논문 초록

Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation
tOxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650◦C, in ambient air, for exposuretimes 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxidescale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by mea-suring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time,the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then,dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initiallyformed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed theparabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequentoxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxidescale was mainly composed of mixed oxides such as FeCr2O4and MnCr2O4along with the binary oxidesof Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increasedmarkedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that theoxidation occurred in a non-selective manner
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