Characterization of Plasma Nitriding Process and Development of A Nitriding Simulation Program

Microstructures in the nitride layer formed during plasma nitriding process in cubic specimens of AISI4140 steel were characterized by means of Optical metalloscope, SEM, XRD and GD-OES. Based on experimental results, a modified Wagner model was proposed to calculate the formation of the compound layer, and the reaction-diffusion model was used to calculate the precipitation of nitrides and the profile of nitrogen concentration in the diffusion zone. An FEM program was developed for predicting the nitrogen profile in the nitride layer and the changing of the nitride layer thickness. The calculated values of nitrogen profile and the nitride layer thickness meet the measured results well. The plasmas nitriding process of gear rings were investigated by using this developed program.