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Low-temperature nitriding method for forming corrosion-resistant hardened layer on surface of stainless steel

A low-temperature nitriding and stainless steel technology, which is applied in coating, solid-state diffusion coating, metal material coating process, etc., can solve the problems of decreased corrosion resistance and reduced chromium content of the substrate

Active Publication Date: 2013-07-24
SHANGHAI SINOTEC +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0007] The purpose of the present invention is to provide an improved low-temperature nitriding method for forming a corrosion-resistant hardened layer on the surface of stainless steel, which can overcome the need to carry out at a temperature of 500-600 ° C or higher in the prior art to remove the passivation film , and when the nitriding treatment is carried out at a temperature higher than 450 ° C, chromium nitrides will be formed in the nitriding layer, resulting in a decrease in the chromium content of the matrix and a decrease in its corrosion resistance. At the same time, the entire nitriding treatment process is complicated insufficient

Method used

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  • Low-temperature nitriding method for forming corrosion-resistant hardened layer on surface of stainless steel
  • Low-temperature nitriding method for forming corrosion-resistant hardened layer on surface of stainless steel
  • Low-temperature nitriding method for forming corrosion-resistant hardened layer on surface of stainless steel

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Embodiment 1

[0027] Firstly, put the flux containing 5-12% borax, 10-18% boric acid, 50-75% potassium fluoroborate, 5-15% potassium fluoride, and 5-15% lithium chloride into the figure 1 In the shown crucible furnace (marked in the drawings are: 1. flux melt 2. crucible 3. heating furnace), heated to 600 ° C until the flux is completely melted into a liquid melt, and then the austenitic stainless steel (such as AISI304 or 316) products are immersed in flux melt for 10 to 15 minutes, then cooled in 10% hydrochloric acid aqueous solution until the flux adhered to the surface of stainless steel products is completely cleaned, and the removal is completed at this time The process of passivation film on the surface of stainless steel. The above-mentioned product that has removed the passivation film is immersed in carbon tetrachloride solution to keep its surface in an activated state, and within 1 hour, it is transferred to a nitriding furnace for nitriding treatment. Because the nitriding fur...

Embodiment 2

[0034] First, put the brazing flux consisting of 5% borax, 10% boric acid, 55% potassium fluoroborate, 15% potassium fluoride, and 15% lithium chloride into the crucible furnace, and heat it to 600°C until the flux is completely melted into a liquid melt. body, immerse stainless steel parts made of 316Ti in flux melt at 500-600 ° C for 12 minutes to remove the passivation film on the surface of the parts, and then soak in 10% hydrochloric acid aqueous solution and carbon tetrachloride solvent for 20 minutes. In the vacuum furnace, after evacuating to -0.1MPa, pass hydrogen (H2) into the furnace and heat up to 420°C. At this temperature, evacuate again to remove the gas in the furnace, and then pass ammonia (NH3) for nitriding After 30 hours, cool to below 100°C and take out the parts.

[0035] After the above-mentioned activation and nitriding treatment steps, the thickness of the hardened layer in different parts of the same part fluctuates in the range of 20-26 μm, and the t...

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Abstract

The invention relates to a low-temperature nitriding method for forming a corrosion-resistant hardened layer on the surface of stainless steel. The low-temperature nitriding method is characterized in that the low-temperature nitriding method comprises the following steps: 1, preparing a soldering flux melt, and putting a stainless steel product in the soldering flux melt for removing a passive film; 2, immersing the stainless steel product in a chloride solution to maintain the surface activity condition of the stainless steel product; and 3, carrying out nitriding heating treatment of the activated stainless steel product to form the corrosion-resistant hardened layer on the surface of the stainless steel product. The surface hardness of the product processed through the nitriding method reaches 900-1300HV0.1, and the wear resistance of the product is greatly improved. Additionally, the method can substantially reduce the frication coefficient of the surface of the product, and is in favor of improving the interlocking and adhesion wearing resistances of stainless steel components working at a high temperature. The method is suitable for the batch production of miniature precise components.

Description

technical field [0001] The invention relates to a nitriding method for stainless steel, especially austenitic stainless steel and its products. Specifically, the stainless steel product is activated in a flux melt and then placed in a nitriding atmosphere. At a certain temperature, the nitrogen element diffuses. A low-temperature nitriding method that forms an austenite hardened layer with a high concentration of nitrogen on the surface of austenitic steel to improve the wear resistance and corrosion resistance of the product. Background technique [0002] Austenitic stainless steel has good corrosion resistance and high temperature resistance, and is widely used in petroleum, chemical industry, papermaking, energy, valves, seals, decoration, medical equipment, instrumentation, precision machinery, aerospace and marine engineering and other industrial fields . However, the hardness of austenitic stainless steel is generally low, the wear resistance is poor, and the surface ...

Claims

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Application Information

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IPC IPC(8): C23C8/26C23C8/02
Inventor 汤建王军伟
Owner SHANGHAI SINOTEC
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