Revista Fuentes El Reventón Energético (Dec 2014)
OXIDACIÓN A ALTA TEMPERATURA DE UN ACERO ASTM A335 P 92 EN CONDICIONES ISOTERMICAS Y DE CICLADO TERMICO
Abstract
This work describes the behavior of ASTM A 335 P92 steel under a process of continuous and cyclic oxidation at high temperatures between 450¿ and 700 ¿C in an oxidizing atmosphere. The gravimetric technique was used to observe the isothermal oxidation and the growth rate of oxides which showed a parabolic trend, X2 =KP t with values for KP [mg2/cm4h]: 0.00013; 0.00014; 0.00089; 0.01134; 0.01432; 0.01560 corresponding to temperatures of 450¿, 500¿, 550¿, 600¿, 650¿ y 700¿C, respectively. For cyclic tests shows that at temperatures between 450¿ and 600 ¿ C. a kinetic behavior parabolic type was present, while at 450¿ and 500¿C there was a mixed kinetic behavior type para-linear. After comparing both tests was observed, that the cyclic oxidation rate was higher than the continuous one due to thermal shock of the oxide layers, which carried a spalling of the external oxide. Results obtained by SEM at 650¿C temperatures and time of exposition equal to 50 hours in the isothermal oxidation presented two types of compound oxide layers due to the mix of Cr and Fe oxides, noting that the quantity of Cr is greater in the outer layer and the quantity of Fe is greater in the internal layer, in the other hand at 700¿ C and time of exposition equal to 168 hours in the cyclic oxidation, only the outer layer presented Fe, which was magnetite.
