A Ni-Al / MCrAlY coating for improving coating / alloy substrate interface stability and preparation method thereof

Abstract

The present invention discloses a Ni‑Al / MCrAlY coating for improving the interface stability of the coating / alloy substrate and a preparation method thereof, belonging to the technical field of high-temperature protective coatings. Specifically, a Ni‑Al coating is first deposited on a high-temperature alloy substrate, and then an MCrAlY coating is deposited, and finally the coating components are evenly diffused by vacuum annealing. Compared with a single MCrAlY coating, the introduction of a Ni‑Al coating can effectively improve the stability of the interface between the coating and the Ni-based high-temperature alloy (especially for single-crystal high-temperature alloys), thereby reducing the deterioration of the mechanical properties of the alloy substrate caused by the coating and extending the service life of the alloy substrate. The method for preparing a coating for improving the interface stability of the coating and the Ni-based high-temperature alloy involved in the present invention has a simple process and good repeatability, and is easy to achieve industrial promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature protective coatings, and in particular to a Ni-Al / MCrAlY coating capable of improving the stability of a coating / alloy substrate interface and a preparation method thereof. Technical Background

[0002] Superalloys have excellent high-temperature mechanical properties and are widely used as materials for key hot-end components in aircraft engines and gas turbines. Over the past few decades, superalloys have evolved from cast polycrystalline, directional solidification to single crystal, and their high-temperature mechanical properties have been significantly improved, but this has come at the expense of resistance to high-temperature oxidation and hot corrosion. Due to the low Al / Cr content in superalloys, a continuous and dense oxide film cannot form to resist the attacks of high-temperature oxidation and hot corrosion. In order to balance the mechanical properties, high-temperature oxidation resistance, and hot corrosion resistance of superalloys under harsh service conditions, the most effective way is to apply a high-temperature protective coating to the surface of the superalloy.

[0003] MCrAlY coatings offer excellent resistance to high-temperature oxidation and hot corrosion, and their composition and thickness can be flexibly controlled. They are often applied to critical hot-end components of aircraft engines and gas turbines, serving as a bond coat for thermal barrier coatings or as a standalone high-temperature protective coating. During high-temperature service, MCrAlY coatings and Ni-based superalloys experience significant interdiffusion due to the chemical composition gradient, reducing the stability of the coating / alloy interface. Especially for single-crystal superalloys, this interdiffusion can disrupt the alloy's γ-γ′ coherent structure, leading to the formation of a secondary reaction zone (SRZ) and a topologically close-packed phase (TCP), significantly degrading the alloy's high-temperature mechanical properties. Therefore, developing a coating preparation method that enhances the interfacial stability of MCrAlY coatings and Ni-based superalloys is crucial for improving the mechanical properties and service life of superalloys.

[0004] Arc ion plating technology offers high deposition efficiency and excellent scalability. Combined with subsequent vacuum annealing, it produces a coating with uniform composition, a dense structure, and a strong bond to the alloy substrate. This method is a common method for preparing MCrAlY coatings. Related application literature includes: ① Chinese invention patent, "An MCrAlY-added composite gradient coating and its preparation process," application number 200710011431.8; ② Chinese invention patent, "An MCrAlY+AlSiY composite coating and its preparation process," application number 200810228097.6; ③ Chinese invention patent, "A NiCrAlYSc coating and its preparation process," application number 201810955193.4. Summary of the Invention

[0005] The present invention aims to provide a Ni-Al / MCrAlY coating that improves the stability of the coating / alloy substrate interface and its preparation method. This method introduces a Ni-Al coating between the MCrAlY coating and the Ni-based superalloy substrate, significantly reducing element interdiffusion between the coating and the alloy substrate, thereby improving the interface stability between the MCrAlY coating and the Ni-based superalloy substrate. In particular, for Ni-based single-crystal superalloys, the introduction of the Ni-Al coating significantly reduces the tendency of TCP phase precipitation in the SRZ, mitigating the coating's adverse effects on the mechanical properties of the Ni-based single-crystal superalloy.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a Ni-Al / MCrAlY coating for improving the stability of the coating / alloy substrate interface comprises the following steps:

[0008] (1) Surface treatment is performed on the high-temperature alloy substrate. The surface treatment process is as follows: first, the alloy substrate is polished with sandpaper, then the substrate is sandblasted with 100-220 mesh alumina, and then ultrasonically cleaned with metal detergent and deionized water for 15-30 minutes respectively, and then placed in the furnace chamber of the arc ion plating equipment after drying.

[0009] (2) The substrate is cleaned by bias bombardment. The process is as follows: after the alloy substrate is loaded into the furnace, the vacuum in the furnace is first pumped to 2×10 -3 ~1×10 -2 Pa, and then Ar gas was introduced to raise the pressure in the furnace to 2×10 -2 ~3×10 -1 Pa, then turn on the target power supply and bias power supply to perform bias bombardment cleaning on the substrate. During the bias cleaning process, the target current is 70-90A, the target-substrate distance is 60-300mm, the pulse bias is -400-600V, the duty cycle of the pulse bias is 20%-40%, and the cleaning time is 2-5min. The target material used in this step is the same as that in step (3).

[0010] (3) Deposition of a Ni-Al coating. During the coating deposition process, the target-substrate distance is 60 to 300 mm, the arc current is 70 to 90 A, the arc voltage is 19 to 25 V, the pulse bias is -150 to -300 V, the duty cycle of the pulse bias is 20% to 40%, the deposition temperature is 80 to 300°C, and the deposition time is 60 to 300 min. The chemical composition (mass percentage) of the selected target material is: Al is 3% to 40%, and the balance is Ni.

[0011] (4) Depositing an MCrAlY coating (M = Ni and / or Co) on the Ni-Al coating deposited in step (3)

[0012] (5) The sample deposited with the Ni-Al coating and the MCrAlY coating in step (4) is subjected to vacuum annealing treatment at an annealing temperature of 850 to 1000° C., a heating rate of ≤10° C. / min, and a holding time of 3 to 5 h. After the holding is completed, the sample is cooled to room temperature in the furnace.

[0013] The present invention has the following advantages and beneficial effects:

[0014] 1. The Ni-Al coating introduced between the MCrAlY and Ni-based superalloy substrates reduces interdiffusion between the coating and the substrate, improves the stability of the coating / alloy interface, and mitigates the coating's deterioration of the alloy substrate's mechanical properties. The present invention is particularly effective in improving the stability of the coating / Ni-based single-crystal superalloy interface.

[0015] 2. The Ni-Al+MCrAlY coating is obtained by combining arc ion plating and vacuum annealing. The coating preparation process is simple, the coating thickness is easy to control, the process repeatability is good, and it is easy to achieve industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the cross-sectional SEM morphology of the Ni-Al+NiCoCrAlYHfZr coating after annealing.

[0017] Figure 2 Cross-sectional morphologies of NiCoCrAlYHfZr coating and Ni-Al+NiCoCrAlYHfZr coating at different oxidation times at 1150°C (a, c, e are cross-sectional morphologies of NiCoCrAlYHfZr coating oxidized for 100h, 150h, and 200h, respectively; b, d, f are cross-sectional morphologies of Ni-Al+NiCoCrAlYHfZr coating oxidized for 100h, 150h, and 200h, respectively. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below through examples and drawings.

[0019] Example 1

[0020] This embodiment aims to improve the stability of the interface between the NiCoCrAlYHfZr coating and the Ni-based single crystal high-temperature alloy. The nominal composition of the high-temperature alloy substrate used is (by mass percentage): Cr 3.5%, Co 9%, W 6%, Al 6%, Mo 1.5%, Re 4%, with the balance being Ni. The sample size is Φ16×1.5mm. A small hole with a diameter of 1.5mm is machined on the edge of the sample using wire cutting to facilitate hanging the sample. Before depositing the Ni-Al coating, the alloy substrate is gradually polished to 800 mesh using sandpaper, then wet-sandblasted with 120 mesh alumina. It is then ultrasonically cleaned for 15 minutes using a metal detergent (Model 83-415-419 High-Performance Metal Cleaner produced by Shenyang Silica Gel Factory Co., Ltd.) and deionized water. After drying, the alloy substrate is placed in the furnace chamber of the arc ion plating equipment; the furnace chamber is vacuumed to 6×10 -3 Pa, and introduce Ar gas with appropriate flow rate to keep the pressure in the furnace chamber at 2.2~2.4×10 -1 Pa. Turn on the target power supply (the same target material as used when depositing the Ni-Al coating) and the bias power supply, and perform bias bombardment cleaning on the alloy substrate. The pulse bias voltage is -400 to -600 V, the duty cycle of the pulse bias voltage is 30%, and the cleaning time is 5 minutes. Then, a domestic multi-arc ion plating (DH-12) device is used to deposit the Ni-Al coating. The target material composition selected is (mass percentage): Al is 15%, and Ni is the balance. On the basis of depositing the Ni-Al coating, the aforementioned equipment is used to continue depositing the NiCoCrAlYHfZr coating. The target material composition selected is as follows (mass percentage): Co is 20% to 24%, Cr is 18% to 22%, Al is 10% to 14%, Y is 0.5% to 0.1%, Hf is 0.1% to 1.5%, Zr is 0.01% to 0.8%, and Ni is the balance. During the deposition process of Ni-Al coating and NiCoCrAlYHfZr coating, the target-substrate distance was 60 mm, the arc voltage was 20-21 V, the arc current was 90 A, the pulse bias was -160 V, and the duty cycle of the pulse bias was 30%. The deposition time of Ni-Al coating was 100 min, and the deposition time of NiCoCrAlYHfZr coating was 180 min.

[0021] The deposited coating sample was placed in a quartz tube, which was first evacuated and then filled with Ar gas to seal. The quartz tube was then placed in a muffle furnace, heated to 900 °C and kept warm for 4 h at a heating rate of 10 °C / min. After the insulation was completed, it was cooled to room temperature with the furnace.

[0022] In this embodiment, a Ni-Al coating is first deposited on a Ni-based single crystal high temperature alloy substrate, and then a NiCoCrAlYHfZr coating is deposited. The cross-sectional morphology of the prepared Ni-Al+NiCoCrAlYHfZr coating sample after annealing is as follows: Figure 1As shown in Figure 2, the coating thickness is approximately 50 μm. Slight interdiffusion occurs between the coating and the substrate.

[0023] The cross-sectional morphologies of NiCoCrAlYHfZr and Ni-Al+NiCoCrAlYHfZr coatings at different oxidation times at 1150℃ are shown in Figure 2. Figure 2 As shown. Figure 2 It can be seen that the SRZ thickness of the Ni-Al+NiCoCrAlYHfZr coating is significantly smaller than that of the NiCoCrAlYHfZr coating.

[0024] The results of the present invention demonstrate that the Ni-Al+NiCoCrAlYHfZr coating deposited on a high-temperature alloy substrate via arc ion plating followed by vacuum annealing significantly inhibits the precipitation of the TCP phase in the SRZ and improves the stability of the coating-alloy interface. This coating preparation method can be applied to improve the stability of the interface between NiCoCrAlYHfZr coatings and Ni-based single-crystal high-temperature alloys.

[0025] The above description is only a preferred embodiment of the invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the invention should be included in the scope of protection of the invention.

Claims

1. A method for preparing a Ni-Al / MCrAlY coating that improves the stability of the coating / alloy substrate interface, characterized in that: The method is to deposit a Ni-Al coating and an MCrAlY coating on a nickel-based high-temperature alloy substrate in sequence, and then perform vacuum annealing treatment, specifically comprising the following steps: (1) Surface treatment of nickel-based high-temperature alloy substrate; (2) performing bias bombardment cleaning on the substrate; (3) Deposition of Ni-Al coating: When depositing Ni-Al coating, a NiAl alloy target is used, and the target composition is: Al is 3-15 wt.%, and Ni is the balance; (4) Deposition of MCrAlY coating; (5) The samples deposited with Ni-Al coating and MCrAlY coating were subjected to vacuum annealing treatment.

2. The method for preparing a Ni-Al / MCrAlY coating for improving the coating / alloy substrate interface stability according to claim 1, characterized in that: In step (1), the substrate surface treatment process is as follows: first, the alloy substrate is polished, then sandblasted with 100-220 mesh alumina, and then ultrasonically cleaned with metal detergent and deionized water for 15-30 minutes respectively, and then dried and loaded into the furnace chamber of the arc ion plating equipment.

3. The method for preparing a Ni-Al / MCrAlY coating for improving the stability of the coating / alloy substrate interface according to claim 1, characterized in that: In step (2), the bias bombardment cleaning process is as follows: after the alloy substrate is placed in the furnace chamber of the arc ion plating equipment, the vacuum in the furnace is first pumped to 2×10 -3 ~1×10 -2 Pa, and then introduce Ar gas to raise the pressure in the furnace to 2×10 -2 ~3×10 -1 After Pa, turn on the target power supply and bias power supply, and perform bias bombardment cleaning on the substrate; during the bias cleaning process: the target current is 70~90A, the target-substrate distance is 60~300mm, the pulse bias is -400~-600V, the duty cycle of the pulse bias is 20%~40%, and the cleaning time is 2~5min.

4. The method for preparing a Ni-Al / MCrAlY coating for improving the coating / alloy substrate interface stability according to claim 1, characterized in that: In step (3), the substrate is subjected to bias bombardment cleaning and then a Ni-Al coating is deposited. During the coating deposition process, the target-substrate distance is 60 to 300 mm, the arc current is 70 to 90 A, the arc voltage is 19 to 25 V, the pulse bias is -150 to -300 V, the duty cycle of the pulse bias is 20% to 40%, the deposition temperature is 80 to 300° C., and the deposition time is 50 to 300 min.

5. The method for preparing a Ni-Al / MCrAlY coating for improving the stability of the coating / alloy substrate interface according to claim 1, characterized in that: The target material in the bias bombardment cleaning in step (2) is the same as the target material in step (3).

6. The method for preparing a Ni-Al / MCrAlY coating for improving the coating / alloy substrate interface stability according to claim 1, characterized in that: In step (5), during the vacuum thermal annealing treatment, the annealing temperature is 850-1000°C, the heating rate is ≤10°C / min, the holding time is 3-5h, and the material is cooled to room temperature in the furnace after the holding is completed.

7. A Ni-Al / MCrAlY coating prepared by the method of claim 1 and having improved coating / alloy substrate interface stability.

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