An electrolytic etching solution for additive manufacturing of CoCrFeNiMn high-entropy alloy and its preparation and use methods

Abstract

The present invention discloses an electrolytic etching solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, and its preparation and usage methods. The method places the electrolytic etching solution in an electrolytic cell, puts the prepared metallographic sample into the electrolytic etching solution, uses the additive manufactured CoCrFeNiMn high-entropy alloy to be etched as the anode, and stainless steel as the cathode; powers on the cathode and anode through a DC power supply to perform electrolytic etching on the additive manufactured CoCrFeNiMn high-entropy alloy; puts the etched sample into a beaker filled with absolute ethanol for ultrasonic cleaning, and then observes it under a scanning electron microscope. The present invention can effectively observe the cellular crystal microstructure of the additive manufactured CoCrFeNiMn high-entropy alloy; this method is faster, more effective, more standardized in operation, and has stronger repeatability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic corrosion, and relates to an electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, and a preparation and use method thereof.

Background Art

[0002] Due to the special process of metal additive manufacturing, the structure of the additive manufacturing deposition state is extremely different from that of the traditional process. For the CoCrFeNiMn high-entropy alloy formed by the additive manufacturing process, there are a large number of dislocation substructures and cellular crystal structures in its structure, making its corrosion particularly difficult to control. In most literatures, aqua regia is used to corrode the additive manufacturing high-entropy alloy CoCrFeNiMn, but the corrosion uniformity is poor, and pitting corrosion is likely to occur, resulting in the shedding of some features in the structure; when using FeCl3 + HCl + H2O for corrosion, the microscopic morphology can be clearly observed under an optical microscope, but the cellular crystal structure cannot be clearly observed under a scanning electron microscope, affecting the observation of the microstructure.

Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art, and provide an electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy and a preparation and use method thereof; to solve the technical problem that there is a lack of a corrosion method for this alloy in additive manufacturing in the prior art.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] An electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, the electrolytic corrosion solution is an aqueous solution of H2CrO4, and the mass fraction of H2CrO4 in the aqueous solution of H2CrO4 is 4% - 16%.

[0006] A further improvement of the present invention lies in:

[0007] Preferably, the mass fraction of H2CrO4 in the aqueous solution of H2CrO4 is 7% - 13%.

[0008] Preferably, the mass fraction of H2CrO4 in the aqueous solution of H2CrO4 is 10%.

[0009] A preparation method of the above-mentioned electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, add H2CrO4 powder into a container and then add H2O, and stir evenly to obtain the electrolytic corrosion solution.

[0010] A use method of the above-mentioned electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, including the following steps:

[0011] Step 1, add the electrolytic corrosion solution into the electrolytic cell;

[0012] Step 2, connect the cathode and anode in the electrolytic cell to a DC power supply, where the anode is a CoCrFeNiMn high-entropy alloy sample and the cathode is stainless steel;

[0013] Step 3, conduct electrolytic corrosion by energizing;

[0014] Step 4, after the electrolytic corrosion is completed, take out and clean the CoCrFeNiMn high-entropy alloy sample to complete the preparation of the CoCrFeNiMn high-entropy alloy sample.

[0015] Preferably, in Step 3, the voltage of the electrolytic corrosion is 5V and the current is 110mA.

[0016] Preferably, in Step 3, the electrolytic corrosion time is 45 - 60s.

[0017] Preferably, in Step 3, the temperature of the electrolytic corrosion solution is 15 - 40°C.

[0018] Preferably, in Step 4, ultrasonically clean the sample after electrolytic corrosion.

[0019] Preferably, in Step 4, the ultrasonic cleaning temperature is 30°C - 40°C and the time is 3min - 5min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention discloses an electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy. The raw material components of the electrolytic corrosion solution are H2CrO4 and H2O. For the CoCrFeNiMn high-entropy alloy prepared by additive manufacturing, due to the particularity of its alloy composition and preparation process, its tissue state is special. Using aqua regia or FeCl3 + HCl + H2O corrosion cannot obtain an ideal corrosion effect, which may be related to the segregation of Mn element at the cell crystal interface. The Mn element is more vulnerable to the erosion of Cl ions compared with other elements of the CoCrFeNiMn high-entropy alloy. The present invention finds that through this electrolytic solution, the cell crystal microstructure of the additive manufacturing CoCrFeNiMn high-entropy alloy can be effectively observed, an ideal corrosion effect can be obtained, and information such as the size and orientation of the cell crystals can be clearly observed.

[0022] Furthermore, it is verified that when the mass fraction of H2CrO4 in the H2CrO4 aqueous solution is 10%, the corrosion effect is the best and the sample after electrolytic corrosion is easier to observe.

[0023] The present invention also discloses a preparation method of an electrolytic corrosion solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, and the preparation process is simple and the raw materials are easy to obtain.

[0024] The present invention also discloses a method for using an electrolytic etching solution for additive manufacturing of CoCrFeNiMn high-entropy alloy. In this method, the electrolytic etching solution is placed in an electrolytic cell, and the prepared metallographic sample is put into the electrolytic etching solution. The additive manufacturing CoCrFeNiMn high-entropy alloy to be etched serves as the anode, and stainless steel serves as the cathode. A DC power supply is used to energize the cathode and the anode to electrolytically etch the additive manufacturing CoCrFeNiMn high-entropy alloy. The etched sample is put into a beaker filled with absolute ethanol for ultrasonic cleaning, and then observed under a scanning electron microscope. The present invention can effectively observe the cellular crystal microstructure of the additive manufacturing CoCrFeNiMn high-entropy alloy. This method is faster, more effective, more standardized in operation, and has stronger repeatability.

Description of the Drawings

[0025] Figure 1 Metallographic microstructure diagram (optical microscope OM) of the additive manufacturing CoCrFeNiMn high-entropy alloy corroded by aqua regia;

[0026] Figure 2 Scanning morphology diagram (field emission scanning electron microscope SEM) of the additive manufacturing CoCrFeNiMn high-entropy alloy corroded by aqua regia;

[0027] Figure 3 Metallographic microstructure diagram (OM) of the additive manufacturing CoCrFeNiMn high-entropy alloy (five main elements) corroded by 10% aqueous H2CrO4 solution in Example 1;

[0028] Figure 4 Scanning morphology diagram (SEM) of the additive manufacturing CoCrFeNiMn high-entropy alloy corroded by 10% aqueous H2CrO4 solution in Example 1;

[0029] Figure 5 Scanning morphology diagram (SEM) of the additive manufacturing CoCrFeNiMn high-entropy alloy corroded by 4% aqueous H2CrO4 solution in Example 2;

[0030] Figure 6 Scanning morphology diagram (SEM) of the additive manufacturing CoCrFeNiMn high-entropy alloy corroded by 7% aqueous H2CrO4 solution in Example 3;

[0031] Figure 7 Scanning morphology diagram (SEM) of the additive manufacturing CoCrFeNiMn high-entropy alloy corroded by 13% aqueous H2CrO4 solution in Example 4;

[0032] Figure 8Scanning morphology diagram (SEM) of the additively manufactured CoCrFeNiMn high-entropy alloy corroded by the 16% H2CrO4 aqueous solution of Example 5;

Detailed implementation manners

[0033] The present invention will be further described in detail below with reference to the accompanying drawings:

[0034] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; in addition, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0035] The present invention discloses an electrolytic corrosion solution for additively manufacturing CoCrFeNiMn high-entropy alloy and its preparation and use methods. The electrolytic solution is an aqueous solution of H2CrO4 with a mass fraction of 4-16%. The H2CrO4 aqueous solution is prepared from chromic acid. The specific preparation method is to first put H2CrO4 powder and then put H2O, and slowly stir with a glass rod until uniform. The use method of the electrolytic solution includes the following steps:

[0036] Step 1, put the uniformly mixed electrolytic corrosion solution in the electrolytic cell;

[0037] Step 2, place the additively manufactured CoCrFeNiMn high-entropy alloy in the electrolytic cell as the anode, use stainless steel as the cathode, and connect the cathode and the anode to a DC power supply through wires; the stainless steel is preferably 316L.

[0038] Step 3, energize the cathode and the anode through the DC power supply to electrolytically corrode the additively manufactured CoCrFeNiMn high-entropy alloy. The voltage of the electrolytic corrosion is 5V, the current is 110mA, the electrolytic corrosion duration is 45-60s, and the temperature of the electrolytic corrosion solution is 15-40°C;

[0039] Step 4, after the electrolytic corrosion ends, put the sample into a beaker filled with anhydrous ethanol for ultrasonic cleaning. The ultrasonic cleaning temperature is 30°C to 40°C, and the time is 3 min to 5 min to remove the electrolytic products remaining on the surface.

[0040] Step 5, dry the cleaned sample and place it in a scanning electron microscope for microstructure observation.

[0041] Sample preparation process:

[0042] (1) Selective laser melting to form a CoCrFeNiMn high-entropy alloy metallographic specimen of 10*10*10 mm;

[0043] (2) Grind and polish the metallographic block. Grinding is carried out successively on sandpapers of 240#, 400#, 600#, 800#, 1000#, 1200#, and 1500#. After grinding, rough polishing is carried out using W2.5μm diamond polishing fluid, and then fine polishing is carried out using W0.5μm diamond polishing fluid;

[0044] Comparative example

[0045] Use aqua regia corrosion solution to corrode the prepared selective laser melting formed metallographic specimen above for 3 - 5 s, quickly wash it with a large amount of clear water, then put it into a beaker filled with acetone for ultrasonic cleaning, and observe the microstructure under an optical microscope and a scanning electron microscope after drying. As Figure 1 and Figure 2 shown, it can be seen from the figure that the metallographic microstructure corrosion is uneven, the microstructure at the corners is prone to corrosion, the molten pool can be seen in some areas, macroscopically observed, the 10*10*10 mm specimen is corroded extremely unevenly, and it is found under the scanning electron microscope that the cellular crystal structure is corroded poorly, pitting corrosion occurs, and some features in the structure fall off.

[0046] Example 1

[0047] (1) Prepare the electrolytic corrosion solution. First, put 2 g of CrO3 powder, and then put 18 mL of H2O to prepare a solution of H2CO4 with a mass fraction of 10%. Slowly stir it evenly with a glass rod.

[0048] (2) Put the evenly mixed electrolytic corrosion solution into the electrolytic cell;

[0049] (3) Place the prepared CoCrFeNiMn high-entropy alloy formed by selective laser melting above in the electrolytic cell as the anode, use 316L stainless steel as the cathode, and connect the cathode and anode to a DC power supply through wires;

[0050] (4) Apply electric current to the cathode and anode through a DC power supply to electrolytically corrode the CoCrFeNiMn high-entropy alloy formed by selective laser melting. The voltage for electrolytic corrosion is 5V, the current is 110mA, the duration of electrolytic corrosion is 55s, and the temperature of the electrolytic corrosion solution is 26°C;

[0051] (5) After the electrolytic corrosion is completed, place the sample in a beaker filled with anhydrous ethanol for ultrasonic cleaning. The ultrasonic cleaning temperature is 35°C and the time is 5 minutes to remove the residual electrolytic products on the surface;

[0052] (6) Dry the cleaned sample and place it under an optical microscope and a field emission scanning electron microscope for microscopic structure observation. The scanning morphologies are as shown in Figure 3 and Figure 4 shown, and columnar crystals and cellular crystal structures can be clearly observed.

[0053] Example 2

[0054] (1) Add CrO3 powder to H2O to prepare a solution of H2CO4 with a mass fraction of 4%, and slowly stir it evenly with a glass rod.

[0055] Steps (2) - (6) are the same as in Example 1, and its scanning morphology is as shown in Figure 5 shown.

[0056] Example 3

[0057] (1) Add CrO3 powder to H2O to prepare a solution of H2CO4 with a mass fraction of 7%, and slowly stir it evenly with a glass rod.

[0058] Steps (2) - (6) are the same as in Example 1, and its scanning morphology is as shown in Figure 6 shown.

[0059] Example 4

[0060] (1) Add CrO3 powder to H2O to prepare a solution of H2CO4 with a mass fraction of 13%, and slowly stir it evenly with a glass rod.

[0061] Steps (2) - (6) are the same as in Example 1, and its scanning morphology is as shown in Figure 7 shown.

[0062] Example 5

[0063] (1) Add CrO3 powder to H2O to prepare a solution of H2CO4 with a mass fraction of 16%, and slowly stir it evenly with a glass rod.

[0064] Steps (2) - (6) are the same as in Example 1, and its scanning morphology is as shown in Figure 8 shown.

[0065] Comparing the corrosion results of Comparative Examples 2 - 5, it can be found that although columnar crystals and cellular crystals may be corroded under the same electrolytic corrosion parameters for all four electrolytes with different mass fractions, the corrosion degree of the 4% and 7% mass fractions is relatively light and the uniformity is poor, making it difficult to clearly observe the tissue characteristics of the CoCrFeNiMn high-entropy alloy; the corrosion of the 13% and 16% mass fractions is too heavy, resulting in pitting corrosion of the cellular crystal interface to varying degrees. Therefore, the 10% H2CO4 solution in Example 1 has the best use effect.

[0066] Example 6

[0067] (1) Prepare the electrolytic corrosion solution. First, put 2 g of CrO3 powder, and then add 18 mL of H2O to prepare a solution of H2CO4 with a mass fraction of 10%. Slowly stir it evenly with a glass rod.

[0068] (2) Put the uniformly mixed electrolytic corrosion solution into the electrolytic cell.

[0069] (3) Place the above-prepared CoCrFeNiMn high-entropy alloy formed by selective laser melting in the electrolytic cell as the anode, use 316L stainless steel as the cathode, and connect the cathode and anode to a DC power supply through wires.

[0070] (4) Pass an electric current through the cathode and anode through the DC power supply to electrolytically corrode the CoCrFeNiMn high-entropy alloy formed by selective laser melting. Among them, the voltage of the electrolytic corrosion is 5 V, the current is 110 mA, the electrolytic corrosion duration is 45 s, and the temperature of the electrolytic corrosion solution is 40 °C.

[0071] (5) After the electrolytic corrosion is completed, put the sample into a beaker filled with absolute ethanol for ultrasonic cleaning. The ultrasonic cleaning temperature is 35 °C and the time is 5 min to remove the residual electrolytic products on the surface to obtain the final sample.

[0072] Example 7

[0073] (1) Prepare the electrolytic corrosion solution. First, put 2 g of CrO3 powder, and then add 18 mL of H2O to prepare a solution of H2CO4 with a mass fraction of 10%. Slowly stir it evenly with a glass rod.

[0074] (2) Put the uniformly mixed electrolytic corrosion solution into the electrolytic cell.

[0075] (3) Place the above-prepared CoCrFeNiMn high-entropy alloy formed by selective laser melting in the electrolytic cell as the anode, use 316L stainless steel as the cathode, and connect the cathode and anode to a DC power supply through wires.

[0076] (4) Apply electric current to the cathode and anode through a DC power supply to electrolytically corrode the additively manufactured CoCrFeNiMn high-entropy alloy. The voltage for electrolytic corrosion is 5 V, the current is 110 mA, the duration of electrolytic corrosion is 45 s, and the temperature of the electrolytic corrosion solution is 40 °C.

[0077] (5) After the electrolytic corrosion is completed, place the sample in a beaker filled with anhydrous ethanol for ultrasonic cleaning at a temperature of 35 °C for 5 min to remove the residual electrolytic products on the surface and obtain the final sample.

[0078] Example 8

[0079] (1) Prepare the electrolytic corrosion solution by first adding 2 g of CrO3 powder and then 18 mL of H2O to form a 10% H2CO4 solution, and slowly stir it evenly with a glass rod.

[0080] (2) Pour the evenly mixed electrolytic corrosion solution into the electrolytic cell.

[0081] (3) Place the additively manufactured CoCrFeNiMn high-entropy alloy prepared above in the electrolytic cell as the anode, use 316L stainless steel as the cathode, and connect the cathode and anode to the DC power supply through wires.

[0082] (4) Apply electric current to the cathode and anode through a DC power supply to electrolytically corrode the additively manufactured CoCrFeNiMn high-entropy alloy. The voltage for electrolytic corrosion is 5 V, the current is 110 mA, the duration of electrolytic corrosion is 60 s, and the temperature of the electrolytic corrosion solution is 15 °C.

[0083] (5) After the electrolytic corrosion is completed, place the sample in a beaker filled with anhydrous ethanol for ultrasonic cleaning at a temperature of 35 °C for 5 min to remove the residual electrolytic products on the surface and obtain the final sample.

[0084] Example 9

[0085] (1) Prepare the electrolytic corrosion solution by first adding 2 g of CrO3 powder and then 18 mL of H2O to form a 10% H2CO4 solution, and slowly stir it evenly with a glass rod.

[0086] (2) Pour the evenly mixed electrolytic corrosion solution into the electrolytic cell.

[0087] (3) Place the additively manufactured CoCrFeNiMn high-entropy alloy prepared above in the electrolytic cell as the anode, use 316L stainless steel as the cathode, and connect the cathode and anode to the DC power supply through wires.

[0088] (4) Apply electric current to the cathode and anode through a DC power supply to electrolytically corrode the CoCrFeNiMn high-entropy alloy formed by selective laser melting. The voltage for electrolytic corrosion is 5V, the current is 110mA, the duration of electrolytic corrosion is 50s, and the temperature of the electrolytic corrosion solution is 30°C;

[0089] (5) After the electrolytic corrosion is completed, place the sample in a beaker filled with anhydrous ethanol for ultrasonic cleaning. The temperature of ultrasonic cleaning is 35°C and the time is 5 minutes to remove the residual electrolytic products on the surface and obtain the final sample.

[0090] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for using an electrolytic etching solution for additive manufacturing of CoCrFeNiMn high-entropy alloy, characterized in that, The electrolytic etching solution is an aqueous solution of H2CrO4, and the mass fraction of H2CrO4 in the aqueous solution of H2CrO4 is 4% - 16%; H2O is added to the container after adding H2CrO4 powder, and the electrolytic etching solution is prepared after stirring evenly; the usage method of the electrolytic etching solution includes the following steps: Step 1, adding the electrolytic etching solution into an electrolytic cell; Step 2, connecting the cathode and anode in the electrolytic cell to a DC power supply, the anode is a CoCrFeNiMn high-entropy alloy sample, and the cathode is stainless steel; Step 3, conducting electrolytic etching by energization; The voltage of the electrolytic etching is 5V and the current is 110mA; the electrolytic etching time is 45 - 60s; the temperature of the electrolytic etching solution is 15 - 40°C; Step 4, after the electrolytic etching is completed, taking out and cleaning the CoCrFeNiMn high-entropy alloy sample to complete the preparation of the CoCrFeNiMn high-entropy alloy sample.

2. The method for using an electrolytic etching solution for additive manufacturing of CoCrFeNiMn high-entropy alloy according to claim 1, characterized in that, In Step 4, the sample after electrolytic etching is cleaned by ultrasonic waves.

3. The method for using an electrolytic etching solution for additive manufacturing of CoCrFeNiMn high-entropy alloy according to claim 1, characterized in that, In Step 4, the ultrasonic cleaning temperature is 30°C - 40°C and the time is 3min - 5min.

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