The oxidation kinetics of SmCo alloys

SmCo alloys form the basis of excellent permanent magnets with potential service applications up to 550 degrees C. It is suspected, however, that their oxidation behaviour may limit their usefulness but this is a relatively unstudied subject. In this present work, two grades of Sm-2 (Co,Fe,Cu,Zr)(17)-based alloys were oxidised in air at temperatures between 300 and 600 degrees C, and the kinetics of the internal oxidation zone (IOZ) measured using SEM examination. The IOZ was found to grow parabolically with time, with an activation energy of similar to 143 kJ mol(-1) for growth in both the directions perpendicular and parallel to the c-axis alignment. The extent of penetration of the IOZ was always greater in the perpendicular than in the parallel directions, however. (C) 2008 Published by Elsevier B.V.