3D printing porous titanium or titanium alloy surface polishing method

Abstract

The invention discloses a 3D printing porous titanium or titanium alloy surface polishing method. The method comprises the steps that firstly, 3D printing porous titanium or titanium alloy is aired after being subjected to ultrasonic cleaning; 2, mixing deionized water, nitric acid, ammonium fluoride and an additive to prepare a polishing solution; thirdly, the cleaned 3D printing porous titanium or titanium alloy is immersed in a polishing solution to be subjected to ultrasonic chemical polishing; and fourthly, the 3D printing porous titanium or titanium alloy subjected to ultrasonic chemical polishing is taken out, cleaned and aired. According to the method, ultrasonic chemical polishing is adopted, components of the polishing solution are designed, the inner and outer surfaces of pores of the 3D printing porous titanium or titanium alloy are evenly polished, the surfaces are smoother, the brightness is remarkably improved, the high polishing rate and the low thinning rate of the 3D printing porous titanium or titanium alloy are achieved, and the method is suitable for SLM layer-by-layer printing of the complex porous titanium alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material surface treatment, and in particular relates to a method for polishing the surface of 3D-printed porous titanium or titanium alloy. Background Art

[0002] Metal 3D printing is a new rapid prototyping technology that gradually builds up metal from lines to surfaces and then to solids. Compared to traditional machining techniques, 3D printing offers the advantages of mold-free, rapid prototyping of dense or porous complex structures, making it a preferred processing technology for personalized fabrication. However, because the laser melts the metal powder in a limited area and rapidly cools it during the molding process, the surface becomes sticky and uneven, making it difficult to meet part requirements. Therefore, it is crucial to use appropriate methods to polish the surface and reduce surface roughness.

[0003] Currently, the commonly used polishing methods include mechanical polishing, magnetic polishing, abrasive flow polishing and chemical polishing. Mechanical polishing is highly efficient and effective, but it is not suitable for asymmetric structures and complex parts. Abrasive flow polishing technology is to push abrasive particles into the surface or interior of the workpiece under pressure, and achieve the purpose of polishing through the extrusion and friction between the abrasive particles and the material surface. It is mainly used for polishing small holes with large aspect ratios and thick walls. However, for complex porous structures in 3D printing, the inside of the hole is difficult to process, and the abrasive particles will remain in the bends and dead corners of the hole, making it impossible to continue processing the workpiece. Chemical polishing is not limited by the complex shape of the parts, and the chemical residue on the surface after polishing is easy to clean. It is especially suitable for processing 3D printed porous titanium or titanium alloy internal parts with complex shapes or structures. The entire process is simple to operate and efficient, but the polishing liquid formula and process details are different for different structures and materials, and require trial and error. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a method for polishing the surface of 3D-printed porous titanium or titanium alloy. This method uses ultrasonic chemical polishing to uniformly polish the inner and outer surfaces of the pores of the 3D-printed porous titanium or titanium alloy. Combined with the design of the polishing liquid components to simplify the corrosion rate, the surface of the 3D-printed porous titanium or titanium alloy after polishing is made smoother and the brightness is significantly improved, achieving a high polishing rate and low thinning rate for the 3D-printed porous titanium or titanium alloy, and solving the technical problem that single chemical polishing is difficult to effectively polish inside the pores of the 3D-printed porous titanium or titanium alloy.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a 3D printed porous titanium or titanium alloy surface polishing method, characterized in that the method comprises the following steps: Step 1: Cleaning: Place the 3D printed porous titanium or titanium alloy in anhydrous ethanol for ultrasonic cleaning to remove residual powder on the surface until the anhydrous ethanol after ultrasonic cleaning is clear and free of suspended powder. Take it out and dry it to obtain the cleaned 3D printed porous titanium or titanium alloy; Step 2: Prepare a polishing solution: Mix deionized water, nitric acid (65% to 68% by mass), ammonium fluoride, and an additive to prepare a polishing solution; the volume ratio of deionized water to nitric acid in the polishing solution is 1000:20 to 40, and 2 g to 5 g of ammonium fluoride and 0.2 to 2 g of the additive are added to every 1000 mL of deionized water; Step 3, ultrasonic chemical polishing: immersing the cleaned 3D printed porous titanium or titanium alloy obtained in step 1 in the polishing solution prepared in step 2 for ultrasonic chemical polishing; the polishing temperature of the ultrasonic chemical polishing is 20°C to 80°C, the ultrasonic frequency is 60kHz to 90kHz, and the polishing time is 3min to 5min; Step 4: Post-processing: Take out the 3D printed porous titanium or titanium alloy after the ultrasonic chemical polishing in step 3, rinse it under running water, and dry it.

[0006] The above-mentioned 3D printed porous titanium or titanium alloy surface polishing method is characterized in that the 3D printed porous titanium or titanium alloy in step one is a three-dimensional entity printed layer by layer by SLM, and there are a large number of connected pores inside the entity, and the pore size is 100μm~500μm.

[0007] The above-mentioned method for polishing the surface of porous titanium or titanium alloy by 3D printing is characterized in that the additive in step 2 is carboxymethyl cellulose. By using carboxymethyl cellulose as a thickener, the viscosity of the polishing liquid is increased, thereby ensuring the uniformity of the polishing liquid.

[0008] The above-mentioned method for polishing the surface of 3D printed porous titanium or titanium alloy is characterized in that the volume ratio of deionized water to nitric acid in the polishing liquid in step 2 is 1000:20, and 3g of ammonium fluoride and 0.2g of additives are added to every 1000mL of deionized water.

[0009] The above-mentioned method for polishing the surface of 3D printed porous titanium or titanium alloy is characterized in that the polishing temperature of the ultrasonic chemical polishing in step three is 40° C., the ultrasonic frequency is 80 kHz, and the polishing time is 4 minutes.

[0010] Compared with the prior art, the present invention has the following advantages: 1. The present invention adopts ultrasonic chemical polishing, that is, ultrasonication is performed simultaneously with chemical polishing. Under the action of ultrasonic waves, the pores inside and outside the 3D printed porous titanium or titanium alloy vibrate, which can effectively polish the inside of the tiny pores. At the same time, the micro-protrusions on the rough surface are more easily corroded, achieving the effect of uniform polishing everywhere, realizing a high polishing rate and low thinning rate for 3D printed porous titanium or titanium alloy.

[0011] 2. The polishing liquid component of the present invention uses ammonium fluoride instead of hydrofluoric acid, and adds an adhesive, which effectively slows down the corrosion rate of ultrasonic chemical polishing, making the surface of the 3D printed porous titanium or titanium alloy smoother and smoother after polishing, and the brightness is significantly improved, ensuring the accuracy of the structural size of the 3D printed porous titanium or titanium alloy bracket.

[0012] 3. The present invention optimizes the composition of the polishing liquid and the ultrasonic chemical polishing process parameters, uses high-frequency ultrasonic waves to promote the contact between the polishing liquid and the surface of the 3D-printed porous titanium or titanium alloy, enhances the chemical reaction effect, and improves the surface quality. It also ensures that the concentration of the polishing liquid is uniform throughout the polishing process, thereby achieving uniform polishing of the internal surface of the 3D-printed porous titanium or titanium alloy structure, reducing the roughness to 12μm, effectively improving the polishing rate of the pores on the surface of the 3D-printed porous titanium or titanium alloy, and achieving efficient polishing of the 3D-printed porous titanium or titanium alloy surface.

[0013] 4. The surface polishing method for 3D printing porous titanium or titanium alloy of the present invention is simple and convenient to operate, is not restricted by the shape of the material, has good processing effect, and has broad application prospects. It is especially suitable for SLM layer-by-layer printing of complex porous titanium alloys.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention provides a flow chart for polishing the surface of 3D-printed porous titanium or titanium alloy.

[0016] Figure 2 This is a diagram showing the effect of the porous TC4 titanium alloy surface polishing in Example 1 of the present invention. DETAILED DESCRIPTION

[0017] Example 1 like Figure 1 As shown, this embodiment includes the following steps: Step 1, cleaning: placing the porous TC4 titanium alloy formed by SLM layer-by-layer printing in anhydrous ethanol and ultrasonically cleaning it three times with 40kHz ultrasound for 15 minutes each time to remove residual powder on the surface until the anhydrous ethanol after ultrasonic cleaning is clear and free of suspended powder, taking it out and drying it to obtain the cleaned porous TC4 titanium alloy; the porous TC4 titanium alloy formed by SLM layer-by-layer printing is a three-dimensional entity, and there are a large number of connected pores inside the entity, the pore size of the pores is 100μm~300μm, and the depth of the pore-containing layer is less than 5mm; Step 2: prepare a polishing solution: mix 1000 mL of deionized water, 20 mL of nitric acid with a mass fraction of 65% to 68%, 3 g of ammonium fluoride and 0.2 g of carboxymethyl cellulose (CMC) to prepare a polishing solution; Step 3, ultrasonic chemical polishing: immerse the cleaned porous TC4 titanium alloy obtained in step 1 in the polishing solution prepared in step 2 and placed in a constant temperature water bath, maintain the polishing temperature at 40°C ± 1°C, turn on the ultrasonic generator, set the ultrasonic frequency to 80kHz, and perform ultrasonic chemical polishing for 4 minutes; Step 4, post-processing: take out the porous TC4 titanium alloy after the ultrasonic chemical polishing in step 3, rinse it under running deionized water, and dry it.

[0018] Figure 2 This is the effect diagram of the polished surface of porous TC4 titanium alloy in this embodiment. Figure 2 It can be seen that the micro-protrusions on the surface of the porous TC4 titanium alloy are small and relatively flat and smooth.

[0019] According to the roughness test, the surface roughness of the porous TC4 titanium alloy in this embodiment after polishing is 15 μm.

[0020] Example 2 like Figure 1 As shown, this embodiment includes the following steps: Step 1, cleaning: The porous TA1 titanium formed by SLM layer-by-layer printing is placed in anhydrous ethanol and ultrasonically cleaned three times with 40kHz ultrasound for 15 minutes each time to remove residual powder on the surface until the anhydrous ethanol after ultrasonic cleaning is clear and free of suspended powder. The porous TA1 titanium is taken out and dried to obtain the cleaned porous TA1 titanium; the porous TA1 titanium formed by SLM layer-by-layer printing is a three-dimensional entity, and there are a large number of connected pores inside the entity, the pore size of the pores is 200μm~400μm, and the depth of the pore-containing layer is less than 5mm; Step 2: prepare a polishing solution: mix 1000 mL of deionized water, 35 mL of 65% to 68% nitric acid, 2.5 g of ammonium fluoride, and 0.27 g of carboxymethyl cellulose (CMC) to prepare a polishing solution. Step 3, ultrasonic chemical polishing: immerse the cleaned porous TA1 titanium obtained in step 1 in the polishing solution prepared in step 2 and placed in a constant temperature water bath, maintain the polishing temperature at 20°C ± 1°C, turn on the ultrasonic generator, set the ultrasonic frequency to 90kHz, and perform ultrasonic chemical polishing for 3 minutes; Step 4: Post-processing: Take out the porous TA1 titanium after the ultrasonic chemical polishing in step 3, rinse it under running deionized water, and dry it.

[0021] According to the roughness test, the surface roughness of the porous TA1 titanium surface after polishing in this embodiment is 15 μm.

[0022] Example 3 like Figure 1 As shown, this embodiment includes the following steps: Step 1, cleaning: placing the porous TC4 titanium alloy formed by SLM layer-by-layer printing in anhydrous ethanol and ultrasonically cleaning it three times with 40kHz ultrasound for 15 minutes each time to remove residual powder on the surface until the anhydrous ethanol after ultrasonic cleaning is clear and free of suspended powder, taking it out and drying it to obtain the cleaned porous TC4 titanium alloy; the porous TC4 titanium alloy formed by SLM layer-by-layer printing is a three-dimensional entity, and there are a large number of connected pores inside the entity, the pore size of the pores is 200μm~500μm, and the depth of the pore-containing layer is less than 5mm; Step 2: prepare a polishing solution: mix 1000 mL of deionized water, 40 mL of nitric acid with a mass fraction of 65% to 68%, 5 g of ammonium fluoride and 2 g of carboxymethyl cellulose (CMC) to prepare a polishing solution; Step 3, ultrasonic chemical polishing: immerse the cleaned porous TC4 titanium alloy obtained in step 1 in the polishing solution prepared in step 2 and placed in a constant temperature water bath, maintain the polishing temperature at 80°C ± 1°C, turn on the ultrasonic generator, set the ultrasonic frequency to 60kHz, and perform ultrasonic chemical polishing for 5 minutes; Step 4, post-processing: take out the porous TC4 titanium alloy after the ultrasonic chemical polishing in step 3, rinse it under running deionized water, and dry it.

[0023] According to the roughness test, the surface roughness of the porous TC4 titanium alloy in this embodiment after polishing is 20 μm.

[0024] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for polishing the surface of 3D printed porous titanium or titanium alloy, characterized in that: The method comprises the following steps: Step 1: Cleaning: Place the 3D printed porous titanium or titanium alloy in anhydrous ethanol for ultrasonic cleaning to remove residual powder on the surface until the anhydrous ethanol after ultrasonic cleaning is clear and free of suspended powder. Take it out and dry it to obtain the cleaned 3D printed porous titanium or titanium alloy; Step 2: Prepare a polishing solution: Mix deionized water, nitric acid (65% to 68% by mass), ammonium fluoride, and an additive to prepare a polishing solution; the volume ratio of deionized water to nitric acid in the polishing solution is 1000:20 to 40, and 2 g to 5 g of ammonium fluoride and 0.2 to 2 g of the additive are added to every 1000 mL of deionized water; Step 3, ultrasonic chemical polishing: immersing the cleaned 3D printed porous titanium or titanium alloy obtained in step 1 in the polishing solution prepared in step 2 for ultrasonic chemical polishing; the polishing temperature of the ultrasonic chemical polishing is 20°C to 80°C, the ultrasonic frequency is 60kHz to 90kHz, and the polishing time is 3min to 5min; Step 4: Post-processing: Take out the 3D printed porous titanium or titanium alloy after the ultrasonic chemical polishing in step 3, rinse it under running water, and dry it.

2. A 3D printing porous titanium or titanium alloy surface polishing method according to claim 1, characterized in that: The 3D printed porous titanium or titanium alloy in step 1 is a three-dimensional entity printed layer by layer by SLM, and there are a large number of connected pores inside the entity, with a pore size of 100μm~500μm.

3. A 3D printing porous titanium or titanium alloy surface polishing method according to claim 1, characterized in that: The additive in step 2 is carboxymethyl cellulose.

4. A 3D printing porous titanium or titanium alloy surface polishing method according to claim 1, characterized in that: The volume ratio of deionized water to nitric acid in the polishing liquid in step 2 is 1000:20, and 3 g of ammonium fluoride and 0.2 g of additives are added to every 1000 mL of deionized water.

5. A 3D printing porous titanium or titanium alloy surface polishing method according to claim 1, characterized in that: The polishing temperature of the ultrasonic chemical polishing in step 3 is 40° C., the ultrasonic frequency is 80 kHz, and the polishing time is 4 min.

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