Non-isothermal nitridation kinetics of Ti6Al4V in Al2O3-based refractories

Abstract

To establish a kinetic model of nitridation of Ti6Al4V in Al2O3-based refractories, the non-isothermal nitridation of Ti6Al4V–Al2O3 composite refractories at various heating rates was investigated using a thermogravimetric (TG) analyzer for large samples. The activation energy (E) and kinetic model (G(α)) for the nitridation of Ti6Al4V were determined using the isoconversional and master plots methods, respectively. The nucleation and growth of nitriding products of the TiN solid solution was the controlling step in the nitridation of Ti6Al4V in Al2O3-based refractories. The Avrami-Erofeev kinetic model, depicted by the G(α) = [-ln (1-α)]4 equation, is the most rational kinetic model. The values of E and A for the nitridation of Ti6Al4V were calculated to be 214.99 kJ/mol and 1.46 × 107 (S−1), respectively.