Some Fundamental Issues in the Simulation of the Surface Treatment of Steels

In this seminar, the fundamental issues in the development of simulation tools for surface hardening processes will be presented and discussed. Models will be presented for gas and vacuum carburizing as well as carbonitriding. In addition, a model will be presented for ferritic nitriding that includes diffusion of nitrogen in ferrite and the formation of nitrides and carbonitrides during the process. The key issues in model development are the determination of the boundary conditions for these processes as well as the carbon and/or nitrogen diffusion coefficients and precipitation kinetics. The selection of a limited mass transfer coefficient at the surface or a constant flux condition will be discussed. In addition, the determination of the diffusion coefficients of carbon and nitrogen in austenite as a function of temperature and alloy composition, as well as the local carbon and nitrogen concentrations, will be presented. Experimental validation of these the simulation tools will also be described. Finally, the potential use of these tools in process optimization will be discussed. These tools will be demonstrated.