Liquid Nitriding Details

The main difference of liquid soft nitriding is that there are Fe3Nε phase and Fe4Nr phase in the nitriding layer, but no Fe2Nξ phase nitride. The ξ phase compound is hard and brittle, which is not good for toughness in nitriding treatment. The method of liquid soft nitriding is to first remove rust, degrease, and preheat the workpiece to be treated before placing it in a nitriding crucible. The crucible is mainly TF-1 salt agent, which is heated to 560-600℃ for several minutes to several hours. The depth of the nitriding layer is determined by the external load on the workpiece. During the treatment, an air pipe must be passed through the bottom of the crucible to decompose a certain amount of air nitriding salt agent into CN or CNO, which penetrates and diffuses to the work surface, so that the outermost compound on the workpiece surface is 8-9%wt of N and a small amount of C and the diffusion layer. Nitrogen atoms diffuse into the α-Fe base to make the steel more fatigue-resistant. During the nitriding period, due to the decomposition and consumption of CNO, the salt agent composition must be continuously tested during the 6-8 hour treatment in order to adjust the air volume or add new salt agent.
The material used for liquid soft nitriding treatment is iron metal. The surface hardness after nitriding is higher if it contains Al, Cr, Mo, and Ti elements. The higher the gold content, the shallower the nitriding depth, such as carbon steel Hv 350~650, stainless steel Hv 1000~1200, and nitrided steel Hv 800~1100.