Application of diffusion and transition state theories on the carburizing of steel AISI 316 by annealing in uranium carbide powder

The steel specimens were tempered in contact with uranium carbide powder by sodium bonding at 500, 600, 700, and 800 °C for 1000h. Carburizing zone of the specimens was determined by measuring of microhardness which is taken as a kinetic variable instead of the corresponding carbon content. Arrhenius equation was determined for the diffusion of carbon atoms in the steel by using the solution of Fick's second law. Temperature dependency of the activation enthalpy, Gibbs energy, and entropy was calculated from the transition state theory by an assumption that the carburizing occurs over an activated complex. Kinetic and thermodynamic for formation an activated complex were discussed depending on the obtained numerical values.