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Nitrogen plasma surface treatment method for metallurgical coating of engineering product

Keywords:

treatment,the,of,is,surface,and,to,can,plasma,nitrogen

Published on:

31 May,2021

Engineering product metallurgical coating nitrogen plasma surface treatment method:
        Metallurgical coating methods are used in various engineering products to improve their corrosion resistance, wear resistance, fatigue strength and surface hardness. There are two coating methods. One is to attach a layer of substance on the surface of the workpiece; the other is to form a diffusion layer of different substances from the surface of the workpiece. This layer has a measurable concentration gradient and is consistent with the workpiece. The near surface becomes one.

Plasma surface treatment

Nitrogen plasma surface treatment method
        These two coatings can also exist at the same time. For example, for high-load workpieces, a hard nitride diffusion layer is generally formed first, and it is used to reliably support a harder TiN adhesion layer. Many such metallurgical coatings are being produced by physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods.
        The PVD coating system solidifies and deposits the solid coating material on the surface of a relatively cold workpiece through vaporization or sputtering. The temperature of the workpiece is generally based on the principle of not reducing the internal properties of the material. However, the adhesion between the PVD coating and even a well-cleaned surface is still not great, so applications are often limited.
        The CVD coating system uses liquid or gaseous coating materials to cause a combination of chemical reactions on the surface of a relatively high temperature workpiece. Although the high temperature of the surface of the workpiece is sufficient to promote the combination of chemical reactions, it is also sufficient to cause unwanted changes in the original properties of the workpiece. In order to restore the internal properties of the material, a follow-up process-heat treatment is required.
        Using a nitrogen plasma surface treatment method, the two electrodes are placed in a mixed gas with an appropriate partial pressure, and a voltage is applied between them to generate a glow discharge for plasma nitriding. One electrode, the anode, is a grounded vacuum cover. The other is the cathode. It is the workpiece to be ion-nitrided. Compared with the grounded vacuum cover, the workpiece is at a negative potential when nitriding. Connect this diode circuit to a transformer power supply. The current limiting resistor can change the resistance in the external circuit, and therefore, can independently adjust the current at any voltage level.
        The currently used power supply can independently select and control the amplitude, duration and period of the voltage, so that the negative nitrogen ions in the plasma zone can be uniformly covered on the surface of the workpiece without causing serious heat generation. The process controller can independently adjust the nitrogen ion concentration and temperature on the surface of the workpiece.
        Nitrogen plasma surface treatment is a normal limited diffusion process. When there are nitrogen atoms, the metallurgical process close to the surface of the workpiece and deep into the workpiece is mainly determined by the concentration gradient of nitrogen element, and the influence of the surrounding plasma parameters is second.
        Nitrogen plasma surface treatment is different from other helium technology. In the process, it uses glow discharge phenomenon to excite nitrogen. Exciting nitrogen in this way has many very important results:
        (1) Plasma nitriding can better control the composition, structure and performance of the surface of the finished product. The result of ammoniation does not produce a mixed phase (compound area) which is often brittle. For non-ferrous metal materials, cast iron and alloy steel, this is an effective surface treatment method.
        (2) Plasma nitriding can be performed at a temperature lower than conventional nitriding, so that the high performance of the core can be maintained. Low temperature sputtering can remove dirt on the surface of the workpiece, and nitriding can be completed in a short time at this low temperature.
        (3) Plasma nitriding can solve environmental problems, because the gas discharged from the ion ammoniation furnace is non-toxic and does not explode, and can be directly discharged outdoors, which requires expensive follow-up cleaning work and in accordance with the EPA approved method Post-processing to clean the falling agent.

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