Oxidation behavior of creep resistant oxide-dispersion-strengthened alloy PM2000

Oxide dispersion strengthened (ODS) alloys show enhanced high temperature c reep and oxidation resistance. Powder metallurgy ferritic alloy PM2000 cont ains a small amount of finely dispersed yttria in the form of dispersoids t hat stabilize the microstructure consisting of coarse elongated grains with high grain aspect ratio, thereby retaining strength up to very high temper atures. The presence of yttria dispersion also has a beneficial effect on t he oxidation resistance of ODS alloys. The oxidation behaviour of alloy PM2000 was investigated in the temperature rantge 880 degreesC - 1400 degreesC. Oxidation kinetics during 200 hours e xposure were determined and parabolic rate constants were calculated from g ravimetric measurements of the extent of attack. SEM, EDX, EPMA, and X-ray diffraction were used to characterize oxide scale morphology, composition, and crystal structure. The influence of surface finish on the propensity of the oxide scale to spall upon cooling to room temperature was analyzed. Te nsile and creep experiments were performed at 1050 degreesC on specimens cu t along two perpendicular directions to address possible anisotropic mechan ical behavior of the material. Creep strength of the alloy was measured and corresponding fractographic analysis was performed.