A method for promoting surface grain corrosion of cobalt-based alloy guide vanes

Abstract

This invention discloses a method for promoting surface grain corrosion of cobalt-based alloy guide vanes, applicable to the field of metal surface chemical treatment. The method includes the following steps: preparing a corrosion agent using CuSO4·5H2O, HCl, and water; removing dust and grease from the vane surface; visually inspecting the vane; immersing it in hot water at 40-60℃ for 5 minutes; dynamically corroding a mixture of nickel-based alloy material and cobalt-based alloy guide vanes; and inspecting the vanes after descaling, neutralization, cleaning, and drying. This invention utilizes a mixed corrosion process of nickel-based and cobalt-based alloys, resulting in mutually promoting corrosion, clearly distinguishable grain size, and the absence of pitting and intergranular corrosion. The corrosion effect is excellent, significantly shortening the corrosion time and improving production efficiency. It completely solves the problem of difficult corrosion of cobalt-based alloy guide vanes and provides a corrosion approach for other cobalt-based alloys.

Description

Technical Field

[0001] This invention relates to the field of metal surface chemical treatment technology, and in particular to a method for promoting surface grain corrosion of cobalt-based alloy guide vanes. Background Technology

[0002] Cobalt-based alloys possess strong oxidation and corrosion resistance, excellent resistance to thermal fatigue, good weldability, and high initial melting temperature, making them particularly suitable for manufacturing guide vanes for advanced aero-engines. FSX-414 is a typical example of a cobalt-based alloy. Since the size, uniformity, and shape of the original grains in cast cobalt-based alloys play a crucial role in their performance, the surface etching process in normal production is particularly important for clearly identifying the surface grain morphology and eliminating blades with columnar grains and uneven distribution. For surface etching of cobalt-based alloy parts, the FeCl3·6H2O+HCl+H2O etching formula is often used for mass production, but the etching effect is poor, resulting in unclear grains and affecting the judgment of results. In such cases, we usually re-polish and sandblast the unclear parts locally, and then continue etching until the grains are clear. However, this method is time-consuming, labor-intensive, inefficient, costly, and the etching effect is difficult to guarantee, making it unsuitable for mass production. Summary of the Invention

[0003] The main objective of this invention is to provide a method for promoting surface grain corrosion of cobalt-based alloy guide vanes, which can effectively solve the problems in the background art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for promoting surface grain corrosion of cobalt-based alloy guide vanes, comprising the following steps:

[0005] 1) Preparation of the etchant: The etchant includes CuSO4·5H2O, HCl and water, wherein the concentration of CuSO4·5H2O in the etchant is above 99% and the concentration of HCl in the etchant is above 31.5%;

[0006] 2) Leaf pretreatment: Remove dust and grease from the leaf surface, visually inspect the leaves, and then soak them in hot water at 40-60℃ for 5 minutes.

[0007] 3) Corrosion: After mixing the nickel-based alloy material with the cobalt-based alloy guide vane, immerse it in the corrosive agent, stir, and dynamically corrode for 5-8 minutes;

[0008] 4) Remove dust: Immerse the corroded blades in tap water and swing them back and forth for 30 seconds;

[0009] 5) Neutralization: Immerse the leaves in a sodium carbonate solution for 5 minutes to neutralize;

[0010] 6) Cleaning: Rinse the neutralized blades thoroughly with a pressurized water gun;

[0011] 7) Drying: Use compressed air to dry the blades;

[0012] 8) Inspection: Visually inspect whether the grains are clear, and perform metallographic examination to check for pitting corrosion and intergranular corrosion.

[0013] Preferably, in step 1), the contents of CuSO4·5H2O, HCl and water of the corrosive are 150g, 500ml and 90ml respectively, and can be increased or decreased proportionally.

[0014] Preferably, the tolerance of each component of the corrosive agent in step 1) is ±3%.

[0015] Preferably, the method for preparing the corrosive in step 1) is to add CuSO4·5H2O, HCl and water to a stirring container in sequence, stir and mix them evenly, and store them in a sealed plastic container for later use.

[0016] Preferably, in step 2), the dust on the blade surface is blown off with compressed air, and the grease on the blade surface is removed by cleaning with alcohol or acetone.

[0017] Preferably, in step 3), the weight ratio of nickel-based alloy material to cobalt-based alloy guide vane is not less than 1:2.

[0018] Preferably, in step 3), the nickel-based alloy material is nickel-based alloy IN738, and the cobalt-based alloy material is cobalt-based alloy FSX-414.

[0019] Compared with traditional technologies, the beneficial effects of this invention are as follows: The etchant formulation selected in this invention is applicable to the surface corrosion of most iron-based and nickel-based high-temperature alloys, with a wide range of applications, long service life, and low cost, making it suitable for corrosion processing in the mass production of multi-material parts; the use of mixed nickel-based and cobalt-based alloys for corrosion promotes mutual corrosion, resulting in clearly distinguishable grain size, no pitting corrosion or intergranular corrosion, and excellent corrosion effect, greatly shortening the corrosion time and improving production efficiency; it completely solves the problem of difficult corrosion of cobalt-based alloy guide vanes and also provides corrosion ideas for other cobalt-based alloys. Attached Figure Description

[0020] To more clearly illustrate the solutions in this invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the wiping and corrosion operation process of the present invention;

[0022] Figure 2 This is a schematic diagram of the two cobalt-based alloy FSX-414 blades in Scheme 1 before corrosion.

[0023] Figure 3 This is a schematic diagram of the two cobalt-based alloy FSX-414 blades after corrosion in Scheme 1;

[0024] Figure 4 This is a schematic diagram of the metallographic examination of a cobalt-based alloy FSX-414 blade after corrosion in Scheme 1.

[0025] Figure 5 This is a schematic diagram of the metallographic examination of another cobalt-based alloy FSX-414 blade after corrosion in Scheme 1;

[0026] Figure 6 This is a schematic diagram of the two cobalt-based alloy FSX-414 blades in Scheme 2 before corrosion.

[0027] Figure 7 This is a schematic diagram of the two cobalt-based alloy FSX-414 blades after corrosion in Scheme 2;

[0028] Figure 8 This is a schematic diagram of the metallographic examination of a cobalt-based alloy FSX-414 blade after corrosion in Scheme 2;

[0029] Figure 9 This is a schematic diagram of the metallographic examination of another cobalt-based alloy FSX-414 blade after corrosion in Scheme 2;

[0030] Figure 10 This is a schematic diagram of the two nickel-based alloy IN738 blades in Scheme 3 before corrosion.

[0031] Figure 11 This is a schematic diagram of the two nickel-based alloy IN738 blades after corrosion in Scheme 3;

[0032] Figure 12 This is a schematic diagram of the metallographic examination of a nickel-based alloy IN738 blade after corrosion in Scheme 3;

[0033] Figure 13 This is a schematic diagram of the metallographic examination of another nickel-based alloy IN738 blade after corrosion in Scheme 3;

[0034] Figure 14 This is a schematic diagram of the two cobalt-based alloy FSX-414 blades in Scheme 4 before corrosion.

[0035] Figure 15 This is a schematic diagram of the two cobalt-based alloy FSX-414 blades after corrosion in Scheme 4;

[0036] Figure 16 This is a schematic diagram of the metallographic examination of a cobalt-based alloy FSX-414 blade after corrosion in Scheme 4;

[0037] Figure 17 This is a schematic diagram of the metallographic examination of another cobalt-based alloy FSX-414 blade after corrosion in Scheme 4;

[0038] Figure 18 This is a schematic diagram of the nickel-based alloy IN738 blade before corrosion in Scheme 4;

[0039] Figure 19 This is a schematic diagram of the nickel-based alloy IN738 blade after corrosion in Scheme 4;

[0040] Figure 20 This is a schematic diagram of the metallographic examination of a nickel-based alloy IN738 blade after corrosion in Scheme 4.

[0041] Figure 21 This is a schematic diagram of the metallographic examination of the IN738 nickel-based alloy blade after corrosion, which is another option in Scheme 4. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0044] Option 1 involves selecting two scrapped cast cobalt-based alloy guide vanes, using traditional corrosion methods to perform surface corrosion on the vanes, and then inspecting the vanes: a) checking whether the grains are clear; b) dissecting the vanes and examining the dissected surfaces under an optical microscope to check for pitting corrosion and intergranular corrosion.

[0045] Option 2 involves sandblasting the two cobalt-based FSX-414 alloy guide vanes from Option 1 to remove the corrosion layer. The vanes are then surface-etched using a etching solution prepared with CuSO4·5H2O, HCl, and water. The vanes are then inspected: a) to check if the grains are clear; b) to dissect the vanes and examine the dissected surfaces under an optical microscope to check for pitting corrosion and intergranular corrosion.

[0046] Option 3: Select two solid solution nickel-based IN738 alloy blades and use a corrosion solution prepared with CuSO4·5H2O, HCl and water to perform surface corrosion on the blades. Then inspect the blades: a) Check whether the grains are clear; b) Dissect the blades and examine the dissected surface under an optical microscope to check for pitting corrosion and intergranular corrosion.

[0047] Option 4 involves sandblasting the two cobalt-based FSX-414 alloy guide vanes and the two solution-treated nickel-based IN738 alloy vanes to remove the corrosion layer. The vanes are then surface-etched using a etching solution prepared with CuSO4·5H2O, HCl, and water. The vanes are then inspected: a) to check if the grains are clear; b) to dissect the vanes and examine the dissected surfaces under an optical microscope to check for pitting corrosion and intergranular corrosion.

[0048] Perform surface etching on the guide vanes according to the four methods described above. If the surface grains of the vanes are clear and there is no pitting or intergranular corrosion after inspection, the method is considered feasible. Conversely, if any condition is not met, the method is considered infeasible.

[0049] The specific implementation plan is as follows:

[0050] Option 1: Traditional corrosion method

[0051] 1) Preparation of the etchant: The etchant consists of FeCl3·6H2O, HCl, and water. The contents of FeCl3·6H2O, HCl, and water in the etchant are 150g, 200ml, and 300ml, respectively, and can be increased or decreased proportionally. The tolerance of each component of the etchant is ±3%. The concentration of FeCl3·6H2O in the etchant is above 97%, and the concentration of HCl in the etchant is above 31.5%. The preparation method of the etchant is to add FeCl3·6H2O, HCl, and water to a stirring container in sequence, stir and mix evenly, and store in a sealed plastic container for later use. Take personal protective measures before preparation, and the order of addition must not be reversed.

[0052] 2) Blade pretreatment: Remove dust and grease from the blade surface. Dust is blown off with compressed air, and grease is cleaned with alcohol or acetone. Visually inspect the blades to ensure that there is no dust or grease on the blade surface. Soak in hot water at 40-60℃ for 5 minutes.

[0053] 3) Corrosion: After installing the cobalt-based alloy FSX-414 guide vane in the material frame, immerse it in the corrosive agent, stir, and dynamically corrode for 18-22 minutes;

[0054] 4) Remove dust: Immerse the corroded blades in tap water and swing them back and forth for 30 seconds;

[0055] 5) Neutralization: Immerse the leaves in a sodium carbonate solution for 5 minutes to neutralize;

[0056] 6) Cleaning: Rinse the neutralized blades thoroughly with a pressurized water gun;

[0057] 7) Drying: Use compressed air to dry the blades;

[0058] 8) Inspection: Visually inspect whether the grains are clear, and perform metallographic examination to check for pitting corrosion and intergranular corrosion.

[0059] Test results: Although the FSX-414 guide vanes showed no pitting corrosion or intergranular corrosion after corrosion ( Figure 4 and Figure 5 ), but the grains are not clearly visible ( Figure 2 and Figure 3 This does not meet the acceptance requirements.

[0060] Option 2: The corrosion method of the present invention, such as... Figure 1 As shown:

[0061] 1) Preparation of the etchant: The etchant consists of CuSO4·5H2O, HCl, and water. The contents of CuSO4·5H2O, HCl, and water in the etchant are 150g, 500ml, and 90ml, respectively, and can be increased or decreased proportionally. The tolerance of each component of the etchant is ±3%. The concentration of CuSO4·5H2O in the etchant is above 99%, and the concentration of HCl in the etchant is above 31.5%. The preparation method of the etchant is to add CuSO4·5H2O, HCl, and water to a stirring container in sequence, stir and mix evenly, and store in a sealed plastic container for later use. Take personal protective measures before preparation, and the order of addition must not be reversed.

[0062] 2) Blade pretreatment: Remove dust and grease from the blade surface. Dust is blown off with compressed air, and grease is cleaned with alcohol or acetone. Visually inspect the blades to ensure that there is no dust or grease on the blade surface. Soak in hot water at 40-60℃ for 5 minutes.

[0063] 3) Corrosion: Immerse the cobalt-based alloy FSX-414 guide vane in the etchant, stir, and dynamically corrode for 13-17 minutes;

[0064] 4) Remove dust: Immerse the corroded blades in tap water and swing them back and forth for 30 seconds;

[0065] 5) Neutralization: Immerse the leaves in a sodium carbonate solution for 5 minutes to neutralize;

[0066] 6) Cleaning: Rinse the neutralized blades thoroughly with a pressurized water gun;

[0067] 7) Drying: Use compressed air to dry the blades;

[0068] 8) Inspection: Visually inspect whether the grains are clear, and perform metallographic examination to check for pitting corrosion and intergranular corrosion.

[0069] Test results: Although the FSX-414 guide vanes showed no pitting corrosion or intergranular corrosion after corrosion ( Figure 8 and Figure 9 ), but no grains were observed ( Figure 6 and Figure 7 This does not meet the acceptance requirements.

[0070] Option 3: The corrosion method of the present invention, such as... Figure 1 As shown:

[0071] 1) Preparation of the etchant: The etchant consists of CuSO4·5H2O, HCl, and water. The contents of CuSO4·5H2O, HCl, and water in the etchant are 150g, 500ml, and 90ml, respectively, and can be increased or decreased proportionally. The tolerance of each component of the etchant is ±3%. The concentration of CuSO4·5H2O in the etchant is above 99%, and the concentration of HCl in the etchant is above 31.5%. The preparation method of the etchant is to add CuSO4·5H2O, HCl, and water to a stirring container in sequence, stir and mix evenly, and store in a sealed plastic container for later use. Take personal protective measures before preparation, and the order of addition must not be reversed.

[0072] 2) Blade pretreatment: Remove dust and grease from the blade surface. Dust is blown off with compressed air, and grease is cleaned with alcohol or acetone. Visually inspect the blades to ensure that there is no dust or grease on the blade surface. Soak in hot water at 40-60℃ for 5 minutes.

[0073] 3) Corrosion: Immerse the nickel-based alloy IN738 blade in the corrosive agent, stir, and perform dynamic corrosion for 13-17 minutes;

[0074] 4) Remove dust: Immerse the corroded blades in tap water and swing them back and forth for 30 seconds;

[0075] 5) Neutralization: Immerse the leaves in a sodium carbonate solution for 5 minutes to neutralize;

[0076] 6) Cleaning: Rinse the neutralized blades thoroughly with a pressurized water gun;

[0077] 7) Drying: Use compressed air to dry the blades;

[0078] 8) Inspection: Visually inspect whether the grains are clear, and perform metallographic examination to check for pitting corrosion and intergranular corrosion.

[0079] Test results: Although the nickel-based alloy IN738 blades showed no pitting corrosion or intergranular corrosion after corrosion ( Figure 12 and Figure 13 ), but the grains are not clearly visible ( Figure 10 and Figure 11 This does not meet the acceptance requirements.

[0080] Option 4: The corrosion method of the present invention, such as... Figure 1 As shown:

[0081] 1) Preparation of the etchant: The etchant consists of CuSO4·5H2O, HCl, and water. The contents of CuSO4·5H2O, HCl, and water in the etchant are 150g, 500ml, and 90ml, respectively, and can be increased or decreased proportionally. The tolerance of each component of the etchant is ±3%. The concentration of CuSO4·5H2O in the etchant is above 99%, and the concentration of HCl in the etchant is above 31.5%. The preparation method of the etchant is to add CuSO4·5H2O, HCl, and water to a stirring container in sequence, stir and mix evenly, and store in a sealed plastic container for later use. Take personal protective measures before preparation, and the order of addition must not be reversed.

[0082] 2) Blade pretreatment: Remove dust and grease from the blade surface. Dust is blown off with compressed air, and grease is cleaned with alcohol or acetone. Visually inspect the blades to ensure that there is no dust or grease on the blade surface. Soak in hot water at 40-60℃ for 5 minutes.

[0083] 3) Corrosion: Mix the nickel-based alloy IN738 blades and the cobalt-based alloy FSX-414 guide blades in the same material frame. The weight ratio of the nickel-based alloy blades to the cobalt-based alloy guide blades should not be less than 1:2. Then immerse the material frame in the corrosive agent, stir, and perform dynamic corrosion for 5-8 minutes.

[0084] 4) Remove dust: Immerse the corroded blades in tap water and swing them back and forth for 30 seconds;

[0085] 5) Neutralization: Immerse the leaves in a sodium carbonate solution for 5 minutes to neutralize;

[0086] 6) Cleaning: Rinse the neutralized blades thoroughly with a pressurized water gun;

[0087] 7) Drying: Use compressed air to dry the blades;

[0088] 8) Inspection: Visually inspect whether the grains are clear, and perform metallographic examination to check for pitting corrosion and intergranular corrosion.

[0089] Test results: The grains of the FSX-414 guide vane are clear after corrosion. Figure 14 and Figure 15 No pitting corrosion or intergranular corrosion ( Figure 16 and Figure 17 The IN738 guide vane has clear grain structure, meeting the acceptance requirements. Figure 18 and Figure 19No pitting corrosion or intergranular corrosion ( Figure 20 and Figure 21 The results meet the acceptance requirements. The two materials effectively promote each other's corrosion.

[0090] Comparing the test results of Scheme 1, Scheme 2, Scheme 3, and Scheme 4 above, we can see that:

[0091] Traditional FeCl3·6H2O+HCl+H2O corrosion formulations are insufficient for corroding cobalt-based alloy parts. Even with extended corrosion times, the required clear grain structure cannot be achieved. While CuSO4·5H2O+HCl+H2O corrosion formulations can achieve no pitting or intergranular corrosion when used alone to corrode nickel-based alloy IN738 blades and cobalt-based alloy FSX-414 guide blades, the time required for individual corrosion is long, and the grain structure remains unclear after corrosion. In Scheme Four, nickel-based alloy IN738 blades and cobalt-based alloy FSX-414 guide blades are mixed at a weight ratio of at least 1:2 before corrosion. This results in shorter corrosion times, clear grain structure after corrosion for both types of blades, and the absence of pitting and intergranular corrosion. The nickel-based alloy IN738 blades and cobalt-based alloy FSX-414 guide blades achieve a mutually reinforcing corrosion effect.

[0092] Compared with Scheme 1, Scheme 2, and Scheme 3, the corrosion method of Scheme 4 has the following advantages: (1) The CuSO4·5H2O+HCl+H2O corrosion formula is suitable for the surface corrosion of most iron-based and nickel-based high-temperature alloys. It has a wide range of applications, a long service life, and low cost, making it suitable for corrosion processing of multi-material parts in batch production; (2) More importantly, the use of mixed IN738 and FSX-414 materials for corrosion promotes each other, resulting in a short corrosion time, good corrosion effect, clear grain size, and no pitting or intergranular corrosion. This completely solves the problem of difficult corrosion of cobalt-based alloy FSX-414 guide vanes and provides corrosion ideas for other cobalt-based alloys. In addition, the mixed nickel-based alloy IN738 material can also achieve a clear grain corrosion effect, and metallographic detection shows no pitting or intergranular corrosion, truly achieving a mutually promoting corrosion effect.

[0093] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A method for promoting surface grain corrosion of cobalt-based alloy guide vanes, characterized in that: Includes the following steps: 1) Preparation of the etchant: The etchant includes CuSO4·5H2O, HCl and water. The concentration of CuSO4·5H2O in the etchant is above 99%, the concentration of HCl in the etchant is above 31.5%, and the contents of CuSO4·5H2O, HCl and water in the etchant are 150g, 500ml and 90ml respectively, and can be increased or decreased proportionally. 2) Leaf pretreatment: Remove dust and grease from the leaf surface, visually inspect the leaves, and then soak them in hot water at 40-60℃ for 5 minutes. 3) Corrosion: After mixing the nickel-based alloy material with the cobalt-based alloy guide vane, immerse it in the corrosive agent, stir, and dynamically corrode for 5-8 minutes; 4) Remove dust: Immerse the corroded blades in tap water and swing them back and forth for 30 seconds; 5) Neutralization: Immerse the leaves in a sodium carbonate solution for 5 minutes to neutralize; 6) Cleaning: Rinse the neutralized blades thoroughly with a pressurized water gun; 7) Drying: Use compressed air to dry the blades; 8) Inspection: Visually inspect whether the grains are clear, and perform metallographic examination to check for pitting corrosion and intergranular corrosion.

2. The method for promoting surface grain corrosion of cobalt-based alloy guide vanes according to claim 1, characterized in that: The tolerance of each component of the corrosive agent in step 1) is ±3%.

3. The method for promoting surface grain corrosion of cobalt-based alloy guide vanes according to claim 1, characterized in that: The method for preparing the corrosive in step 1) is to add CuSO4·5H2O, HCl and water to a stirring container in sequence, stir and mix them evenly, and store them in a sealed plastic container for later use.

4. The method for promoting surface grain corrosion of cobalt-based alloy guide vanes according to claim 1, characterized in that: In step 2), the dust on the blade surface is blown off with compressed air, and the grease on the blade surface is cleaned with alcohol or acetone.

5. The method for promoting surface grain corrosion of cobalt-based alloy guide vanes according to claim 1, characterized in that: In step 3), the weight ratio of nickel-based alloy material to cobalt-based alloy guide vane shall not be less than 1:

2.

6. The method for promoting surface grain corrosion of cobalt-based alloy guide vanes according to claim 1, characterized in that: In step 3), the nickel-based alloy material is nickel-based alloy IN738, and the cobalt-based alloy material is cobalt-based alloy FSX-414.

Images