CN114147169A

CN114147169A - Method for improving interface stability of metal core coating

Info

Publication number: CN114147169A
Application number: CN202010932055.1A
Authority: CN
Inventors: 刘恩泽; 张冲; 郑志; 宁礼奎; 佟健; 纪慧思; 谭政
Original assignee: Institute of Metal Research of CAS
Current assignee: Institute of Metal Research of CAS
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2022-03-08
Anticipated expiration: 2040-09-08
Also published as: CN114147169B

Abstract

The invention discloses a method for improving interface stability of a metal core coating, belongs to the technical field of metal protective coatings, mainly aims at solving the interface problem of silicon oxide and high-temperature alloy, and specifically comprises the following steps: optimizing a coating and a pre-oxidation technology, reducing the generation of silicon oxide and maximizing the content of aluminum oxide in an inert oxidation film; and the second step is to utilize a high-melting-point metal coating, wherein the high-melting-point metal coating is deposited on the surface of the core inert oxide film, and silicon oxide and deposited metal elements are subjected to chemical reaction and diffusion in a vacuum and high-temperature environment to form a more stable interface type, so that the stability of the interface is greatly improved, and the coating structure is an intermetallic compound layer/an inert oxide layer/a metal coating. The invention can be used in the field of precision casting and is used for producing hollow blades.

Description

Method for improving interface stability of metal core coating

Technical Field

The invention relates to the technical field of metal protective coatings, in particular to a method for improving interface stability of a metal core coating.

Background

The turbine blade is one of hot end key parts of an aircraft engine and a gas turbine, and the higher the temperature bearing capacity of the blade is, the higher the working efficiency is. In order to improve the working efficiency, the blade is improved from the aspects of materials and structures, the higher the melting point of the blade material is, the higher the working efficiency is, however, the working temperature of the blade exceeds the melting point of the high-temperature alloy, and the temperature bearing capacity of the material is very close to the limit; on the other hand, then design the structure of blade, the hollow structure of blade can not form through machining, can only place the precision casting core in advance before pouring the blade, then gets rid of the core through chemical corrosion means, and then reaches hollow structure, lets in cooling air and takes away the heat, has realized air cooling, and air cooling can the effectual service temperature who improves the blade, therefore cooling efficiency is especially important to turbine blade.

With the development of cooling technology and casting technology, the service performance requirement of the casting core is higher and higher, the ceramic core is more elaborate and complex in cooling channel design and the corresponding size is more elaborate and fine in pursuit of high cooling efficiency at present. However, the fine part of the ceramic core has reduced performance, especially reduced strength and thermal shock resistance, so that the ceramic material is limited in size by its own properties. In order to solve the problem of the part of the ceramic material, a molybdenum-based metal core is adopted to replace the part of a fine ceramic core, so that a ceramic-metal composite core with a more advanced cooling structure is prepared, however, the key point of the application of the molybdenum-based metal core is the reasonable design of a protective coating of the molybdenum alloy.

The preparation and service process of the molybdenum-based metal core comprises the steps of pre-depositing an intermetallic compound layer on a molybdenum-based metal core, pre-oxidizing to form an inert oxide coating, performing a series of precision casting processes including core assembly, wax mold preparation, shell molding, dewaxing and the like, putting a ceramic module into a directional furnace, vacuumizing, heating to 1000-1300 ℃, preserving heat, heating to 1500-1650 ℃, preserving heat for a period of time, pouring high-temperature alloy, keeping a certain speed for extraction, taking out after cooling, removing the shell and removing the core.

As shown in fig. 1(a), after pouring the DSM11 superalloy at 1550 ℃, the coating resists the alloy erosion and protects the molybdenum-based metal core matrix, but the DSM11 alloy surface can undergo severe interfacial reactions (as shown in fig. 1 (b)), which may be due to silicon oxide chemically reacting with the active elements Al, Cr, Ti, etc. in the superalloy above 1550 ℃ causing silicon oxide to stick to the casting surface and cause surface defects (as shown in fig. 2). To avoid the effects of silica, it is necessary to improve the stability of the metal core coating interface and the surface quality of the cast part.

Disclosure of Invention

In order to solve the problem of unstable interface between silicon oxide and high-temperature alloy in an inert oxide layer of a metal molybdenum core, the invention provides a method for improving the interface stability of a metal core coating.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for improving interface stability of metal core coating is provided, which improves the interface stability between the core and the coating by optimizing the coating components and pre-oxidation technology in the process of preparing the coating on the surface of the molybdenum-based metal core; the method specifically comprises the following steps:

(1) pure molybdenum or molybdenum alloy is taken as a metal core matrix, and the codeposition of silicon and aluminum elements is carried out on the core matrix by adopting a chemical vapor deposition or in-situ chemical vapor deposition process (carried out in a heating furnace or a chemical vapor deposition furnace), wherein the deposition temperature is 900-1300 ℃, and the deposition time is 2-30 h; and after the deposition is finished, cooling to 800 ℃ at a cooling rate of 1-15 ℃/min, then closing the heating system, and cooling to room temperature along with the furnace to form the composite coating containing aluminum silicon on the substrate.

(2) Pre-oxidation treatment: pre-oxidizing the core substrate with the coating deposited in the step (1), wherein the treatment process comprises the following steps: firstly introducing air or oxygen, controlling the flow at 1-100 sscm, then heating to 1000-1100 ℃, and preserving the heat for 1-5 h; heating to 1200-1400 ℃ at the heating rate of 1-15 ℃/min, and preserving heat for 1-8 h; and after the heat preservation is finished, opening a vacuum system for vacuumizing or introducing inert gas to reduce the concentration of oxygen in the furnace, closing a heating system, and cooling along with the furnace.

(3) Depositing a high-melting-point metal coating on the surface of the sample subjected to the pre-oxidation treatment in the step (2), wherein the deposition mode is arc ion plating, electroplating, magnetron sputtering, vacuum evaporation, chemical vapor deposition and the like; the melting point of the high melting point metal coating is higher than 1600 ℃.

In the step (1), the metal core substrate is pretreated before use, and the process is as follows: firstly, grinding with 240# -800# sandpaper, then sequentially cleaning in deionized water and absolute alcohol, and drying for later use.

In the step (1), when co-deposition of silicon and aluminum elements is performed, due to the difference of aluminum and silicon elements, the coating first forms a low-melting-point aluminide coating, and then is converted (wholly or partially) into a high-melting-point silicide coating.

In the step (1), when codeposition of silicon and aluminum elements is carried out, an aluminum-containing intermetallic compound layer is formed on the substrate, and then an inert oxide layer (aluminum oxide and silicon oxide) is formed on the intermetallic compound layer; the total thickness of the composite coating is more than 30 mu m, and the low-melting-point phase can disappear in the later pre-oxidation process.

In the step (3), the refractory metal coating is a chromium, hafnium, iridium or platinum coating.

In the step (1), when the codeposition of silicon and aluminum elements is carried out on the core substrate, one or more of chromium, zirconium, titanium and magnesium elements can be simultaneously deposited.

In the step (2), after pre-oxidation, the mixture is cooled to below 500 ℃ along with the furnace in the cooling process and taken out.

In the step (3), the thickness of the deposited metal coating is 0.1-20 μm.

The design mechanism of the invention is as follows:

firstly, co-depositing aluminum and silicon elements on a molybdenum-based metal core substrate to prepare a composite coating, wherein the composite coating is in a structure of a substrate/intermetallic compound layer/inert oxide layer/metal coating; during codeposition, different differences appear in the deposition process due to the self characteristics of Al and Si elements, the melting point of Al is 660 ℃, the melting point of Si is 1414 ℃, the activity of Al is higher than that of Si under the condition of 1000 ℃, Al is deposited on the coating firstly, Al8Mo3 phase appears, the activity of Si is increased along with the increase of temperature, and the diffusion coefficient of Si in a matrix is increased (Dsi is more than D)_Al) With increased Si content instead of Al₈Mo₃Presence of Mo (Si, Al)₂To Al₈Mo₃Partly or wholly converted to Mo (Si, Al)₂Even the innermost layer is MoSi₂. The coating thus first forms low melting Al below 1600 deg.C₈Mo₃Phase, then the modified silicide phase (Mo (Si, Al) above 1600 ℃ appears₂And MoSi₂). And then adopting a pre-oxidation technology, wherein the growth process of the oxide film in the pre-oxidation technology is multi-stage step heating oxidation, and the oxide film is cooled to below 500 ℃ along with the furnace in the cooling process and taken out. The temperature of the pre-oxidation technique must be higher than 1000 ℃ to ensure possible residues in the coatingDeposited low melting point Al₈Mo₃The phases decompose at high temperatures and their total coating thickness is above 30 μm to ensure their disappearance during pre-oxidation. In the pre-oxidation technology, after the content of aluminum oxide in an oxide film reaches the maximum, vacuumizing or introducing argon to reduce the oxygen concentration and protect a sample;

and finally, depositing a high-melting-point metal coating on the surface of the metal core, and forming a more stable interface type by utilizing element chemical reaction and diffusion in a vacuum and high-temperature environment, so that the influence of silicon oxide is reduced, and the stability of the interface is improved. The melting point of the high-melting-point coating metal is above 1600 ℃, so that the high-melting-point coating metal is guaranteed not to melt before the high-temperature alloy is poured, and after the high-temperature alloy is poured, the metal enters the alloy melt and does not affect or improve the performance of the alloy.

The beneficial results of the present invention are as follows:

1. active elements are added into the coating to adjust the structure of the coating, so that the effect of the coating on resisting the corrosion of the high-temperature alloy is ensured, the toughness of the coating is obviously enhanced, and the bonding force with a substrate interface is increased.

2. The content of alumina in the coating is maximized by optimally controlling pre-oxidation parameters (time, temperature, oxygen concentration).

3. The metal coating is deposited in advance, the matrix protective coating of the core is coated, the deposited metal elements react with silicon oxide under high-temperature vacuum, the interface of an external oxide layer is more stable, and meanwhile, the deposited metal elements are melted into the high-temperature alloy to avoid influencing the performance of the high-temperature alloy.

4. By stabilizing the interface, the interfacial clearance of the core and superalloy is reduced to a maximum of 23um, which facilitates precise control of the cavity dimensions of the blade.

Drawings

FIG. 1 shows low melting point Al₈MO₃A picture of the failure section of the sample when the phase exists; wherein: (a) a core substrate after pouring a DSM11 superalloy at 1550 ℃ (b) a DSM11 superalloy surface after pouring at 1550 ℃.

FIG. 2 is a core prior to modification by the present invention; wherein: (a) an interface of the core with the alloy, (b) a surface of the DSM11 alloy, (c) a surface of the core.

FIG. 3 is a core resulting from a modification of the process of the present invention; wherein: (a) an interface of the core with the alloy, (b) a surface of the DSM11 alloy, (c) a surface of the core.

Detailed Description

For a further understanding of the present invention, the following description is given in conjunction with the examples which are set forth to illustrate, but are not to be construed to limit the present invention, features and advantages.

The invention improves the stability of the coating interface of the metal core by optimizing the coating and pre-oxidation technology and utilizing the high-melting-point metal coating, and adopts the following specific scheme:

the optimized coating adopts aluminum and silicon elements for codeposition, and beneficial elements such as chromium, zirconium, titanium, magnesium and the like can be further added into the coating. Due to the difference of the self-properties of the elements, Al is firstly formed in the aluminum-silicon codeposition process₈Mo₃Coating, then forming silicide coating, coating low-melting point Al₈Mo₃The phase should be completely eliminated after the pre-oxidation technology, and the structure of the high-melting-point coating is kept, so that the cast sample is ensured not to lose efficacy. The method comprises the following steps: firstly, grinding with 240# -800# abrasive paper in advance, sequentially cleaning in deionized water and absolute alcohol, and drying for later use, secondly, adopting chemical vapor deposition-codeposition elements at 900-1300 ℃ for 2-30 h, thirdly, cooling to 800 ℃ at 1-15 ℃/min according to a program, closing a heating system, and cooling to room temperature along with a furnace.

The pre-oxidation technology is carried out according to the sequence of placing a sample in advance, opening a pre-heating program and cooling under the vacuum low-oxygen condition, and comprises the following steps: step one, putting a deposited coating sample which is cooled to room temperature into an alumina crucible, wherein a certain gap is formed between the samples, and 5-120 meshes of alumina can be filled into the samples in order to keep uniform heating and no deformation of the samples; step two, opening a heating device, heating to 1000-1100 ℃, preheating and preserving heat for 1-5 h, wherein the heat preservation time can be determined according to the size of the sample; step three, heating the preheated coating sample to 1200-1400 ℃ at the speed of 1-15 ℃/min, and keeping the temperature for 1-8 h; opening a vacuum system or introducing inert gas to reduce the concentration of oxygen in the furnace; and simultaneously, closing the heating system and cooling along with the furnace.

The high melting point metal coating is deposited, and the metal coating can be deposited by different methods, such as vacuum evaporation, arc ion plating, electroplating and the like, and can be set according to the deposition method of the deposited metal element.

The service environment of the high-melting-point coating is put into a directional furnace: the die set is put into a vacuum directional furnace for a certain time before the high-temperature alloy is poured.

The melting point of the high-melting-point metal coating is higher than 1600 ℃, and the high-temperature alloy is not melted in the vacuum orientation furnace without pouring. Meanwhile, after the high-temperature alloy is poured, the metal does not influence or improve the performance of the alloy after entering the alloy melt.

The high-melting-point metal can perform interface chemical reaction with silicon oxide in a vacuum and high-temperature environment to form more stable oxide, reduce the influence of the silicon oxide on the surface of the coating and further improve the interface.

Comparative example 1

Using a cold-rolled molybdenum plate (with the purity of 99.99%) as a core substrate, cutting the core substrate into the core substrate with the size of 24mm x 20mm x 0.4mm by using spark lines, polishing the surface by using No. 240-800 abrasive paper, cleaning by using deionized water, drying, ultrasonically cleaning by using absolute ethyl alcohol, and drying. Silicon-aluminum codeposition is carried out by adopting an in-situ chemical vapor deposition method, wherein the raw materials are as follows: silicon powder (300-500 meshes, analytical purity 99.95%), aluminum powder (300-500 meshes, analytical purity 99.95%), and activating agent (NH)₄Cl, analytical grade 99.5%), inert filler (Al)₂O₃100-300 meshes), according to the silicon powder: aluminum powder: activating agent: mixing inert filler in a ratio of 15:3:2:80 (wt%), mixing the powder for 10 hours in a powder ball mill, putting the core substrate and the mixed powder into a deposition tank, putting the deposition tank into the central area of a heating furnace, closing the furnace door of the heating furnace, keeping good air tightness, opening an air outlet valve of the heating furnace, opening argon, introducing argon for 15-20 minutes or longer, heating to 200 ℃ at a speed of 5 ℃/min, keeping the temperature for 30 minutes, and simultaneously introducing argon againClosing the air inlet valve after 30min, then opening the vacuum pump, adjusting the vacuum pressure to-0.06 Mpa to-0.02 Mpa, closing the air outlet valve, heating to 1000 ℃ at 5 min/DEG C, heating to 1100 ℃ at 2 ℃/min, keeping the pressure at +0Mpa to 0.04Mpa, preserving the temperature for 5-20 h, then heating to 1000 ℃ at 2 ℃/min, and naturally cooling to the room temperature. The co-deposited coating is detected to find that the low melting point Al exists in the core coating₈Mo₃Phase, such as direct casting of the DSM11 alloy, caused failure of the coating, as shown in fig. 1, the low melting phase melted at the high temperature of the casting and the coating was quickly destroyed.

Cleaning the surface of the metal core subjected to in-situ chemical vapor deposition by using deionized water, drying, cleaning the surface of a sample by using absolute ethyl alcohol, drying, putting the sample into an alumina crucible, and then putting the sample into a muffle furnace; introducing air into the furnace, controlling the air flow at 5sscm, carrying out isothermal oxidation at 1300 ℃ for 1-10 h, taking out and cooling. Assembling the core into wax film, making shell (dipping slurry, sand spraying repeatedly until required thickness, drying), steam dewaxing at 100-260 deg.C, heating to 900 deg.C, and holding temperature for 1h to fire the shell. Putting the shell group into a vacuum directional furnace, vacuumizing to below 1Pa, heating to 1550 ℃, pouring DSM11 high-temperature alloy, extracting at 6mm/min, cooling to room temperature, and taking out and removing the shell.

In the example, the core after the co-deposition of Si and Al is subjected to isothermal oxidation, although the low-melting-point phase is completely converted into the high-melting-point phase (aluminum oxide and silicon oxide), the silicon oxide generated on the surface of the coating is high in content, and the quality of the alloy is influenced after the DSM11 high-temperature alloy is poured.

Comparative example 2

In this example, the difference from comparative example 1 is: the coating is prepared by chemical vapor deposition, and the process is as follows: perforating a matrix, putting the matrix on a sample rack conveniently, putting the sample rack into a reaction chamber, closing a CVD furnace door, vacuumizing the reaction chamber to be below 200pa, heating to 900-1200 ℃, opening a flow controller, and controlling the volume flow ratio to be H₂：AlCl₃：SiCl₄1: 1.2: 2, preserving the heat for 2 to 20 hours, then cooling to 800 ℃ at a speed of 10 ℃/min according to the program, closing the heating system, and cooling along with the furnace. Taking out the sample, cleaning the surface of the sample by using deionized water, drying, cleaning the surface of the sample by using absolute ethyl alcohol, drying, putting the sample into an alumina crucible, and then putting the sample into a muffle furnace; introducing air into the furnace, controlling the air flow at 5sscm, carrying out isothermal oxidation at 1300 ℃ for 1-10 h, taking out and cooling. Assembling the core into wax film, making shell (dipping slurry, sand spraying repeatedly until required thickness, drying), steam dewaxing at 100-260 deg.C, heating to 900 deg.C, and holding temperature for 1h to fire the shell. Putting the shell group into a vacuum directional furnace, vacuumizing to below 1Pa, heating to 1550 ℃, pouring DSM11 high-temperature alloy, extracting at 6mm/min, cooling to room temperature, and taking out and removing the shell.

Comparative example 3

In this example, the difference from comparative examples 1 to 2 is that: the surface of the core substrate is subjected to different pre-oxidation processes after a coating containing Al and Si is prepared by adopting chemical vapor deposition or in-situ chemical vapor deposition; the pre-oxidation process in this example is: putting the samples into a heating furnace, putting the deposited coating samples cooled to room temperature into an alumina crucible, and filling 36-mesh alumina into the samples to keep uniform heating and prevent the samples from deforming; introducing air into the furnace, controlling the air flow at 5sscm, opening a heating device, heating to 1100 ℃, preheating and preserving heat for 2 hours, wherein the heat preservation time can be determined according to the size of a sample; heating the preheated coating sample to 1300 ℃ at the speed of 5 ℃/min, and keeping the temperature for 2 h; opening a vacuum system or introducing inert gas to reduce the concentration of oxygen in the furnace; and simultaneously, closing the heating system and cooling along with the furnace. And after the deposition is finished, closing the substrate, stopping, opening the chamber after the substrate is cooled to room temperature, and taking out the workpiece. Assembling the core into wax film, making shell (dipping slurry, sand spraying repeatedly until required thickness, drying), steam dewaxing at 100-260 deg.C, heating to 900 deg.C, and holding temperature for 1h to fire the shell. Putting the shell group into a vacuum directional furnace, vacuumizing to below 1pa, heating to 1550 ℃, pouring DSM11 high-temperature alloy, extracting at 6mm/min, cooling to room temperature, and taking out and removing the shell.

In this example, the core after the co-deposition of Si and Al was subjected to a step oxidation to form a low-melting-point phase Al₈Mo₃The phase is decomposed and converted into a high-melting-point phase, and the silicon oxide generated on the surface of the coating is low due to the step oxidation, but a small amount of silicon oxide still damages the surface of the alloy after the DSM11 high-temperature alloy is poured due to the existence of the silicon oxide, so that the quality of the alloy is influenced.

Example 1

In the present example, the difference from comparative examples 1-3 is that after the pre-oxidation treatment of comparative example 3, the metal coating is deposited by arc ion plating, the sample is installed in the coating chamber, and the vacuum system is opened to vacuumize to 1X 10^-3And pa, heating the sample in the chamber to 300-600 ℃, introducing working gas argon, applying a negative bias of 1000-300V to the sample, sequentially increasing the negative pressure at intervals of a certain time to carry out ion bombardment, then applying a negative bias of 200V to the sample with the distance between the substrate and the target material of 260mm, adjusting the negative bias to 100V and the chromium plating time to 35min, adjusting the negative bias to 70V and the chromium plating time to 300min, and repeating until the thickness of the chromium layer is 4 mu m and the chromium plating is finished. After deposition, stopping heating, cooling the substrate to room temperature, opening the chamber, taking out the workpiece, assembling the core into a wax film, making a shell (dipping slurry and sanding are repeated until the required thickness is reached, and drying), performing steam dewaxing at 100-260 ℃, heating to 900 ℃, and keeping the temperature for 1h to fire the shell. Putting the shell group into a vacuum directional furnace, vacuumizing to below 1pa, heating to 1550 ℃, pouring DSM11 high-temperature alloy, extracting at 6mm/min, cooling to room temperature, and taking out and removing the shell.

The modified core is shown in fig. 3: (a) the interface of the core and the alloy, (b) the surface of the DSM11 alloy, and (c) the surface of the core, it can be seen that after the high-temperature alloy is poured, the coating prepared by the invention can resist the corrosion of the high-temperature alloy, the obdurability of the coating is obviously enhanced, and the bonding force with the interface of the matrix is increased. The influence of silicon oxide on the alloy can be blocked due to the existence of the metal coating.

Example 2

In the present example, the difference from comparative examples 1 to 3 is that: the sample subjected to the pre-oxidation treatment in comparative example 3 was plated with a platinum metal layer using an ion sputtering apparatus. The target material is pure platinum, the pre-oxidized sample is placed in a reaction chamber of an ion sputtering instrument, the vacuum pump is started to adjust the pressure to 10Pa, the time is set to 400s, after the deposition is finished, the power supply is turned off, and the sample is taken out. Filling the core into wax film, making shell (dipping and sanding are repeated until the required thickness is reached, drying is carried out), steam dewaxing is carried out at 100-260 ℃, and the shell is fired by heating to 900 ℃ and keeping the temperature for 1 h. Putting the shell group into a vacuum directional furnace, vacuumizing to below 1pa, heating to 1550 ℃, pouring DSM11 high-temperature alloy, pumping out at the speed of 6mm/min, cooling to room temperature, taking out and removing shells.

The coating prepared by the invention can resist the corrosion of high-temperature alloy, the toughness of the coating is obviously enhanced, and the bonding force with the substrate interface is increased. The influence of silicon oxide on the alloy can be blocked due to the existence of the metal coating.

The above embodiments are not limited to the present invention, and any modification and variation within the spirit and scope of the present invention will be apparent to those skilled in the art from the following claims.

Claims

1. A method of improving interfacial stability of a metal core coating, comprising: the method is that in the process of preparing a coating on the surface of a molybdenum-based metal mold core, the stability of an interface between the mold core and the coating is improved by optimizing the components of the coating and a pre-oxidation technology; the method specifically comprises the following steps:

(1) pure molybdenum or molybdenum alloy is taken as a metal core matrix, and the codeposition of silicon and aluminum elements is carried out on the core matrix by adopting a chemical vapor deposition or in-situ chemical vapor deposition process, wherein the deposition temperature is 900-1300 ℃, and the deposition time is 2-30 h; after deposition, cooling to 800 ℃ at a cooling rate of 1-15 ℃/min, then closing a heating system, and cooling to room temperature along with a furnace to form the composite coating containing aluminum silicon on the substrate;

(2) pre-oxidation treatment: pre-oxidizing the core substrate with the coating deposited in the step (1), wherein the treatment process comprises the following steps: firstly introducing air or oxygen, controlling the flow at 5-100 sscm, then heating to 1000-1100 ℃, and preserving the heat for 1-5 h; heating to 1200-1400 ℃ at the heating rate of 1-15 ℃/min, and preserving heat for 1-8 h; after the heat preservation is finished, opening a vacuum system for vacuumizing or introducing inert gas to reduce the concentration of oxygen in the furnace, closing a heating system, and cooling along with the furnace;

(3) depositing a high-melting-point metal coating on the surface of the sample subjected to the pre-oxidation treatment in the step (2), wherein the deposition mode is arc ion plating, electroplating, magnetron sputtering, vacuum evaporation or chemical vapor deposition and the like; the melting point of the high melting point metal coating is higher than 1600 ℃.

2. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (1), the metal core matrix is pretreated before use, and the process is as follows: firstly, grinding with 240# -800# sandpaper, then sequentially cleaning in deionized water and absolute alcohol, and drying for later use.

3. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (1), when the codeposition of silicon and aluminum elements is carried out, the coating firstly forms low-melting-point Al due to the difference of the aluminum and silicon elements₈MO₃Coating and then converting, in whole or in part, to a high melting point silicide coating.

4. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (1), when codeposition of silicon and aluminum elements is carried out, firstly, an aluminum-silicon-containing intermetallic compound layer is formed on a substrate, and then an inert oxide layer is formed on the intermetallic compound layer; the total thickness of the composite coating is more than 30 μm, and the low-melting-point phase in the composite coating can disappear in the later pre-oxidation process.

5. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (3), the high-melting-point metal coating is a chromium coating, a hafnium coating, an iridium coating or a platinum coating.

6. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (1), when the codeposition of silicon and aluminum elements is carried out on the core substrate, one or more of chromium, zirconium, titanium and magnesium elements can be simultaneously deposited.

7. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (2), after pre-oxidation, the mixture is cooled to below 500 ℃ along with the furnace in the cooling process and taken out.

8. The method of increasing the interfacial stability of a metallic core coating of claim 1, wherein: in the step (3), the thickness of the deposited metal coating is 1-20 μm.