Co composite modified PtAl diffusion layer suitable for nickel-based superalloy and preparation method thereof

Abstract

The present application relates to the technical field of alloy coating, and particularly relates to a Co composite modified PtAl diffusion layer suitable for nickel-based high-temperature alloy and a preparation method thereof. The preparation method provided by the present application comprises the following steps: after plating platinum on the surface of the nickel-based high-temperature alloy, vacuum heat treatment is performed to obtain the nickel-based high-temperature alloy with a surface comprising a Ni-Pt interdiffusion layer; a cobalt-aluminum co-diffusion treatment is performed on the nickel-based high-temperature alloy with the surface comprising the Ni-Pt interdiffusion layer by using a chemical vapor deposition method to obtain the Co composite modified PtAl diffusion layer; the cobalt source used in the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the reaction gas of the cobalt source is hydrogen iodide; the aluminum source used in the chemical vapor deposition is aluminum particles, and the reaction gas of the aluminum source is hydrogen chloride. The preparation method solves the problem of low cobalt diffusion efficiency caused by excessively high aluminum diffusion temperature by adjusting the composition of the cobalt source.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy coating, in particular to a Co composite modified PtAl coating layer suitable for nickel-based superalloy and a preparation method thereof. BACKGROUND

[0002] Nickel-based superalloy is widely used in the hot end components of aero-engine and gas turbine due to its excellent high-temperature mechanical properties. In order to improve the performance of nickel-based superalloy at ultra-high temperature, and to enhance the oxidation resistance and hot corrosion resistance of the alloy, the industry generally uses embedding infiltration, slurry aluminizing, vapor aluminizing and chemical vapor deposition to diffuse a layer of β-NiAl aluminizing layer on the nickel-based alloy. The aluminum content in the aluminizing layer is generally as high as 35wt%, so a dense alumina film can be formed on the surface of the part during high-temperature service, thereby preventing oxygen from further diffusing into the substrate and improving the oxidation resistance of the substrate. The introduction of other beneficial elements, such as Pt, Pd, Si, Cr, Hf, etc., can better improve the corrosion resistance of the aluminizing layer. So far, the PtAl coating is the most successful, and has been widely used in the turbine blades and guide vanes of industrial aero-engines and gas turbines, such as the high-pressure turbine guide vanes of the LM25000 type gas turbine in the United States.

[0003] Although PtAl coating has excellent anti-oxidation and hot corrosion performance, the high temperature mechanical properties of the alloy, such as creep and tensile properties, are directly reduced by about 5% to 10%. After long-term service, due to the difference in thermal matching between PtAl layer, oxide layer and substrate, "wrinkling" phenomenon will appear on the surface of the coating, and eventually cause the coating to break and the service life to decrease. Therefore, how to solve the "wrinkling" phenomenon of PtAl coating after high temperature service is one of the main directions of the current PtAl coating development. Co element can be completely solid-solved with Ni and segregated in the γ phase. The introduction of Co can stabilize the γ phase of nickel-based alloy and improve the mechanical properties of nickel-based alloy. Sun Xiaofeng et al. (Chenggang Tian, Guomnig Han, Chuanyong Cui, Xiaofeng Sun, Effects of Co content on tensile properties and deformation behaviors of Ni-based disk superalloys at different temperatures [J]. Materials and Design, 2015) found that the yield strength and strain hardening capacity of the material at 725℃ were significantly improved when the Co content in the nickel-based alloy increased from 5wt% to 23wt%. It was found that increasing the cobalt content in CMSX-10 nickel-based alloy could improve the creep life of the alloy at 850℃ (Effects of cobalt on creep rupture properties and dislocation structures in nickel base superalloys [J]. Materials Science & Engineering A, 2015). Considering the effect of Co on nickel-based alloy, it is expected that the introduction of Co into PtAl coating will improve the mechanical properties of PtAl coating.

[0004] For the above prior art, the team of Zhou Chun-gen of Beihang University and the team of Sun Chao of Metal Research Institute of Chinese Academy of Sciences (Effect of Y2O3 content in the pack on microstructure and hot corrosion resistance of Y-Co-modified aluminide coating[J]. Corrosion Science; The isothermal and cyclic oxidation behaviour of two Co modified aluminide coatings at high temperature[J]. Corrosion Science) both adopt the method of pack cementation to prepare CoAl coating on nickel-based alloy, the raw materials for pack cementation are Co powder (below 100 mesh), Al powder (below 100 mesh), ammonium chloride and alumina powder, etc., by burying the parts in the powder, CoAl co-permeation is realized after 1050℃ for a period of time. However, there are many problems in pack cementation CoAl: 1. The hot end parts generally have gas film holes, and the powder of pack cementation will block the gas holes, so it cannot be applied to aluminizing of hot end parts; 2. The pack cementation temperature is high, which has a deteriorating effect on the structure of the alloy; 3. The pack cementation layer is uneven, and there may be breakpoints; 4. Since cobalt powder is a toxic substance, pack cementation of cobalt and aluminum may cause “cobalt poisoning” of production workers; 5. There is a lot of dust, and the environmental protection pressure is great. In view of the above problems, the Chinese patent with publication number CN107858662A adopts the method of chemical vapor deposition to realize cobalt and aluminum co-permeation, cobalt source adopts cobalt particles, CoCl2 is generated by reaction of HCl with cobalt particles, but since the boiling point of CoCl2 is as high as 1049℃, the aluminizing temperature must be controlled above this temperature, and almost all commercial alloys are difficult to withstand this temperature, and the cobalt permeation efficiency of this method is low in actual production. SUMMARY

[0005] The purpose of the present application is to provide a Co composite modified PtAl permeation layer suitable for nickel-based superalloy and a preparation method thereof, which solves the problem of low cobalt permeation efficiency caused by too high aluminizing temperature by adjusting the composition of cobalt source.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a preparation method of a Co composite modified PtAl permeation layer suitable for nickel-based superalloy, comprising the following steps:

[0008] After electroplating platinum on the surface of the nickel-based superalloy, vacuum heat treatment is carried out to obtain a nickel-based superalloy with a surface including a Ni-Pt interdiffusion layer;

[0009] The surface of the nickel-based superalloy including the Ni-Pt interdiffusion layer is subjected to cobalt-aluminum co-permeation treatment by chemical vapor deposition to obtain the Co composite modified PtAl permeation layer.

[0010] The cobalt source used in the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the reaction gas of the cobalt source is hydrogen iodide; the aluminum source used in the chemical vapor deposition is aluminum particles, and the reaction gas of the aluminum source is hydrogen chloride.

[0011] Preferably, the electroplating solution used in the electroplating of platinum includes a main salt, a conductive salt, a pH adjuster, an additive, and p-aminobenzenesulfonic acid;

[0012] The main salt includes P salt or Q salt;

[0013] The conductive salt is one or more of sodium chloride, ammonium chloride, sodium dihydrogen phosphate, ammonium nitrate, sodium nitrite, sodium pyrophosphate, and diammonium hydrogen phosphate;

[0014] The pH adjuster includes one or more of potassium hydroxide, sodium hydroxide, and ammonia;

[0015] The additive includes sodium dodecyl benzene sulfonate;

[0016] The pH value of the electroplating solution is 10-11.

[0017] Preferably, the electroplating temperature of the electroplating of platinum is 80-100°C, and the current density is 0.1-0.8 ampere per square decimeter;

[0018] The thickness of the plating layer obtained by the electroplating of platinum is 1-3 micrometers.

[0019] Preferably, the temperature of the vacuum heat treatment is 900-950°C, the time is 4-8 hours, and the vacuum degree is ≤10 -3 Pa.

[0020] Preferably, the mass ratio of ammonium iodide to cobalt particles in the mixture of ammonium iodide and cobalt particles is (4-10):100; and the cobalt source is located in a first reactor of the chemical vapor deposition;

[0021] The aluminum source is located in a second reactor of the chemical vapor deposition;

[0022] The cobalt-aluminum co-permeation treatment is performed in a reaction furnace.

[0023] Preferably, the reducing atmosphere in the first reactor is hydrogen, and the carrier gas is argon;

[0024] The reducing atmosphere in the second reactor is hydrogen, and the carrier gas is argon;

[0025] The pressure of the reaction furnace is ≤10-3 Pa.

[0026] Preferably, the flow rate of hydrogen in the first reactor is 5-10 L / min, the flow rate of argon is 10-20 L / min, and the flow rate of hydrogen iodide is 0.5-2 L / min.

[0027] The flow rate of argon in the second reactor is 5-20 L / min, the flow rate of hydrogen is 2-10 L / min, and the flow rate of hydrogen chloride is 1-4 L / min, and the flow rate ratio of hydrogen and hydrogen chloride in the second reactor is (2-3):1.

[0028] Preferably, the temperature of the first reactor is 800-1100℃.

[0029] The temperature of the second reactor is 900-1100℃.

[0030] The temperature of the reaction furnace is 900-1100℃.

[0031] Preferably, the cobalt-aluminum co-permeation treatment time is 4-10 h, and the temperature is 900℃-1100℃.

[0032] The present application also provides a Co composite modified PtAl permeated layer prepared by the preparation method described in the above technical solution, and the thickness of the Co composite modified PtAl permeated layer is 20-60 μm.

[0033] The mass percentage of Co in the Co composite modified PtAl permeated layer is 13-30%.

[0034] The application provides a preparation method of a Co composite modified PtAl diffusion layer suitable for a nickel-based high-temperature alloy, and comprises the following steps: after plating platinum on the surface of the nickel-based high-temperature alloy, vacuum heat treatment is performed to obtain the nickel-based high-temperature alloy with a surface comprising a Ni-Pt interdiffusion layer; a cobalt-aluminum co-diffusion treatment is performed on the nickel-based high-temperature alloy with the surface comprising the Ni-Pt interdiffusion layer by using a chemical vapor deposition method to obtain the Co composite modified PtAl diffusion layer; the cobalt source used in the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the reaction gas of the cobalt source is hydrogen iodide; the aluminum source used in the chemical vapor deposition is aluminum particles, and the reaction gas of the aluminum source is hydrogen chloride. Since Co can improve the thermal performance of the aluminized layer and slow down the wrinkle deformation caused by long-term thermal stress, and since the gasification temperature of cobalt iodide is very low (about 580 DEG C), which is much lower than the boiling point of cobalt chloride (about 1050 DEG C), the existing CVD aluminizing cobalt generally has a reaction temperature above 1050 DEG C, and due to the very high boiling point of cobalt chloride, it is not easy to gasify and has low reactivity at this temperature. The low boiling point of cobalt iodide can make aluminizing cobalt at a lower temperature, and can greatly improve the production efficiency of aluminizing by adjusting the flow. The lower the temperature, the shorter the production cycle, the faster the aluminizing, and thus the aluminizing efficiency is improved. Therefore, the preparation method mainly solves the problem that after the PtAl coating is used at a high temperature above 1000 DEG C for a long time, due to the difference in thermal matching between the substrate, the platinum-aluminum layer and the oxidation layer, and the harsh temperature change, the platinum-aluminum coating surface forms a wrinkle phenomenon, and finally causes the coating to be partially cracked and aged; meanwhile, the application reduces the reaction temperature by adjusting the components of the cobalt source, the reaction gas and the components of the aluminum source and the reaction gas, and solves the problem of low cobalt efficiency caused by high aluminizing temperature. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The cross-sectional view and EDS element characterization diagram of the Ni-Pt interdiffusion layer in the nickel-based high-temperature alloy with the surface comprising the Ni-Pt interdiffusion layer prepared in Example 1 are shown in the following figure:

[0036] Figure 2 The cross-sectional view and EDS element characterization diagram of the Co composite modified PtAl diffusion layer prepared in Example 1 are shown in the following figure:

[0037] Figure 3 The cross-sectional view and EDS element characterization diagram of the Co composite modified PtAl diffusion layer prepared in Example 2 are shown in the following figure. DETAILED DESCRIPTION

[0038] The application provides a preparation method of a Co composite modified PtAl diffusion layer suitable for a nickel-based high-temperature alloy, and comprises the following steps:

[0039] After plating platinum on the surface of the nickel-based superalloy, vacuum heat treatment is carried out to obtain the nickel-based superalloy with a surface including a Ni-Pt interdiffusion layer;

[0040] Co-aluminizing treatment is carried out on the nickel-based superalloy with a surface including a Ni-Pt interdiffusion layer by chemical vapor deposition to obtain the Co composite modified PtAl diffusion layer.

[0041] The cobalt source for the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the reaction gas of the cobalt source is hydrogen iodide; the aluminum source for the chemical vapor deposition is aluminum particles, and the reaction gas of the aluminum source is hydrogen chloride.

[0042] In the present application, all the raw materials for preparation are commercially available products well known to those skilled in the art, unless otherwise specified.

[0043] After plating platinum on the surface of the nickel-based superalloy, vacuum heat treatment is carried out to obtain the nickel-based superalloy with a surface including a Ni-Pt interdiffusion layer.

[0044] The present application does not have any special limitation on the type of the nickel-based superalloy, and any type well known to those skilled in the art can be used. In the embodiments of the present application, the type of the nickel-based superalloy is specifically IN738 superalloy.

[0045] In the present application, the electroplating solution for electroplating platinum preferably comprises a main salt, a conductive salt, a pH regulator, an additive and p-aminobenzenesulfonic acid. In the present application, the main salt preferably comprises P salt or Q salt; the concentration of the main salt in the electroplating solution is preferably 4-10 g / L, more preferably 5-9 g / L, and most preferably 6-8 g / L. In the present application, the conductive salt is preferably one or more of sodium chloride, ammonium chloride, sodium dihydrogen phosphate, ammonium nitrate, sodium nitrite, sodium pyrophosphate and diammonium hydrogen phosphate; when the conductive salt is two or more of the above-mentioned specific choices, the present application does not have any special limitation on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio. In the present application, the content of the conductive salt in the electroplating solution is preferably 50-200 g / L, more preferably 80-160 g / L, and most preferably 120-140 g / L. In the present application, the pH regulator preferably comprises one or more of potassium hydroxide, sodium hydroxide and ammonia water; when the pH regulator is two or more of the above-mentioned specific choices, the present application does not have any special limitation on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio. In the present application, the pH value of the electroplating solution is preferably 10-11, more preferably 10.2-10.8, and most preferably 10.4-10.6. In the present application, the additive preferably comprises sodium dodecyl benzene sulfonate, and the concentration of the additive in the electroplating solution is preferably 0.1 g / L. In the present application, the concentration of p-aminobenzenesulfonic acid in the electroplating solution is preferably 1-10 g / L, more preferably 2-8 g / L, and most preferably 4-6 g / L.

[0046] In the present application, the electroplating temperature for electroplating platinum is preferably 80-100℃, more preferably 85-95℃, and most preferably 88-92℃; the current density is preferably 0.1-0.8 ampere per square decimeter (ASD), more preferably 0.2-0.7 ASD, and most preferably 0.3-0.6 ASD.

[0047] In the present application, the thickness of the plating layer obtained by electroplating platinum is preferably 1-10 μm, more preferably 2 μm-8 μm, and most preferably 3 μm-6 μm.

[0048] In the present application, the temperature for vacuum heat treatment is preferably 900-950℃, more preferably 910-940℃, and most preferably 920-930℃; the time is preferably 4-8 h, more preferably 5-7 h, and most preferably 5.5-6.5 h; the vacuum degree is preferably ≤10 -3 Pa.

[0049] In the present application, the purpose of vacuum heat treatment is to realize mutual diffusion between the platinum plating layer and the substrate (the nickel-based high-temperature alloy), so as to obtain a stable Ni-Pt interdiffusion layer.

[0050] After obtaining the nickel-based superalloy with the surface comprising the Ni-Pt interdiffusion layer, the nickel-based superalloy with the surface comprising the Ni-Pt interdiffusion layer is subjected to cobalt-aluminum co-permeation treatment by chemical vapor deposition to obtain the Co composite modified PtAl permeation layer; the cobalt source used in the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the reaction gas of the cobalt source is hydrogen iodide; the aluminum source used in the chemical vapor deposition is aluminum particles, and the reaction gas of the aluminum source is hydrogen chloride.

[0051] In the present application, the cobalt source used in the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the mass ratio of ammonium iodide to cobalt particles in the mixture of ammonium iodide and cobalt particles is preferably (4-10):100, more preferably (4-8):100, and most preferably (5-6):100; the cobalt source is preferably located in the first reactor of the chemical vapor deposition. The aluminum source used in the chemical vapor deposition is aluminum particles; the aluminum source is preferably located in the second reactor of the chemical vapor deposition; and the cobalt-aluminum co-permeation treatment is preferably carried out in a reaction furnace.

[0052] In the present application, the reaction gas in the first reactor is hydrogen iodide, the reducing atmosphere is preferably hydrogen, and the carrier gas is preferably argon; the flow rate of hydrogen in the first reactor is preferably 5-10 L / min, more preferably 6-9 L / min, and most preferably 7-8 L / min; the flow rate of argon is preferably 10-20 L / min, more preferably 12-18 L / min, and most preferably 14-16 L / min; and the flow rate of hydrogen iodide is preferably 0.5-2 L / min, more preferably 1-1.8 L / min, and most preferably 1.2-1.6 L / min.

[0053] In the present application, the reaction gas in the second reactor is hydrogen chloride, the reducing atmosphere is preferably hydrogen, and the carrier gas is preferably argon; the flow rate of argon in the second reactor is preferably 5-20 L / min, more preferably 8-16 L / min, and most preferably 12-13 L / min; the flow rate of hydrogen is preferably 2-10 L / min, more preferably 3-8 L / min, and most preferably 4-6 L / min; the flow rate of hydrogen chloride is preferably 1-4 L / min, more preferably 1.5-3.5 L / min, and most preferably 2-3 L / min; and the flow rate ratio of hydrogen to hydrogen chloride in the second reactor is preferably (2-3):1, more preferably (2.2-2.8):1, and most preferably (2.4-2.6):1.

[0054] In the present application, since the atomic radius of Co is close to that of Ni and larger than that of Al, the diffusion of Co is more difficult. Therefore, the supply amount of the carrier gas in the first reactor needs to be increased and the supply amount of the carrier gas in the second reactor needs to be appropriately reduced during the chemical vapor deposition.

[0055] In the present application, the pressure of the reaction furnace is preferably ≤10 -3 Pa.

[0056] In the present application, the cobalt and hydrogen iodide react to form cobalt iodide in the first reactor, and since the boiling point of the cobalt iodide is 570℃, the temperature in the first reactor needs to be controlled at 800-1100℃; since the melting point of aluminum in the second reactor is 660℃, if the aluminum is in liquid phase, it is easy to adsorb gas to produce sponge-like expansion, resulting in a larger profit in the internal of the second reactor, so the reactor temperature should be controlled below the melting point of aluminum; at the same time, the reactor temperature is too different from the reaction furnace temperature, and the reaction gas will reduce the furnace temperature, so the temperature in the second reactor needs to be controlled at 900-1100℃.

[0057] In the present application, the temperature of the first reactor is preferably 800-1100℃, more preferably 850-1050℃, and most preferably 900-1000℃; the temperature of the second reactor is preferably 900-1100℃, more preferably 950-1050℃, and most preferably 980-1020℃; the temperature of the reaction furnace is preferably 900-1100℃, more preferably 950-1050℃, and most preferably 980-1020℃.

[0058] In the present application, the cobalt-aluminum co-diffusion treatment time is preferably 4-10h, more preferably 5-9h, and most preferably 6-8h; the temperature is preferably 900℃-1100℃, more preferably 950℃-1050℃, and most preferably 950℃-980℃. In the present application, the lower the temperature of the cobalt-aluminum co-diffusion treatment, the more widely applicable the alloy, and a large number of alloys are easy to induce harmful TCP phase at 1000℃ ultra-high temperature.

[0059] In the present application, the process of the cobalt-aluminum co-diffusion treatment is as follows: the cobalt source is placed in the first reactor, and the aluminum source is placed in the second reactor; first, the pressure in the reaction furnace, the first reactor, the second reactor and the gas pipeline is pumped to low vacuum by mechanical pump and maintenance pump, and the pressure of the low vacuum is ≤10 -3 Pa; then the temperature of the reaction furnace and the first reactor is set respectively to heat to the specified temperature, hydrogen, argon and hydrogen iodide are introduced into the first reactor, and after the cobalt iodide gas and IN738 substrate react for 1-3h; the second reactor is opened, the temperature of the second reactor is set to heat to the specified temperature, hydrogen, argon and hydrogen chloride are introduced into the second reactor, 960℃ for 6h, the holding system is closed, and the first reactor and the second reactor are closed, and the furnace is cooled to room temperature.

[0060] In the present application, the role and mechanism of each component or between components during the cobalt-aluminum co-permeation treatment; the chemical reaction formula involved in the first reactor during the gas phase aluminizing is: 2CoI2+H2=2CoI+2HI; the chemical equation involved in the second reactor is: Al+HCl=AlCl+H2; Al+HCl=AlCl2+H2; Al+HCl=AlCl3+H2; after the active CoI, CoI2, AlCl, AlCl2 gases enter the reaction furnace, they react with the nickel-based alloy substrate under high temperature and H2 reducing atmosphere, active Al atoms and Co atoms are generated on the alloy substrate, and then diffuse into the inside of the nickel-based alloy substrate to form a permeation layer mainly composed of β-(Ni, Co, Pt)Al phase and PtAl2 phase.

[0061] The present application also provides a Co composite modified PtAl permeation layer prepared by the preparation method.

[0062] The mass percentage content of Co in the Co composite modified PtAl permeation layer is preferably 13-30%, more preferably 16-25%, and most preferably 20-23%.

[0063] In the present application, the thickness of the Co composite modified PtAl permeation layer is 20-60 μm, preferably 30-50 μm, and more preferably 35-45 μm; and the mass percentage content of Co in the Co composite modified PtAl permeation layer is 13-30%, preferably 13-23%, and more preferably 15%.

[0064] The Co composite modified PtAl permeation layer suitable for nickel-based high-temperature alloy and the preparation method thereof provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0065] Example 1

[0066] After plating a platinum layer with a thickness of 2 μm on the surface of the IN738 high-temperature alloy (the pH of the plating solution is 10.8, and the composition is (the main salt is Q salt, and the concentration of the main salt is 10 g / L; the types of conductive salts are sodium dihydrogen phosphate and sodium chloride, and the concentrations are 50 g / L and 40 g / L, respectively; the pH regulator is a 1% potassium hydroxide solution, the concentration of sodium dodecylbenzenesulfonate is 0.1 g / L, and the concentration of p-aminobenzenesulfonic acid is 2 g / L); the plating temperature is 85°C, the current density is 0.5 ASD, and the plating time is 15 min), vacuum heat treatment is performed (the temperature is 950°C, the time is 4 h, the vacuum degree is 3×10 -4 The interface diagram and the EDS element distribution diagram of the Ni-Pt interdiffusion layer are shown in FIGS. 1 and 2, respectively.Figure 1 As shown in Figure 1 It can be seen that the Ni-Pt interdiffusion layer is about 20 μm, and the mass concentration of Pt can reach 25-50 wt%, which decreases with the increase of thickness;

[0067] The cobalt source (mass ratio of ammonium iodide to cobalt particles is 1:9) is placed in the first reactor, and the aluminum source (aluminum particles) is placed in the second reactor. First, the pressure in the reaction furnace, the first reactor, the second reactor and the gas pipeline is pumped to low vacuum by a mechanical pump and a maintenance pump, and the pressure of the low vacuum is ≤10 -3 Pa. Then the temperature of the reaction furnace and the first reactor is set to a specified temperature (the specified temperature of the reaction furnace is 980℃, and the specified temperature of the first reactor is 950℃), and hydrogen gas (flow rate is 6 L / min), argon gas (flow rate is 15 L / min) and hydrogen iodide (flow rate is 3 L / min) are introduced into the first reactor. After the cobalt iodide gas and the IN738 substrate react for 4 h, the second reactor is opened, the temperature of the second reactor is set to a specified temperature (the specified temperature of the second reactor is 950℃), and hydrogen gas (flow rate is 6 L / min), argon gas (flow rate is 10 L / min) and hydrogen chloride (flow rate is 2 L / min) are introduced into the second reactor. The cobalt-aluminum co-permeation treatment is carried out at 980℃ for 4 h. The heating system is closed, and the first reactor and the second reactor are closed. The furnace is cooled to room temperature, and a Co composite modified PtAl permeation layer with a thickness of 35 μm is obtained (the mass percentage content of Co is 13.21 wt%-23.32 wt%, the concentration of Co in the PtAl permeation layer is not fixed, and decreases from top to bottom, and the cross-sectional view and the EDS element distribution map are as shown in Figure 2 As shown in Figure 2 It can be seen that Co and Pt are uniformly distributed in the permeation layer.

[0068] Example 2

[0069] After electroplating a platinum layer with a thickness of 2 μm on the surface of the IN738 superalloy (the pH of the electroplating solution is 10.8, and the composition is (the main salt is Q salt, the concentration of the main salt is 10 g / L; the types of conductive salt are sodium dihydrogen phosphate and sodium chloride, and the concentrations are 50 g / L and 40 g / L, respectively; the pH regulator is a potassium hydroxide solution with a mass concentration of 1%, the concentration of sodium dodecylbenzenesulfonate is 0.1 g / L, and the concentration of p-aminobenzenesulfonic acid is 2 g / L); the electroplating temperature is 90℃, the current density is 0.3 ASD, and the electroplating time is 20 min), vacuum heat treatment is carried out (the temperature is 950℃, the time is 4 h, and the vacuum degree is 3×10 -4 Pa), and a nickel-based superalloy including a Ni-Pt interdiffusion layer is obtained.

[0070] A cobalt source (ammonium iodide and cobalt granules in a mass ratio of 1:9) is placed in the first reactor, and an aluminum source (aluminum granules) is placed in the second reactor. The pressure in the reactor, the first reactor, the second reactor, and the gas pipeline is first evacuated to a low vacuum using a mechanical pump and a maintaining pump. The pressure of this low vacuum is ≤10. -3 Pa, then the temperatures of the reactor and the first reactor were set and raised to the specified temperatures (980℃ for the reactor and 760℃ for the first reactor). Hydrogen (6 L / min), argon (15 L / min), and hydrogen iodide (3 L / min) were then introduced into the first reactor. After the cobalt iodide gas reacted with the IN738 substrate for 4 hours, the second reactor was opened, and its temperature was raised to the specified temperature (950℃). Hydrogen (6 L / min), argon (10 L / min), and hydrogen chloride (2 L / min) were then introduced into the second reactor. The reactor was held at 980℃ for 4 hours for cobalt-aluminum co-diffusion treatment. The holding system was then shut down, and both the first and second reactors were closed. The reactor was cooled to room temperature with the furnace, resulting in a 33 μm thick Co-modified PtAl infiltration layer (Co mass percentage 0 wt%–1.28 wt%, cross-sectional view and EDS elemental distribution diagram are shown below). Figure 3 As shown, by Figure 3 It can be seen that the platinum content is relatively lower than that of the Co-Pt-Al system, and platinum segregation exists, making the infiltrated layer more brittle than that of the Co-Pt-Al system.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made 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 preparing a Co composite modified PtAI diffusion coating suitable for nickel-based superalloys, characterized in that, Comprise the following steps: After electroplating platinum on the surface of the nickel-based superalloy, vacuum heat treatment is carried out to obtain a nickel-based superalloy with a surface including a Ni-Pt interdiffusion layer; The surface of the nickel-based superalloy including the Ni-Pt interdiffusion layer is subjected to cobalt-aluminum co-permeation treatment by chemical vapor deposition to obtain the Co composite modified PtAl permeation layer; The cobalt source used in the chemical vapor deposition is a mixture of ammonium iodide and cobalt particles, and the reaction gas of the cobalt source is hydrogen iodide; the aluminum source used in the chemical vapor deposition is aluminum particles, and the reaction gas of the aluminum source is hydrogen chloride; The mass ratio of ammonium iodide to cobalt particles in the mixture is (4-10):100; the cobalt source is located in the first reactor of the chemical vapor deposition; The aluminum source is located in the second reactor of the chemical vapor deposition; The cobalt-aluminum co-permeation treatment is carried out in a reaction furnace; The reducing atmosphere in the first reactor is hydrogen, and the carrier gas is argon; The reducing atmosphere in the second reactor is hydrogen, and the carrier gas is argon; The pressure of the reactor is < 10 -3 Pa; The flow rate of hydrogen in the first reactor is 5-10 L / min, the flow rate of argon is 10-20 L / min, and the flow rate of hydrogen iodide is 0.5-2 L / min; The flow rate of argon in the second reactor is 5-20 L / min, the flow rate of hydrogen is 2-10 L / min, and the flow rate of hydrogen chloride is 1-4 L / min; the flow rate ratio of hydrogen to hydrogen chloride in the second reactor is (2-3):1; The cobalt-aluminum co-permeation treatment time is 4 h, and the temperature is 980℃; The mass percentage of Co in the Co composite modified PtAl permeation layer is 13-30%; The electroplating temperature for electroplating platinum is 80-100℃, and the current density is 0.1-0.8 ampere per square decimeter; The thickness of the plating layer obtained by electroplating platinum is 1-3 μm; The temperature of the vacuum heat treatment is 900-950℃, the time is 4-8h, and the vacuum degree is ≤10 -3 Pa; The temperature of the first reactor is 800-1100℃; The temperature of the second reactor is 900-1100℃; The temperature of the reaction furnace is 900-1100℃.

2. The production method according to claim 1, wherein The electroplating solution used for electroplating platinum includes main salt, conductive salt, pH adjuster, additive, and p-aminobenzenesulfonic acid; The main salt includes P salt or Q salt; The conductive salt is one or more of sodium chloride, ammonium chloride, sodium dihydrogen phosphate, ammonium nitrate, sodium nitrite, sodium pyrophosphate, and diammonium hydrogen phosphate; The pH adjuster includes one or more of potassium hydroxide, sodium hydroxide, and ammonia; The additive includes sodium dodecyl benzene sulfonate; the pH value of the electroplating solution is 10-11.

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