Oxidation Kinetics and Surface Chemistry of an Fe–Cr–Al–Y Alloy Medium Made of 12-μm Diameter Fibers at Elevated Temperatures in Dry Air

摘要

Fiber media composed of Fe–Cr–Al–Y alloy are being used increasingly as materials for high-temperature applications for their excellent oxidation resistance. The oxidation kinetics of Fe–Cr–Al–Y alloy fiber medium as a heat-resistant material for high-temperature applications was studied in dry air at 1073, 1188, 1255, and 1318 K. The oxidation process followed the parabolic kinetic law. The alumina-scale growth was found to be influenced by short-circuit diffusion and the presence of stresses related to oxide-scale growth. The surface of the oxide scale formed on the fiber medium was analyzed using X-ray photoelectron spectroscopy, which revealed that the outer surface of the oxide scale formed on the fiber medium composed of 12-μm diameter Fe–Cr–Al–Y alloy fibers, consisted of θ-Al2O3, α-Al2O3, and Cr-oxide. The metastable θ-Al2O3 subsequently partially transformed into the more stable α-phase following a time-temperature-transformation relationship. The surface morphology and the cross section of the oxide scale formed on the fiber medium in the temperature range 1073–1318 K in dry air, have been studied by scanning-electron spectroscopy (SEM) and focused-ion beam, respectively.