Cyclic Oxidation Behavior of Simulated Post-Weld Heat-Treated P91

For long-term service life it is desirable that the high-temperature components posses slow-growing oxide scale. The growth and degradation of the oxide scale on P91 were studied by a thermal cycling method. The oxidation temperature was 780 A degrees C and the duration of each cycle was 2 h. The mass gain and integrity of the scale was examined using a thermogravimetric balance. Any lack of integrity is monitored by the transient mass gain associated with the exposure of fresh surface. The scale retained the integrity throughout 100 cycles. Post-oxidation examination was carried out by scanning electron microscopy, energy dispersive spectroscopy and laser Raman spectroscopy. The nature of the scale was characterized and the reason for the compositional segregation is analyzed.