High-density plasma uniform nitriding device and working method for soft base material surface

Abstract

The present invention relates to the technical field of surface strengthening of soft base materials, in particular to a high-density plasma uniform nitriding device and working method for the surface of soft base materials. The device includes 4 arc sources respectively arranged on the left side, right side, front side and rear side in the chamber. A permanent magnet device is arranged behind each of the arc sources. Each arc source is electrically connected to the negative pole of an arc source power supply, and the positive pole of the arc source power supply is grounded; it also includes 4 auxiliary anodes respectively arranged at the four corners in the chamber; an electromagnetic coil is arranged behind each auxiliary anode; each auxiliary anode is electrically connected to the positive pole of an auxiliary anode power supply through an adjustable resistor, and the negative pole of the auxiliary anode power supply is grounded.

Description

Technical Field

[0001] The present invention relates to the technical field of surface strengthening of soft base materials, and specifically to a high-density plasma uniform nitriding device and working method for the surface of soft base materials. Background Art

[0002] High-speed steel, stainless steel, etc. (soft base materials) have wide applications in industrial production due to their excellent physical and mechanical properties, such as corrosion resistance, good plasticity and finish. However, the hardness and wear resistance of high-speed steel and stainless steel materials are relatively low. In a harsh service environment, cracks will occur on the inner surface due to high-temperature oxidation, friction and corrosion, etc., seriously affecting the service life and causing a large amount of economic losses. When facing a complex and harsh service environment, in order to obtain better comprehensive performance, specific nitriding surface strengthening treatment needs to be carried out on them to improve the service life and ensure service safety.

[0003] Currently, although the inner surface can be treated by electroplating and electroless plating methods, due to problems such as poor uniformity, less deposited material by electroplating, influence on the morphology of the inner surface and environmental pollution, researchers in this field have been seeking a more excellent technical solution.

[0004] When depositing a coating on a relatively soft metal substrate, in fact, the relatively soft metal substrate cannot support the thin hard coating, and plastic deformation will occur under high load, resulting in coating failure. The "eggshell effect" caused will reduce the load-bearing capacity of the coating surface, thus limiting its working performance. And surface nitriding is a recognized economical and effective treatment method to improve the hardness and wear resistance of stainless steel. After nitriding treatment, a supersaturated solid solution phase with high hardness will be formed on the surface of stainless steel, which will greatly improve the hardness and wear resistance of the stainless steel surface and extend the service life. Therefore, specific nitriding surface strengthening treatment needs to be carried out on the soft base materials, and then surface hard thin film coating treatment is carried out on them. This dual surface treatment is particularly effective in improving the surface load-bearing capacity of relatively soft substrates.

[0005] Among many nitriding technologies, there are often problems such as uneven nitriding, inability to precisely control the nitriding phase structure, easy occurrence of arcing phenomenon, edge effect, temperature rise effect, inability to integrate nitriding and plating, and electron shielding effect caused by increased loading on the surface of special-shaped substrates in large-scale industrial production of nitriding and plating integration. As a result, stable production of large-size and large-batch parts cannot be achieved by plasma nitriding in industrial production.

[0006] For example, CN115261777A discloses a device and method for optimizing ion nitriding on the inner wall of a pipe. This device uses a multi-arc ion plating plasma source and belongs to a multi-arc nitriding device. This type of device cannot avoid the surface arcing phenomenon of tip parts, cannot achieve the adjustment of the plasma density region, cannot achieve industrial-scale loading capacity, and cannot achieve the uniformity of nitriding, etc. Summary of the Invention

[0007] The purpose of the present invention is to provide a device and working method for uniform nitriding of high-density plasma on the surface of a soft base material. This device can obtain a multi-stage magnetic field with an adjustable magnetic mirror ratio distributed along the axis by coupling the magnetic field distribution of a PVD multi-arc ion source and an auxiliary anode, and realize a scalable annular plasma with 360° lateral variable characteristic parameters, so as to achieve true integrated nitriding and plating.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A device for uniform nitriding of high-density plasma on the surface of a soft base material includes 4 arc sources respectively arranged on the left, right, front, and rear sides in the chamber. A permanent magnet device is arranged behind each arc source. Each arc source is electrically connected to the negative electrode of an arc source power supply, and the positive electrode of the arc source power supply is grounded; it also includes 4 auxiliary anodes respectively arranged at the four corners in the chamber; an electromagnetic coil is arranged behind each auxiliary anode; each auxiliary anode is electrically connected to the positive electrode of a secondary anode power supply through an adjustable resistor, and the negative electrode of the secondary anode power supply is grounded.

[0010] Furthermore, the electromagnetic coil is adjustable. By adjusting and coupling with the magnetic field of the permanent magnet device, a multi-stage magnetic field with an adjustable magnetic mirror ratio distributed along the axis is achieved, a scalable annular plasma with 360° lateral variable characteristic parameters is achieved, and uniform immersion plasma nitriding is realized.

[0011] Furthermore, the arc source power supply connected to the arc source can adjust the current magnitude. By adjusting the current magnitude of the arc source power supply, the electron emission ability of the arc source is further controlled, and thus the plasma density is controlled to regulate the composition and structure of the software material to be nitrided.

[0012] Furthermore, the secondary anode power supply connected to the auxiliary anode can adjust the current magnitude. By adjusting the current magnitude of the secondary anode power supply, the absorption of electrons generated by the arc source by the auxiliary anode is further controlled, and thus the plasma density is controlled to regulate the composition and structure of the software material to be nitrided.

[0013] Furthermore, a rotating rack is provided in the middle of the chamber.

[0014] Furthermore, the rotating rack is loaded with the soft base material of the part to be nitrided.

[0015] Further, the arc source power supply and the auxiliary anode power supply can be pulse power supplies or DC power supplies, and the power supplies are adjustable. The positive electrode of the arc source and the negative electrode of the auxiliary anode are both connected to the vacuum chamber, and the vacuum chamber is grounded.

[0016] Further, the current of the auxiliary anode can be adjusted through an adjustable resistor.

[0017] Further, each electromagnetic coil is electrically connected to a separate DC power supply.

[0018] The working method of the high-density plasma uniform nitriding device on the surface of the soft base material of the present invention is specifically as follows:

[0019] A large number of electrons evaporated by the arc source are attracted by the auxiliary anode in the chamber, and by adjusting the magnetic field distribution area coupled by the permanent magnet device and the electromagnetic coil, a large number of electrons perform spiral motion under the action of the electromagnetic field to fill the chamber and ionize the introduced gas atoms, so that the gas atoms form a plasma state and are injected and diffused into the interior of the soft base material of the work piece to be nitrided loaded on the turntable for nitriding; the current of the auxiliary anode is adjusted through an adjustable resistor to control the ability to absorb electrons, ensuring that the plasma region ionized by the electrons extends and submerges the soft base material to be nitrided, and realizing precise control of the nitriding composition and structure;

[0020] Or, by adjusting the position of the permanent magnet device to couple the magnetic field of the electromagnetic coil, a multi-stage magnetic mirror field with an adjustable magnetic mirror ratio distributed circumferentially along the chamber is realized for plasma nitriding work;

[0021] Or, by adjusting the current of the arc source to couple the electric field of the auxiliary anode, the control of the plasma density and energy is realized, and then the nitriding work of the soft base material of the work piece to be nitrided is completed.

[0022] The technical principle of this device: A large number of electrons generated by the arc source are attracted by the anode in the chamber, and perform spiral motion to fill the chamber under the magnetic enhancement device coupled by the permanent magnet device and the electromagnetic coil, and ionize the introduced gas atoms, so that the gas atoms form a plasma state and are injected and diffused into the interior of the soft base material for nitriding.

[0023] Compared with the conventional multi-arc nitriding device, this device can not only control the distribution area of the coupled magnetic field by adjusting the current of the auxiliary anode electromagnetic coil, control the movement trajectory of a large number of electrons generated by the arc source under the action of the electromagnetic field, thereby controlling the plasma density region, realizing uniform immersion plasma nitriding, and then precisely controlling the nitriding composition and structure; at the same time, it can avoid the generation of the electron shielding effect during large-scale industrial loading.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) The device realizes uniform discharge of the arc source structure for large-area targets (with a diameter of 160 mm), generates more electrons, and ionizes gas atoms.

[0026] (2) Based on the magnetic mirror field scanning and multi-arc ion source technology of the large-area target arc source structure, the device obtains a multi-stage magnetic field with an adjustable magnetic mirror ratio distributed along the axis by coupling the magnetic field distributions of the multi-arc ion source and the auxiliary anode, realizes a scalable annular plasma with 360° lateral variable characteristic parameters, and achieves uniform immersion plasma nitriding.

[0027] (3) The device can control the coupled magnetic field distribution region by adjusting the current of the auxiliary anode electromagnetic coil, thereby controlling the plasma density and energy, and then precisely regulating the nitriding composition and structure.

[0028] (4) The device can control the ability to absorb electrons by adjusting the auxiliary anode current, thereby controlling the plasma density, and then precisely regulating the nitriding composition and structure.

[0029] (5) The device can confine electrons in the side area of the furnace body between the target and the auxiliary anode, increasing the plasma density and energy around the soft base material of the workpiece to be nitrided. At the same time, the soft base part rotates three-dimensionally, allowing more ions to reach the nitriding area and ensuring the density of the coating.

[0030] (6) When performing side plasma nitriding, the device, on the one hand, increases the loading capacity of industrial production, and on the other hand, avoids the electron shielding effect during full load. Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of a device for uniform nitriding of high-density plasma on the surface of a soft base material.

[0032] Among them, 100 - chamber; 1 - arc source; 2 - permanent magnet device; 3 - auxiliary anode; 4 - adjustable resistor; 5 - electromagnetic coil; 6 - rotating frame; 7 - arc source power supply; 8 - auxiliary anode power supply; 9 - soft base material of the workpiece to be nitrided. Detailed Embodiments

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0034] Embodiment 1

[0035] As Figure 1As shown in the figure, a high-density plasma uniform nitriding device for the surface of soft base materials includes four arc sources 1 respectively arranged on the left, right, front, and rear sides inside the chamber 100. The arc source 1 is an electron generation source, and a permanent magnet device 2 is arranged behind each arc source 1.

[0036] Each arc source 1 is electrically connected to the negative electrode of an arc source power supply 7, and the positive electrode of the arc source power supply 7 is grounded; it also includes four auxiliary anodes 3 respectively arranged at the four corners inside the chamber 100; an electromagnetic coil 5 is arranged behind each auxiliary anode 3. The auxiliary anode 3 serves as an electron collector and has a certain traction effect on the electrons generated by the arc source 1; the electromagnetic coil 5 is magnetically coupled with the permanent magnet device 2, and a multi-stage magnetic field with an adjustable magnetic mirror ratio distributed along the axis is obtained by coupling the magnetic field distributions of the electromagnetic coil 5 and the permanent magnet device 2, so that the electrons generated by the arc source 1 perform spiral motion under the action of the electromagnetic field and reach the auxiliary anode 3 to be absorbed.

[0037] Each auxiliary anode 3 is electrically connected to the positive electrode of a secondary anode power supply 8 through an adjustable resistor 4, and the negative electrode of the secondary anode power supply 8 is grounded.

[0038] The positive electrodes of the secondary anode power supplies 8 located on the left side of the chamber 100 are respectively electrically connected to an adjustable resistor 4, and the two adjustable resistors 4 are respectively connected to the two auxiliary anodes 3 located on the left side of the chamber 100, thus forming a parallel circuit with the arc source circuit; the positive electrodes of the secondary anode power supplies 8 located on the right side of the chamber 100 are respectively electrically connected to an adjustable resistor 4, and the two adjustable resistors 4 are respectively connected to the two auxiliary anodes 3 located on the right side of the chamber 100, thus forming a parallel circuit with the arc source circuit. The secondary anode power supply 8 is adjustable.

[0039] The adjustable resistor 4 can adjust the magnitude of the current of the auxiliary anode 3 to control the electron absorption ability, control the plasma density, and further precisely regulate the nitriding composition and structure.

[0040] A turntable 6 is arranged in the middle of the chamber 100, and the turntable 6 is loaded with the nitrided base material parts, that is, the soft base material 9 to be nitrided. The soft base material 9 to be nitrided performs three-dimensional self-rotation and revolution motions in a certain direction.

[0041] The negative electrode of the arc source power supply 7 is connected to the arc source, and the positive electrode is grounded. The arc source power supply 7 is adjustable, and at the same time, the potential of the chamber 100 is also grounded.

[0042] Each electromagnetic coil 5 is electrically connected to a separate DC power supply, and its power supply is adjustable.

[0043] A large number of electrons evaporated by the arc source 1 are attracted by the auxiliary anode 3 in the chamber 100, and pass through the magnetic field distribution area coupled by the permanent magnet device 2 and the electromagnetic coil 5. Under the action of the electromagnetic field, a large number of electrons perform spiral motion to fill the chamber and ionize the introduced gas atoms, so that the gas atoms form a plasma state and are injected and diffused into the interior of the nitrided soft base material 9 loaded on the turntable 6 for nitriding. By adjusting the auxiliary anode current through the adjustable resistor 4, the ability to absorb electrons is accurately controlled, ensuring that the plasma region ionized by the electrons extends to immerse the nitrided soft base material, and realizing the accurate control of the nitriding composition and structure.

[0044] This device can not only control the movement trajectory of a large number of electrons generated by arc source evaporation under the action of the electromagnetic field by adjusting the magnitude of the electromagnetic coil current to couple the magnetic field distribution area of the permanent magnet, so as to control the plasma density region, realize the scalable annular plasma with 360° lateral variable characteristic parameters, and then accurately control the nitriding composition and structure; at the same time, it can avoid the generation of electron shielding effect during large-scale industrial loading.

[0045] Example 2

[0046] The difference from Example 1 is that a large number of electrons generated by the arc source 1 are attracted by the auxiliary anode 3 in the chamber 100, and the magnetic field of the electromagnetic coil 5 is coupled by adjusting the position of the permanent magnet device 2 to realize plasma nitriding work with a multi-stage magnetic mirror field of adjustable magnetic mirror ratio distributed along the circumferential direction of the chamber.

[0047] Example 3

[0048] The difference from Example 1 is that a large number of electrons generated by the arc source 1 are attracted by the auxiliary anode 3 in the chamber 100, and the electric field of the auxiliary anode is coupled by adjusting the current of the arc source 1 to realize the control of plasma density and energy, and then complete the nitriding work of the nitrided soft base material.

[0049] Application Example

[0050] The 316L austenitic stainless steel thermocouple is a commonly used temperature measuring element in temperature measuring instruments. It is used to directly measure temperature, convert the temperature signal into a thermoelectromotive force signal, and convert it into the temperature of the measured medium through an electrical instrument. The working process of the thermocouple will cause problems such as unstable performance, low measurement accuracy, extended thermal response time, small thermoelectric power rate, poor mechanical strength, short service life, and low overall efficiency. These factors seriously restrict the development and popularization of austenitic stainless steel thermocouples. In the face of complex and harsh service environments, in order to obtain better comprehensive performance, it is necessary to carry out specific nitriding surface strengthening treatment to improve the service life and ensure service safety. Select a thermocouple sample (diameter 20mm X 5mm) of austenitic stainless steel as the base material, and the surface hardness of the base material is 300HV 0.05,

[0051] After nitriding treatment by the high-density plasma uniform nitriding device for the surface of the soft base material in Example 1, the hardness of the stainless steel thermocouple soft base material increased from 300 HV to 1789 HV. At the same time, an AlCrN coating was prepared on the stainless steel thermocouple soft base material after nitriding treatment, and it was found that the hardness and bonding strength of the composite coating (3986 HV, 100 N) were about 2.5 times those of the single-layer coating (1602 HV, 40 N).

[0052] This is because the nitrided layer generates a hardness gradient between the substrate and the coating to reduce the mismatch of the substrate and coating system and further improve the performance of the composite coating.

[0053] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-density plasma uniform nitriding device for the surface of soft base materials, characterized in that: It includes 4 arc sources (1) respectively arranged on the left side, right side, front side and rear side inside the chamber (100). A permanent magnet device (2) is arranged behind each of the arc sources (1). Each arc source (1) is electrically connected to the negative pole of an arc source power supply (7), and the positive pole of the arc source power supply (7) is grounded; It also includes 4 auxiliary anodes (3) respectively arranged at the four corners inside the chamber (100); An electromagnetic coil (5) is arranged behind each auxiliary anode (3); Each auxiliary anode (3) is electrically connected to the positive pole of an auxiliary anode power supply (8) through an adjustable resistor (4), the negative pole of the auxiliary anode power supply (8) is grounded, the arc source power supply (7) connected to the arc source (1) can adjust the current magnitude, and the auxiliary anode power supply (8) connected to the auxiliary anode (3) can adjust the current magnitude.

2. The high-density plasma uniform nitriding device for the surface of soft base materials according to claim 1, wherein: The electromagnetic coil (5) has adjustability, and the magnetic fields of the electromagnetic coil (5) and the permanent magnet device (2) are coupled by adjustment.

3. The high-density plasma uniform nitriding device for the surface of soft base materials according to claim 1, wherein: A turntable (6) is arranged in the middle of the chamber (100).

4. The high-density plasma uniform nitriding device for the surface of soft base materials according to claim 3, characterized in that: A work-piece to be nitrided soft base material (9) is placed on the turntable (6).

5. The high-density plasma uniform nitriding device for the surface of soft base materials according to claim 4, wherein: The current of the auxiliary anode (3) can be adjusted through the adjustable resistor (4).

6. The high-density plasma uniform nitriding device for the surface of soft base materials according to claim 5, characterized in that: The arc source power supply (7), the auxiliary anode power supply (8) and the chamber (100) are all grounded.

7. The high-density plasma uniform nitriding device for the surface of soft base materials according to claim 6, characterized in that: Each electromagnetic coil (5) is electrically connected to a separate DC power supply.

8. The working method of the high-density plasma uniform nitriding device for the surface of the soft base material according to any one of claims 1-7, characterized in that: A large number of electrons evaporated by the arc source are attracted by the auxiliary anode in the chamber, and by adjusting the magnetic field distribution area coupled by the permanent magnet device and the electromagnetic coil, a large number of electrons perform spiral motion under the action of the electromagnetic field to fill the chamber and ionize the introduced gas atoms, so that the gas atoms form a plasma state and are injected and diffused into the interior of the work-piece to be nitrided soft base material placed on the turntable for nitriding; The current of the auxiliary anode is adjusted through the adjustable resistor to control the ability to absorb electrons, ensure that the plasma region ionized by the electrons extends to submerge the soft base material to be nitrided, and realize the precise control of the nitriding composition and structure; Or, the position of the permanent magnet device is adjusted to couple the magnetic field of the electromagnetic coil, and a multi-stage magnetic mirror field with an adjustable magnetic mirror ratio distributed circumferentially in the chamber is realized for plasma nitriding work; Or, the current of the arc source is adjusted to couple the electric field of the auxiliary anode, and the control of the plasma density and energy is realized, and then the nitriding work of the work-piece to be nitrided soft base material is completed.

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