An MCrAlY coating containing a ReCr-based diffusion barrier and a preparation method thereof

Abstract

The present invention discloses an MCrAlY coating containing a ReCr-based diffusion barrier and a preparation method thereof, belonging to the technical field of high-temperature protective coatings. A composite coating capable of inhibiting the interdiffusion between the coating and the substrate in a high-temperature environment, slowing down the coating degradation rate, and thus improving the service life of the coating is prepared on a superalloy substrate through electroplating technology, arc ion plating technology, and vacuum diffusion annealing. The specific steps are as follows: surface treatment; electroplating a Re-Ni layer; depositing a pure Cr layer by arc ion plating technology; performing heat treatment after the deposition of the pure Cr layer; electroplating the Re-Ni layer for the second time; after completing the second electroplating, depositing an MCrAlY coating on the surface of the Re-Ni layer by arc ion plating technology; and finally performing vacuum heat treatment to obtain the MCrAlY coating containing the ReCr-based diffusion barrier.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature protective coatings, and particularly relates to an MCrAlY coating containing a ReCr-based diffusion barrier and a preparation method thereof. Background Art

[0002] Superalloys are generally used in the turbine blades of aeroengines. Under high-temperature service conditions, in addition to excellent high-temperature mechanical properties, they should also have good oxidation resistance. Depositing a coating on the surface of a superalloy can effectively improve its high-temperature oxidation resistance while maintaining the mechanical properties of the superalloy.

[0003] The MCrAlY (M = Ni, Co or NiCo) coating has excellent high-temperature oxidation and hot corrosion resistance, and its composition and thickness can be precisely controlled to meet the requirements of different working conditions. Therefore, it is widely used in superalloys. However, severe interdiffusion often occurs between the coating and the substrate, accelerating the degradation of the coating, thereby having a negative impact on the oxidation resistance of the coating. Adding a diffusion barrier between the coating and the substrate can effectively solve the problem of interdiffusion at the coating-substrate interface.

[0004] Diffusion barriers are generally divided into metal-type diffusion barriers and ceramic-type diffusion barriers. Ceramic-type diffusion barriers can effectively prevent element interdiffusion. However, ceramic-type diffusion barriers such as Al-O-N or Al2O3 will damage the bonding strength at the substrate-coating interface; while metal-type diffusion barriers have good bonding strength with both the substrate and the coating because they are metallurgically bonded to the substrate and the coating.

[0005] In order to improve the efficiency of the engine, the turbine inlet temperature is continuously increased, and more severe interdiffusion will occur between the superalloy and the protective coating, thus posing higher requirements for the diffusion barrier used between the superalloy and the coating. Therefore, developing a metal-type diffusion barrier for higher service temperatures and greater stability is still the research direction of researchers. Summary of the Invention

[0006] The purpose of the present invention is to provide an MCrAlY coating containing a ReCr-based diffusion barrier and a preparation method thereof, so as to form a uniform, continuous and stable ReCr-based diffusion barrier at the coating-substrate interface. During high-temperature service, this ReCr-based diffusion barrier can prevent the interdiffusion between the substrate and the coating and improve the service life of the coating.

[0007] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0008] A preparation method of an MCrAlY coating containing a ReCr-based diffusion barrier. The method first electroplates a Re-Ni layer on a superalloy substrate; then uses arc ion plating technology to deposit a pure Cr layer on the surface of the Re-Ni layer; then performs vacuum heat treatment to cause interdiffusion between the Re-Ni layer and Cr to form a ReCr-rich layer; after the vacuum heat treatment, electroplate another Re-Ni layer on its surface; then use arc ion plating technology to deposit an MCrAlY coating on the surface of the Re-Ni layer; finally, perform vacuum heat treatment to obtain a stable MCrAlY coating containing a ReCr-based diffusion barrier. The method specifically includes the following steps:

[0009] (1) Pretreatment before electroplating: The pretreatment before electroplating includes sequentially performing electro-chemical degreasing and activation treatment to remove the oxide layer on the substrate surface through pretreatment and improve the bonding force between the Re-Ni layer and the substrate;

[0010] (2) Composite electroplating of the Re-Ni layer. The electroplating solution composition is: 0.1 - 0.4 mol / L of citric acid, 0.1 - 0.5 mol / L of NiSO4·6H2O, 0.005 - 0.1 mol / L of KReO4, and the rest is deionized water; adjust the pH of the electroplating solution to 7 - 11 with ammonia water, heat the prepared solution to 30 - 70 °C, and electroplate the superalloy substrate located at the cathode at a current density of 0.5 - 10 A / dm 2 after power-on, and the anode material is a nickel plate; the electroplating time is determined according to the required coating thickness and current density, and the thickness of the Re-Ni coating is between 1 and 5 μm;

[0011] (3) Use arc ion plating technology to deposit a pure Cr layer on the Re-Ni coating, and the deposition time is 1 - 4 h;

[0012] (4) After depositing the pure Cr layer, perform vacuum annealing treatment on the substrate containing the Re-Ni coating and the pure Cr layer to form a ReCr-rich layer on the substrate surface;

[0013] (5) Electroplate a Re-Ni layer on the surface after vacuum annealing. The electroplating solution composition is: 0.1 - 0.4 mol / L of citric acid, 0.1 - 0.5 mol / L of NiSO4·6H2O, 0.005 - 0.1 mol / L of KReO4, and the rest is deionized water; adjust the pH of the electroplating solution to 7 - 11 with ammonia water, heat the prepared solution to 30 - 70 °C, and electroplate the superalloy substrate located at the cathode at a current density of 0.5 - 10 A / dm 2 after power-on, and the anode material is a nickel plate; the electroplating time is determined according to the required coating thickness and current density, and the thickness of the Re-Ni coating is between 1 and 5 μm;

[0014] (6) The arc ion plating technology is adopted to deposit an MCrAlY coating on the Re-Ni coating, and the deposition time is 4 - 10 h;

[0015] (7) After the MCrAlY coating is deposited, the substrate with the composite coating is subjected to vacuum annealing treatment at a high temperature. Through the above steps, an MCrAlY coating containing a ReCr-based diffusion barrier can be obtained.

[0016] In the above step (1), the substrate is a Ni-based superalloy.

[0017] In the above step (1), the substrate is first surface-treated and then pretreated; the process of the surface treatment is as follows: the substrate is polished on a pre-grinder in sequence with 150#, 240#, 400#, 600#, and 800# SiC sandpapers to grind out the fresh surface of the metal, and then the sample is subjected to wet sandblasting treatment. After that, the sample is ultrasonically treated with tap water, deionized water, and acetone in sequence to remove the residual oil stains and the like on the surface of the sample.

[0018] In the electroplating in the above step (2), a double anode is used. The centers of the two anode surfaces are respectively opposite to the centers of the two cathode surfaces. The relative distance between the anode and the cathode is 30 - 60 mm, the single-sided area ratio of the anode / cathode is (2 - 5):1, and the thickness of the Re-Ni layer is 1 - 5 μm.

[0019] In the above step (3), during the deposition of the pure Cr layer: the target-substrate distance is 200 - 250 mm, the arc voltage is 20 - 25 V, the arc current is 70 - 90 A, the pulsed bias voltage is -90 - -200 V, the duty cycle is 20% - 50%, the deposition temperature is 100 - 300 °C, the deposition time is 1 - 4 h, and the coating thickness is 2 - 8 μm.

[0020] In the above step (4), the pure Cr layer deposited in step (3) is subjected to vacuum heat treatment, i.e., vacuum diffusion annealing. During the vacuum diffusion annealing, the temperature is 900 - 1100 °C, the holding time is 1 - 4 h, the heating rate ≤ 10 °C / min, and after the holding is completed, it is cooled to room temperature with the furnace.

[0021] In the electroplating in the above step (5), a double anode is used. The centers of the two anode surfaces are respectively opposite to the centers of the two cathode surfaces. The relative distance between the anode and the cathode is 30 - 60 mm, the single-sided area ratio of the anode / cathode is (2 - 5):1, and the thickness of the Re-Ni layer is 1 - 5 μm.

[0022] In the above step (6), during the deposition of the MCrAlY coating: the target-substrate distance is 200 - 250 mm, the arc voltage is 20 - 25 V, the arc current is 70 - 90 A, the pulsed bias voltage is -150 - -300 V, the duty cycle is 20% - 50%, the deposition temperature is 100 - 300 °C, the deposition time is 4 - 10 h, and the coating thickness is 30 - 75 μm. When depositing, an MCrAlY target is used. By weight percentage, the chemical composition of the target is: Cr is 16% - 24%, Al is 8% - 16%, Y is 0.1% - 1%, Si is 0.5% - 2%, and Ni is the balance.

[0023] In the above step (7), the deposited MCrAlY coating is subjected to vacuum heat treatment, namely vacuum diffusion annealing. During the vacuum diffusion annealing, the temperature is 800 - 1000 °C, the holding time is 3 - 6 h, the heating rate ≤ 20 °C / min, and after the holding is completed, it is cooled to room temperature with the furnace.

[0024] The advantages of the present invention are as follows:

[0025] 1. The present invention prepares a continuous and stable ReCr-based diffusion barrier by combining electroplating a Re-Ni layer, arc ion plating to deposit a pure Cr layer, and vacuum heat treatment. Then, through subsequent electroplating a Re-Ni layer, arc ion plating to deposit an MCrAlY coating, and vacuum heat treatment, the ReCr-based diffusion barrier has excellent bonding strength with the coating and the substrate, and at the same time makes the structure more uniform.

[0026] 2. During high-temperature service, the ReCr-based diffusion barrier can prevent the diffusion of coating elements into the substrate, and at the same time inhibit the diffusion of refractory elements in the substrate into the coating, slow down the coating degradation, weaken the adverse effects of substrate elements, and extend the service life of the MCrAlY coating.

[0027] 3. Compared with ordinary Re-based diffusion barriers, the ReCr-based diffusion barrier has better stability in a high-temperature service environment. Description of the Drawings

[0028] Figure 1 It is the cross-sectional SEM morphology after electroplating a Re-Ni layer on the substrate surface first, depositing a pure Cr layer by arc ion plating technology, and performing vacuum heat treatment.

[0029] Figure 2 It is the cross-sectional SEM morphology of the MCrAlY coating containing the ReCr-based diffusion barrier after annealing.

[0030] Figure 3 It is the surface SEM morphology of the MCrAlY coating containing the ReCr-based diffusion barrier after annealing.

[0031] Figure 4XRD diffraction pattern of the MCrAlY coating with ReCr-based diffusion barrier after annealing. Detailed implementation mode

[0032] The present invention will be described in detail below in conjunction with embodiments and accompanying drawings.

[0033] Embodiment 1:

[0034] In this embodiment, an MCrAlY coating containing a ReCr-based diffusion barrier is prepared on a nickel-based superalloy substrate. The chemical composition of the used nickel-based superalloy is as follows (mass percentage): Cr: 14.0%, Co: 9.5%, Al: 3.0%, Ti: 2.8%, Mo: 1.5%, W: 3.8%, B: 0.015%, C: 0.10%, Ni: the balance. The substrate used is circular, with a diameter of 15 mm and a thickness of 2 mm. A hole with a diameter of 1.5 mm is wire-cut 1 mm from the edge to facilitate hanging the specimen during electroplating and arc ion plating processes.

[0035] Surface treatment and pretreatment are carried out on the specimen: The substrate is polished on a pre-grinder with SiC sandpaper to 800# sandpaper. After grinding out the fresh surface of the metal, the specimen is subjected to wet sandblasting treatment with a mixture of 200-mesh corundum sand and glass sand at 1 - 2 atm. Then, the sandblasted specimen is successively ultrasonically treated with tap water, deionized water, and acetone to remove surface residual oil and the like.

[0036] The pretreated nickel-based superalloy substrate is suspended as the cathode in the plating solution, and electroplating is carried out according to the following steps. The plating solution composition is: citric acid 0.3 mol / L, NiSO4·6H2O 0.2 mol / L, KReO4 0.01 mol / L, and the rest is deionized water. The pH is adjusted to 8 - 9 with ammonia water. The electroplating temperature is 55 °C, and electroplating is carried out for 30 minutes at a current density of 1 A / dm 2 ².

[0037] After electroplating Re-Ni, a pure Cr layer is deposited by arc ion plating technology. During the deposition of the pure Cr layer, the target-substrate distance is 250 mm, the arc voltage is 20 V, the arc current is 90 A, the pulsed bias voltage is -100 V, the duty cycle is 30%, the deposition temperature is 200 °C, and the deposition time is 90 min.

[0038] The obtained coating sample is placed in a quartz glass tube, evacuated, and then filled with argon for protection. It is heated to 1000 °C in a muffle furnace and held for 3 h at a heating rate of 10 °C / min. After holding, it is cooled to room temperature with the furnace. The cross-sectional SEM morphology after annealing is as Figure 1 shown. It can be seen that the ReCr-rich layer formed on the substrate surface is continuous and complete, and has excellent adhesion to the substrate.

[0039] After the vacuum diffusion annealing is completed, the annealed sample is suspended as the cathode in the plating solution, and electroplating is carried out according to the following steps. The composition of the plating solution is: 0.3 mol / L citric acid, 0.2 mol / L NiSO4·6H2O, 0.01 mol / L KReO4, and the rest is deionized water. The pH is adjusted to 8 - 9 with ammonia water. The electroplating temperature is 55 °C, and electroplating is carried out at a current density of 1 A / dm 2 for 30 minutes.

[0040] After the electroplating of Re-Ni is completed, an MCrAlY coating is deposited using an arc ion plating equipment. When depositing the coating, the target-substrate distance is 250 mm, the arc voltage is 20 V, the arc current is 90 A, the pulsed bias voltage is -150 V, the duty cycle is 30%, the deposition temperature is 200 °C, and the deposition time is 8 h.

[0041] The obtained coated sample is placed in a quartz glass tube, evacuated, and then filled with argon for protection. It is heated to 1000 °C in a muffle furnace and held for 4 h at a heating rate of 10 °C / min. After the holding is completed, it is cooled to room temperature with the furnace.

[0042] The cross-sectional morphology of the MCrAlY coating with a ReCr-based diffusion barrier after annealing is as shown in Figure 2 As shown, after annealing, a continuous and complete ReCr-based diffusion barrier is formed between the superalloy substrate and the MCrAlY coating. Figure 2 As shown in

[0043] The surface morphology of the MCrAlY coating with a ReCr-based diffusion barrier after annealing is as shown in Figure 3 As shown, as shown in Figure 3 the surface of the deposited coating is relatively rough, and some particles of inconsistent sizes are distributed on the coating surface.

[0044] The XRD pattern of the MCrAlY coating with a ReCr-based diffusion barrier after annealing is as shown in Figure 4 As shown, it can be seen from Figure 4 that after vacuum annealing, the MCrAlY coating with a ReCr-based mainly consists of β-NiAl, γ' / γ, and α-Cr phases.

Claims

1. A preparation method of an MCrAlY coating containing a ReCr-based diffusion barrier, characterized in that: This method first electroplates a Re-Ni layer on a superalloy substrate; then uses arc ion plating technology to deposit a pure Cr layer on the surface of the Re-Ni layer; then performs vacuum heat treatment, during which Re-Ni layer and Cr undergo interdiffusion to form a ReCr-rich layer; after the vacuum heat treatment, electroplate another Re-Ni layer on its surface; then use arc ion plating technology to deposit an MCrAlY coating on the surface of the Re-Ni layer; finally, perform vacuum heat treatment to obtain an MCrAlY coating containing a ReCr-based diffusion barrier with excellent bonding strength; This method specifically includes the following steps: (1) Pretreatment before electroplating: The pretreatment before electroplating includes electro-chemical degreasing and activation treatment carried out in sequence. The oxide layer on the substrate surface is removed through the pretreatment to improve the bonding strength between the Re-Ni layer and the substrate; the substrate is a Ni-based superalloy; (2)Composite electroplated Re-Ni layer: The plating solution composition is as follows: citric acid 0.1 - 0.4 mol / L, NiSO4·6H2O 0.1 - 0.5 mol / L, KReO4 0.005 - 0.1 mol / L, and the rest is deionized water; the pH of the plating solution is adjusted to 7 - 11 with ammonia water, the prepared plating solution is heated to 30 - 70 °C, and electroplating is carried out on the substrate located at the cathode after power-on at a current density of 0.5 - 10 A / dm 2 ², and the anode material is a nickel plate; (3) Use arc ion plating technology to deposit a pure Cr layer on the Re-Ni coating, and the deposition time is 1-4 h; (4) After the pure Cr layer is deposited by arc ion plating, the substrate with the Re-Ni layer and the pure Cr layer is subjected to vacuum annealing treatment under vacuum conditions, and then a ReCr layer can be formed on the substrate surface; (5) Surface electroplated Re-Ni layer after vacuum annealing: The plating solution composition is: 0.1 - 0.4 mol / L of citric acid, 0.1 - 0.5 mol / L of NiSO4·6H2O, 0.005 - 0.1 mol / L of KReO4, and the rest is deionized water; adjust the pH of the plating solution to 7 - 11 with ammonia water, heat the prepared plating solution to 30 - 70 °C, and electroplate the substrate located at the cathode after power-on at a current density of 0.5 - 10 A / dm 2 2, and the anode material is a nickel plate; (6) Use arc ion plating technology to deposit an MCrAlY coating on the Re-Ni coating, and the deposition time is 4-10 h; (7) After the MCrAlY coating is deposited by arc ion plating, the substrate with the composite coating is subjected to vacuum annealing treatment under vacuum conditions, and then an MCrAlY coating containing a ReCr-based diffusion barrier is obtained.

2. The coating preparation method according to claim 1, characterized in that: In step (1), the substrate is first subjected to surface treatment and then pretreatment; the process of the surface treatment is as follows: The substrate is polished on a pre-grinder using 150#, 240#, 400#, 600#, and 800# SiC sandpapers in sequence. After grinding out the fresh surface of the metal, the sample is subjected to wet sandblasting treatment, and then the sample is ultrasonically treated with tap water, deionized water, and acetone in sequence to remove the residual oil on the sample surface.

3. The coating preparation method according to claim 1, characterized in that: In step (2), double anodes are used for electroplating. The centers of the two anode surfaces are respectively opposite to the centers of the two cathode surfaces. The relative distance between the anode and the cathode is 30-60 mm, the single-sided area ratio of the anode / cathode is (2-5):1, and the thickness of the Re-Ni layer is 1-5 μm.

4. The coating preparation method according to claim 1, characterized in that: In step (3), during the deposition of the pure Cr layer: the target-substrate distance is 200-250 mm, the arc voltage is 20-25 V, the arc current is 70-90 A, the pulsed bias voltage is -90 to -200 V, the duty cycle is 20%-50%, the deposition temperature is 100-300 °C, the deposition time is 1-4 h, and the coating thickness is 2-8 μm.

5. The coating preparation method according to claim 1 or 4, characterized in that: In step (4), the pure Cr layer deposited in step (3) is subjected to vacuum heat treatment, i.e., vacuum diffusion annealing. During the vacuum diffusion annealing, the temperature is 900-1100 °C, the holding time is 1-4 h, the heating rate ≤ 10 °C / min, and after the holding is completed, it is cooled to room temperature with the furnace.

6. The coating preparation method according to claim 1, characterized in that, In step (5), double anodes are used for electroplating. The centers of the two anode surfaces are respectively opposite to the centers of the two cathode surfaces. The relative distance between the anode and the cathode is 30 - 60 mm, the single-sided area ratio of the anode / cathode is (2 - 5):1, and the thickness of the Re-Ni layer is 1 - 5 μm.

7. The coating preparation method according to claim 1, characterized in that: In step (6), during the deposition of the MCrAlY coating: the target-substrate distance is 200 - 250 mm, the arc voltage is 20 - 25 V, the arc current is 70 - 90 A, the pulsed bias voltage is -150 - 300 V, the duty cycle is 20% - 50%, the deposition temperature is 100 - 300 °C, the deposition time is 4 - 10 h, and the coating thickness is 30 - 75 μm.

8. The coating preparation method according to claim 1 or 7, characterized in that, In step (7), the deposited MCrAlY coating is subjected to vacuum heat treatment, i.e., vacuum diffusion annealing. During vacuum diffusion annealing, the temperature is 800 - 1000 °C, the holding time is 3 - 6 h, the heating rate ≤ 20 °C / min, and after the holding is completed, it is cooled to room temperature with the furnace.

9. An MCrAlY coating containing a ReCr-based diffusion barrier prepared by the method according to claim 1.

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