g / L and the molecular weight was 8000, the concentration of nitric acid was 200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid was 1:2.5, and the concentration of disodium hydrogen phosphate was 25 g / L;

[0087] (2) A second surface treatment solution was prepared using deionized water, ethylene glycol, polyethylene glycol, nitric acid, hydrofluoric acid, disodium hydrogen phosphate, polyoxyethylene laurate, and hexamethylenetetramine; wherein the concentration of ethylene glycol was 100 mL / L, the concentration of polyethylene glycol was 1 g / L and the molecular weight was 2000, the concentration of nitric acid was 200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid was 1:2, the concentration of disodium hydrogen phosphate was 20 g / L, the concentration of polyoxyethylene laurate was 0.4 g / L, and the concentration of hexamethylenetetramine was 0.2 g / L.

[0088] (3) A third surface treatment solution was prepared using deionized water, ethylene glycol, polyethylene glycol, nitric acid, hydrofluoric acid, dodecylphenol polyoxyethylene ether, and hexamethylenetetramine; wherein the concentration of ethylene glycol was 50 mL / L, the concentration of polyethylene glycol was 0.5 g / L and the molecular weight was 400, the concentration of nitric acid was 200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid was 1:1.5, the concentration of disodium hydrogen phosphate was 15 g / L, the concentration of dodecylphenol polyoxyethylene ether was 0.2 g / L, and the concentration of hexamethylenetetramine was 0.2 g / L.

[0089] 2. The temperature of the first surface treatment solution was controlled within the range of 28±2℃. The titanium alloy workpiece was immersed in the solution without stirring. After 5 minutes, the workpiece was removed and its surface roughness was measured to be approximately 23.2 μm, and the thinning amount was approximately 80 μm. The sample was then immersed in the solution again, and measured every 1 minute. When the total immersion time reached 7 minutes, the surface roughness of the workpiece was measured to be approximately 17.3 μm, and the thinning amount was approximately 120 μm.

[0090] 3. Control the temperature of the second surface treatment solution within the range of 30±2℃. Immerse the titanium alloy workpiece in the solution, and place the container holding the solution in an ultrasonic cleaner with an ultrasonic stirring power of 1500W. After 3 minutes, remove the workpiece and measure its surface roughness, which is approximately 12.1μm, and the total thinning is approximately 180μm. Continue immersing the sample in the solution, removing it every 1 minute for measurement. When the total immersion time reaches 13 minutes, the surface roughness is measured to be approximately 7.5μm, and the thinning is approximately 230μm.

[0091] 4. Control the temperature of the third surface treatment solution within the range of 30±2℃. Immerse the titanium alloy workpiece in the solution, and place the container holding the solution in an ultrasonic cleaner with an ultrasonic stirring power of 1500W. After 3 minutes, remove the workpiece and measure its surface roughness to be approximately 5.2μm, with a total thinning of approximately 280μm. At this point, the thinning is close to the upper limit. Continue immersing the workpiece for another minute, and measure the surface roughness to be approximately 4.5 micrometers, with a total thinning of approximately 300 micrometers. Figure 2 As shown, the surface of the titanium alloy is smooth and clean.

[0092] Example 2

[0093] This embodiment focuses on the chemical surface treatment of a laser-3D printed TC11 titanium alloy compressor blade. The original surface roughness is approximately 42.6 μm (three-point average), and the requirement is to reduce the surface roughness to 5 μm or below with a thinning amount not exceeding 300 μm. The specific steps of the chemical surface treatment are as follows.

[0094] 1. Prepare three surface treatment solutions:

[0095] (1) A first surface treatment solution was prepared using deionized water, ethylene glycol, polyethylene glycol, nitric acid, hydrofluoric acid and disodium hydrogen phosphate; wherein the concentration of ethylene glycol was 150 mL / L, the concentration of polyethylene glycol was 2 g / L and the molecular weight was 8000, the concentration of nitric acid was 200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid was 1:2.5, and the concentration of disodium hydrogen phosphate was 25 g / L;

[0096] (2) A second surface treatment solution was prepared using deionized water, ethylene glycol, polyethylene glycol, nitric acid, hydrofluoric acid, disodium hydrogen phosphate, polyoxyethylene laurate, and hexamethylenetetramine; wherein the concentration of ethylene glycol was 100 mL / L, the concentration of polyethylene glycol was 1 g / L and the molecular weight was 2000, the concentration of nitric acid was 200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid was 1:2, the concentration of disodium hydrogen phosphate was 20 g / L, the concentration of polyoxyethylene laurate was 0.4 g / L, and the concentration of hexamethylenetetramine was 0.3 g / L.

[0097] (3) A third surface treatment solution was prepared using deionized water, ethylene glycol, polyethylene glycol, nitric acid, hydrofluoric acid, dodecylphenol polyoxyethylene ether, and hexamethylenetetramine; wherein the concentration of ethylene glycol was 50 mL / L, the concentration of polyethylene glycol was 0.5 g / L and the molecular weight was 400, the concentration of nitric acid was 200 mL / L, the concentration ratio of hydrofluoric acid to nitric acid was 1:1.5, the concentration of disodium hydrogen phosphate was 15 g / L, the concentration of dodecylphenol polyoxyethylene ether was 0.2 g / L, and the concentration of hexamethylenetetramine was 0.3 g / L.

[0098] 2. The temperature of the first surface treatment solution was controlled within the range of 28±2℃. The titanium alloy workpiece was immersed in the solution without stirring. After 5 minutes, the workpiece was removed and its surface roughness was measured to be approximately 27.1 μm, and the thinning amount was approximately 90 μm. The sample was then immersed in the solution for an extended period of 1 minute, and the workpiece was removed and measured at each interval. When the total immersion time reached 7 minutes, the surface roughness was measured to be approximately 21.5 μm, and the thinning amount was approximately 140 μm. When the total immersion time reached 8 minutes, the surface roughness was measured to be approximately 19.0 μm, and the thinning amount was approximately 160 μm, which exceeded the upper limit of 150 μm, but the surface roughness did not reach the range of 15-18 μm.

[0099] 3. Adjust the ethylene glycol concentration in the first surface treatment solution to 180 mL / L and the polyethylene glycol concentration to 2.3 g / L. Repeat step 2 with a new workpiece. After 5 minutes, the surface roughness was measured to be approximately 25.5 μm, and the thinning amount was approximately 80 μm. When the total immersion time reached 8 minutes, the surface roughness was measured to be approximately 17.8 μm, and the thinning amount was approximately 130 μm.

[0100] 4. Control the temperature of the second surface treatment solution within the range of 30±2℃. Immerse the titanium alloy workpiece in the solution, and place the container holding the solution in an ultrasonic cleaner with an ultrasonic stirring power of 1500W. After 3 minutes, remove the workpiece and measure its surface roughness, which is approximately 14.1μm, and the total thinning is approximately 170μm. Continue immersing the sample in the solution, removing it every 1 minute for measurement. When the total immersion time reaches 15 minutes, the surface roughness is measured to be approximately 8.6μm, and the thinning is approximately 200μm.

[0101] 5. Control the temperature of the third surface treatment solution within the range of 30±2℃. Immerse the titanium alloy workpiece in the solution, and place the container holding the solution in an ultrasonic cleaner with an ultrasonic stirring power of 1500W. After 3 minutes, remove the workpiece and measure its surface roughness, which is approximately 6.1μm, with a total thinning of approximately 300μm. At this point, the thinning amount has reached its upper limit, so the immersion treatment cannot continue, and the process needs to be adjusted again.

[0102] 6. Take a new sample and repeat steps 1-4. Turn off the ultrasonic stirring in step 5. After 3 minutes, the surface roughness measured by orientation is approximately 5.8 μm, and the total thinning is approximately 280 μm. Measurements are then taken every minute thereafter. When the total immersion time reaches 19 minutes, the surface roughness is approximately 5.3 μm, and the total thinning is approximately 290 μm. When the total immersion time reaches 20 minutes, the surface roughness is approximately 5.0 μm, and the total thinning is approximately 300 μm, meeting the process requirements.

[0103] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A chemical treatment method for improving the surface finish of a laser 3D printed titanium alloy, characterized in that, Comprising: Step S1, preparing a plurality of surface treatment solutions, the plurality of surface treatment solutions comprising a first surface treatment solution, a second surface treatment solution and a third surface treatment solution; The plurality of surface treatment solutions all comprise a passivation agent, a dissolving agent, a viscosity regulator, a surfactant and a solvent; the passivation agent is nitric acid, the dissolving agent is hydrofluoric acid; in the first surface treatment solution, the viscosity regulator comprises ethylene glycol and disodium hydrogen phosphate, and the surfactant is polyethylene glycol; In the second surface treatment solution, the viscosity regulator comprises ethylene glycol and disodium hydrogen phosphate, and the surfactant comprises polyethylene glycol and polyoxyethylene laurate; In the third surface treatment solution, the viscosity regulator is ethylene glycol, and the surfactant comprises polyethylene glycol and polyoxyethylene dodecylphenol ether; Step S2, placing a titanium alloy workpiece in the first surface treatment solution for first-stage immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to 15-18 μm; Step S3, placing the titanium alloy workpiece in the second surface treatment solution for second-stage immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to 8-10 μm; Step S4, placing the titanium alloy workpiece in the third surface treatment solution for third-stage immersion treatment until the surface roughness of the titanium alloy workpiece is reduced to less than 5 μm; Wherein, the viscosity of the first surface treatment solution, the second surface treatment solution and the third surface treatment solution decreases in turn, and the adsorption amount of the surfactant on the surface of the titanium alloy increases in turn.

2. The method according to claim 1, characterized in that: The second surface treatment solution and the third surface treatment solution further comprise hexamethylenetetramine.

3. The method of claim 2, wherein, In the first surface treatment solution, the concentration of the nitric acid is 150-200 mL / L, the concentration ratio of the hydrofluoric acid to the nitric acid is 1:2-1:2.5, the concentration of the ethylene glycol is 100-150 mL / L, the concentration of the disodium hydrogen phosphate is 20-25 g / L, the concentration of the polyethylene glycol is 1-2 g / L, and the molecular weight is ≥6000; and / or, In the second surface treatment solution, the concentration of the nitric acid is 150-200 mL / L, the concentration ratio of the hydrofluoric acid to the nitric acid is 1:1.5-1:2, the concentration of the ethylene glycol is 80-100 mL / L, the concentration of the disodium hydrogen phosphate is 15-20 g / L, the concentration of the polyethylene glycol is 0.5-1 g / L, and 1000≤molecular weight≤2000, the concentration of the polyoxyethylene laurate is 0.2-0.4 g / L, and the concentration of the hexamethylenetetramine is 0.1-0.3 g / L; and / or, The concentration of the nitric acid is 150-200 mL / L, the concentration ratio of the hydrofluoric acid to the nitric acid is 1:1-1:1.5, the concentration of the disodium hydrogen phosphate is 10-15 g / L, the concentration of the ethylene glycol is 20-50 mL / L, the concentration of the polyethylene glycol is 0.2-0.5 g / L, and 200≤molecular weight≤400, the concentration of the dodecyl phenol polyoxyethylene ether is 0.1-0.2 g / L, and the concentration of the hexamethylenetetramine is 0.1-0.3 g / L.

4. The method of claim 1, wherein, In the step S3 and the step S4, ultrasonic stirring is performed simultaneously with the soaking treatment, and the ultrasonic power is 800-2000 W.

5. The method of claim 4, wherein, In the step S2, when the surface roughness of the titanium alloy workpiece reaches the range of 15-18 μm, the thinning amount of the titanium alloy workpiece is controlled to be within 150 μm; and / or, In the step S3, when the surface roughness of the titanium alloy workpiece reaches the range of 8-10 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 200 μm; and / or, In the step S4, when the surface roughness of the titanium alloy workpiece reaches below 5 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 300 μm.

6. The method of claim 5, wherein, In the three-stage soaking treatment, if the total thinning amount of the titanium alloy workpiece reaches the maximum thinning amount requirement of the current stage, and the surface roughness still does not reach the target requirement of the current stage, the ultrasonic power of the ultrasonic stirring is adjusted, and / or the concentration of at least one of the passivator, the viscosity regulator and the surfactant in the surface treatment solution is adjusted.

7. The method of claim 6, wherein, The concentration of at least one of the passivator, the viscosity regulator and the surfactant is increased by 15-20%.

8. The method of claim 7, wherein, In the step S2, if the thinning amount of the titanium alloy workpiece reaches 150 μm, and the surface roughness still does not decrease to below 18 μm, the concentration of at least one of the nitric acid, the ethylene glycol and the polyethylene glycol in the first surface treatment solution is increased by 15-20%, and the soaking treatment is performed again.

9. The method of claim 7, wherein, In the step S3, when the surface roughness of the titanium alloy workpiece reaches the range of 8-10 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 200 μm; If the thinning amount of the titanium alloy workpiece reaches 200 μm, and the surface roughness still does not decrease to below 10 μm, the ultrasonic power is decreased, and the soaking is continued; If the ultrasonic power is decreased to 0, and the surface roughness still does not decrease to below 10 μm, the concentration of at least one of the nitric acid, the ethylene glycol, the polyethylene glycol and the laureic acid polyoxyethylene ether in the second surface treatment solution is increased by 15-20%, and the soaking treatment is performed again.

10. The method of claim 7, wherein, In the step S4, when the surface roughness of the titanium alloy workpiece reaches below 5 μm, the total thinning amount of the titanium alloy workpiece is controlled to be within 300 μm; If the thinning amount of the titanium alloy workpiece reaches 300 μm, and the surface roughness still does not decrease to below 5 μm, the ultrasonic power is decreased, and the soaking is continued; If the surface roughness is still not reduced to below 5 μm when the ultrasonic power is reduced to 0, the concentration of at least one of the nitric acid, the ethylene glycol, the polyethylene glycol, and the dodecylphenol polyoxyethylene ether in the third surface treatment solution is increased by 15-20%, and the immersion treatment is performed again.

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