Gas nitriding: The workpiece is put into the furnace and NH3 gas is directly input into the nitrogen nitriding furnace at 500-550 C for 20-100 hours. The NH3 gas is decomposed into atomic (N) gas (H) gas nitriding treatment. The main purpose of the surface is the wear resistance of steel and the corrosion composite layer. The thickness is about 0.02-0.02 m/m, the extremely hard property is Hv 1000-1200, and the NH3 is very brittle. The NH3 depends on the flow decomposition rate. The larger the decomposition degree, the lower the flow rate, the larger the flow rate, the smaller the decomposition rate, the higher the decomposition rate, the higher the temperature, the lower the temperature and the lower the decomposition rate. The thermal decomposition of NH3 gas at 570 C is as follows:
Decomposition in N forms diffusion to the surface of steel. Fe2 phase - 3N gas nitriding, hardening of the general shortcomings are thin and long nitriding time.
Through NH3 gas nitriding decomposition of low nitriding efficiency, it is generally applicable to fixed selection of nitriding steel, such as containing Al, Cr, Mo and other nitride elements, a small number of nitrides can not be added, general purpose JIS, SACM1 new JIS, SACM645 and SKD61 toughening treatment, also known as Al, Cr, Mo tempering treatment, is to improve the transformation point temperature of elements, high quenching temperature, and common structure alloy steel tempering treatment. The tempering temperature is higher, and the nitriding temperature is between long time heating and tempering brittleness, so quenching and toughening treatment is carried out in advance. NH3 gas nitriding, surface roughness due to long time, hard and brittle, not easy to grind, long time uneconomical injection pipe and screw rod nitriding machine.