Plasma precise regulation and control system for metal surface hydrophobic nitride layer

Abstract

The invention discloses a plasma precise regulation and control system for a metal surface hydrophobic nitride layer. The plasma precise regulation and control system comprises a reaction cavity unit, a control unit and a plasma unit. The reaction cavity unit is used for placing a to-be-treated metal substrate material and preparing a hydrophobic nitride layer for accurately regulating and controlling plasma on the metal substrate material; the plasma unit is connected with the reaction cavity unit and used for providing plasma for the reaction cavity unit in the reaction process; the control unit is respectively connected with the plasma unit and the reaction cavity unit and is used for realizing precise regulation and control of plasmas in the reaction process. According to the scheme, in the plasma modification process of the metal, the temperature and the magnetic field of the metal surface are accurately regulated and controlled, so that in the plasma modification process, on one hand, the nitriding layer is promoted to form a micro-nano coral array, the surface energy of the nitriding layer is increased, and the polar nitriding layer has the surface water conveying characteristic; the control over the temperature and the magnetic field can promote the formation of a micro-nano coral array and inhibit array agglomeration, then a polar nitride layer with the hydrophobic surface is achieved, finally, accurate control over the hydrophobic nitride layer on the metal surface is achieved, the hydrophobic surface comes from a surface micro-nano structure instead of a material, no chemical reagent needs to be introduced in the regulation and control process, and the preparation method is simple and convenient. The uniformity is good, and a certain practical prospect is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of metal surface modification, and in particular relates to a plasma precision control system for a hydrophobic nitride layer on a metal surface. Background Art

[0002] Transition metal nitrides have broad application prospects in the fields of catalysis, protection, and sensors. Conventional physical and chemical modification strategies can directly prepare transition metal nitrides, but the prepared nitrides are in the form of powders, and adhesives must be added when coating them on the substrate surface, which will inevitably affect the physical and chemical properties and mechanical properties of the nitrides. In addition, conventional physical and chemical modification strategies inevitably add different chemical reagents or introduce high temperatures during the preparation of nitrides, which will increase the modification cost and hinder subsequent applications.

[0003] Plasma technology can achieve low power consumption and harmless surface modification to a certain extent. CN116344749A discloses a method for in-situ generation of nitride composite lithium by plasma; CN202210279445.2 discloses a method for preparing ternary nitride coatings by microwave plasma chemical vapor deposition. Although the above preparation strategies have certain effects in the preparation of nitride coatings, the above methods all cause continuous high temperatures on the surface of the metal substrate during the interface modification process. This is due to the thermal effect caused by the continuous interaction between the plasma and the powder surface, which will cause cracking of the surface nitride layer and damage the hydrophobic structure of the surface. The high surface temperature caused by the thermal effect can also cause modification failure, including denitrification of the nitrided structure in a high temperature environment. At the same time, local high temperatures will lead to low uniformity of plasma modification and low degree of practicality.

[0004] In addition, the existing nitride layer is mainly based on a hydrophilic coating. This is because the nitride layer is a polar coating, which makes the surface of the nitride layer easy to contact water molecules in the air, making the nitride layer easy to corrode. CN113462014A discloses a two-dimensional layered metal carbide hydrophobic coating. This hydrophobic coating comes from the non-polarity of the metal carbide. CN112159955A discloses a method for preparing a micro-nano hard hydrophobic coating, which infiltrates carbon into the metal surface to form a carbide layer. Based on the above preparation strategy, the hydrophobic layer mainly comes from the non-polar material itself, not the surface micro-nano structure. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a plasma precision control system for the hydrophobic nitride layer on the metal surface, so as to achieve accurate control of the hydrophobic nitride layer on the metal surface. The surface hydrophobicity comes from the surface micro-nano structure rather than the material itself. The control process does not require the introduction of any chemical reagents and has good uniformity.

[0006] The specific technical solution for achieving the purpose of the present invention is:

[0007] A plasma precision control system for a hydrophobic nitride layer on a metal surface, comprising a reaction chamber unit, a control unit, and a plasma unit;

[0008] The reaction chamber unit is used to place the metal substrate material to be processed, and to prepare a hydrophobic nitride layer on the metal substrate material by precise plasma control;

[0009] The plasma unit is connected to the reaction chamber unit and is used to provide plasma to the reaction chamber unit during the reaction process;

[0010] The control unit is connected to the plasma unit and the reaction chamber unit respectively, so as to realize precise control of the plasma during the reaction process.

[0011] Furthermore, a grounding electrode is provided in the reaction chamber unit for setting the metal substrate material to be processed, and a working electrode is provided at a position corresponding to the grounding electrode and connected to the plasma unit for providing plasma to the metal substrate material to be processed;

[0012] The reaction chamber unit is also connected to a coolant, and the control unit regulates the inflow, outflow and flow rate of the coolant;

[0013] A magnet is arranged around the ground electrode to provide a magnetic field to the metal substrate material to be processed.

[0014] Furthermore, the process of preparing the hydrophobic nitride layer of the metal substrate material by plasma precise control is as follows:

[0015] Performing vacuum treatment on the reaction chamber unit;

[0016] Using a plasma unit, glow discharge is performed in a reaction chamber unit based on a plasma source to generate low-pressure plasma, and the low-pressure plasma interacts with a metal substrate material to form a hydrophobic nitride layer on the surface of the metal substrate material;

[0017] The control unit detects and regulates the temperature of the metal substrate material and the magnetic field around it in real time during the interaction between the low-pressure plasma and the metal substrate material, and regulates the glow discharge of the plasma unit based on the detection results.

[0018] Furthermore, the control unit detects the surface temperature of the metal substrate material by an intrusive detection method or a non-intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material, and controls the plasma unit to stop glow discharge when the detected temperature is higher than a set threshold value;

[0019] When the detected temperature is lower than the set threshold, the plasma unit is controlled to start glow discharge.

[0020] Furthermore, the control unit detects the surface temperature of the metal substrate material by an intrusive detection method or a non-intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material. When the detected temperature is higher than a set threshold, the plasma unit is controlled to stop glow discharge and increase the flow rate of the coolant to reduce the surface temperature to below the set threshold.

[0021] When the detected temperature is lower than the set threshold, the plasma unit is controlled to start glow discharge and the coolant flow rate is reduced.

[0022] Furthermore, the control unit detects the magnetic field direction and magnetic field density on the surface of the metal substrate material by an intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material, and controls the magnet to provide a magnetic field with adjustable direction and size around the metal substrate material according to the detection result:

[0023] When the surface magnetic field of the metal substrate changes significantly during the interaction with the plasma, the current density and direction flowing into the magnet are synchronously adjusted based on the instant feedback results to stabilize the magnetic field on the substrate surface within a predetermined range in a timely manner.

[0024] The control magnet provides a magnetic field with adjustable direction and size around the metal substrate material, that is, by controlling the current density and current direction flowing into the magnet, the density and direction of the magnetic flux lines released by the magnet are controlled, thereby providing a magnetic field with adjustable direction and size around the metal substrate material;

[0025] The intrusive detection method includes determining the magnitude and direction of the surface magnetic field of the metal substrate material by using a Tesla meter.

[0026] Further, the intrusive detection method includes determining the surface temperature of the metal substrate material by means of a thermocouple;

[0027] The non-intrusive detection method includes infrared thermal imaging to determine the surface temperature of the metal substrate material.

[0028] Further, the metal substrate material to be processed includes metal iron, metal nickel, metal cobalt, iron-nickel alloy or carbon steel;

[0029] The area of ​​the metal substrate material to be processed ranges from 2 to 30 cm 2 , thickness range is 0.01~3mm, preferably area range is 10~15cm 2 , thickness range is 0.01~0.3mm.

[0030] Furthermore, the plasma unit performs glow discharge in the following ways: AC discharge, radio frequency discharge, microwave discharge, and spiral wave discharge;

[0031] The plasma source includes nitrogen, nitrogen-argon mixed gas, nitrogen-hydrogen mixed gas;

[0032] The discharge power of the plasma unit needs to be maintained at 50-2000W, preferably 300-800W.

[0033] Furthermore, the reaction chamber unit needs to maintain a chamber pressure of 10-100 Pa, preferably 20-40 Pa, during the process of preparing the hydrophobic nitride layer with precise plasma control.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) Compared with the conventional plasma modification, the solution of the present invention controls the temperature field and magnetic field of the plasma and the substrate surface to promote the formation of a micro-nano coral array in the nitride layer. The coral array increases the surface energy of the nitride layer, resulting in the polar nitride layer having a surface water transport property, which inhibits the probability of the nitride layer surface contacting with water and improves the corrosion resistance of the nitride layer. In addition, the temperature control can prevent the aggregation of micron structures caused by local high temperature, promote the formation of hydrophobic micro-nano structures in the nitride layer, and keep the surface energy of the nitride layer at a high level.

[0036] (2) During the modification process of conventional plasma, an adjustable magnetic field is not constructed on the surface of the substrate. During the plasma modification process, for magnetic substrates containing iron, cobalt, and nickel components, the dipoles in the metal are in a randomly distributed state, which causes the nitride layer formed on the surface to usually have a planar structure. During the plasma modification process, the scheme of the present invention constructs an adjustable magnetic field environment on the surface of the metal substrate. Under the action of the magnetic field, the metal dipoles will be arranged in a directional manner. During the plasma modification process, the movement of the metal particles is affected by the directional magnetic field, which promotes the formation of micro-nano coral arrays and inhibits the agglomeration of the arrays, thereby realizing a surface hydrophobic polar nitride layer.

[0037] The present invention is further described below in conjunction with specific implementation modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of a plasma precise control system for a hydrophobic nitride layer on a metal surface in an embodiment of the present invention.

[0039] Figure 2 This is a SEM schematic diagram of the nitrided layer on the surface of carbon steel after conventional plasma modification in Example 1 of the present invention.

[0040] Figure 3This is a SEM schematic diagram of the nitrided layer on the surface of carbon steel after precise control of plasma in Example 1 of the present invention.

[0041] Figure 4 Schematic diagram of the water contact angle of the nitrided layer on the surface of carbon steel after conventional plasma modification in Example 1 of the present invention.

[0042] Figure 5 Schematic diagram of the water contact angle of the nitride layer on the surface of carbon steel after precise plasma regulation in Example 1 of the present invention.

[0043] Figure 6 This is a SEM schematic diagram of the nitride layer on the surface of metallic iron after precise plasma regulation in Example 2 of the present invention.

[0044] Figure 7 Schematic diagram of the water contact angle of the nitride layer on the surface of metallic iron after precise plasma regulation in Example 2 of the present invention. DETAILED DESCRIPTION

[0045] A plasma precision control system for a hydrophobic nitride layer on a metal surface, comprising a reaction chamber unit, a control unit, and a plasma unit;

[0046] The reaction chamber unit is used to place the metal substrate material to be processed, and to prepare a hydrophobic nitride layer on the metal substrate material by precise plasma control;

[0047] The plasma unit is connected to the reaction chamber unit and is used to provide plasma to the reaction chamber unit during the reaction process;

[0048] The control unit is connected to the plasma unit and the reaction chamber unit respectively, so as to realize precise control of the plasma during the reaction process.

[0049] A grounding electrode is arranged in the reaction chamber unit for arranging the metal substrate material to be processed, and a working electrode is arranged at a position corresponding to the grounding electrode and connected to the plasma unit for providing plasma to the metal substrate material to be processed. In a specific implementation, the discharge distance between the grounding electrode and the working electrode needs to be maintained at 10 to 80 cm, preferably 30 to 60 cm;

[0050] The reaction chamber unit is also connected to a coolant, and the control unit regulates the inflow, outflow and flow rate of the coolant. Generally speaking, the coolant includes water, silicone oil, and isopropanol. The flow rate control adjustment range of the control unit is 1 to 200 mL s -1 , preferably 5~20mLs -1 ;

[0051] A magnet is arranged around the ground electrode to provide a magnetic field to the metal substrate material to be processed.

[0052] The process of preparing the hydrophobic nitride layer of the metal substrate material by plasma precise control is as follows:

[0053] Performing vacuum treatment on the reaction chamber unit;

[0054] Using a plasma unit, glow discharge is performed in a reaction chamber unit based on a plasma source to generate low-pressure plasma, and the low-pressure plasma interacts with a metal substrate material to form a hydrophobic nitride layer on the surface of the metal substrate material;

[0055] The control unit detects and regulates the temperature of the metal substrate material and the magnetic field around it in real time during the interaction between the low-pressure plasma and the metal substrate material, and regulates the glow discharge of the plasma unit based on the detection results.

[0056] The control unit detects the surface temperature of the metal substrate material by an intrusive detection method or a non-intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material, and controls the plasma unit to stop glow discharge when the detected temperature is higher than a set threshold value;

[0057] When the detected temperature is lower than the set threshold, the plasma unit is controlled to start glow discharge.

[0058] In another specific embodiment, the control unit detects the surface temperature of the metal substrate material by an intrusive detection method or a non-intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material. When the detected temperature is higher than a set threshold, the plasma unit is controlled to stop glow discharge, and at the same time, the coolant flow rate is increased to reduce the surface temperature to below the set threshold.

[0059] When the detected temperature is lower than the set threshold, the plasma unit is controlled to start glow discharge and the coolant flow rate is reduced.

[0060] In the process of conventional plasma modification of metal substrates, a large number of active particles continuously bombard the substrate surface, causing the substrate surface temperature to continue to rise, causing the surface to tend to return to the ground state, that is, a state with lower surface energy. In the process of plasma modification, the present invention controls the temperature of the metal substrate surface, stabilizes the surface temperature at a specific temperature, prevents the aggregation of microstructures caused by local high temperature, promotes the formation of hydrophobic micro-nanostructures of the nitride layer, and keeps the surface energy of the nitride layer at a high level.

[0061] In addition, the intrusive detection method here includes determining the surface temperature of the metal substrate material by means of a thermocouple;

[0062] Non-intrusive detection methods include infrared thermal imaging to determine the surface temperature of metal substrate materials.

[0063] The control unit detects the magnetic field direction and magnetic field density on the surface of the metal substrate material by an intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material, and controls the magnet to provide a magnetic field with adjustable direction and size around the metal substrate material according to the detection result:

[0064] When the surface magnetic field of the metal substrate changes significantly during the interaction with the plasma, the current density and direction flowing into the magnet are synchronously adjusted based on the instant feedback results to stabilize the magnetic field on the substrate surface within a predetermined range in a timely manner.

[0065] The control magnet provides a magnetic field with adjustable direction and size around the metal substrate material, that is, by controlling the current density and current direction flowing into the magnet, the density and direction of the magnetic flux lines released by the magnet are controlled, thereby providing a magnetic field with adjustable direction and size around the metal substrate material;

[0066] The intrusive detection method includes determining the surface magnetic field size and magnetic field direction of the metal substrate material by a Tesla meter. In a specific implementation, the magnetic field direction includes horizontal and vertical substrate surfaces, and the magnetic field size is 0.001 to 3T, preferably 0.5 to 1T.

[0067] Conventional plasma does not construct an adjustable magnetic field on the substrate surface during the modification process. During the plasma modification process, for magnetic substrates containing iron, cobalt, and nickel, the dipoles in the metal are in a randomly distributed state, which causes the nitride layer formed on the surface to be usually a planar structure. This scheme constructs an adjustable magnetic field environment on the metal substrate surface during the plasma modification process. Under the action of the magnetic field, the metal dipoles will be arranged in a directional manner. During the plasma modification process, the movement of metal particles is affected by the directional magnetic field, which promotes the formation of micro-nano coral arrays and inhibits the agglomeration of the arrays, thereby achieving a hydrophobic polar nitride layer on the surface.

[0068] In the process of conventional plasma modifying metal substrates, particles penetrate into the metal surface to form a metal nitride layer. Since an ionic bond is formed between metal and nitrogen and the electronegativity difference between metal and nitrogen is large, the nitride layer is a polar coating. The polar coating must be a hydrophilic coating in terms of material composition. Therefore, water molecules in the air are easily adsorbed on the coating surface, increasing the probability of corrosion of the coating. This scheme controls the temperature field and magnetic field of the plasma and the substrate surface to promote the formation of a micro-nano coral array in the nitride layer. This coral array increases the surface energy of the nitride layer, causing the polar nitride layer to have surface water transport characteristics, which inhibits the probability of contact between the nitride layer surface and water and improves the corrosion resistance of the nitride layer.

[0069] The metal substrate material to be processed includes metal iron, metal nickel, metal cobalt, iron-nickel alloy or carbon steel;

[0070] The area of ​​the metal substrate material to be processed ranges from 2 to 30 cm 2 This area range is related to the size of the selected electrode, the thickness range is 0.01 to 3 mm, and the preferred area range is 10 to 15 cm 2 , thickness range is 0.01~0.3mm.

[0071] The plasma unit performs glow discharge in the following ways: AC discharge, radio frequency discharge, microwave discharge, and spiral wave discharge;

[0072] The plasma source includes nitrogen, nitrogen-argon mixed gas, and nitrogen-hydrogen mixed gas. The gas flow rate of the plasma source is 10 to 300 sccm, preferably 20 to 60 sccm.

[0073] The discharge power of the plasma unit needs to be maintained at 50-2000W, preferably 300-800W.

[0074] The reaction chamber unit needs to maintain a chamber pressure of 10-100 Pa, preferably 20-40 Pa, during the process of preparing the hydrophobic nitride layer with precise plasma control, and the chamber pressure of the metal substrate to be modified needs to be maintained at 0.1-0.01 Pa, preferably 0.05-0.02 Pa before modification.

[0075] Example

[0076] Example 1

[0077] In this embodiment, the discharge mode of the plasma unit adopts radio frequency discharge as a precise control mode, and carbon steel is selected as the research object of plasma modification. The area of ​​carbon steel is 10cm 2 , thickness is 1mm.

[0078] The carbon steel to be modified is placed on the cathode platform in the reaction chamber to start precise plasma control. The formation process of the low-pressure plasma is as follows: the pressure in the reaction chamber is reduced to 0.01Pa through a molecular pump vacuum system; a nitrogen-hydrogen mixed gas is introduced through a gas pipeline on the chamber wall, and the atmosphere flow rate is adjusted to maintain the chamber pressure at 30Pa; the discharge power and discharge interval of the plasma unit are adjusted to start glow discharge;

[0079] During the discharge process, active particles continuously bombard the material surface, causing the surface temperature of the metal substrate to continue to rise. At this time, the control unit continuously detects the temperature and controls the start and stop of the discharge to maintain the surface reaction temperature below the set temperature to promote uniform and precise modification.

[0080] At the same time, during this discharge process, the active nitrogen-containing particles react physically and chemically with the carbon steel surface. Due to continuous temperature control, the substrate surface temperature is moderate and uniform, and local decomposition and cracking of the nitride layer on the substrate surface are not likely to occur. The array caused by physical action and the nitridation caused by chemical action can be controlled within the expected range; in addition, the relatively moderate reaction temperature on the surface can promote the nitrogen-containing particles to enter the nitride layer and increase the thickness of the nitride layer. After the plasma is turned on for a total of 300 seconds, the plasma unit is turned off to remove the modified carbon steel substrate.

[0081] Scanning electron microscopy was used to observe the morphological changes of conventional plasma modified and precisely controlled carbon steel substrates: Figure 2 and Figure 3 The surface morphology of carbon steel after precise plasma control is a coral array, but the surface of carbon steel modified by conventional plasma shows less micro-nanostructure; combined with Figure 4 and Figure 5 The surface of the nitride layer after conventional plasma modification is a hydrophilic structure, while the surface of the carbon steel after precise plasma control is a hydrophobic structure.

[0082] Example 2

[0083] In this embodiment, the discharge mode of the plasma unit adopts microwave discharge as a precise control mode, and metallic iron is selected as the research object of plasma modification. The area of ​​metallic iron is 20 cm 2 , thickness is 0.2mm.

[0084] The carbon steel to be modified is placed on the cathode platform in the reaction chamber to start precise plasma control. The formation process of the low-pressure plasma is as follows: the pressure in the reaction chamber is reduced to 0.005Pa through a molecular pump vacuum system; nitrogen is introduced through a gas pipeline on the chamber wall, and the atmosphere flow rate is adjusted to maintain the chamber pressure at 50Pa; the discharge power and discharge interval of the plasma unit are adjusted to start glow discharge;

[0085] During the discharge process, active particles continuously bombard the material surface, causing the surface temperature to continue to rise. At this time, the control unit continuously detects the temperature and controls the start and stop of the discharge to maintain the surface reaction temperature below the set temperature to promote uniform and precise modification.

[0086] At the same time, during this discharge process, the active nitrogen-containing particles react physically and chemically with the carbon steel surface. Due to continuous temperature control, the substrate surface temperature is moderate and uniform, and local decomposition and cracking of the nitride layer on the substrate surface are not likely to occur. The array caused by physical action and the nitridation caused by chemical action can be controlled within the expected range; in addition, the relatively moderate reaction temperature on the surface can promote the nitrogen-containing particles to enter the nitride layer and increase the thickness of the nitride layer. After the plasma is turned on for a total of 600 seconds, the plasma unit is turned off to remove the modified carbon steel substrate.

[0087] like Figure 6 and Figure 7 As shown, the surface of the metallic iron after precise control of plasma is a coral array, and this structure exhibits obvious hydrophobicity.

[0088] The above embodiments show and describe the basic principles and main features of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A plasma precision control system for a hydrophobic nitride layer on a metal surface, characterized in that: It includes a reaction chamber unit, a control unit and a plasma unit; The reaction chamber unit is used to place the metal substrate material to be processed, and to prepare a hydrophobic nitride layer on the metal substrate material by precise plasma control; The plasma unit is connected to the reaction chamber unit and is used to provide plasma to the reaction chamber unit during the reaction process; The control unit is connected to the plasma unit and the reaction chamber unit respectively, so as to realize precise control of the plasma during the reaction process.

2. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 1, characterized in that: A grounding electrode is arranged in the reaction chamber unit for arranging the metal substrate material to be processed, and a working electrode is arranged at a position corresponding to the grounding electrode and connected to the plasma unit for providing plasma to the metal substrate material to be processed; The reaction chamber unit is also connected to a coolant, and the control unit regulates the inflow, outflow and flow rate of the coolant; A magnet is arranged around the ground electrode to provide a magnetic field to the metal substrate material to be processed.

3. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 2, characterized in that: The process of preparing the hydrophobic nitride layer of the metal substrate material by plasma precise control is as follows: Performing vacuum treatment on the reaction chamber unit; Using a plasma unit, glow discharge is performed in a reaction chamber unit based on a plasma source to generate low-pressure plasma, and the low-pressure plasma interacts with a metal substrate material to form a hydrophobic nitride layer on the surface of the metal substrate material; The control unit detects and regulates the temperature of the metal substrate material and the magnetic field around it in real time during the interaction between the low-pressure plasma and the metal substrate material, and regulates the glow discharge of the plasma unit based on the detection results.

4. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 3, characterized in that: The control unit detects the surface temperature of the metal substrate material by an intrusive detection method or a non-intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material, and controls the plasma unit to stop glow discharge when the detected temperature is higher than a set threshold value; When the detected temperature is lower than the set threshold, the plasma unit is controlled to start glow discharge.

5. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 3, characterized in that: The control unit detects the surface temperature of the metal substrate material by an intrusive detection method or a non-intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material. When the detected temperature is higher than a set threshold, the plasma unit is controlled to stop glow discharge and increase the flow rate of the coolant to reduce the surface temperature to below the set threshold. When the detected temperature is lower than the set threshold, the plasma unit is controlled to start glow discharge and the coolant flow rate is reduced.

6. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 3, characterized in that: The control unit detects the magnetic field direction and magnetic field density on the surface of the metal substrate material by an intrusive detection method during the interaction between the low-pressure plasma and the metal substrate material, and controls the magnet to provide a magnetic field with adjustable direction and size around the metal substrate material according to the detection result: When the surface magnetic field of the metal substrate changes significantly during the interaction with the plasma, the current density and direction flowing into the magnet are synchronously adjusted based on the instant feedback results to stabilize the magnetic field on the substrate surface within a predetermined range in a timely manner. The control magnet provides a magnetic field with adjustable direction and size around the metal substrate material, that is, by controlling the current density and current direction flowing into the magnet, the density and direction of the magnetic flux lines released by the magnet are controlled, thereby providing a magnetic field with adjustable direction and size around the metal substrate material; The intrusive detection method includes determining the magnitude and direction of the surface magnetic field of the metal substrate material by using a Tesla meter.

7. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 4 or 5, characterized in that: The intrusive detection method includes determining the surface temperature of the metal substrate material by means of a thermocouple; The non-intrusive detection method includes infrared thermal imaging to determine the surface temperature of the metal substrate material.

8. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to any one of claims 1 to 6, characterized in that: The metal substrate material to be processed includes metal iron, metal nickel, metal cobalt, iron-nickel alloy or carbon steel; The area of ​​the metal substrate material to be processed ranges from 2 to 30 cm 2 , thickness range is 0.01~3mm, preferably area range is 10~15cm 2 , thickness range is 0.01~0.3mm.

9. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 3, characterized in that: The plasma unit performs glow discharge in the following ways: AC discharge, radio frequency discharge, microwave discharge, and spiral wave discharge; The plasma source includes nitrogen, nitrogen-argon mixed gas, nitrogen-hydrogen mixed gas; The discharge power of the plasma unit needs to be maintained at 50-2000W, preferably 300-800W.

10. The plasma precise control system for the hydrophobic nitride layer on the metal surface according to claim 3, characterized in that: The reaction chamber unit needs to maintain a chamber pressure of 10 to 100 Pa, preferably 20 to 40 Pa, during the process of preparing the hydrophobic nitride layer with precise plasma control.

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