CN201082898Y - Vacuum surface strengthening device - Google Patents

Abstract

The utility model relates to a vacuum surface strengthening device, belonging to plasma surface modification technical field. The device comprises a vacuum furnace, an air inlet system, a vacuumizing system, a power supply system, a temperature measurement system, a cooling system, an object stage and an insulator. The utility model is characterized in that: the vacuum surface strengthening device also comprises a double-layer cylinder which is positioned in a vacuum furnace and is insulated form a furnace body through the insulator; the object stage is positioned in the double-layer cylinder and is insulated form the furnace body; a negative pole of the power supply system is electrically connected with the double-layer cylinder. When subject to treatment of surface strengthening, a workpiece is placed on the object state, is then conducted with a high-voltage DC power supply, and then, with the furnace as a positive pole of the power supply, the double-layer cylinder as the negative pole of the power supply, undergoes surface nitridation under the hollow cathode effect of the double-layer cylinder. The utility model has the advantages of rapid nitridation on the surface of the workpiece, simple technique, maintenance of the original finish of the surface of the workpiece, thick compound layer on the surface of the workpiece, high density, simplicity and low costs.

Description

A New Vacuum Surface Strengthening Equipment

technical field

The utility model relates to the technical field of plasma surface modification, in particular to a device for performing ion nitriding treatment on the surface of a workpiece under vacuum conditions.

Background technique

Ion nitriding is to place the workpiece in the vacuum container of the glow discharge device, use the workpiece as the cathode, and set the container wall or another metal plate as the anode, fill a thin nitrogen-containing gas, and under the action of a DC high-voltage electric field, the gas Atoms are ionized into ions, and the ions hit the cathode workpiece at a relatively high speed. The nitrogen ions on the surface of the workpiece lose energy and are absorbed by the workpiece, and diffuse to the inside to form a nitrided layer.

Ion nitriding can not only realize the advantages of controllable nitriding, local hardening, use of pure hydrogen and nitrogen as the gas source without environmental pollution, but also does not generate brittle phases, and the permeated layer is dense, which is more effective than gas nitriding. High wear resistance, corrosion resistance and fatigue resistance. However, ion nitriding also has the following disadvantages: 1) temperature inhomogeneity: the existing ion nitriding heating is difficult to ensure temperature uniformity. When plasma is heated, the temperature of the workpiece not only depends on the energy of the plasma, but also It is related to the surface area and volume. Under certain parameters such as voltage and gas composition, the larger the surface area to volume ratio, the greater the energy input by ion bombardment, and the temperature rises rapidly. The workpieces of different shapes are heated unevenly, resulting in workpieces Performance degradation; 2) Surface arcing: When there are organic substances in some parts of the surface of the workpiece due to unclean cleaning, it will cause arcing and generate extremely high temperatures, causing the metal materials in this part to melt or sputter out, damaging The surface of the workpiece; 3) Edge effect: Due to the inhomogeneity of heating, the temperature of the edge and the center area are different, the surface color is uneven, and the thickness of the nitride layer is inconsistent.

Contents of the invention

The purpose of this utility model is to provide a new type of vacuum surface strengthening equipment, which has the advantages of fast nitriding speed, simple process, maintaining the original smoothness of the workpiece surface, thick compound layer on the workpiece surface, high density, simple equipment and low cost.

In order to achieve the above object, the technical scheme of the utility model is as follows:

A new type of vacuum surface strengthening equipment, including a vacuum furnace, an air intake system 12, a vacuum pumping system 13, a power supply system 14, a temperature measurement system 15, a cooling system, a stage 6 and an insulator 7, and the air intake system 12 passes through the air inlet 8 is connected to the vacuum furnace, the vacuum system 13 is connected to the interlayer air chamber of the furnace body of the vacuum furnace, the anode of the power supply system 14 is electrically connected to the vacuum furnace body through the anode interface 5, and the temperature measurement system 15 is connected to the workpiece 1 to be processed , the cooling system is connected with the vacuum furnace body; the strengthening equipment also includes a double-layer cylinder, which is located in the vacuum furnace and is electrically insulated from the vacuum furnace body by an insulator 7. The double-layer cylinder is composed of a small circle The small cylinder 2 is located in the large cylinder 3, the distance between the small cylinder 2 and the large cylinder 3 is 10mm, and the holes with a diameter of 5mm to 6mm are distributed on the small cylinder on average. The distance is 30mm-40mm, the stage 6 is located in the small cylinder 2, and is electrically insulated from the vacuum furnace body through the insulator 7, and the cathode of the power supply system 14 is electrically connected to the large cylinder 3 through the cathode interface 4.

The air intake system 12 is mainly composed of a gas cylinder and a pressure stabilizing valve, and its function is to ensure that the ammonia gas can be continuously and evenly supplied to the vacuum furnace.

The above-mentioned vacuum system 13 is mainly composed of a rotary vane mechanical pump and a resistance vacuum gauge. Its function is to vacuumize the interlayer air chamber of the vacuum furnace body through the rotary vane mechanical pump, making it a vacuum heat insulation layer, and using a resistance vacuum The gauge measures the air pressure in the vacuum furnace.

The above-mentioned power supply system 14 is mainly composed of a transformer and a rectifier, which are mainly used to adjust the voltage applied to the vacuum furnace.

The above-mentioned temperature measurement system 15 is mainly composed of armored thermocouples, insulating parts, shielding parts, gap protection parts and anti-electric field interference parts. All can be adjusted, the contact is reliable, and no discharge phenomenon occurs. The temperature measurement system 15 is mainly used to measure the temperature of the workpiece and control the nitriding process.

The above-mentioned vacuum furnace is mainly composed of a discharge cover, a bottom plate and a sealing ring. The discharge cover and the bottom plate are composed of two layers of steel plates, and the cooling system is cooled by water in the middle to ensure that the vacuum furnace will not lose its sealing effect due to temperature rise and deterioration.

The above-mentioned cooling system is mainly composed of a water pump, a water inlet 9, a cooling observation window 10 and a water outlet 11. The water inlet 9, the cooling observation window 10 and the water outlet 11 are placed between the discharge cover and the two layers of steel plates on the bottom plate.

The beneficial effects of the utility model are as follows:

1) Compared with gas nitriding: the utility model does not have the problem of nitrogen potential control, the nitriding speed is increased by 3 to 5 times, the waste gas emission is about 1/10000 of gas nitriding, 1/100 of vacuum nitriding, and the energy Consumption is 1/3 of gas nitriding;

2) Compared with ordinary ion nitriding: the nitriding matrix of the utility model has nothing to do with the discharge process, arc discharge will no longer occur on the surface of the workpiece, and the shape of the workpiece will no longer be a limiting factor for uneven nitriding. The temperature uniformity is good and the surface is basically No ion bombardment and sputtering, maintain the original smoothness of the workpiece surface, the compound layer on the surface of the workpiece is thick and dense, and the working pressure range is wide (10Pa～1000Pa);

3) Compared with omnidirectional plasma injection: the utility model does not need high-voltage power supply and high-vacuum equipment, and the equipment is simple and low in cost.

Description of drawings

Fig. 1 is a structural schematic diagram of a novel vacuum surface strengthening equipment of the present invention.

In the figure: 1. workpiece, 2. small cylinder, 3. large cylinder, 4. cathode interface, 5. anode interface, 6. stage, 7. insulator, 8. air inlet, 9. water inlet, 10 1. Cooling observation window, 11. Water outlet, 12. Air intake system, 13. Vacuum pumping system, 14. Power supply system, 15. Temperature measuring system.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in further detail:

As shown in Figure 1, a new type of vacuum surface strengthening equipment of the present utility model is to connect the negative pole of the power supply system 14 to an iron mesh double-layer cylinder in the vacuum furnace, and the double-layer cylinder is composed of a small cylinder 2 Composed with the large cylinder 3, the diameter of the double-layer cylinder is about 300mm ~ 350mm, the distance between the small cylinder 2 and the large cylinder 3 is 10mm, and the holes with a diameter of 5mm ~ 6mm are evenly distributed on the small cylinder, and the hole spacing is 30mm ~ 40mm , these holes are material transmission channels for nitriding; the workpiece 1 to be processed is placed in the middle of the small cylinder 2, and the workpiece 1 is in an electric levitation state or connected to a DC bias voltage. When the DC high-voltage power supply provided by the power supply system 14 is After switching on, the ammonia gas in the vacuum furnace is ionized; under the action of a DC electric field, it can be seen from the glow discharge characteristics that when the distance L between the two cathodes, the length of the cathode discharge L _k and the width of the cathode drop zone d _k satisfy When d _k <L/2, L>L _k >L/2, there will be a phenomenon that the light intensity increases due to the superposition of the two negative glow areas, that is, the hollow cathode effect, which will cause electronic oscillation between the cathodes, Increase the probability of collision between electrons and gas molecules, resulting in more excitation and ionization, thereby increasing the current and ion density between electrodes. The hollow cathode effect of plasma discharge produces high-concentration and highly active infiltrating atoms, which combine with highly active nitrogen atoms to form FeN on the surface of the workpiece through adsorption. FeN on the surface of the workpiece is unstable. As the surface continues to Adsorption and absorption of active nitrogen atoms, nitrogen atoms in the initial permeation layer diffuse deep into the matrix metal to form Fe ₂ N→Fe ₃ N→Fe ₄ N. Part of the particles diffused to form a γ′-phase compound layer, while some particles reacted with the adsorbed nitrogen to form an ε-phase compound layer.

In the ion nitriding process, the double-layer cylinder plays two roles: one is as a cathode to protect the workpiece; the other is to heat the workpiece through radiation. In the arc discharge process, there are three forms of electron emission, namely photoelectron emission, thermal Electron emission and field emission, the energy of these electrons is mostly 20ev~70ev, which can heat the workpiece to the temperature required for nitriding treatment; because during the nitriding treatment, the gas ions bombard the double-layer cylinder instead of directly The surface of the workpiece is bombarded, so the problems existing in the DC ion nitriding technology will be solved, such as workpiece arcing, edge effect, electric field effect, temperature measurement, etc. At the same time, the requirements for the ion nitriding power supply are also greatly reduced. The current limiting resistor that consumes a large amount of electric energy in the past is cancelled.

The operation process of a new type of vacuum surface strengthening equipment of the present invention is as follows:

(1) Workpiece cleaning and furnace loading

Clean the surface of the workpiece 1 with an industrial cleaning agent, then load the furnace, place the workpiece 1 on the stage 6, and isolate it from the power supply through the insulator 7, which is different from the existing ion nitriding that uses the workpiece as a cathode. The way of heat treatment.

(2) Vacuumizing and glowing

Start the mechanical pump of the vacuum system 13 to evacuate the interlayer air chamber of the vacuum furnace body, and start the cooling system at the same time, enter the water from the water inlet 9, and drain water through the water outlet 11. During the period, observe whether the water flow is smooth according to the cooling observation window 10 ; When the vacuum degree in the furnace reaches 13.3Pa～133Pa, the air intake system 12 fills the vacuum furnace with purified ammonia through the air inlet 8, and the ammonia gas passes through the holes of the small cylinder 2 and is evenly distributed throughout the vacuum furnace inside, make the concentration of ammonia gas around the workpiece 1 equal; adjust the flow rate of ammonia gas, keep the pressure in the vacuum furnace at 133Pa ~ 1333Pa, turn on the power supply of the power supply system 14, and the ammonia gas in the vacuum furnace will be generated under the action of high-voltage electric field ionization, resulting in a glow discharge effect.

(3) Heating stage

According to different nitriding process parameters, an appropriate amount of ammonia gas can be continuously fed into the vacuum furnace to make the pressure in the furnace reach a vacuum degree of 50Pa to 3000Pa, and the voltage and current can be gradually adjusted through the power supply system 14 to control the nitriding temperature. Adjust the air pressure in the furnace so that the double-layer cylinder maintains the hollow cathode discharge effect.

(4) Insulation stage

According to the requirements of the nitriding process parameters, the nitriding temperature in the vacuum furnace is kept at 450° C. to 650° C. for 3 hours to 6 hours.

(5) Cooling stage

Start the vacuum system 13 to evacuate the vacuum furnace into a low vacuum, turn off the power supply of the power supply system 14, and when the workpiece 1 is cooled to 200° C. with the vacuum furnace, the workpiece 1 is taken out from the furnace.

Claims (1)

1. novel evacuated surface-strengthening equipment, comprise vacuum oven, inlet system (12), pumped vacuum systems (13), power supply system (14), temp measuring system (15), cooling system, Stage microscope (6) and isolator (7), inlet system (12) inserts in the vacuum oven by inlet mouth (8), pumped vacuum systems (13) inserts in the furnace sandwich wind box of vacuum oven, the anode of power supply system (14) is electrically connected with the vacuum oven body of heater by anode interface (5), temp measuring system (15) is connected with pending workpiece (1), cooling system is connected with the vacuum oven body of heater, it is characterized in that, this strengthening device also comprises a double-layered cylinder, this double-layered cylinder is positioned at vacuum oven, by isolator (7) and vacuum oven body of heater electrical isolation, this double-layered cylinder is made up of little cylinder (2) and large cylinder (3), little cylinder (2) is positioned at large cylinder (3), little cylinder (2) is 10mm with the spacing of large cylinder (3), be evenly distributed the hole that diameter is 5mm～6mm on the little cylinder, the spacing of adjacent two holes is 30mm～40mm, Stage microscope (6) is positioned at little cylinder (2), and by isolator (7) and vacuum oven body of heater electrical isolation, the negative electrode of power supply system (14) is electrically connected with large cylinder (3) by negative electrode interface (4).

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