Method for improving flowability of small-particle-size spraying powder based on supercharging device

Abstract

The invention belongs to the technical field of spraying, particularly relates to a method for improving the flowability of small-particle-size spraying powder based on a supercharging device, discloses a method for improving the flowability of the small-particle-size spraying powder based on the supercharging device, and aims to solve the problems that the flowability of the small-particle-size spraying powder is poor, blockage is prone to occurring, and the powder feeding flow is unstable. The coating porosity is high; the deposition efficiency is low; the repeatability is poor, and the like. The method is characterized in that a composite pressure field formed by superposition of reference carrier gas pressure and high-frequency dynamic pulse pressure is established in a closed powder feeder tank body, and precise closed-loop control is carried out by a system composed of a central control unit, a conveying device, a main conveying gas circuit, a dynamic pulse gas circuit and a pressure sensing and adjusting module. By the adoption of the technical scheme, stable and continuous conveying of small-particle-size powder can be achieved, the porosity of a coating is remarkably reduced, the deposition efficiency and the production efficiency are improved, and the application range is widened.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spraying, and particularly relates to a method for improving the flowability of small-particle-size spraying powder based on a supercharging device. BACKGROUND

[0002] Under the macro-background of the continuous evolution of semiconductor manufacturing technology towards higher integration and more precise structure, the performance and service life of the internal parts of the plasma etching equipment, as key manufacturing equipment, are directly related to the stability of the process window, the yield and the overall production cost. In order to effectively protect the cavity components from physical bombardment and chemical erosion of high-energy plasma, the atmospheric plasma spraying (APS) technology has become an indispensable core process in this field due to its ability to prepare ceramic protective coatings with high melting point, high hardness and corrosion resistance. The quality of the coating, especially its density, bonding strength with the substrate and resistance to plasma erosion, constitutes the core index for evaluating the protective performance. Under this technical framework, the academic and industrial circles generally believe that the use of smaller spraying powder is the key technical path to realize the fine structure of the coating, reduce the porosity and thus obtain higher density and better protective performance.

[0003] In early technical practice, such as the protective coating preparation method disclosed in Chinese patent CN103215535B, the technical focus is mainly on improving the thermal expansion coefficient matching between the coating and the substrate and improving the bonding strength by optimizing the material composition of the powder (for example, using a mixture of pure aluminum powder and Y2O3-Al2O3 composite powder). This scheme uses high-speed carrier gas to transport powder with a particle size range of 1-50 μm into the plasma jet, which effectively solves the cracking and peeling of the coating and substrate due to thermal stress mismatch under the technical conditions at that time, and makes an important contribution to improving the basic performance of the coating. However, with the continuous rise of the performance requirements of the coating, the trend of technological development clearly points to the use of smaller particle size powder. The recently disclosed Chinese patent CN118222967B embodies this trend, which uses a double-layer spraying structure and explicitly uses 1-5 μm ultra-fine powder in the preparation of the key surface layer, aiming to build a high-density anti-plasma erosion coating through effective filling of small particles. This application of small particle size, even micron / submicron level powder, although theoretically opens up a path for the leap of coating performance, inadvertently exacerbates a deep-seated, physically inherent technical contradiction.

[0004] The deep-seated contradiction lies in that when the particle size of the sprayed powder is significantly reduced, especially into the interval below 20 pm, its physical behavior changes qualitatively, while the traditional powder feeding system has not made adaptive adjustments in design principles. Specifically, the reduction in particle size leads to an exponential increase in the specific surface area of the particles, which makes the short-range forces such as van der Waals force and electrostatic adsorption force on the surface of the particles relative to the gravity of the particles jump from a negligible secondary factor to a dominant factor. These significantly enhanced inter-particle forces lead to a sharp increase in the cohesiveness of the powder, and the flowability deteriorates severely. Instead of behaving as a collection of discrete particles, the powder tends to form unstable and easily collapsed agglomerates or "powder bridges". Therefore, when dealing with such small particle size powder, the traditional powder feeder, which relies on gravity and conventional carrier gas drag force, can no longer output a stable and continuous powder flow. Instead, a "clogging-collapse-gushing" pulsed delivery mode emerges, i.e. intermittent powder clogging in the powder feeding pipeline, followed by an instant burst under the accumulated carrier gas pressure, resulting in a large amount of powder being sprayed out in a short time, and then clogging again. This unstable mass flow pulsation has a cascading negative impact on the plasma spraying process. On the one hand, when a large amount of powder rushes into the relatively constant energy field of the plasma jet, the energy allocated to each particle per unit time drops sharply, resulting in a large amount of powder that cannot be fully melted or reach the ideal melting state. These unmelted or semi-melted solid particles impact the substrate at high speed, not only failing to effectively form a dense layered structure, but also causing the internal porosity of the coating to increase sharply, and even causing sputtering due to impact, significantly reducing the effective deposition efficiency (i.e. powder deposition rate) of the powder. On the other hand, during the clogging stage, the powder feeding is interrupted, resulting in the plasma jet running empty, which not only wastes energy but also reduces overall production efficiency. The existing technology, such as the aforementioned CN118222967B, although indicates the technical direction of using small particle size powder, does not provide an effective means to overcome this inherent physical limitation, making it difficult to ensure the stability of the coating quality and the repeatability of the process in actual industrial application.

[0005] Therefore, how to develop a powder feeding method that can fundamentally break the bondage of inter-particle forces and ensure stable, continuous and uniform powder feeding in the plasma spraying process for the inherent low flowability physical properties of small particle size ceramic powder, to solve a series of problems such as coating quality degradation, low powder deposition rate and increased production cost caused by powder pulsation, has become a key challenge and technical problem to be solved by technical personnel in the field to promote the development of high-performance semiconductor equipment protective coating technology. SUMMARY

[0006] The present application aims to provide a method for improving the flowability of small particle size spraying powder based on a pressurizing device, which is intended to solve the technical problems in the background art that small particle size spraying powder is prone to clogging and pulse-like gushing when using a traditional atmospheric plasma spraying (APS) powder feeding system due to its inherent high cohesion and low flowability, resulting in unstable powder feeding flow, and further causing high porosity of the coating, low deposition efficiency and poor process repeatability.

[0007] To achieve the above-mentioned application purposes, the present application provides a method for improving the flowability of small particle size spraying powder based on a pressurizing device, which is realized by improving the structure and control logic of the powder feeding system of the existing atmospheric plasma spraying equipment. The core of the method is to establish a composite pressure field environment composed of a reference carrier gas pressure and a high-frequency dynamic pulse pressure in a closed powder feeder tank. This composite pressure field environment provides stable and continuous powder delivery driving force on the one hand, and actively and continuously breaks the mechanical balance and agglomeration structure formed between powder particles on the other hand, thereby converting low-flowability small particle size powder into a continuously flowing, uniform fluid-like state, ensuring that the delivery process of the powder to the plasma jet is stable, continuous and constant in mass flow.

[0008] Specifically, the technical solution provided by the present application is executed by a system integrating precise gas path control and closed-loop feedback regulation. The system at least includes a central control unit, a specially modified powder delivery device, a main delivery gas path module, a dynamic pulse gas path module, and a pressure sensing and pressure relief regulation module.

[0009] The central control unit is specifically an industrial-grade programmable logic controller (PLC) or a dedicated microcontroller with high-speed computing capability and multi-channel input / output interface. The central control unit, as the core of the entire method execution, has a firmware program containing a specific control algorithm preset inside. The control algorithm cooperatively controls each execution component of the main delivery gas path module, the dynamic pulse gas path module and the pressure sensing and pressure relief regulation module according to the target powder flow setting value input from the outside and the real-time collected system state parameters.

[0010] The powder delivery device has a powder feeder tank body with pressure-bearing capacity and an internal surface subjected to precise polishing treatment. The tank body material is SS316L stainless steel, and the internal surface roughness Ra is not greater than 0.4 microns to minimize the adhesion between the powder and the tank wall. The lower part of the tank body is provided with a conical structure with a cone angle of 60 degrees to facilitate the mass flow of the powder under the action of gravity. At the bottom of the conical structure, a powder output port is provided, which is connected to the powder feeding pipeline leading to the plasma torch.

[0011] The main conveying gas path module, which is used to provide the basic carrier gas flow required for conveying powder. The module includes a first mass flow controller (MFC-1) connected to an inert gas source and the corresponding gas path pipeline. The inert gas is argon (Ar) or nitrogen (N2) with a purity of not less than 99.999%. The output end of the first mass flow controller is connected to the upper space of the powder feeder tank through the first gas path pipeline, so as to establish a basic positive pressure environment in the tank and serve as the main carrier for conveying powder. The control signal input end of the first mass flow controller is electrically connected with the analog output port of the central control unit, and the flow setting value is dynamically set by the central control unit according to the overall process requirements.

[0012] The dynamic pulse gas path module is the key part to realize the core technical effect of the application, which is used to inject high-frequency and controlled pressure pulses into the bottom of the powder bed in the powder feeder tank. The module includes a second mass flow controller (MFC-2) connected to an inert gas source, a high-frequency response electromagnetic valve, and a gas distributor. The second mass flow controller is used to accurately control the gas flow into the pulse generation link, thereby indirectly controlling the amplitude of the pressure pulse. The high-frequency response electromagnetic valve, specifically a proportional electromagnetic valve with a response time of less than 2 milliseconds and a maximum working frequency of not less than 200 Hz, has a valve body made of SS316L stainless steel and a corrosion-resistant perfluoroether rubber (FFKM) sealing element. The control signal input end of the high-frequency response electromagnetic valve is electrically connected with the pulse width modulation (PWM) output port of the central control unit. The central control unit drives the electromagnetic valve to open and close at high frequency by outputting a PWM signal with a specific frequency and duty cycle, thereby chopping the continuous gas flow from the second mass flow controller into a pulse gas flow. The gas distributor is installed at the bottom of the conical structure of the powder feeder tank and above the powder output port. The gas distributor is specifically a ring-shaped or disc-shaped component made of sintered metal microporous material, which is uniformly distributed with micron-sized gas outlet holes. The output end of the high-frequency response electromagnetic valve is connected to the gas distributor through the second gas path pipeline. This structural design ensures that the pulse gas flow can uniformly and diffusely act on the powder area about to enter the output port, thereby realizing efficient fluidization and deagglomeration locally, while avoiding the powder channeling effect or reverse blowing caused by single-point gas flow impact.

[0013] The pressure sensing and pressure relief regulating module is used for real-time monitoring and closed-loop regulation of the overall pressure in the powder feeder tank. The module includes a high-precision pressure sensor and a proportional pressure relief valve. The pressure sensor, specifically a piezoresistive pressure sensor with a response time less than 1 millisecond and a measurement accuracy better than 0.1% of the full scale, has its probe installed on the upper part of the powder feeder tank for real-time monitoring of the absolute pressure value in the tank. The signal output end of the pressure sensor is electrically connected to the analog input port of the central control unit. The proportional pressure relief valve has its valve port connected to the upper part of the powder feeder tank, and its other end leading to the waste gas treatment system. The pressure relief valve is driven by a 4-20mA analog control signal, and its control signal input end is electrically connected to another analog output port of the central control unit.

[0014] Based on the above system configuration, the specific execution steps of the method of the application are as follows:

[0015] First step, system initialization and parameter setting. The operator inputs the key physical parameters of the small particle size powder to be sprayed, including its average particle size, particle size distribution, material density and angle of repose, to the central control unit through the human-machine interaction interface. At the same time, according to the requirements of the spraying process, the target powder mass delivery rate is set. The internal firmware program of the central control unit has a parameter mapping database built in, which stores the corresponding relationship between different powder characteristic parameters and the optimal operation parameters (including the basic carrier gas flow, pulse frequency, pulse duty cycle, pulse air flow amplitude and target working pressure range in the tank). The central control unit retrieves the optimal initial operation parameter set from the database or calculates it through the built-in algorithm according to the input powder parameters and target rate.

[0016] Second step, establish a reference carrier gas pressure environment. The central control unit issues an instruction to the first mass flow controller (MFC-1) to set its output to a predetermined basic carrier gas flow value (for example, 5-15 standard liters / minute). The gas flow enters the upper part of the powder feeder tank and starts to establish a basic positive pressure in the closed tank.

[0017] Third step, dynamic pulse deagglomeration and fluidization. While establishing the baseline gas pressure, the central control unit sends a command to the second mass flow controller (MFC-2) to set its output to a predetermined gas flow rate value (e.g., 0.5-5 standard liters per minute) for generating pulses. Then, the PWM output module of the central control unit starts generating a square wave signal with a predetermined frequency (e.g., 20-150 Hz) and a predetermined duty cycle (e.g., 10-50%) and applies it to the high-frequency response solenoid valve. The high-frequency solenoid valve then opens and closes at a high speed, converting the stable gas flow from MFC-2 into a high-frequency pulsed gas flow, which is uniformly injected into the powder bed at the bottom of the powder feeder tank through the gas distributor. This periodic small pressure pulse propagates in the powder bed, which acts as a kind of pneumatic, high-frequency micro-vibration, which can continuously destroy the force chain network and micro-arch structure formed by van der Waals force, electrostatic adsorption force and liquid bridge force between powder particles. This process effectively breaks up the small particle size powder agglomerates that are in a state of rest or near consolidation, significantly weakens the cohesiveness of the powder, and macroscopically exhibits effective activation and fluidization of the powder bed, thereby fundamentally eliminating the physical basis of powder clogging.

[0018] Fourth step, implementation of multivariable closed-loop feedback control. During system operation, the central control unit executes a complex closed-loop control algorithm. The algorithm includes at least one main pressure control loop and one flow feedforward adjustment logic. The main pressure control loop is composed of the pressure sensor, the central control unit and the proportional pressure relief valve. The pressure sensor feeds back the real-time monitored tank pressure value to the central control unit. The central control unit compares it with the preset target working pressure range (e.g., 5.0 psi ± 0.2 psi). When the real-time pressure is higher than the upper limit of the range, the central control unit proportionally increases the control signal applied to the proportional pressure relief valve, increasing its opening, thereby accurately releasing part of the gas to reduce the pressure. Conversely, when the pressure is lower than the lower limit of the range, the opening of the pressure relief valve is reduced. The response speed of this closed-loop is extremely fast, ensuring that the working pressure in the tank is always accurately maintained within a very narrow set window, providing a constant pressure gradient for stable delivery. At the same time, the central control unit adjusts the set value of the first mass flow controller (MFC-1) according to the target powder mass delivery rate, ensuring that the basic delivery power matches the required powder flow. Throughout the process, the frequency and duty cycle of the dynamic pulse remain constant or are fine-tuned according to more advanced adaptive algorithms as key fluidization parameters.

[0019] Through the synergistic effect of the above steps, the small particle size powder is no longer a collection of particles with poor flowability in the traditional sense when leaving the output port of the powder feeder, but a gas-solid two-phase flow with good flowability that is fully activated and uniformly mixed in the carrier gas. This two-phase flow is then stably, continuously and uniformly transported to the plasma torch through the powder delivery pipeline under the driving of a constant pressure gradient, thereby ensuring that the powder mass flow entering the plasma jet is constant in time. This directly ensures that each powder particle can be fully and equally heated and accelerated to achieve the ideal melting state, ultimately forming a dense, uniform, low-porosity high-quality coating on the substrate surface, and significantly improving the effective deposition efficiency of the powder.

[0020] As a preferred embodiment of the present application, a pressure threshold monitoring and alarm module is further integrated into the logic program of the central control unit. The module is provided with an absolute safety pressure upper limit and an alarm threshold for abnormal operating pressure. If the measured value of the pressure sensor exceeds the alarm threshold (e.g., 10% extension outside the upper and lower limits of the preset working pressure range) and lasts for a predetermined time (e.g., 500 milliseconds), the central control unit will drive an audible and visual alarm device connected to its digital output module to issue an alarm to prompt the operator to pay attention to the equipment status. If the pressure reaches the absolute safety pressure upper limit, the system will automatically shut off all air intake and fully open the pressure relief valve to ensure the safety of the equipment.

[0021] As another preferred embodiment of the present application, the method is particularly suitable for processing small particle size spraying powder with a particle size range of 0.1 to 20 microns, especially ultra-fine powder with a D50 particle size of less than 10 microns, such as yttrium oxide (Y2O3), aluminum oxide (Al2O3), or composite ceramic powder thereof.

[0022] As another preferred embodiment of the present application, the target working pressure preset value in the powder feeder tank is in the range of 1 to 10 psi (pounds per square inch), and the specific optimal value depends on the type, particle size, and delivery distance of the powder.

[0023] The present application has the following beneficial effects: The method for improving the flowability of small particle size spraying powder based on the pressurizing device provided by the present application fundamentally solves the technical problem of stable and continuous delivery of small particle size powder due to strong cohesion by constructing a composite pressure field composed of a reference carrier gas and high-frequency dynamic pressure pulses, and combining precise multivariable closed-loop feedback control. Compared with the prior art, the present application has the following beneficial effects:

[0024] First, it significantly improves coating quality. By ensuring a constant powder mass flow rate, the uniformity and sufficiency of powder heating in the plasma jet are guaranteed, thereby enabling the stable preparation of protective coatings with extremely low porosity (e.g., reduced from 5.87% to 2.28%), dense structure, and excellent performance.

[0025] Second, it significantly improves production efficiency and material utilization. It eliminates the ineffective spraying time caused by the powder feeding "blockage-spraying" cycle and the sputtering loss caused by incomplete powder melting, which significantly improves the effective powder deposition efficiency, increases overall production efficiency by about 120%, and reduces production costs by about 54.5%.

[0026] Third, it broadens the application range of small-particle-size powders. This invention provides a reliable technical approach for the application of ultrafine powders in the 0.1-20 micrometer range, especially sub-10 micrometer range, in industrial plasma spraying, making it possible to prepare more advanced and precise coatings using such powders. This is of great significance for promoting technological progress in high-tech fields such as semiconductor equipment protection. Attached Figure Description

[0027] Figure 1 This is a system block diagram according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the powder conveying device in an embodiment of the present invention;

[0029] Figure 3 for Figure 2 A cross-sectional view of the powder conveying device shown.

[0030] Figure 4 for Figure 3 Schematic diagram of the gas distributor in the middle;

[0031] Figure 5 This is a schematic flowchart of the method of the present invention;

[0032] Figure 6 This is a schematic diagram illustrating the change of the composite pressure field inside the tank as described in this invention over time.

[0033] The reference signs are as follows: 10, central control unit; 20, powder conveying device; 21, powder feeder tank; 22, conical structure; 23, powder output port; 30, main conveying gas path module; 31, first mass flow controller; 32, first gas path pipeline; 40, dynamic pulse gas path module; 41, second mass flow controller; 42, high-frequency response electromagnetic valve; 43, second gas path pipeline; 44, gas distributor; 50, pressure sensing and pressure relief adjustment module; 51, high-precision pressure sensor; 52, proportional pressure relief valve; 100, system initialization and parameter setting step; 200, establishing a reference carrier gas pressure environment step; 300, starting dynamic pulse deagglomeration and fluidization step; 400, implementing multivariable closed-loop feedback control step. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the present application clearer, the following will combine the drawings and specific examples to make a detailed and reproducible description of the method for improving the flowability of small-particle-size sprayed powder based on a pressurizing device. It should be understood that the specific implementation described herein is only used to explain the present application, and does not constitute any form of limitation on the protection scope of the present application.

[0035] REFERENCE Figure 1 With reference to the system block diagram shown in the figure, the method described in the present application is implemented through a highly integrated precision pneumatic and control system. The system is logically and physically an organic whole, and its core components include a central control unit 10 as the core of system operation and control, a powder conveying device 20 specially structured and designed, a main conveying gas path module 30 responsible for establishing the basic conveying power, a dynamic pulse gas path module 40 as the technical core of the present application for actively activating powder, and a pressure sensing and pressure relief adjustment module 50 for realizing closed-loop feedback control of the system pressure. The five modules work together under the unified and coordinated scheduling of the central control unit 10 to fundamentally improve the flowability of small-particle-size sprayed powder.

[0036] Specifically, the central control unit 10, in a specific engineering implementation, selects a Siemens S7-1500 series industrial programmable logic controller (PLC) equipped with a high-speed processor module and multi-channel, high-precision analog and digital input / output (I / O) modules. The PLC runs a control program inside according to the logic of the method of the present application. This program not only performs basic sequential logic control, but also embeds complex multivariable coupling and decoupling algorithms, parameter self-adaptive matching algorithms based on a powder characteristic database, and closed-loop PID (proportional-integral-derivative) control algorithms for ensuring stable operation of the system. The operator sets the process parameters and monitors the system state through the touch screen human-machine interface (HMI) connected to the PLC.

[0037] Next, the core physical component of the system, the powder delivery device 20, is described in detail. Its specific structure can be referred to the overall schematic diagram of Figure 2 and the internal cross-sectional view of Figure 3 . The main body of the device is a powder feeder tank 21 with excellent pressure-bearing capacity. To ensure sufficient safety margin in a pressurized environment, the tank 21 is made of 5mm thick SS316L stainless steel plate through precise argon arc welding process, and the weld quality is ensured by non-destructive testing, with a design pressure capacity of not less than 1.5 megapascals. The inner surface of the tank 21 is a key interface affecting the flowability of small particle size powder, so it is treated by multiple passes of mechanical polishing and electrochemical polishing, and the final surface roughness Ra value is strictly controlled to be not more than 0.4 microns. This mirror level of inner wall treatment greatly reduces the electrostatic adsorption force and van der Waals force between the powder particles and the tank wall, reducing the powder wall adhesion and accumulation phenomenon from the source. To utilize gravity to assist the smooth flow of powder and eliminate flow dead zones, the lower part of the powder feeder tank 21 is designed as a conical structure 22 with a conical angle of 60 degrees. This angle is the optimal angle for achieving mass flow of various ceramics and metal powders in powder mechanics. At the bottom of the conical structure 22, a powder outlet 23 is provided for connecting to the external powder conveying pipeline.

[0038] The main function of the main conveying gas path module 30 is to provide stable and adjustable basic carrier gas for the entire conveying process, thereby establishing a macroscopic and continuous pressure gradient in the powder feeder tank 21 as the main driving force for the movement of the powder along the powder conveying pipeline. The core component of this module is a high-precision mass flow controller of Brooks SLA5850S series, i.e. the first mass flow controller 31. The controller is connected to an industrial-grade argon gas source with a purity of up to 99.9995%. Its output end is connected to a special gas nozzle on the top cover of the powder feeder tank 21 through a first gas path pipe 32 made of SS316L stainless steel with an outer diameter of 6mm. The gas enters from the upper part of the tank, aiming to form a uniform downward pressure gas cushion. The flow setting value of the first mass flow controller 31 is precisely controlled by the 4-20mA analog output signal of the central control unit 10, and its setting range can be continuously adjustable between 0 and 20 standard liters per minute (SLPM) according to process requirements.

[0039] The dynamic pulse gas path module 40 is the key innovation of the present application, which is distinguished from the prior art. The design purpose is to apply a high-frequency, controlled, diffuse pneumatic energy to the most critical area of the powder bed, that is, the cone bottom area about to enter the powder outlet 23, so as to actively disperse the small particle size powder agglomerates in the resting or near-solidified state, and realize in-situ and continuous fluidization. The module is composed of a second mass flow controller 41, a high-frequency response electromagnetic valve 42, and a specially designed gas distributor 44. The second mass flow controller 41 is also selected from the Brooks SLA5850S series, which provides a stable and accurate reference gas flow for pulse generation. The high-frequency response electromagnetic valve 42, specifically a specific model of proportional electromagnetic valve from ASCO company, has light internal moving parts and fast response speed of the driving coil, which ensures that the delay time from the electrical signal to the valve opening and closing action is less than 2 milliseconds, so that it can stably and accurately switch on and off at a frequency of up to 200 Hz. The valve body material is SS316L stainless steel, and the dynamic seal is made of corrosion-resistant and low permanent deformation rate perfluoroether rubber (FFKM) to ensure the air tightness and service life under long-term high-frequency operation. The driving signal of the electromagnetic valve comes from a high-speed pulse width modulation (PWM) output port of the central control unit 10. The central control unit 10 directly controls the number of switchings per second and the duration of each opening of the electromagnetic valve by precisely adjusting the frequency (Frequency) and duty cycle (Duty Cycle) of the output PWM signal, so as to "chop" the continuous gas flow from the second mass flow controller 41 into a series of micro-pulse gas flows with precise control of pressure and flow.

[0040] This series of high-frequency pulse gas flow is guided to the position near the top of the powder outlet 23 through a separate second gas path pipe 43, which is installed at the bottom of the cone structure 22 inside the powder feeder tank 21. At this position, there is an essential component, the gas distributor 44, whose specific structure can be referred to Figure 4The gas distributor 44 is designed as a ring-shaped component in this embodiment, which is made of 316L stainless steel porous material sintered by powder metallurgy process. It has a complex interconnected three-dimensional pore structure inside, and on its working surface facing the powder bed, there are uniformly distributed micropores with a pore size of 5 to 10 microns. After the pulsed gas flow enters the internal cavity of the gas distributor 44, it is forced to seep out uniformly and diffusely through these micropores. This design avoids the risk of "tunneling effect" (i.e. the gas flow creates a fixed channel in the powder) or the risk of blowing the powder upwards and causing blockage caused by direct impact of a single gas nozzle. On the contrary, it can form a uniform and oscillating fluidized bed in the local area near the powder outlet, which acts like a non-contact, high-frequency micro-vibration on the powder, with enough energy to continuously break the mechanical balance between powder particles due to electrostatic, liquid bridge and van der Waals forces, so that the powder agglomerates are broken down as soon as they are formed, thus maintaining the loose and "activated" state of the entire powder bed at the bottom.

[0041] In order to ensure the absolute stability of the above-mentioned composite pressure environment and maintain it accurately within the optimal window set by the process, the system is also equipped with a pressure sensing and pressure relief adjustment module 50. The core of this module is a WIKA A-10 series high-precision pressure sensor 51 installed on the top of the powder feeder tank 21, which has a response time of less than 1 millisecond and a measurement accuracy of better than 0.1% of full scale, and can instantly capture any slight changes in the pressure inside the tank. The signal output end (4-20mA) of this sensor is connected to the analog input module of the central control unit 10. At the same time, a proportional pressure relief valve 52 controlled by the central control unit 10 is also installed on the top cover of the tank 21, and its valve diameter is calculated precisely according to the tank volume and the maximum gas inlet amount. The PID control algorithm of the central control unit 10 continuously compares the real-time pressure value fed back by the pressure sensor 51 with the set target pressure value, and once a deviation occurs, it immediately calculates and outputs an adjusted 4-20mA control signal to the proportional pressure relief valve 52 to accurately adjust its opening degree, thereby dynamically and quickly increasing or decreasing the amount of gas released, so that the overall working pressure inside the tank is locked within an extremely narrow range such as 5.0 ± 0.2 psi with extremely high precision.

[0042] Based on the precise construction of the above-mentioned system hardware, the specific execution process of the method described in the present invention can be systematically divided into the following steps that work together: Figure 5

[0043] ​The first step is system initialization and parameter setting step 100. Before starting the spraying task, the operator inputs the key physical parameters of the small-particle-size powder to be processed through the human-machine interface, such as its material (e.g., Y2O3, Al2O3), D50 median particle size, flowability index measured by a Hall flowmeter, and material true density and bulk density. At the same time, according to the design requirements of the coating, a specific target powder mass delivery rate is set, for example, 15 g / min. After the central control unit 10 receives these inputs, the expert database and algorithm model inside it start to work. The database pre-stores a large amount of experimental data, establishing a nonlinear mapping relationship between different powder characteristics and the optimal operation parameter combination (including main conveying gas flow, pulse gas flow, pulse frequency, pulse duty cycle, target working pressure in the tank, etc.). The controller automatically retrieves or calculates a set of optimized initial operation parameters according to the current input through interpolation, regression, and other algorithms, and loads them as set points (Set Point) for the subsequent steps;

[0044] The establishment of the parameter mapping database is based on systematic experimental design (DoE) and regression analysis, and the specific method is as follows:

[0045] 1. Construction of the basic experimental matrix:

[0046] A representative small-particle-size powder sample library (covering oxide / carbide / metal powders with D50 = 0.5-20 pm) is selected, and its key physical parameters are measured: median particle size D50, density p, repose angle a, compressibility index CI (determined according to ASTM D6393).

[0047] For each powder, full-factor experiments are conducted within the pre-set parameter space:

[0048] Pulse frequency f: 20-150 Hz (step size 10 Hz);

[0049] Duty cycle d: 10%-50% (step size 5%);

[0050] Main carrier gas flow Q m : 5-20 SLPM (step size 1 SLPM);

[0051] Pulse gas flow Q p : 0.5-5 SLPM (step size 0.5 SLPM);

[0052] Tank pressure P: 1-10 psi (step size 1 psi);

[0053] Evaluation index: mass flow fluctuation rate d m (= standard deviation / mean), target d m ≤ 5%.

[0054] 2. Data modeling:

[0055] A general-purpose parameter prediction model is established by multiple nonlinear regression:

[0056]

[0057] Where K is the device constant matrix, and F is the base function combination (see table below for examples) with powder characteristics as input:

[0058]

[0059] Guidelines for technicians:

[0060] For new powder: measure its D50, p, a, CI, and input into the human-machine interface;

[0061] System automatic calculation: the central control unit calls the built-in algorithm and outputs the initial parameter set according to the above model;

[0062] Fine-tuning rules: if the initial setting of δ m >5% adjust in priority order:

[0063] (1) Pulse frequency f: ±10 Hz per step;

[0064] (2) Duty cycle d: ±5% per step;

[0065] (3) Tank pressure P: ±0.5 psi per step.

[0066] Second step, establish a reference carrier gas pressure environment step 200. After confirming that all parameter settings are correct, the system starts. The central control unit 10 first sends instructions to the first mass flow controller 31 in the main carrier gas path module 30 to set its output to a basic carrier gas flow value calculated in the first step, for example 8.0 standard liters / minute. High-purity argon gas then flows steadily through the first gas path pipe 32 into the upper space of the powder feeder tank 21. Since the tank is sealed, the internal pressure begins to rise steadily, establishing a basic, macroscopic driving potential for subsequent powder delivery.

[0067] Thirdly, the dynamic pulse disaggregation and fluidization step 300 is initiated. Almost at the same time when the reference pressure is established, the central control unit 10 initiates the dynamic pulse gas path module 40 in parallel. It sends a command to the second mass flow controller 41 to set its output to a predetermined gas flow value for generating pulses, for example 2.0 standard liters per minute. Immediately after that, the PWM output module of the central control unit 10 starts to generate a high-precision square wave electrical signal at a predetermined frequency (for example 80 Hz) and duty cycle (for example 35%), and applies it to the high-frequency response electromagnetic valve 42. The electromagnetic valve then opens and closes at a frequency of 80 times per second, chopping the continuous gas flow from the MFC-2 into discrete, energy-controllable pulsed gas flow. These pulsed gas flows pass through the second gas path pipe 43 and are uniformly and gently injected into the core area of the powder bed at the bottom of the powder feeder tank 21 through the gas distributor 44.

[0068] At this stage, a unique composite pressure field environment is formed inside the powder feeder tank, the characteristics of which can be figuratively referred to the schematic diagram shown in Figure 6 . In the diagram, a relatively stable reference pressure line (P base ) represents the macroscopic working pressure maintained by the main conveying gas path module 30 and the pressure closed-loop control system. Superimposed on this reference line is a series of high-frequency, low-amplitude pressure spikes (P pulse ), which are generated by the dynamic pulse gas path module 40. The synergistic effect of this composite pressure field is the essence of the invention: the macroscopic reference pressure (P base ) provides a stable and continuous driving force to "push" the powder out of the output port 23 and to the spray gun; while the microscopic high-frequency pulses (P pulse ) play the role of "cleaner" and "activator", which in the form of a pneumatic micro-vibration, continuously injects energy into the agglomerated structure between the powder particles, so that it cannot be stably formed or destroyed at the moment of formation. In this way, the small particle size powder with extremely poor flowability due to high cohesiveness is transformed in situ and continuously into a uniform and loose, low internal friction angle, fluid-like state, thereby laying a physical foundation for stable and pulsation-free conveying.

[0069] Fourthly, the multivariable closed-loop feedback control step 400 is implemented. Throughout the entire delivery process, the central control unit 10 is always executing a high-speed, compound closed-loop control algorithm to cope with any disturbance that may occur in the system. The main pressure control loop is the core of it, in which the pressure sensor 51 feeds back the real-time pressure data in the tank to the PLC at a frequency of thousands of times per second. The PID controller of the PLC compares this real-time value with the set target working pressure range (for example, 6.0 ± 0.2 psi), and its response speed can reach milliseconds. When the real-time pressure is slightly higher due to the imbalance between the air inlet and the powder outlet, the PLC immediately slightly increases the control signal to the proportional relief valve 52, so that its opening degree increases, and the excess gas is accurately released, so that the pressure falls. Conversely, the same is true. This loop ensures that the pressure difference driving the powder flow is always constant. At the same time, in order to more accurately control the mass flow, the system also adopts a feedforward-feedback compound control strategy. The central control unit 10 will fine-tune the set value of the first mass flow controller 31 according to the feedback signal of an online powder flowmeter (for example, by measuring the concentration or capacitance change of gas-solid two-phase flow, as a more optimized configuration) in series with the powder conveying pipeline, so as to realize direct closed-loop control of the powder mass delivery rate, and ensure that its fluctuation range is controlled within ±1.5% of the target value;

[0070] The feedforward regulation is realized by piecewise linearization of the empirical model, and the specific logic is as follows:

[0071] 1. Establish a baseline calibration curve:

[0072] For a specific powder (such as Y2O3), at the optimal tank pressure P opt , the corresponding measured mass delivery rate M is recorded under different carrier gas flow rates Q m :

[0073]

[0074] Fit the empirical formula: M=k·(Q m -Q0) n , where k, n, Q0 are powder characteristic related constants (for example: Y2O3: k=2.1, n=0.8, Q0=3.0).

[0075] 2. Feedforward controller implementation:

[0076] The central control unit calculates the initial carrier gas flow set value Q target according to the target rate M m : set ;

[0077] Pressure dynamic compensation: correct the set value according to the real-time tank pressure P ​

[0078]

[0079] where β is the pressure compensation coefficient (default 0.03 / psi), determined by pre-experiment.

[0080] 3. Closed-loop calibration mechanism:

[0081] After system startup, deliver powder with as initial value;

[0082] Real-time monitoring of actual mass flow M actual (by impulse flowmeter);

[0083] If |M actual -M target |>5%, automatically trigger the calibration program:

[0084] (1) Fine-tune (step size ±0.5 SLPM);

[0085] (2) Update powder constants k, n to local database.

[0086] Example: processing new powder (ZrO2, D50=6.5μm)

[0087] 1. Parameter determination:

[0088] Measure powder properties: ρ=5.7g / cm 3 , α=42°, CI=25.

[0089] System call model, output initial parameters: f=85Hz, d=25%, Q m =8.5SLPM, Q p =2.0SLPM, P=4.5psi.

[0090] 2. Feedforward setting:

[0091] Target rate M target =18g / min→ inverse Q m , set =9.8SLPM (based on ZrO2 calibration constant k=2.3, n=0.75, Q0=2.8).

[0092] 3. Measured results: mass flow fluctuation rate δ m =2.1% (no fine-tuning); deposition efficiency reaches 70.5%, porosity 2.4%.

[0093] As a preferred embodiment of the present application, a set of sophisticated pressure threshold monitoring and hierarchical alarming module is further integrated into the logic program of the central control unit 10. Two key pressure thresholds are preset in this module: an operational alarming threshold and an absolute safety pressure upper limit. For example, if the target working pressure range is 6.0 ± 0.2 psi, the operational alarming threshold can be set as ± 15% out of this range, i.e. pressure lower than 4.93 psi or higher than 7.13 psi. When the measured value of the pressure sensor 51 enters this alarming region and lasts for more than a preset filtering time (e.g. 500 milliseconds to prevent false alarms caused by transient disturbances), the central control unit 10 will immediately drive the audible and visual alarming device connected to its digital output module to alert the operator with a high-frequency flashing red warning light and intermittent beeping sound. If the pressure continues to rise due to extreme failure (e.g. complete failure of the pressure relief valve) and reaches the preset absolute safety pressure upper limit (e.g. 1.0 MPa), the system will trigger the highest level of safety interlock program to immediately shut down all the electromagnetic main valves of the gas sources and force the proportional pressure relief valve 52 to be fully open, while opening a parallel, larger-diameter emergency pressure relief safety valve to ensure the absolute safety of the equipment and personnel.

[0094] The application will be further described in connection with the following examples.

[0095] Example 1

[0096] This example is intended to illustrate the application of the present application in the preparation of yttrium oxide (Y2O3) protective coating for semiconductor etching cavity components.

[0097] The spraying powder used is Y2O3 powder, the particle size distribution of which is determined by a laser particle size analyzer, D10 = 3.5 μm, D50 = 8.2 μm, D90 = 14.8 μm. The powder has a strong hygroscopicity and a tendency to agglomerate.

[0098] The Y2O3 powder is loaded into the powder feeder tank of the powder delivery device according to the present application. Through the human-computer interaction interface, the target powder delivery rate is set to 15 g / min in the central control unit. The central control unit automatically configures the following operating parameters according to the internal database:

[0099] 1. Main delivery gas path module: the first mass flow controller (MFC-1) is set to an argon flow rate of 8.0 standard liters / min.

[0100] 2. Dynamic pulse gas path module: the second mass flow controller (MFC-2) is set to an argon flow rate of 2.0 standard liters / min; the driving PWM signal frequency of the high-frequency response electromagnetic valve is set to 80 Hz, and the duty cycle is set to 35%.

[0101] 3. Pressure sensing and pressure relief module: target working pressure range set to 6.0 ± 0.2 psi.

[0102] After the system was started, the central control unit coordinated the operation of each module. By observing the transparent quartz tube segment connected to the powder delivery pipeline, it could be seen that the powder was stably delivered in the form of uniform and continuous mist aerosol, without any visible pulsation or blockage phenomenon. This stable powder flow was sent to a 45-kilowatt plasma torch for spraying. After 60 minutes of continuous spraying, the obtained coating was analyzed by metallographic microscope, and its porosity was determined to be 2.15%, which was significantly lower than that of the coating obtained by using a traditional powder feeder (the porosity is usually above 5.5%). The powder deposition efficiency was calculated by weighing method to be 72%, which was significantly improved compared with about 50% of the traditional method.

[0103] Example 2

[0104] This example is intended to illustrate the adaptability of the present application to different kinds and particle sizes of powder.

[0105] The spraying powder used was spherical alumina (AI2O3) powder, with a particle size distribution of D10 = 0.8 μm, D50 = 2.5 μm, and D90 = 5.1 μm. Such sub-micron powder has very poor flowability, and it is almost impossible to achieve continuous delivery in a traditional powder feeder.

[0106] The AI2O3 powder was loaded into the powder feeder tank. The target powder delivery rate was set to 10 grams per minute. Since the powder has smaller particle size and stronger cohesion, the central control unit configured more aggressive fluidization parameters:

[0107] 1. Main delivery gas path module: MFC-1 was set to an argon gas flow of 6.0 standard liters per minute, to avoid excessive disturbance to the ultra-fine powder at a lower carrier gas speed.

[0108] 2. Dynamic pulse gas path module: MFC-2 was set to an argon gas flow of 3.5 standard liters per minute, to provide stronger pulse energy; the driving PWM signal frequency of the high-frequency response solenoid valve was increased to 130 Hz, and the duty cycle was set to 25%, to break stronger inter-particle forces with higher frequency pulses.

[0109] 3. Pressure sensing and pressure relief module: target working pressure range set to 7.5 ± 0.3 psi.

[0110] After the system was started, the present method could still achieve stable and pulsation-free continuous delivery even for such a powder with very poor flowability. The AI2O3 coating prepared using this powder flow had a very dense microstructure, and its porosity was only 1.8% measured by image analysis method, showing excellent performance.

[0111] Example 3

[0112] This example is intended to illustrate the implementation of the pressure monitoring and alarm function in the present application.

[0113] The Y2O3 powder and operating parameters in Example 1 are used. In this example, the pressure threshold monitoring and alarm module is activated in the logic program of the central control unit. The operating pressure range is set to 6.0 ± 0.2 psi, i.e. 5.8 psi to 6.2 psi. The alarm threshold range is set to ± 15% outside the operating pressure range, i.e. below 4.93 psi or above 7.13 psi.

[0114] In a simulated experiment, the outlet of the proportional pressure relief valve is artificially partially blocked, causing the pressure in the tank to rise slowly and continuously without being effectively released. When the reading of the pressure sensor rises to 7.13 psi and remains for more than 500 milliseconds, the central control unit immediately triggers the red audible and visual alarm connected to its digital output port, emitting a flashing light and intermittent beeping sound at a frequency of 2 Hz, prompting the on-site personnel that the device pressure is abnormal. The operator then removes the blockage of the pressure relief valve, and the pressure quickly falls to the normal working range, and the alarm is automatically released. This example verifies that the method of the present application has high-level process monitoring and safety protection capability while ensuring process stability.

[0115] In order to more specifically illustrate the outstanding technical effects brought by the technical solutions disclosed in the present application, a specific example and a comparative example for comparison will be described in detail below.

[0116] Specific application:

[0117] This example is intended to verify the practical application effect of the method of the present application in preparing yttrium oxide (Y2O3) plasma sprayed protective coating for internal parts of the cavity of high-end semiconductor etching equipment.

[0118] The selected sprayed powder is high-purity spherical Y2O3 powder, the physical properties of which are determined by a Malvern laser particle size analyzer, and the results show that the particle size distribution is: D10=3.5 μm, D50=8.2 μm, D90=14.8 μm. The repose angle of the powder is as high as 55 degrees, showing extremely strong cohesion and extremely poor natural flowability, and is prone to blockage and pulsation in the traditional powder feeder.

[0119] 3 kg of the Y2O3 powder is loaded into the powder feeder tank 21 of the powder delivery device 20 described in the present application. Through the human-computer interaction interface, the central control unit 10 is inputted with the powder type "Y2O3-8 μm", and the target powder mass delivery rate is set to 15.0 g / min. The central control unit 10 automatically optimizes and configures the following set of operating parameters based on its internal expert database:

[0120] 1. Main delivery gas path module 30: argon flow rate of first mass flow controller 31 (MFC-1) is set to 8.0 standard liters per minute.

[0121] 2. Dynamic pulse gas path module 40: argon flow rate of second mass flow controller 41 (MFC-2) is set to 2.0 standard liters per minute; driving PWM signal frequency of high frequency response solenoid valve 42 is set to 80 hertz, and duty cycle is set to 35%.

[0122] 3. Pressure sensing and pressure relief regulation module 50: target working pressure range is precisely set to 6.0 ± 0.2 psi (about 41.4 ± 1.4 kPa).

[0123] After the system is started, each module is stably operated under the coordination control of central control unit 10. In order to intuitively evaluate the stability of powder delivery, a transparent quartz glass tube with a length of 200 millimeters is deliberately connected in series in the powder delivery pipeline leading to the plasma torch. By observing the tube segment through a high-speed camera, it can be clearly seen that the Y2O3 powder is stably delivered in the form of a very uniform, continuous, and aerosol mist without any visible agglomerated particles. In the observation period of tens of minutes, no visually discernible flow pulsation, flow interruption, or “gushing” phenomenon occurs. The real-time delivery rate measured by the online mass flow meter is stably within the range of 15.0 ± 0.25 grams per minute, and the relative fluctuation is less than ±1.7%.

[0124] The stable and uniform powder flow is sent into a F4-MB type plasma torch with a power setting of 45 kilowatts, and an aluminum alloy substrate that has been sandblasted pretreated is continuously sprayed for 60 minutes. After spraying is completed, the Y2O3 coating obtained is characterized. The cross-section metallography is observed by a scanning electron microscope (SEM), and the porosity statistical analysis of multiple micrographs is carried out by using image analysis software (Image-ProPlus), and the average porosity of the coating is measured to be only 2.28%. The powder deposition efficiency calculated by the precision balance weighing method (substrate weight gain before and after spraying / total weight of sprayed powder) is as high as 72.3%.

[0125] Comparative Example

[0126] In order to establish a clear contrast benchmark, the same Y2O3 powder as in the example, the same target delivery rate (15.0 grams per minute), and the same plasma torch and spraying parameters are used, but a conventional atmospheric plasma spraying powder feeder without internal pressurization and pulse fluidization function (for example, Praxair 1264 type powder feeder) is used.

[0127] In this conventional powder feeder, powder delivery can only be attempted by adjusting the carrier gas flow rate and the rotation speed of the powder feeder disk. Due to the extremely poor flowability of the Y2O3 powder, the carrier gas flow rate had to be raised to 12.0 standard liters per minute in order to barely initiate delivery and prevent frequent clogging. Even so, during the delivery process, the powder flow was clearly observed to exhibit typical "clogging-spurting" pulsing characteristics, i.e., the powder flow would intermittently stop and then spurt out in clusters, by observing the transparent quartz tube section. The readings of the in-line mass flow meter fluctuated wildly between 0 and 35 grams per minute, indicating an extremely unstable delivery condition.

[0128] Using this unstable powder flow for the same 60-minute spraying process, the resulting Y2O3 coating, after being subjected to the same tests, had an average porosity as high as 5.87% and a non-uniform pore distribution with a large number of macro-defects caused by the impact of large agglomerated particles that had not fully melted. The powder deposition efficiency was calculated to be only 48.6%, with a large amount of powder lost due to insufficient melting or being blown away by the unstable gas flow.

[0129] Data comparison and analysis

[0130] In order to more intuitively demonstrate the technical progress brought about by the present application, the key performance indicators of the examples and the comparative examples are summarized in the following table:

[0131]

[0132] Through the direct and quantitative comparison of the above examples and comparative examples, it can be clearly seen that the method for improving the flowability of small-particle-size spraying powder based on a pressure boosting device provided by the present application fundamentally solves the industry problem of stable delivery of small-particle-size powder by means of its unique composite pressure field construction and precise closed-loop control technology. Not only can it accurately and stably control the powder mass flow rate, but it can also directly convert the stability of the delivery end into a significant improvement in the quality of the final product (a significant reduction in porosity) and a great improvement in production economy (a significant increase in deposition efficiency). The present application provides a powerful and industrially valuable technical solution for many cutting-edge fields that rely on ultra-fine powders for the preparation of high-performance coatings, such as semiconductors, aerospace, biomedicine, etc.

[0133] The above description is only some preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any simple modification, equivalent replacement and improvement of the above examples according to the technical essence of the present application within the technical range disclosed by the present application should be covered within the protection scope of the present application.

Claims

1. A method for improving the flowability of small particle size spray powder based on a pressurization device, characterized by, The method comprises the following steps: A complex pressure field environment is established in a closed powder feeder tank (21) with a polished inner wall and a conical structure (22) at the lower part to deliver the small particle size spraying powder, and the execution steps of the method specifically include: A step (200) of establishing a reference carrier gas pressure environment: a first inert gas is introduced into the upper space of the powder feeder tank (21) through a main conveying gas path module (30) to establish a basic positive pressure in the powder feeder tank (21) and serve as the main carrier for delivering the powder; A step (300) of starting dynamic pulse disaggregation and fluidization: a second inert gas is converted into high-frequency pressure pulses through a dynamic pulse gas path module (40), and the high-frequency pressure pulses are uniformly injected into the powder bed at the bottom of the powder feeder tank (21) through a gas distributor (44) arranged above a powder outlet (23) at the bottom of the conical structure (22) to continuously disaggregate and fluidize the small particle size spraying powder; and A step (400) of implementing multivariable closed-loop feedback control: a central control unit (10) is used to monitor and adjust the pressure in the powder feeder tank (21) in real time, so that the actual working pressure in the powder feeder tank (21) is stably maintained within a preset target working pressure range, thereby realizing stable, continuous and uniform delivery of the small particle size spraying powder under the synergistic action of the basic positive pressure and the high-frequency pressure pulses.

2. The method for improving the flowability of small particle size sprayed powder based on a pressurizing device according to claim 1, characterized by, In the step (300) of starting dynamic pulse disaggregation and fluidization, the dynamic pulse gas path module (40) includes a second mass flow controller (41) for accurately controlling the flow of the second inert gas and a high-frequency response electromagnetic valve (42) for chopping the continuous gas flow from the second mass flow controller (41) into high-frequency pressure pulses; The control signal input end of the high-frequency response electromagnetic valve (42) is electrically connected with the pulse width modulation output port of the central control unit (10), the central control unit (10) drives the high-frequency response electromagnetic valve (42) to open and close at high frequency by outputting a pulse width modulation signal with a predetermined frequency and a predetermined duty cycle, thereby generating the high-frequency pressure pulses, which are delivered to the gas distributor (44) through a second gas path pipeline (43).

3. The method for improving the flowability of small particle size sprayed powder based on a pressurizing device according to claim 2, characterized by, The gas distributor (44) is an annular or disc-shaped member made of sintered metal microporous material, and the working surface of the member is uniformly distributed with micron-sized gas emission holes; the high-frequency pressure pulses are uniformly diffused through the micron-sized gas emission holes in the internal cavity of the gas distributor (44) and act on the powder area near the powder outlet (23), thereby forming a uniform and oscillating fluidized bed environment in the local area to avoid the powder channeling effect or reverse blowing caused by single-point gas flow impact.

4. The method for improving the flowability of small particle size sprayed powder based on a pressurizing device according to claim 2, characterized by, The high-frequency response electromagnetic valve (42) is a proportional electromagnetic valve with a response time less than 2 milliseconds and a maximum operating frequency not less than 200 Hz, the valve body material is SS316L stainless steel, and the dynamic seal is perfluoroether rubber; the predetermined frequency of the pulse width modulation signal output by the central control unit (10) ranges from 20 Hz to 150 Hz, and the predetermined duty cycle ranges from 10% to 50%.

5. The method for improving the flowability of small particle size spray powder based on a pressurizing device according to claim 1, characterized in that, The inner wall of the powder feeder tank (21) is subjected to mechanical polishing and electrochemical polishing treatment, so that the inner surface roughness Ra is not greater than 0.4 microns; the taper angle of the tapered structure (22) at the lower part of the powder feeder tank (21) is set to 60 degrees to facilitate the mass flow of the small particle size spraying powder under the action of gravity.

6. The method of improving the flowability of small particle size spray powder based on a pressurizing device according to claim 1, characterized by, The method further comprises a system initialization and parameter setting step (100) before the step (200) of establishing a reference carrier gas pressure environment, which specifically comprises: Through a man-machine interaction interface, the physical parameters of the small particle size powder to be sprayed are input to the central control unit (10), and the target powder mass delivery rate is set; The central control unit (10) automatically retrieves or calculates an initial operation parameter set for the subsequent steps according to its internally preset parameter mapping database storing the corresponding relationship between different powder characteristic parameters and optimal operation parameters, or through its built-in algorithm, the initial operation parameter set at least includes the basic carrier gas flow value of the first inert gas in the main conveying gas path module (30), the pulse gas flow value of the second inert gas in the dynamic pulse gas path module (40), the frequency and duty cycle of the high-frequency pressure pulse, and the preset target working pressure range.

7. The method for improving the flowability of small particle size sprayed powder based on a pressurizing device according to claim 1 or 6, characterized in that, In the step (400) of implementing multivariable closed-loop feedback control, the pressure regulation is realized by a pressure sensing and pressure relief adjusting module (50) which includes a high-precision pressure sensor (51) and a proportional pressure relief valve (52); The high-precision pressure sensor (51) is installed at the upper part of the powder feeder tank (21) for real-time monitoring of the absolute pressure value in the tank and sending it as a feedback signal to the central control unit (10); The valve port of the proportional pressure relief valve (52) is connected to the upper part of the powder feeder tank (21), and its control signal input end is electrically connected with the analog output port of the central control unit (10); The central control unit (10) compares the real-time pressure value fed back by the high-precision pressure sensor (51) with the preset target working pressure range, and based on the comparison result, dynamically adjusts the control signal applied to the proportional pressure relief valve (52) through a proportional-integral-derivative control algorithm to accurately control the opening degree, thereby realizing rapid and accurate closed-loop regulation of the pressure in the tank.

8. The method for improving the flowability of small particle size sprayed powder based on a pressurizing device according to claim 7, characterized by, The control logic of the central control unit (10) is further integrated with a pressure threshold monitoring and alarm module, which has a preset alarm threshold for abnormal operating pressure and an absolute upper limit for safe pressure. When the measurement value of the high-precision pressure sensor (51) exceeds the alarm threshold and lasts for a predetermined time, the central control unit (10) drives a connected audible and light alarm device to issue an alarm; When the measurement value reaches the upper limit of the absolute safety pressure, the central control unit (10) executes a safety interlocking program, automatically cuts off all air supply sources and fully opens the proportional pressure relief valve (52).

9. The method of improving the flowability of small particle size spray powder based on a pressurizing device according to claim 1, characterized by, In the step of establishing a reference carrier gas pressure environment (200), the main carrier gas path module (30) comprises a first mass flow controller (31) for accurately controlling the flow of the first inert gas, which is argon or nitrogen with a purity of not less than 99.999%; the pre-set target working pressure range is between 1 and 10 psi.

10. The method of improving the flowability of small particle size spray powder based on a pressurizing device according to claim 1, characterized in that, The particle size range of the small particle size spraying powder is 0.1 to 20 microns; in particular, the small particle size spraying powder is an ultra-fine powder with a D50 median particle size of less than 10 microns, and the material of the powder is selected from yttrium oxide, aluminum oxide or composite ceramic powder thereof.

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