Simulation of the residual stress development in the diffusion layer of low alloy plasma nitrided steels

Abstract

A computer program has been developed to simulate the changes of residual macro stress during plasma nitriding as a function of time and distance from the material surface. This program is based on a model which considers the superposition of the several contributions to stress. The only inputs required are the plasma nitriding and substrate material parameters. The variables are the change of nitrogen concentration in solution in the substrate matrix, the volume misfit between the matrix and the increasing volume fraction of nitrides, the dissolution of carbides during the nitriding process in addition to the relaxation of stress at the nitriding temperature and the thermal stresses. A comparison shows that the simulated residual stress profiles are very similar to those measured by the X-ray diffraction technique for short and long nitriding times at different temperatures.