Liquid nitriding

Liquid nitriding is a relatively new chemical heat treatment process, the temperature is not more than 570 ℃, the treatment time is short, only 1-3H; and it does not need special steel. The test shows that the anti-wear ability of 40Cr treated by liquid nitriding is 50% higher than that of general quenching and tempering; the anti-wear ability of cast iron treated by liquid nitriding is more improved. Not only that, the practice has proved that: the parts treated by liquid nitriding have different degrees of improvement in fatigue resistance, corrosion resistance and other aspects; the high-speed steel cutting tool can generally improve the service life by 20-200% after liquid nitriding treatment; the service life of 3Cr2W8V die casting die can be increased by 3-5 times after liquid nitriding treatment. The surface layer of liquid nitriding is hard but not brittle, and has certain toughness, so it is not easy to peel off.

However, liquid nitriding also has its disadvantages: for example, the thickness of the nitride layer in the nitriding surface layer is relatively thin, only 0.01-0.02MM. Cyaniding salt is widely used as raw material for liquid nitriding in foreign countries, and non toxic raw material has been used for liquid nitriding in China. The formula of liquid nitriding without poison in China is: urea 40%, sodium carbonate 30%, potassium chloride 20%, potassium hydroxide 10% (the melting point of mixed salt is about 340 ℃). Liquid nitriding has many advantages, but because of the toxicity of salt dissolving reaction, it affects the health of operators, and the waste salt is not easy to deal with. As a result, it is increasingly limited.