Surface nitriding process of stainless steel plate

Stainless steel sheet is widely used. The surface modification of sheet metal is a low-cost way and can significantly enhance the hardness and wear resistance of materials.

Because the surface oxide film of the stainless steel plate will exist, it is very difficult to make ordinary gas nitriding. Although the surface activated stainless steel can be processed by gas nitriding, the process is complex and difficult to control. Therefore, some new nitriding processes have been used in the industry. Ion nitriding technology is the most used one.

Conventional ion nitriding is carried out in a mixed atmosphere of N2 and H2 or NH3 at the temperature of 500 to 560. Because plasma nitriding can directly remove the passive film on the surface of stainless steel, and it is easy to achieve local nitriding and easier control of nitrogen potential. It can show obvious superior performance in stainless steel surface reinforcement.

The results of nitriding experiments for some martensitic stainless steels show that plasma nitriding can produce a certain thickness of nitriding layer on the surface of stainless steel plates, and there is no need to remove the oxide film pretreatment. The hardness and wear resistance of the stainless steel after nitriding will be obviously enhanced. However, conventional ion nitriding is easy to form CrN on stainless steel surface, resulting in poor chromium formation on stainless steel substrate, thus reducing the corrosion resistance of stainless steel. Therefore, even if the ion nitriding treatment of stainless steel surface hardness, wear resistance and abrasion resistance, bonding ability has increased greatly, but if handled properly, very easy to produce surface peeling, hardening layer of uneven thickness and corrosion resistance greatly reduced the quality problems.

In order to prevent the formation of CrN at high temperature and damage the original corrosion resistance of stainless steel, it is necessary to develop a low temperature treatment process. The plasma low temperature nitriding process developed in the 80s of last century has successfully tackled the technical difficulty of the corrosion resistance of austenitic stainless steel after treatment. The key is to do it at low temperature, so as to prevent the formation of CrN and reduce the corrosion resistance of the matrix after chromium poor.

Although low temperature nitriding technology solves the problem of reducing corrosion resistance of stainless steel after nitriding, ionic nitriding also has its own disadvantages, such as boundary effect, hollow cathode effect, and uneven temperature of workpiece. In order to solve the shortcomings of ion nitriding, the activated screen ion nitriding technology has been developed in the industry.

Source: China Stainless Steel Plates Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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