Akademik Veri Yönetim Sistemi
JOURNAL OF ALLOYS AND COMPOUNDS, cilt.542, ss.253-256, 2012 (SCI-Expanded)
Diffusion theory (DT) and activated complex theory (ACT) were applied to the carburizing process of austenitic stainless steel 1.4988 with uranium carbide by sodium bonding at 773, 873, 973 and 1073 K for 1000 h. Microhardness profiles of the carburized steel specimens were obtained. Diffusion coefficient (D) of carbon atoms into the steel were calculated for each temperature by using the microhardness values instead of the carbon concentrations in the approximate solution of the second Fick's equation. Arrhenius equation for the carburizing process was found as: D = 2.6 x 10 (11) exp (-66753/RT) in m(2) s (1). Equilibrium constant (K-#) and enthalpy of activation (Delta H-#) for the formation of an activated complex calculated for each temperature from the Eyring equation using the diffusion coefficient instead of the reaction rate constant. Temperature dependence of the Delta H-# and change in heat capacities (Delta C-p(#)) by the carburizing were graphically determined as: Delta H-# = 66741 - 8.3T in J mol (1) and Delta C-p(#) = 8.3 J K (1) mol (1). Temperature dependence of lnK(#), Gibbs energy of activation (Delta G(#)) and entropy of activation (Delta S-#) were found respectively as follows: lnK(#) = -66741/RT = (8.3/R)lnT -48.3, Delta G(#) = 66741 + 8.3T lnT + 48.3 RT in J mol (1), and Delta S-# = -409.9-8.3 lnT in J K (1) mol (1). Based on these results, formation, size, and composition of the activated complex were discussed. (C) 2012 Published by Elsevier B.V.