Gas nitriding in 1923 published by the German AF ry, the workpiece in a furnace, and NH3 gas feed directly into the 500 ~ 550 ℃ in the nitriding furnace, 20 ~ 100 hours, make the NH3 gas is decomposed into the atomic state (N) (H) and gas for gas nitriding treatment, in the steel surface wear resistance, corrosion resistance of the compound layer as the main purpose, and its thickness is about 0.02 ~ 0.02 m/m, whose nature is extremely hard Hv 1000 ~ 1200, and brittle, the decomposition rate of NH3 inspects the size of the flow and temperature change, the more flow decomposition degree is low, The lower the flow rate, the higher the decomposition rate, the higher the temperature, and the lower the temperature, the lower the decomposition rate. The thermal decomposition of NH3 gas at 570℃ is as follows:
NH3 → [N] Fe + 3/2 H2
The decomposed N diffuses into the surface of the steel to form. The general disadvantage of phase FE2-3N nitriding is that the hardening layer is thin and the nitriding treatment time is long.
NH3 gas nitriding for the decomposition of nitriding efficiency is low, so the general all fixed choose suitable for nitriding steel grades, such as Al, Cr, Mo, etc nitrogen element, or a few to nitride, generally use JIS, SACM1 new JIS, SACM645, and SKD61 with strong processing, also known as conditioning for Al, Cr, Mo, etc are to improve the abnormal temperature of elements, so the high quenching temperature and tempering temperature is also a common structure with high alloy steel, which is between nitriding temperature heating for a long time, and temper brittleness, so advance to tempering toughness.NH3 gas nitriding, because the long surface rough, hard and brittle is not easy to grind, and the long time is not economical, used for the plastic injection molding machine feeding pipe and screw nitriding.
