Semi-empirical methods for estimation/prediction of metal matrices behavior during thermochemical processing

Abstract

Abstract Series of solutions for estimations/predictions of the behavior of metal matrices during thermochemical treatments are described on basis on minimal number of experimental results under relatively random chosen processing conditions. Three methods were considered: Popov, Kazeev and Baram. The Popov method is based on the solutions of the second differential equation of diffusion (Fick’s second law), obtained by analytical and criterial solving under third boundary conditions; in this way, the kinetic parameters D, h*, and k are estimated. The Kazeev method is based on the correct hypothesis that besides the atomic diffusion takes place also other phenomena/interactions in the metallic matrix. All these complex processes can be described by specific equations whose solutions allow to determine certain parameters which change continuously during the diffusion process. The Baram method considers the generalized equation of kinetics of heterogeneous chemical reactions. This was resulted by taking into account the law of mass action and the phenomenological dependence of change over time of the inter-phases separation surfaces positions in solid materials subjected to thermochemical processing. It was thus possible to describe the phenomena occurred during thermochemical processing. The algorithms for the utilization of these methods are exemplified by experimental data resulted from the gaseous nitriding of the pure technical iron (ARMCO).