Abstract
A mathematical model has been developed to simulate the nitriding process of plain carbon steel, considering the simultaneous diffusion of nitrogen in different iron-nitrogen (Fe-N) phases and the precipitation dynamics of γ’e and iron-nitride. The model can predict the distribution of nitrogen concentration, volume fraction of Fe-N phases and hardness. Furthermore, a finite element method (FEM) post-process technology is presented to avoid the limit of FEM mesh improvement and time-saving. The uniform-sum-division algorithm is adopted as local refinement algorithm (LRA) of meshes. The modified inverse distance weighting (IDW) method is used to interpolate the FEM simulated results. Then, the nitriding model and post-process technology are incorporated within the framework of the developed FEM code COSMAP (COmputer Simulation of MAnufacturing Process) based on metallo-thermo-mechanical theory. In order to validate the nitriding model and FEM post-process technology, the nitriding process of S30C steel is modeled by COSMAP software. The simulated distributions of nitrogen content and hardness are consistent with the measured ones. In addition, the simulated results at different mesh size are compared for two-dimensional model. It is indicated that the interpolated results agree well with the simulated results of fine mesh model and the experimental ones.Keywords: finite element, nitriding, S30C, iron nitride, inverse distance weighting
Highlights
Nitriding is a universal thermochemical heat treatment technology
Hassani-Gangaraj[7] proposed a finite element simulation to predict the kinetics of layer growth and nitrogen distribution during nitriding according the analogy between diffusion and heat conduction. Both the above models were processed by implementing modifications in the kinetics and modified layers properties into commercial finite element method (FEM) codes
A modified nitriding model is developed by coupling a phenomenological phase transformation dynamic model with the previous developed FEM code COSMAP (COmputer Simulation of MAnufacturing Process) based on metallothermo-mechanical theory
Summary
Nitriding is a universal thermochemical heat treatment technology It involves the diffusion of atomic nitrogen on the surface of a workpiece. The growth of a compound layer and diffusion layer, and the nitrogen concentration distribution in the nitrided layers could be precisely predicted by this model. Hassani-Gangaraj[7] proposed a finite element simulation to predict the kinetics of layer growth and nitrogen distribution during nitriding according the analogy between diffusion and heat conduction. Both the above models were processed by implementing modifications in the kinetics and modified layers properties into commercial FEM codes. The model is applied to simulate the nitriding process in S30C steel, and simulated results are compared with the measured ones
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