A comparison of the growth kinetics and scale morphology for three superalloys at 930 degrees C in air and low P-O2 environments

This study assessed the oxidation behavior of three commercial alloys in ai r and low partial pressures of oxygen (P-O2). The kinetics of oxidation in air were compared with values obtained in an atmosphere of low P-O2. The lo w partial pressure of oxygen was of the order of 10(-16) atm at 930 degrees C and was generated using an H-2/4% H2O mixture. The nature of the corrosi on products, structure, morphology, and composition were assessed and chara cterised using scanning electron microscopy (SEM), X-ray mapping and scanni ng Auger microscopy (SAM). The results were compared with those obtained fo r 99.99% pure chromium. Parabolic kinetics were Exhibited by all of the all oys, with the overall k(p) values being of the order constant for chromia-f orming alloys. Large variations in the morphologies of the oxide scales wer e observed as a result of oxidation in the high and low P-O2 environments.