Low-temperature rapid ion nitriding method of austenitic stainless steel

Abstract

The invention relates to a surface treatment method and particularly relates to a low-temperature rapid ion nitriding method of austenitic stainless steel. According to the method disclosed by the invention, a thicker ion nitriding layer can be obtained by changing gas pressure in an ion nitriding furnace and performing heat preservation for a period of time at the ion nitriding temperature of 350-370 DEG C. The preparation method comprises the following steps of: firstly removing oil stains on the austenitic stainless steel, performing pre-grinding treatment on a test sample, and then performing ultrasonic cleaning and drying in an organic solvent; then placing the well prepared test sample into a vacuum chamber of an ion nitriding device, performing vacuum-pumping operation to the required vacuum degree, and then introducing hydrogen to perform ion bombard cleaning; and finally adjusting ion nitriding pressure and heat preservation time during the low-temperature ion nitriding process to obtain the thicker nitriding layer so as to solve the problems of thin ion nitriding layer and poor wear resistance under low-temperature conditions. By using the method disclosed by the invention to perform ion nitriding and respectively perform heat preservation for 4h, 6h and 8h, the maximum thickness of the nitriding layer can respectively achieve 22.2 mu m, 29.6 mu m and 51.7 mu m.

Description

technical field [0001] The invention relates to a surface treatment method, in particular to a method for low-temperature rapid ion nitriding of austenitic stainless steel. Background technique [0002] Austenitic stainless steel is widely used in various fields of modern industry due to its excellent corrosion resistance, cold formability, weldability and other repair points, such as: biomedical, food processing, petrochemical and nuclear industries. However, due to its low hardness, poor wear resistance and inability to be strengthened by phase transformation, its application in many other fields is limited. [0003] As a clean and energy-saving surface modification heat treatment process, ion nitriding has many advantages such as uniform layer, simple process, good repeatability, low nitriding temperature, low energy consumption, short treatment time, and no pollution. been widely applied. Studies have shown that when using ion nitriding technology to treat austenitic s...

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Problems solved by technology

However, when the stainless steel ion nitriding process is carried out at a higher temperature (>450°C), due to the fast ion movement speed, a thicker nitriding layer can be obtained to improve its wear resistance, but it will be caused by the precipitation of chromium nitrides. The lack of chromium in the stainless steel substrate deteriorates its corrosion resistance; at present, in order to control the precipitation of chromium nitrides during the ion nitriding process, a lower ion nitriding temperature (figure 1 As shown, it is the metallographic structure obtained by ion nitriding at 360°C for 8 hours at a nitriding pressure of 400 Pa. It can be seen from the figure that the nitriding layer at this time is relatively thin, which is not conducive to improving its wear resistance and corrosion resistance at the same time.

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