Adhesive layer material resistant to molten salt thermal corrosion and preparation method thereof

Abstract

The present invention discloses a bonding layer material resistant to molten salt hot corrosion and a method for preparing the same. The material is an AlCoCrNiZr high-entropy alloy. The alloy contains relatively high levels of Zr, Al, and Cr, all of which are uniformly dispersed throughout the alloy. These Zr, Al, and Cr are uniformly consumed during oxidation and hot corrosion, forming a mixed oxide layer of Zr2O3, Al2O3, and Cr2O3 that is highly resistant to molten salts and can resist hot corrosion from sulfates or mixed sulfate and chloride salts.

Description

Technical Field

[0001] The present invention relates to the technical field of bonding layer materials, and in particular to a bonding layer material resistant to molten salt thermal corrosion and a preparation method thereof. Background Art

[0002] Thermal barrier coatings (TBCs) are primarily used in the hot-end components of gas turbines, providing thermal protection for turbine blades or the high-temperature alloys in the combustion chamber substrate. TBCs typically have a two-layer structure: an outer ceramic layer for thermal insulation and an inner bond layer for oxidative corrosion resistance. The bond layer offers excellent resistance to high-temperature oxidative corrosion. The dense alumina film formed after high-temperature oxidation slows further oxidation of the bond layer and the high-temperature alloy, thereby extending the service life of the component.

[0003] MCrAlY (M=Ni, Co, or Ni+Co) is a mainstream bond coat material. Its composition is independent of high-temperature alloys, allowing for flexible adjustment based on the service environment. While the Co, Cr, and Al in traditional NiCoCrAlY contribute to its hot corrosion resistance, the oxide film still dissolves and delaminates in molten salt hot corrosion environments, hindering long-term stable service under extremely harsh conditions. This makes it difficult to meet the higher requirements for bond coat materials in next-generation aircraft engine thermal barrier coatings. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a bonding layer material resistant to molten salt thermal corrosion and a preparation method thereof, so as to improve the thermal corrosion resistance of the bonding layer.

[0005] In order to solve the above technical problems, an embodiment of the present invention proposes a bonding layer material that is resistant to molten salt thermal corrosion, and the material is an AlCoCrNiZr high entropy alloy.

[0006] Furthermore, the alloy includes the following elements in atomic percentages:

[0007] Al 17~23 at.%;

[0008] Co 17~23 at.%;

[0009] Cr 17~23 at.%;

[0010] Zr 17~23 at.%;

[0011] Ni remainder;

[0012] The alloy has a eutectic structure and includes 2-3 phases.

[0013] Furthermore, the alloy includes the following elements in atomic percentages:

[0014] Al 20~23 at.%;

[0015] Co 18~20 at.%;

[0016] Cr 20~23 at.%;

[0017] Zr 19~20 at.%;

[0018] Ni remainder;

[0019] The alloy has a eutectic structure and includes 2-3 phases.

[0020] Furthermore, the alloy has a NiCoAlZr-rich phase as a matrix and a Cr-rich phase as a precipitated phase in the eutectic.

[0021] Furthermore, the alloy contains a CoZr-rich phase and appears in a eutectic structure similar to the NiCoAlZr+Cr eutectic.

[0022] Accordingly, an embodiment of the present invention further provides a method for preparing a bonding layer material resistant to molten salt thermal corrosion, comprising:

[0023] Step 1: Convert the atomic ratio into a mass ratio, weigh and mix the raw materials, and then melt and solidify them in sequence to obtain a primary eutectic alloy;

[0024] Step 2: Repeatedly melting and solidifying the primary eutectic alloy to obtain an AlCoCrNiZr high entropy alloy.

[0025] Furthermore, the mixing is performed by laying the active element raw material, Al raw material, Ni raw material, Co raw material, Cr raw material and Zr raw material in order from bottom to top.

[0026] Furthermore, the smelting is carried out under a protective atmosphere; the smelting temperature is 1500-1700°C.

[0027] Furthermore, the process includes placing a deoxidizer in the smelting equipment before smelting; the deoxidizer includes titanium blocks or titanium sheets.

[0028] Furthermore, in step 2, the number of repetitions is 4 to 5 times.

[0029] The beneficial effects of the present invention are as follows: the alloy of the present invention contains relatively high contents of Zr, Al and Cr, which are uniformly dispersed in the alloy and can be uniformly consumed during oxidation and thermal corrosion to form a mixed oxide layer of Zr2O3, Al2O3 and Cr2O3 that has extremely high resistance to molten salts and can resist thermal corrosion by sulfate or a mixture of sulfate and chloride salts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1This is a scanning electron microscope backscattered electron image of the alloy prepared in Example 1 of the present invention.

[0031] Figure 2 This is a cross-sectional morphology of the AlCoCrAlZr sample prepared in Example 1 of the present invention after hot corrosion for 240 hours.

[0032] Figure 3 This is a cross-sectional morphology of the NiCoCrAlYHf comparison sample prepared in Example 1 of the present invention after hot corrosion for 240 hours.

[0033] Figure 4 1 is the corrosion weight loss curve of the AlCoCrNiZr high entropy alloy and the NiCoCrAlYHf comparison sample in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] It should be noted that, unless there is a conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention is further described in detail below with reference to the drawings and specific embodiments.

[0035] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back, etc.), they are only used to explain the relative position relationship and movement status of the various components under a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0036] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0037] The bonding layer material for resisting molten salt hot corrosion in the embodiment of the present invention is AlCoCrNiZr high entropy alloy. The AlCoCrNiZr high entropy alloy includes the following elements in atomic percentages:

[0038] Al 17~23 at.%;

[0039] Co 17~23 at.%;

[0040] Cr 17~23 at.%;

[0041] Zr 17~23 at.%;

[0042] Ni remainder;

[0043] The alloy has a eutectic structure and includes a NiCoAlZr phase and a Cr-rich phase.

[0044] In the present invention, the AlCoCrNiZr high entropy alloy comprises 17-23 at.% Al, preferably 20-23 at.% Al, in terms of atomic percentage content;

[0045] In the present invention, the AlCoCrNiZr high entropy alloy comprises 17-23 at.% Co, preferably 18-20 at.%, in terms of atomic percentage.

[0046] In the present invention, the AlCoCrNiZr high entropy alloy includes 17-23 at.% Cr, preferably 20-23 at.% Cr, in terms of atomic percentage. In the present invention, the Cr can improve the hot corrosion resistance of the eutectic alloy.

[0047] In the present invention, the AlCoCrNiZr high-entropy alloy includes 17 to 23 at.% Zr, preferably 17 to 20 at.%, in terms of atomic percentage. Generally, adding chromium to an alloy improves the hot corrosion resistance of the alloy. However, in the present invention, a relatively high content of Zr is added to the eutectic alloy. The ZrO2 generated by oxidation has good resistance in sodium sulfate and sodium chloride, thereby further improving the hot corrosion resistance of the eutectic alloy.

[0048] In the present invention, the AlCoCrNiZr high entropy alloy further includes a balance of Ni in terms of atomic percentage.

[0049] In the present invention, the eutectic alloy has a uniform and fine two-phase structure that is stable at high temperatures. The micron-scale rod-shaped eutectic structure promotes the uniform distribution of alloy elements, allowing Al, Cr and Zr to exert their respective elemental properties and improve the hot corrosion resistance of the alloy.

[0050] The eutectic alloy provided by the present invention does not basically peel off under the hot corrosion condition of Na2SO4+25 wt% NaCl mixed salt coated at 900°C, only a small amount of spinel phase is generated on the outermost surface, and the oxide film is a complete and uniform mixed oxide of Al, Cr and Zr.

[0051] The preparation method of the bonding layer material resistant to molten salt thermal corrosion of the present invention comprises:

[0052] Step 1: Mix the raw materials according to the atomic ratio and then melt and solidify them in sequence to obtain a primary eutectic alloy;

[0053] Step 2: Repeatedly melting and solidifying the primary eutectic alloy to obtain the AlCoCrNiZr high entropy alloy.

[0054] The present invention combines raw materials in atomic ratios, then sequentially melts and solidifies them to produce a primary eutectic alloy. In the present invention, the raw materials are preferably metals of the corresponding elements, and the purity of the metals is preferably independently 99.5% or higher, more preferably 99.6% to 99.9%. In the present invention, the raw materials of each element in the AlCoCrNiZr high-entropy alloy are independently preferably particles, and the particle size of the particles is preferably independently 2 to 5 mm, more preferably 3 to 4 mm.

[0055] In the present invention, the mixing preferably further includes: washing and drying the raw materials in sequence. In the present invention, the washing preferably includes a first ultrasonic washing and a second ultrasonic washing performed in sequence. In the present invention, the solvent for the first ultrasonic washing is preferably water, and the water is preferably deionized water; the solvent for the second ultrasonic washing is preferably acetone. In the present invention, the power of the first ultrasonic washing and the second ultrasonic washing is independently preferably greater than 100W; the time of the first ultrasonic washing and the second ultrasonic washing is independently preferably 8~12min, more preferably 10~11min. In the present invention, the drying is preferably oven drying; the drying temperature is preferably 50~100℃, more preferably 60~80℃; the drying time is preferably 10~40min, more preferably 20~30min.

[0056] In the present invention, the smelting process preferably includes placing a deoxidizer in the smelting equipment before smelting; the deoxidizer preferably comprises a titanium block or sheet, more preferably a titanium sheet. In the present invention, the deoxidizer is preferably placed in a reserved crucible in the smelting equipment to facilitate absorption of residual oxygen in the protective atmosphere after melting, thereby reducing oxidation during the alloy smelting process. In the present invention, the deoxidizer is preferably melted for 3-4 minutes. The present invention does not specifically limit the amount of the deoxidizer used, as long as it can remove residual oxygen in the protective atmosphere. The present invention has no special requirements for the smelting equipment; conventional smelting equipment can be used. In an embodiment of the present invention, the smelting equipment is a smelting furnace.

[0057] In the present invention, the melting temperature is preferably 1500-1700°C, more preferably 1550-1650°C. In the present invention, the melting is preferably carried out under a protective atmosphere; the protective atmosphere preferably includes argon. In the present invention, the melting is preferably non-consumable vacuum arc melting. In the embodiment of the present invention, the specific method of forming the protective atmosphere is: evacuating the arc melting furnace and then filling it with a protective gas; the vacuum degree of the evacuation is 3×10 -3 ~5×10 -3 After the protective gas is filled, the pressure is 0-100 Pa. In the present invention, the current of the non-consumable vacuum arc melting is preferably 58-62 A, more preferably 60 A.

[0058] In the present invention, after the raw materials are melted, stirring is preferably performed, preferably by electromagnetic stirring; the electromagnetic stirring time is preferably 40 to 80 seconds, more preferably 50 to 60 seconds. In the present invention, the raw materials are uniformly mixed under the action of electromagnetic stirring. In the present invention, the melting time is the sum of the melting time and the stirring time.

[0059] In the present invention, the solidification is preferably carried out in a water-cooled copper crucible. The present invention has no special requirements for the solidification, and conventional means in the art can be used.

[0060] After obtaining a primary eutectic alloy, the present invention repeatedly melts and solidifies the primary eutectic alloy to obtain the eutectic alloy. In the present invention, the solid obtained from the previous solidification is preferably flipped before the repeated melting and solidification, preferably using a robot. In the present invention, the number of repetitions is preferably 3 to 6, more preferably 4 to 5.

[0061] The bonding layer material resistant to molten salt thermal corrosion provided by the present invention has excellent thermal corrosion resistance as a bonding layer material. Example 1

[0062] Aluminum particles, cobalt particles, chromium particles, nickel particles, platinum particles with a purity of 99.9% and an average particle size of 3 mm, yttrium particles with a purity of 99.9% and an average particle size of 2 mm, and hafnium wire with a purity of 99.9% were ultrasonically cleaned for 10 minutes using deionized water as a solvent at a power of 120 W, and then ultrasonically cleaned for 10 minutes using acetone as a solvent at a power of 120 W; dried at 80°C for 20 minutes and then set aside;

[0063] Al: 9.4 g (accounting for 20 at.% of the atomic content of AlCoCrNiZr high entropy alloy), Ni: 20.4 g (accounting for 20 at.% of the atomic content of AlCoCrNiZr high entropy alloy), Co: 20.5 g (accounting for 20 at.% of the atomic content of AlCoCrNiZr high entropy alloy), Cr: 18.1 g (accounting for 20 at.% of the atomic content of AlCoCrNiZr high entropy alloy), Zr: 31.7 g (accounting for 20 at.% of the atomic content of AlCoCrNiZr high entropy alloy) are placed in the arc melting furnace in order from bottom to top; the titanium sheet is placed in the crucible reserved in the melting furnace and the vacuum arc melting furnace is filled with vacuum to 3×10 -3Pa, filled with argon to 5 Pa; arc-melted titanium sheet for 3 minutes to absorb residual oxygen in the protective atmosphere; under argon protection, non-consumable vacuum arc melting was carried out at a current of 60A and a temperature of 1600℃ for 1 minute. After the raw materials were fully melted, electromagnetic stirring was turned on and maintained for 60 seconds. After the melt was solidified in a water-cooled copper crucible, the ingot was flipped over by a robot, and the melting and solidification were repeated 5 times to obtain 100g eutectic AlCoCrNiZr high-entropy alloy button ingot.

[0064] The molten salt hot corrosion resistance of the bonding layer material resistant to molten salt hot corrosion prepared in Example 1 was tested according to the following steps:

[0065] (1) The eutectic high entropy alloy in Example 1 was cut into test pieces of 10 mm × 10 mm × 2 mm, and polished with 240#, 600#, and 1000# sandpaper in sequence. The pieces were then ultrasonically cleaned with deionized water and acetone for 10 min, and then dried at 80°C for 20 min.

[0066] (2) Referring to the main element ratio of commercial NiCoCrAlYHf (Ni: 48g, Co: 23g, Cr: 17g, Al: 12g), and co-doping with Y and Hf active elements (Y: 0.09g, Hf: 0.18g) to melt the alloy ingot as a Zr-free comparison reference sample, and prepare the material test piece according to the same steps as NiCoCrAlZr in (1);

[0067] (3) The surfaces of the AlCoCrNiZr specimens in (1) and the NiCoCrAlYHf specimens in (2) were coated with 2.0 mg ± 0.1 mg / cm2 of a mixed salt of Na2SO4 + 25 wt% NaCl, and placed directly in a muffle furnace. The thermal corrosion behavior test was conducted in an atmospheric environment at 900 °C. The samples were taken out every 20 hours, cleaned with plasma water, weighed, and re-coated with the mixed salt for the next thermal corrosion test cycle. The experimental results are shown in Figure 4 .

[0068] Comparing the corrosion weight gain curves of the NiCoCrAZr high-entropy alloy of the present invention and the commercial NiCoCrAl alloy, the commercial NiCoCrAl alloy begins to spall and lose weight from the beginning of corrosion, and eventually fails due to catastrophic corrosion; while the alloy proposed by the present invention only experiences corrosion weight gain without spalling or alloy failure.

[0069] The cross section of the sample after 240 h of hot corrosion was observed using an electron microscope. Figure 1 This is the scanning electron microscope backscattered electron image of the alloy prepared in Example 1. Figure 2 It is NiCoCrAlZr alloy, the corrosion depth is 50 microns, and the surface is a dense oxide film. Figure 3The NiCoCrAlYHf alloy sample has a corrosion depth of about 200 microns and no complete protective oxide film exists on the surface, indicating that the eutectic alloy prepared in Example 1 exhibits excellent hot corrosion resistance and spalling resistance.

[0070] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A bonding layer material resistant to molten salt thermal corrosion, characterized in that: The bonding layer material is AlCoCrNiZr high entropy alloy; The high entropy alloy includes the following elements in atomic percentages: Al 17~23 at.%; Co 17~23 at.%; Cr 17~23 at.%; Zr 17~23 at.%; Ni remainder; The high entropy alloy has a eutectic structure and includes 2-3 phases.

2. The bonding layer material resistant to molten salt thermal corrosion according to claim 1, characterized in that: The high entropy alloy includes the following elements in atomic percentages: Al 20~23 at.%; Co 18~20 at.%; Cr 20~23 at.%; Zr 19~20 at.%; Ni remainder; The high entropy alloy has a eutectic structure and includes 2-3 phases.

3. The bonding layer material resistant to molten salt thermal corrosion according to claim 2, characterized in that: The high entropy alloy has a NiCoAlZr-rich phase as a matrix, and a Cr-rich phase as a precipitated phase in the eutectic.

4. The bonding layer material resistant to molten salt thermal corrosion according to claim 3, characterized in that: The high entropy alloy includes a CoZr-rich phase and appears in a eutectic structure with a NiCoAlZr-rich phase+Cr-rich phase eutectic.

5. A method for preparing a bonding layer material resistant to molten salt thermal corrosion according to claim 2, characterized in that: include: Step 1: Convert the atomic ratio into a mass ratio, weigh and mix the raw materials, and then melt and solidify them in sequence to obtain a primary eutectic alloy; Step 2: Repeatedly melting and solidifying the primary eutectic alloy to obtain an AlCoCrNiZr high entropy alloy.

6. The method for preparing the bonding layer material resistant to molten salt thermal corrosion according to claim 5, characterized in that: The mixing is performed by laying Al raw material, Ni raw material, Co raw material, Cr raw material and Zr raw material in order from bottom to top.

7. The method for preparing a bonding layer material resistant to molten salt thermal corrosion according to claim 5, characterized in that: The smelting is carried out under a protective atmosphere; the smelting temperature is 1500-1700°C.

8. The method for preparing a bonding layer material resistant to molten salt thermal corrosion according to claim 5, characterized in that: The method further includes placing a deoxidizer in the smelting equipment before smelting; the deoxidizer includes titanium blocks or titanium sheets.

9. The method for preparing a bonding layer material resistant to molten salt thermal corrosion according to claim 5, characterized in that: In step 2, repeat 4 to 5 times.

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