Method for uniformly and controllably removing stress layers on surfaces of nickel-based single-crystal superalloy and precision casting of nickel-based single-crystal superalloy
By using specific chemical milling fluids and parameter conditions, the problem of surface stress layer in nickel-based single-crystal superalloys was solved, achieving uniform removal and suppression of recrystallization, thus improving the performance stability of the alloy.
Patent Information
- Application Number
- CN202511390630.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2025-12-12
AI Technical Summary
In the preparation of nickel-based single-crystal superalloys and their precision castings, the thin plastic deformation layer generated on the surface leads to residual stress, which causes recrystallization during subsequent solution heat treatment and use, affecting performance.
A chemical milling fluid containing a specific ratio of nitric acid, hydrochloric acid, hydrofluoric acid, water, dispersant, and corrosion inhibitor is used to perform chemical milling treatment on nickel-based single-crystal superalloys and their precision castings under specific temperature and time conditions to remove the surface stress layer.
Uniform and controllable removal of the surface stress layer inhibits recrystallization, avoids damage to the alloy matrix, and improves the stability of alloy performance.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of alloy processing technology, and in particular to a method for uniformly and controllably removing the stress layer from the surface of nickel-based single-crystal superalloys and their precision castings. Background Technology
[0002] Nickel-based single-crystal superalloys are the main materials for turbine blades of aero-engines and ground gas turbines. They are prepared by combining composition optimization and crystal selection technology with directional solidification technology to completely eliminate the transverse grain boundaries perpendicular to the grain growth direction and prepare single grains with
[001] preferred orientation growth.
[0003] Nickel-based single-crystal superalloys significantly improve the heat resistance of engine turbine blades. However, during the preparation of nickel-based single-crystal superalloys, due to inconsistent shrinkage between the alloy melt and the casting mold during casting, as well as processes such as shell / core removal, surface grinding, and machining, a very thin plastic deformation layer is formed on the surface of the nickel-based single-crystal superalloy and its precision castings (including the inner surface of hollow castings). Residual stress exists in this deformation layer, leading to recrystallization on the surface of the nickel-based single-crystal superalloy and its precision castings during subsequent solution heat treatment and actual use. This results in the formation of new transverse grain boundaries, causing a decline in the performance of the nickel-based single-crystal superalloy and its precision castings. Therefore, it is essential to avoid the formation of surface recrystallization on single-crystal superalloys and their precision castings. Summary of the Invention
[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for uniformly and controllably removing the stress layer on the surface of nickel-based single crystal superalloys and their precision castings. The processing method provided in this application can uniformly and controllably remove the stress layer on the surface of nickel-based single crystal superalloys and their precision castings without damaging the alloy matrix.
[0005] This application provides a method for uniformly and controllably removing the surface stress layer of nickel-based single-crystal superalloys and their precision castings, comprising the following steps:
[0006] Pretreatment of nickel-based single-crystal superalloys and their precision castings;
[0007] The pretreated nickel-based single-crystal superalloy and its precision castings are subjected to chemical milling treatment in a chemical milling fluid, which comprises: 30wt%–50wt% nitric acid; 1wt%–20wt% hydrochloric acid; 1wt%–2wt% hydrofluoric acid; and the balance being water.
[0008] Each 100mL of chemical milling fluid also includes 0.1g to 0.2g of dispersant and 0.2g to 0.4g of corrosion inhibitor;
[0009] The temperature of the chemical milling treatment is 40-80℃, and the time of the chemical milling treatment is 5-60 minutes.
[0010] In some specific implementations, the dispersant is sodium dodecyl sulfate.
[0011] In some specific implementations, the corrosion inhibitor is sodium benzoate.
[0012] In some specific implementations, the preprocessing includes:
[0013] Surface impurities are cleaned from the nickel-based single-crystal high-temperature alloy and its precision castings.
[0014] In some specific implementations, the chemical milling process is performed under water bath heating conditions.
[0015] Some specific implementations also include:
[0016] The nickel-based single-crystal superalloy and its precision castings after chemical milling were washed and dried.
[0017] In some specific implementations, the nickel-based single-crystal superalloy and its precision castings are plates or turbine rotor blades.
[0018] This application also provides a chemical milling fluid, comprising: 30wt% to 50wt% nitric acid; 1wt% to 20wt% hydrochloric acid; 1wt% to 2wt% hydrofluoric acid; and the balance being water;
[0019] Each 100mL of chemical milling fluid also contains 0.1g to 0.2g of dispersant and 0.2g to 0.4g of corrosion inhibitor.
[0020] In some specific implementations, the dispersant is sodium dodecyl sulfate; the corrosion inhibitor is sodium benzoate.
[0021] This application provides a method for processing nickel-based single-crystal superalloys and their precision castings, comprising the following steps: pre-treating the nickel-based single-crystal superalloys and their precision castings; subjecting the pre-treated nickel-based single-crystal superalloys and their precision castings to chemical milling treatment in a chemical milling fluid, wherein the chemical milling fluid comprises: 30wt%–50wt% nitric acid; 1wt%–20wt% hydrochloric acid; 1wt%–2wt% hydrofluoric acid; the balance being water; and each 100mL of the chemical milling fluid further comprises 0.1g–0.2g of dispersant and 0.2g–0.4g of corrosion inhibitor; the temperature of the chemical milling treatment is 40–80℃, and the time of the chemical milling treatment is 5min–60min. This application employs a specific chemical milling fluid to treat nickel-based single-crystal superalloys and their precision castings under specific parameter conditions. This process can uniformly and controllably remove the deformation stress layer generated on the surface of the nickel-based single-crystal superalloys and their precision castings during the preparation process. Furthermore, the chemical milling reaction is slow-release and controllable, which can effectively inhibit the nucleation of surface recrystallization of the nickel-based single-crystal superalloys and their precision castings during subsequent heat treatment and use, thus avoiding recrystallization. At the same time, it causes virtually no damage to the alloy matrix, and the method is simple to operate. Attached Figure Description
[0022] Figure 1 The surface morphology of the IC20 sample prepared in Example 1 of this application after only sandblasting;
[0023] Figure 2 The surface morphology of the IC20 sample prepared in Example 1 of this application after sandblasting and then chemical milling.
[0024] Figure 3 The surface morphology of the IC20 sample prepared for Comparative Example 1 of this application after sandblasting and subsequent chemical milling is shown. Detailed Implementation
[0025] This invention provides a method for uniformly and controllably removing the surface stress layer of nickel-based single-crystal superalloys and their precision castings. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. The method and application of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.
[0026] This application provides a method for uniformly and controllably removing the surface stress layer of nickel-based single-crystal superalloys and their precision castings, comprising the following steps:
[0027] Pretreatment of nickel-based single-crystal superalloys and their precision castings;
[0028] The pretreated nickel-based single-crystal superalloy and its precision castings are subjected to chemical milling treatment in a chemical milling fluid, which comprises: 30wt%–50wt% nitric acid; 1wt%–20wt% hydrochloric acid; 1wt%–2wt% hydrofluoric acid; and the balance being water.
[0029] Each 100ml of chemical milling fluid also contains 0.1g to 0.2g of dispersant and 0.2g to 0.4g of corrosion inhibitor;
[0030] The temperature of the chemical milling treatment is 40-80℃, and the time of the chemical milling treatment is 5-60 minutes.
[0031] This application first pre-treats nickel-based single-crystal superalloys and their precision castings. As mentioned above, nickel-based single-crystal superalloys are prepared by combining composition optimization and crystal selection techniques with directional solidification technology to completely eliminate transverse grain boundaries perpendicular to the grain growth direction, thus producing single grains with a preferred
[001] orientation. In some specific implementations, this is a Ni3Al-based single-crystal alloy, such as Ni3Al-based single-crystal alloy plates. Precision castings of nickel-based single-crystal superalloys refer to precision castings made from nickel-based single-crystal superalloys, such as plates, turbine rotor blades, etc. In some specific implementations, when the nickel-based single-crystal superalloy and its precision castings have a hollow inner cavity, the surface mentioned in this application includes both its outer surface and its inner surface, and this application has no special limitations on this.
[0032] This application first pre-treats the nickel-based single-crystal superalloy and its precision castings, for example, by cleaning surface impurities. After cleaning, it is chemically milled in a chemical milling fluid to uniformly and controllably remove the surface stress layer.
[0033] In some specific implementations, the chemical milling fluid includes 30wt%–50wt% nitric acid; 1wt%–20wt% hydrochloric acid; 1wt%–2wt% hydrofluoric acid; the balance being water; and 0.1g–0.2g of dispersant and 0.2g–0.4g of corrosion inhibitor per 100ml of chemical milling fluid. Nitric acid, hydrochloric acid, and hydrofluoric acid are used to corrode nickel-based single-crystal superalloys and their precision castings. The dispersant ensures that the chemical milling fluid acts uniformly on the surface and internal cavities during corrosion, avoiding uneven corrosion that could lead to localized over-corrosion and damage to the alloy matrix. The corrosion inhibitor allows the chemical milling fluid to act slowly and continuously on the surface and internal cavities of the nickel-based single-crystal superalloys and their precision castings, thus inhibiting corrosion and preventing over-corrosion of the alloy and its precision castings due to excessively rapid reaction caused by high initial solution concentration.
[0034] In some specific implementations, the chemical milling fluid comprises 34wt% to 49wt% nitric acid; 5wt% to 18wt% hydrochloric acid; 1.1wt% to 1.5wt% hydrofluoric acid; and the balance being water.
[0035] Each 100ml of chemical milling fluid also contains 0.11g to 0.18g of dispersant and 0.25g to 0.35g of corrosion inhibitor.
[0036] In some specific implementations, the dispersant includes, but is not limited to, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, stearic acid, sodium stearate, etc., and is preferably sodium dodecyl sulfate.
[0037] In some specific implementations, the corrosion inhibitor includes, but is not limited to, sodium benzoate, urea, thiourea, etc., and is preferably sodium benzoate.
[0038] Specifically, the chemical milling fluid provided in this application is prepared according to the following method:
[0039] It provides nitric acid with a concentration of 65wt% to 85wt%, hydrochloric acid with a concentration of 35wt% to 38wt%, and hydrofluoric acid with a concentration of 35wt% to 40wt%.
[0040] The above-mentioned nitric acid, hydrochloric acid, hydrofluoric acid, and water are mixed, wherein the volume of nitric acid is 25 vol%–35 vol%, the volume of hydrochloric acid is 5 vol%–15 vol%, the volume of hydrofluoric acid is 1 vol%–1.2 vol%, and the balance is water. After thorough mixing, 0.1 g–0.2 g of dispersant and 0.2 g–0.4 g of corrosion inhibitor are added to every 100 mL of solution to obtain the chemical milling fluid.
[0041] This application preferably involves completely immersing the nickel-based single-crystal superalloy and its precision castings in a chemical milling solution to remove the surface stress layer. In some specific implementations, the temperature of the chemical milling treatment is 40–80°C, preferably 45°C–75°C, more preferably 50°C–70°C, and the treatment time is 5 min–60 min, preferably 10 min–50 min, more preferably 15 min–45 min. In some specific implementations, the chemical milling treatment is performed under water bath heating conditions.
[0042] For chemical milling treatment, this application preferably involves washing and drying the chemically milled nickel-based single-crystal superalloy and its precision castings.
[0043] This application employs a specific chemical milling fluid to treat nickel-based single-crystal superalloys and their precision castings under specific parameter conditions. This process uniformly and controllably removes the deformation stress generated on the surface of the nickel-based single-crystal superalloys and their precision castings during the casting, sandblasting, grinding, and impact processes. This prevents surface recrystallization caused by surface stress, effectively treating the inner cavity surface of nickel-based single-crystal superalloy turbine blades with complex hollow cavities. This prevents recrystallization during subsequent heat treatment, effectively reducing the risk of blade failure due to recrystallization during use. Furthermore, the method provided in this application avoids over-corrosion and does not damage the alloy matrix.
[0044] The following embodiments further illustrate a method for uniformly and controllably removing the surface stress layer of nickel-based single-crystal superalloys and their precision castings provided in this application.
[0045] Example 1
[0046] Comparative tests were conducted on Ni3Al-based single-crystal alloy IC20 samples to remove the surface stress layer, following the steps outlined below:
[0047] (1) Ni3Al-based single crystal alloy IC20 test plates were prepared by spiral crystallization and directional solidification. 30mm×10mm×2mm samples were cut from the test plates by wire cutting, with the 30mm×10mm surface parallel to the single crystal growth direction. The 30mm×10mm surface was ground and polished. The polishing process was kept gentle to avoid the formation of a deformation stress layer. The polished samples were then subjected to sandblasting treatment with a sandblasting pressure of 0.5MPa and a sandblasting time of 4min.
[0048] (2) Measure 30 ml of 65 wt% nitric acid, 10 ml of 35 wt% hydrochloric acid, 1 ml of 35 wt% hydrofluoric acid, and 59 ml of deionized water using a graduated cylinder. Weigh 0.1 g of sodium dodecyl sulfate and 0.3 g of sodium benzoate using a precision balance.
[0049] (3) Prepare the chemical milling fluid in the corrosion tank: First, dissolve 0.1g sodium dodecyl sulfate and 0.3g sodium benzoate in deionized water, and then add nitric acid, hydrochloric acid and hydrofluoric acid respectively and mix evenly;
[0050] (4) Immerse the IC20 sample completely in the chemical milling solution. The chemical milling process is carried out by water bath heating, and the temperature of the chemical milling solution is maintained at 50℃ for 30 minutes.
[0051] (5) Remove the IC20 sample after chemical milling from the etching tank, wash it with clean water and then air dry it.
[0052] Comparative Example 1
[0053] Comparative tests were conducted on Ni3Al-based single-crystal alloy IC20 samples to remove the surface stress layer, following the steps outlined below:
[0054] (1) Ni3Al-based single crystal alloy IC20 test plates were prepared by spiral crystallization and directional solidification. 30mm×10mm×2mm samples were cut from the test plates by wire cutting, with the 30mm×10mm surface parallel to the single crystal growth direction. The 30mm×10mm surface was ground and polished. The polishing process was kept gentle to avoid the formation of a deformation stress layer. The polished samples were then subjected to sandblasting treatment with a sandblasting pressure of 0.5MPa and a sandblasting time of 4min.
[0055] (2) Use a graduated cylinder to measure 30 ml of 65 wt% nitric acid, 10 ml of 35 wt% hydrochloric acid, 1 ml of 35 wt% hydrofluoric acid, and 59 ml of deionized water.
[0056] (3) Prepare the chemical milling fluid in the corrosion tank: Add nitric acid, hydrochloric acid and hydrofluoric acid to deionized water and mix evenly;
[0057] (4) Immerse the IC20 sample completely in the chemical milling solution. The chemical milling process is carried out by water bath heating, and the temperature of the chemical milling solution is maintained at 50℃ for 30 minutes.
[0058] (5) Remove the IC20 sample after chemical milling from the etching tank, wash it with clean water and then air dry it.
[0059] The surface morphology of IC20 samples from Example 1 that underwent only sandblasting and those that underwent sandblasting followed by chemical milling, as well as the samples treated in Comparative Example 1, was observed. The results are shown in [reference needed]. Figure 1 , Figure 2 and Figure 3 , Figure 1 The surface morphology of the IC20 sample prepared in Example 1 of this application after only sandblasting. Figure 2 The surface morphology of the IC20 sample prepared in Example 1 of this application after sandblasting and subsequent chemical milling is shown. Figure 3 The surface morphology of the IC20 sample prepared in Comparative Example 1 of this application after sandblasting and subsequent chemical milling is shown. Figure 2 and Figure 3 The comparison shows that the method provided in this application can uniformly and controllably remove the deformed layer on the sample surface caused by sandblasting, without causing over-corrosion of the sample.
[0060] Example 2
[0061] The recrystallization suppression test of the third-generation nickel-based single-crystal superalloy DD10 turbine rotor blades was conducted according to the following steps:
[0062] (1) The third-generation nickel-based single crystal high-temperature alloy DD10 turbine rotor blade was prepared by spiral crystallization directional solidification. The shell and core of the blade were removed and the surface was pickled to remove the alkaline solution remaining on the blade surface during the removal of the shell and core and the oxide scale formed on the surface during the casting process.
[0063] (2) Measure 1500ml of 65wt% nitric acid, 500ml of 35wt% hydrochloric acid, 50ml of 35wt% hydrofluoric acid, and 2950ml of deionized water using a graduated cylinder. Weigh 5g of sodium dodecyl sulfate and 15g of sodium benzoate using a precision balance.
[0064] (3) Prepare the chemical milling fluid in the corrosion tank: First, dissolve 5g sodium dodecyl sulfate and 15g sodium benzoate in deionized water, then add nitric acid, hydrochloric acid and hydrofluoric acid respectively and mix evenly.
[0065] (4) The DD10 turbine rotor blades are completely immersed in the chemical milling fluid. The chemical milling process is carried out by water bath heating, and the temperature of the chemical milling fluid is maintained at 50℃. The chemical milling time is 45min.
[0066] (5) Remove the DD10 blades that have been chemically milled from the corrosion tank, wash them with clean water and then dry them;
[0067] (6) The DD10 blades were subjected to standard vacuum solution heat treatment;
[0068] (7) The DD10 blades after standard vacuum solution heat treatment were subjected to surface recrystallization corrosion. After inspection, it was found that no recrystallization structure was found on the surface of the DD10 turbine rotor blades.
[0069] The method provided in this application can effectively remove the deformation stress layer on the surface of nickel-based single-crystal superalloys, suppress the surface recrystallization nucleation of single-crystal superalloys under high-temperature conditions, and avoid recrystallization.
[0070] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for uniformly and controllably removing the surface stress layer of nickel-based single-crystal superalloys and their precision castings, comprising the following steps: Pretreatment of nickel-based single-crystal superalloys and their precision castings; The pretreated nickel-based single-crystal superalloy and its precision castings are subjected to chemical milling treatment in a chemical milling fluid, which comprises: 30wt%–50wt% nitric acid; 1wt%–20wt% hydrochloric acid; 1wt%–2wt% hydrofluoric acid; the balance being water; and each 100ml of chemical milling fluid also contains 0.1g–0.2g of dispersant and 0.2g–0.4g of corrosion inhibitor. The temperature of the chemical milling treatment is 40-80℃, and the time of the chemical milling treatment is 5-60 minutes.
2. The method according to claim 1, characterized in that, The dispersant is sodium dodecyl sulfate.
3. The method according to claim 1 or 2, characterized in that, The corrosion inhibitor is sodium benzoate.
4. The method according to claim 1, characterized in that, The preprocessing includes: Surface impurities are cleaned from the nickel-based single-crystal high-temperature alloy and its precision castings.
5. The method according to claim 1, characterized in that, The chemical milling process is performed under water bath heating conditions.
6. The method according to claim 1, characterized in that, Also includes: The nickel-based single-crystal superalloy and its precision castings after chemical milling were washed and dried.
7. The method according to claim 1, characterized in that, The nickel-based single-crystal superalloy and its precision castings are plates or turbine rotor blades.
8. A chemical milling fluid, characterized in that, include: 30wt%–50wt% nitric acid; 1wt%–20wt% hydrochloric acid; 1wt%–2wt% hydrofluoric acid; balance water; Each 100ml of chemical milling fluid also contains 0.1g to 0.2g of dispersant and 0.2g to 0.4g of corrosion inhibitor.
9. The chemical milling fluid according to claim 8, characterized in that, The dispersant is sodium dodecyl sulfate.
10. The chemical milling fluid according to claim 8 or 9, characterized in that, The corrosion inhibitor is sodium benzoate.