High-temperature vacuum chemical vapor aluminizing and coating equipment based on vacuum heat treatment furnace

Abstract

The invention provides high-temperature vacuum chemical vapor aluminizing and coating equipment based on a vacuum heat treatment furnace, which relates to the technical field of material surface modification and comprises an electric appliance, a gas control cabinet, an external aluminum generator, the vacuum heat treatment furnace, a cold trap, a vacuum pump, a pressure control valve and a tail gas neutralization station. Efficient activation of reactants is achieved through double cooperation of the external aluminum generator and the internal aluminum generator, the precise temperature control function, the pressure closed-loop control function and the gas flow regulation and control function of the vacuum heat treatment furnace are matched, the defects that a traditional gas phase method is uncontrollable in process and cannot achieve inner cavity aluminizing are overcome, the problem that conventional CVD equipment is expensive is avoided, and the production cost is reduced. And a uniform aluminized layer or a CVD (Chemical Vapor Deposition) coating on a hard alloy tool and mold can be formed on an aluminized workpiece in a vacuum high-temperature environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material surface modification, and particularly relates to a high-temperature vacuum chemical vapor aluminum infiltration and coating equipment based on a vacuum heat treatment furnace. BACKGROUND

[0002] In the surface protection treatment of high-temperature components (such as high-temperature turbine blades in the field of aerospace), the aluminizing process is a key technical means to improve the high-temperature corrosion resistance of the components and prolong the service life. The mainstream high-temperature turbine blade aluminizing process in the industry is mainly divided into two categories: traditional gas phase method and chemical vapor deposition (CVD) method.

[0003] The traditional gas phase aluminizing process, as an earlier applied process scheme, its core principle is to generate a gas phase state of aluminizing reactants by the reaction of process gas and aluminizing raw materials, and then make the reactants deposit on the surface of the component substrate and form an aluminizing layer in a high-temperature environment. The advantage of this process is that the technical threshold is relatively low, the technical requirements for equipment are not high, and a complex temperature control and pressure control system is not required, so the overall cost of the process is relatively low. In the scene where the aluminizing precision requirement is not high, the process still has certain application. However, it has significant defects: on the one hand, the process lacks effective control means, and the reaction temperature, system pressure and gas flow are difficult to control accurately, resulting in uneven thickness of the aluminizing layer and poor composition stability, which cannot meet the protection needs of high-precision components; on the other hand, due to the limitation of gas flow path and reaction environment, the process cannot realize the aluminizing treatment of complex structures such as the inner cavity of the component, and is difficult to adapt to key components such as turbine blades with inner cavity channels; in addition, the process produces tail gas containing corrosive components, and lacks effective collection and processing measures, resulting in a poor production environment, which not only harms the health of the operators, but also easily causes environmental pollution.

[0004] As a new process developed in recent years, the chemical vapor deposition (CVD) method effectively makes up for the shortcomings of the traditional gas phase method. The process is carried out in a low-pressure environment, and by precisely controlling the flow path of the process gas, the gas flows through the aluminizing raw material and generates high-activity aluminizing reactants, which then uniformly cover the surface of the component base (including the internal cavity structure) and complete the aluminizing. The outstanding advantage of this process is that it precisely controls the key process parameters (temperature, pressure, and gas flow), significantly improves the uniformity and composition stability of the aluminized layer, and can meet the aluminizing requirements of the internal cavity of the component. Moreover, due to the good sealing of the process environment, the safety of the production environment is improved. However, this process also has obvious limitations: on the one hand, it requires high precision of the equipment, including high-precision temperature control modules, vacuum systems, and gas flow control systems, resulting in high equipment manufacturing costs; on the other hand, the process operation is complex, and the professional level of the technicians is strictly required. The maintenance of the low-pressure environment and the precise equipment also increases the process cost, making the process face high cost pressure in large-scale industrial applications.

[0005] In summary, the two mainstream aluminizing processes currently have technical contradictions that are difficult to reconcile: the traditional gas phase method is low in cost but poor in process controllability, has a narrow application range, and lacks environmental protection; the CVD method is advanced in process and strong in controllability but has high equipment and maintenance costs. The industry urgently needs a high-temperature aluminizing technical solution that can integrate the advantages of the two processes while avoiding their defects, and has low cost, process controllability, internal cavity aluminizing capability, and environmental safety, to meet the demand for high-quality aluminizing treatment of key components such as high-temperature turbine blades. SUMMARY

[0006] To solve the above technical problems, the application provides a high-temperature vacuum chemical vapor aluminizing and coating equipment based on a vacuum heat treatment furnace.

[0007] The technical scheme adopted by the application is as follows:

[0008] A high-temperature vacuum chemical vapor aluminizing and coating equipment based on a vacuum heat treatment furnace, comprising: an electrical and gas control cabinet provided with a control module and a process gas supply device, the process gas supply device being electrically connected with the control module for controlling the process gas flow; an external aluminum generator 2, the gas inlet end of which is connected with the process gas supply device through a gas inlet pipeline one, for generating primary reactants at a first temperature; a vacuum heat treatment furnace, the gas inlet thereof being connected with the gas outlet end of the external aluminum generator through a gas outlet pipeline one; an internal aluminum generator and a workpiece tool being arranged inside the vacuum heat treatment furnace, for reacting the primary reactants with the surface of the aluminizing workpiece under vacuum and high temperature conditions, realizing aluminizing or chemical vapor deposition coating on the surface of the hard alloy workpiece; and a cold trap, the gas inlet end of which is connected with the vacuum suction port of the vacuum heat treatment furnace through a tail gas pipe, for cooling the process tail gas and trapping solid particles;

[0009] A vacuum pump, the gas inlet end of which is connected with the gas outlet end of the cold trap through the second gas inlet pipeline, is used for pumping and maintaining the negative pressure in the vacuum heating furnace; a pressure control valve is connected with the second gas inlet pipeline and electrically connected with the control module, and is used for adjusting the pressure in the vacuum heat treatment furnace; and a tail gas neutralization station is connected with the gas outlet end of the vacuum pump through the second gas outlet pipeline, and is used for treating the acidic tail gas.

[0010] Further, the high-temperature vacuum heat treatment furnace comprises: a heating furnace shell; an internal support platform installed in the heating furnace shell; and an internal reaction chamber installed on the internal support platform; wherein at least one workpiece tooling and one internal aluminum generator are arranged in the internal reaction chamber, the workpiece tooling is used for arranging the aluminum infiltration workpiece to be treated, and the process gas enters the internal reaction chamber from the gas inlet and is discharged from the vacuum pumping port.

[0011] Further, the heating furnace shell has a double-layer structure, and a cooling water jacket is arranged in the double-layer structure.

[0012] Further, the inner wall of the heating furnace shell is provided with a heat insulation layer, and the heat insulation layer is provided with an electric heating element.

[0013] Further, a pressure measuring sensor is installed on the heating furnace shell, and a temperature measuring sensor is arranged on the heating furnace shell.

[0014] Further, the gas outlet end of the cold trap is connected with one pipe opening of a three-way pipe, one pipe opening of the three-way pipe is connected with the second gas inlet pipeline, and the other pipe opening is provided with a blind plug.

[0015] Further, an exhaust pipe is connected with the three-way pipe, and the exhaust pipe is used for connecting an exhaust device.

[0016] Further, the external aluminum generator, the cold trap, the vacuum pump, the pressure control valve, the electric heating element, the tail gas neutralization station, the pressure measuring sensor and the temperature measuring sensor are electrically connected with the control module.

[0017] The beneficial effects of the present application are as follows:

[0018] The application integrates the low-cost advantage of traditional gas phase method and the process controllability of chemical vapor deposition (CVD) method, realizes efficient activation of reactants through the double synergy of external aluminum generator and internal aluminum generator, cooperates with the precise temperature control, pressure closed loop control and gas flow regulation function of the vacuum heat treatment furnace, solves the defects of uncontrollable process and inability to realize internal cavity aluminizing of traditional gas phase method, avoids the problem of expensive conventional CVD equipment, can form uniform aluminizing layer or coating for aluminizing workpiece in vacuum high temperature environment; at the same time, the solid particles in the tail gas are intercepted by the cold trap to protect the vacuum pump, the acidic tail gas is harmlessly treated by the tail gas neutralization station, the poor production environment of traditional aluminizing process is improved, and the double cooling water jacket and heat insulation layer design of the vacuum heat treatment furnace further ensures the stable operation and safe operation of the equipment, realizes efficient, controllable, environmentally friendly and safe aluminizing and coating preparation. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a plan view of the high-temperature vacuum chemical vapor aluminizing and coating equipment based on the vacuum heat treatment furnace of the embodiment of the application;

[0020] Figure 2 It is a sectional view of the vacuum heat treatment furnace of one embodiment of the application;

[0021] Figure 3 It is a schematic view of the overall structure of the high-temperature vacuum chemical vapor aluminizing and coating equipment based on the vacuum heat treatment furnace of one embodiment of the application;

[0022] Figure 4 It is a schematic view of the cold trap connection structure of one embodiment of the application;

[0023] Figure 5 It is a plan view of the internal structure of the vacuum heat treatment furnace of one embodiment of the application.

[0024] BRIEF DESCRIPTION OF DRAWINGS:

[0025] 1 - electrical and gas control cabinet, 2 - external aluminum generator, 3 - vacuum heat treatment furnace, 4 - cold trap, 5 - pressure control valve, 6 - vacuum pump, 7 - tail gas neutralization station, 8 - gas inlet pipeline one, 9 - tail gas pipe, 10 - cooling water jacket, 11 - heating furnace shell, 12 - vacuumizing port, 13 - pressure measuring sensor, 14 - heat insulation layer, 15 - electric heating element, 16 - internal reaction chamber, 17 - workpiece tooling, 18 - aluminizing workpiece, 19 - internal aluminum generator, 20 - internal support platform, 21 - gas inlet; 22 - gas inlet pipeline two; 23 - gas outlet pipeline two, 24 - temperature measuring sensor, 25 - tee, 26 - blind plug, 27 - exhaust pipe. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0027] As shown in Figures 1-5 The high-temperature vacuum chemical vapor aluminum infiltration and coating equipment based on the vacuum heat treatment furnace in the embodiments of the present application comprises an electric and gas control cabinet 1, an external aluminum generator 2, a vacuum heat treatment furnace 3, a cold trap 4, a vacuum pump 6, a pressure control valve 5 and a tail gas neutralization station 7.

[0028] The electric and gas control cabinet 1 is provided with a control module and a process gas supply device, and the process gas supply device is electrically connected with the control module. The control module can adopt a PLC or an industrial computer, and the process gas supply device comprises a process gas cylinder, a gas mass flow controller and the like, and the process gas supply device is electrically connected with the control module. The gas mass flow controller is linked through the control module to realize accurate adjustment of the flow of gases required for the aluminum infiltration process, such as hydrogen chloride, argon and hydrogen.

[0029] The gas inlet end of the external aluminum generator 2 is connected with the process gas supply device through a gas inlet pipeline 1. The external aluminum generator 2 is a sealed cavity structure, and aluminum particle raw materials can be placed in the cavity, and a single-zone heating device is provided, such as a resistance wire heating method, to ensure that the temperature in the cavity is uniform and stable. The external aluminum generator 2 is used to generate the primary reactant required for aluminum infiltration. Specifically, the external aluminum generator 2 generates aluminum chloride AlCl3 by chemical reaction of the process gas (such as hydrogen chloride) delivered from the electric and gas control cabinet 1 and the aluminum particles in the cavity at the temperature set by the control module (usually 300-500℃), to provide a material basis for the subsequent aluminum infiltration reaction in the vacuum heat treatment furnace.

[0030] The gas inlet 21 of the vacuum heat treatment furnace 3 is connected with the gas outlet end of the external aluminum generator 2 through a gas outlet pipeline 1; and the inside of the vacuum heat treatment furnace 3 is provided with an internal aluminum generator 19 and a workpiece tooling 17, which are used to make the reactant react with the surface of the aluminum infiltration workpiece 18 under vacuum and high-temperature conditions, to realize aluminum infiltration or chemical vapor deposition coating on the surface of the hard alloy workpiece.

[0031] The vacuum heat treatment furnace 3 is the core reaction place of the aluminizing process, and its functions include three points: first, providing a vacuum environment (cooperating with a vacuum pump to realize negative pressure) to avoid air interference with the aluminizing reaction; second, providing a high-temperature environment (realizing a process temperature of 800-1200 DEG C through an electric heating element in the furnace) to meet the temperature requirement of the reaction of reactants and the surface of the workpiece; and third, realizing aluminizing or CVD coating generation. Specifically, after the aluminum chloride delivered by the external aluminum generator enters the furnace, the internal aluminum generator further activates the aluminum chloride to generate a highly active aluminum chloride derivative, which then contacts and reacts with the surface of the aluminizing workpiece 18 in the workpiece tooling 17, and finally forms a uniform aluminized layer (or CVD coating) on the surface of the workpiece, and can realize internal cavity aluminizing, solving the defect that the traditional gas phase method cannot realize internal cavity aluminizing.

[0032] The gas inlet end of the cold trap 4 is connected with the vacuum exhaust port 12 of the vacuum heat treatment furnace 3 through the exhaust pipe 9, for cooling the process exhaust gas and preventing solid particles generated after the process exhaust gas is cooled from entering the vacuum pump.

[0033] The cold trap 4 is a cavity structure with cooling function, and is internally provided with a cooling assembly (such as a cooling coil), which can quickly reduce the temperature of the gas flowing through it. After the reaction, the exhaust gas (containing unreacted aluminum chloride vapor, hydrogen chloride, etc.) enters the cold trap from the vacuum heat treatment furnace 3, and the cooling assembly of the cold trap quickly reduces the temperature of the exhaust gas to below 100 DEG C, among which the aluminum chloride vapor will condense into solid particles and be intercepted by the cold trap, avoiding these solid particles from entering the vacuum pump 6 with the exhaust gas, causing internal wear of the vacuum pump 6 and reducing its service life.

[0034] It should be noted that the cold trap 4 is an existing device commonly used in the industrial field for gas cooling and solid particle interception, which is made of corrosion-resistant stainless steel (such as 316L) into a sealed cylindrical cavity. The cavity is internally integrated from top to bottom with a spiral cooling coil, a gas flow guide plate, and a particle interception basket, etc. core components, for realizing the cooling and solid particle interception of the process exhaust gas. Since the specific structure and principle of the cold trap are prior art, the present application does not improve it, and therefore will not be described in detail. Its core role in the present application is to cool the process exhaust gas (containing unreacted HCl, AlCl3 vapor, etc.) discharged from the vacuum heat treatment furnace 3, so that the solid particles (such as AlCl3 particles) in the exhaust gas that are prone to condensation are condensed and intercepted, preventing the solid particles from entering the vacuum pump 6 with the exhaust gas, causing pump body wear, and ensuring the stable operation of the vacuum pump.

[0035] The gas inlet end of the vacuum pump 6 is connected with the gas outlet end of the cold trap 4 through the gas inlet pipeline II, for pumping and maintaining the negative pressure in the vacuum heat treatment furnace 3. The vacuum pump 6 can adopt a liquid ring vacuum pump, which is suitable for working conditions containing corrosive exhaust gas (such as hydrogen chloride), and has stable vacuum pumping capacity and can maintain the system negative pressure for a long time.

[0036] Specifically, before the process starts, the vacuum pump 6 removes the air in the vacuum heat treatment furnace 3 through the cold trap 4 to provide an oxygen-free environment for the aluminizing reaction; at the same time, during the entire aluminizing process, the vacuum pump 6 continuously pumps air to maintain a set negative pressure (usually 10-100 Pa) in the furnace, and cooperates with the pressure control valve 5 to realize precise regulation of the pressure in the furnace, solving the problem of uncontrollable pressure in the traditional gas phase method.

[0037] The pressure control valve 5 is connected to the second air inlet pipeline and is used to regulate the pressure in the vacuum heat treatment furnace 3. The pressure control valve adopts an electric control mode and can accurately regulate the valve opening. It is connected in series to the second air inlet pipeline and is located between the cold trap 4 and the vacuum pump 6. Specifically, the control module receives real-time signals from the pressure measuring sensor in the vacuum heat treatment furnace 3, adjusts the valve opening, and if the pressure in the furnace is higher than the set value, increases the valve opening and improves the pumping efficiency; if the pressure in the furnace is lower than the set value, reduces the valve opening and reduces the pumping efficiency, so that the pressure in the furnace is finally stabilized in the required range, realizing controllable pressure.

[0038] The tail gas neutralization station 7 is connected to the outlet of the vacuum pump 6 through the second air outlet pipeline 23. The tail gas neutralization station includes an alkali tank (containing sodium hydroxide solution), a circulating pump, a stirrer, a gas-liquid separator, a heat exchanger and other components, forming a complete tail gas neutralization treatment system.

[0039] In the present application, the tail gas delivered by the vacuum pump 6 contains unreacted hydrogen chloride (acidic gas), which will pollute the environment and harm the health of the operators if directly discharged; after the tail gas enters the neutralization station, the sodium hydroxide solution in the alkali tank reacts with the hydrogen chloride (HCl + NaOH = NaCl + H2O) to remove the acidic substances, and then the gas and liquid are separated by the gas-liquid separator, so that the tail gas (mainly inert gas and water vapor) is finally discharged up to standard, solving the defect of poor production environment in the traditional gas phase method.

[0040] It should be noted that the tail gas neutralization station 7 is a conventional existing device in the industrial field for harmless treatment of acidic waste gas, and its core function is to remove acidic components in the process tail gas, such as unreacted HCl gas in the present application, through chemical neutralization reaction, to ensure that the discharged gas meets the requirements of the atmospheric pollutant comprehensive emission standard. The main structure of the device includes an alkali storage tank, a circulating spray system, a packed reaction layer, a gas-liquid separator and a dosing device, and its basic working logic is: acidic tail gas is fully contacted with alkaline absorption liquid for reaction → gas-liquid separation → up-to-standard discharge. Since the specific structure and principle of the tail gas neutralization station are mature existing technologies, the present application does not improve them, and therefore will not be described in detail; its core role in the present application is to receive the pretreated tail gas delivered by the vacuum pump 6, to remove acidic pollutants through neutralization reaction with NaOH solution and other alkaline absorption liquid, and to discharge the harmless gas into the atmosphere after gas-liquid separation, avoiding the pollution of corrosive gas to the environment or the harm to the health of the operators.

[0041] In one embodiment of the present application, as shown in Figure 2 The high-temperature vacuum heat treatment furnace 3 comprises a heating furnace shell 11, an internal support platform 20, and an internal reaction chamber 16. The internal support platform 20 is fixedly installed in the heating furnace shell 11. The internal reaction chamber 16 is installed on the internal support platform 20. At least one workpiece tooling 17 for arranging the aluminumizing workpieces 18 to be treated and an internal aluminum generator 19 are arranged in the internal reaction chamber 16. Process gas enters the internal reaction chamber 16 from a gas inlet 21 and is discharged from a vacuum outlet 12. The gas inlet 21 and the vacuum outlet 12 are connected to and communicate with the internal reaction chamber 16.

[0042] In the embodiment of the present application, the workpiece tooling 17 is a turbine blade, which can fix a batch of aluminumizing workpieces and ensure the uniformity of the aluminumizing process. The internal aluminum generator 19 further activates the AlCl3 generated by the external aluminum generator, such as generating AlCl2 with higher reactivity, to solve the problem of insufficient reactivity of conventional CVD aluminumizing reactants.

[0043] In one embodiment of the present application, as shown in Figure 2 The heating furnace shell 11 has a double-layer structure, and a cooling water jacket 10 is arranged in the double-layer structure. Although conventional vacuum heat treatment furnaces have cooling functions, the present application involves corrosive gas (HCl). The double-layer cooling water jacket can quickly remove the heat of the furnace shell, prevent the shell from being corroded by high temperature (HCl has enhanced corrosion at high temperature), and prevent the external temperature of the furnace body from being too high to ensure the safety of operation. The lower part of the heating furnace shell 11 is provided with a cooling water inlet, and the upper part is provided with a cooling water outlet. The inlet and the outlet are both provided with flange interfaces for connecting an external circulating cooling system, such as a circulating water pump, a cooling tower, and a water storage tank. After the equipment is started, the circulating water pump of the external circulating cooling system is started synchronously. The normal temperature cooling water (usually 20-30℃) in the water storage tank is pressurized and then injected into the annular cavity of the cooling water jacket 10 through the water inlet. When the electric heating element 15 works, high temperature (800-1200℃) is generated, part of which is conducted to the inner wall of the furnace shell through the heat insulation layer 14. After the cooling water contacts the inner wall, it quickly absorbs heat, and the water temperature rises. The hot water after absorbing heat is discharged from the water outlet at the upper part of the heating furnace shell, flows into the external cooling tower, and is cooled to normal temperature by air cooling or water cooling, and then returns to the water storage tank, and then is re-injected into the cooling water jacket by the circulating water pump, forming a continuous closed-loop circulation.

[0044] In one embodiment of the present application, as shown in Figure 2 and Figure 5 The inner wall of the heating furnace shell 11 is provided with a heat insulation layer 14, and the heat insulation layer 14 is provided with an electric heating element 15.

[0045] The heat insulation layer 14 can be made of high-purity alumina or graphite felt to reduce the transfer of high temperature inside the furnace to the outer shell and reduce the load on the cooling water jacket. When multiple electric heating elements 15 are provided, they are distributed at equal angles with the central axis of the heating furnace outer shell 11 as the center. The electric heating elements 15 ensure uniform temperature in the internal reaction chamber and solve the problem of uneven temperature in the traditional gas phase method leading to differences in aluminizing thickness. Multiple electric heating elements 15 can be used for zoned heating.

[0046] In one embodiment of the present invention, such as Figure 1 As shown, a pressure measuring sensor 13 is installed on the heating furnace shell 11, and a temperature measuring sensor is provided on the heating furnace shell 11.

[0047] Pressure sensor 13 monitors the furnace pressure in real time and feeds the signal back to the control module, which is linked with pressure control valve 5 to achieve closed-loop pressure control. Temperature sensor 24 can be a thermocouple, such as type K or type S, which is inserted into the internal reaction chamber to monitor the reaction temperature in real time and feeds the signal back to the control module. The control module is linked with electric heating element 15 to achieve closed-loop temperature control.

[0048] In one embodiment of the present invention, such as Figure 4 As shown, the outlet of the cold trap 4 is connected to a three-way pipe 25. One port of the three-way pipe 25 is connected to the second air inlet pipe 22, and the other port is equipped with a blind flange plug 26. The blind flange plug 26 is used to close the cold trap during normal operation. When the cold trap 4 needs cleaning, if solid particles accumulate, the blind flange plug can be opened for maintenance without disassembling the entire air circuit.

[0049] In one embodiment of the present invention, such as Figure 4 As shown, an exhaust pipe 27 is connected to the tee pipe 25, which is used to connect to exhaust equipment. Specifically, the exhaust pipe 27 can be connected to the workshop exhaust system. When the pressure inside the furnace rises abnormally, such as in the event of a gas leak, emergency exhaust can be carried out through the exhaust pipe to avoid danger.

[0050] In one embodiment of the present invention, the external aluminum generator 2, cold trap 4, vacuum pump 6, pressure control valve 5, electric heating element 15, pressure measuring sensor 13 and temperature measuring sensor are electrically connected to the control module, and the detection ends of pressure measuring sensor 13 and temperature measuring sensor are located in the internal reaction chamber 16.

[0051] The working process of this invention needs to follow the flow of vacuum establishment → gas supply → reactive aluminizing → tail gas treatment. The coordination relationship between each step and component is as follows:

[0052] 1. Pretreatment stage: Establishing a vacuum environment

[0053] The control module starts the vacuum pump 6, which removes the air from the vacuum heat treatment furnace 3 through the cold trap 4 and the exhaust pipe 9.

[0054] The pressure measuring sensor 13 feeds back the pressure in the furnace in real time. When the pressure falls below 10 Pa (satisfying the low pressure requirement of the CVD process), the vacuum pump enters the maintenance mode, and the pressure control valve 5 fine-tunes the opening degree to keep the pressure in the furnace stable.

[0055] 2. Heating and gas supply stage: generating reactants

[0056] The electric heating element 15 is started, and the temperature is raised at a preset rate (such as 10 ℃ / min). The temperature measuring sensor 24 monitors the temperature of the internal reaction chamber 16 until it reaches 800-1200 ℃ (aluminizing process temperature);

[0057] The process gas supply device of the electric and gas control cabinet 1 is started. First, Ar gas (inert gas) is introduced to purge the gas path (to avoid residual air); then HCl gas (process gas) is introduced, and the flow rate is controlled by a gas mass flow meter, such as 50-200 sccm;

[0058] The HCl gas enters the external aluminum generator 2, and the resistance wire of the external aluminum generator is heated to 300-500 ℃. The HCl reacts with aluminum particles to generate AlCl3 (primary reactant), and the AlCl3 enters the gas inlet 21 of the vacuum heat treatment furnace 3 through the gas outlet pipeline.

[0059] 3. Aluminizing reaction stage: surface modification of workpiece

[0060] After the AlCl3 enters the internal reaction chamber 16, it flows through the internal aluminum generator 19. The internal aluminum generator further reacts the AlCl3 to generate highly active AlCl2 (secondary reactant) at high temperature (800-1200 ℃) in the furnace;

[0061] The highly active AlCl2 diffuses to the surface of the aluminizing workpiece 18 in the workpiece tooling 17 along with the gas flow, reacts with elements such as Fe and Ni in the workpiece (such as high-temperature alloy), generates an Al-Fe-Ni alloy layer (or a pure Al coating), and realizes simultaneous aluminizing of the inner and outer cavities (because the gas flow can enter the inner cavity of the workpiece).

[0062] 4. Tail gas treatment stage: environmental protection up to standard

[0063] The tail gas (containing unreacted HCl, AlCl3 vapor, and Ar gas) after the reaction enters the cold trap 4 through the vacuum suction port 12. The cooling coil in the cold trap lowers the temperature of the tail gas to below 100 ℃, and the AlCl3 vapor condenses into solid particles (which are filtered and retained by the cold trap);

[0064] The cooled tail gas (mainly containing HCl and Ar gas) enters the vacuum pump 6 and then enters the tail gas neutralization station (7) through the gas outlet pipeline two (23).

[0065] The NaOH solution of the tail gas neutralization station reacts with HCl (HCl+NaOH=NaCl+H2O), and the neutralized tail gas (Ar gas+water vapor) is separated by a gas-liquid separator and discharged up to standard.

[0066] The high-temperature vacuum chemical vapor aluminum infiltration and coating equipment based on the vacuum heat treatment furnace integrates the low-cost advantage of the traditional gas phase method and the process controllability of the chemical vapor deposition (CVD) method, realizes efficient activation of reactants through the dual synergy of the external aluminum generator and the internal aluminum generator, cooperates with the precise temperature control (isometric distribution of electric heating elements), pressure closed-loop control (linkage of pressure measurement sensors and pressure control valves) and gas flow regulation function of the vacuum heat treatment furnace, solves the defects of uncontrollable process and inability to realize internal cavity aluminum infiltration of the traditional gas phase method, avoids the problem of high cost of conventional CVD equipment, can form a uniform aluminum infiltration layer or CVD coating for the aluminum infiltration workpiece in a vacuum high-temperature environment, and improves the poor production environment of the traditional aluminum infiltration process. The design of the double cooling water jacket and the heat insulation layer of the vacuum heat treatment furnace further guarantees the stability and safety of the equipment operation, realizes efficient, controllable, environmentally friendly and safe aluminum infiltration and CVD coating preparation.

[0067] In the description of the present application, the terms "first", "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. The meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0068] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0069] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature is "over", "above" and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature is "under", "below" and "underneath" the second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0070] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. The illustrative description of the above terms in the present specification does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0071] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace, characterized in that, include: Electrical and gas control cabinet (1) is equipped with a control module and a process gas supply device. The process gas supply device is electrically connected to the control module and is used to control the flow rate of the process gas. An external aluminum generator (2) has its inlet end connected to a process gas supply device via an inlet pipe (8) to generate primary reactants at a first temperature. The vacuum heat treatment furnace (3) has its air inlet (21) connected to the air outlet of the external aluminum generator (2) through an air outlet pipe; it is equipped with an internal aluminum generator (19) and a workpiece fixture (17) to react the primary reactants with the surface of the aluminized workpiece (18) under vacuum and high temperature conditions to achieve aluminization or chemical vapor deposition coating. The cold trap (4) has its inlet end connected to the vacuum port (12) of the vacuum heat treatment furnace (3) through the tail gas pipe (9) for cooling the process tail gas and trapping solid particles. The vacuum pump (6) has its inlet end connected to the outlet end of the cold trap (4) through the inlet pipe 2, and is used to evacuate and maintain the negative pressure inside the vacuum heating furnace (3); Pressure control valve (5) is connected to the second air inlet pipe and electrically connected to the control module. It is used to regulate the pressure inside the vacuum heat treatment furnace (3). The tail gas neutralization station (7) is connected to the outlet end of the vacuum pump (6) through the outlet pipe two (23) and is used to treat acidic tail gas.

2. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 1, characterized in that, High-temperature vacuum heat treatment furnace (3) includes: Furnace outer shell (11); An internal support platform (20) is installed inside the outer shell (11) of the heating furnace; An internal reaction chamber (16) is installed on an internal support platform (20); wherein, at least one workpiece fixture (17) and an internal aluminum generator (19) are arranged in the internal reaction chamber (16). The workpiece fixture (17) is used to arrange the aluminizing workpiece (18) or mold workpiece to be processed. The process gas enters the internal reaction chamber (16) from the air inlet (21) and is discharged from the vacuum port (12).

3. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 2, characterized in that, The outer shell (11) of the heating furnace is a double-layer structure with an inner and outer layer, and a cooling water jacket (10) is provided inside the double-layer structure.

4. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 3, characterized in that, The inner wall of the heating furnace shell (11) is provided with a heat insulation layer (14), and an electric heating element (15) is provided on the heat insulation layer.

5. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 4, characterized in that, A pressure measuring sensor (13) is installed on the outer shell (11) of the heating furnace, and a temperature measuring sensor (24) is provided on the outer shell (11) of the heating furnace.

6. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 5, characterized in that, The outlet of the cold trap (4) is connected to one port of the three-way pipe (25). One port of the three-way pipe (25) is connected to the second air inlet pipe (22), and the other port is equipped with a blind flange plug (26).

7. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 6, characterized in that, The tee pipe (25) is connected to an exhaust pipe (27), which is used to connect to the exhaust equipment.

8. The high-temperature vacuum chemical vapor deposition and coating equipment based on a vacuum heat treatment furnace according to claim 7, characterized in that, The external aluminum generator (2), cold trap (4), vacuum pump (6), pressure control valve (5), electric heating element (15), exhaust gas neutralization station (7), pressure measuring sensor (13) and temperature measuring sensor (24) are electrically connected to the control module respectively.

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