Oxidation of Stainless Steel Powder

To understand the corrosion behavior of a model 304L(p)–ZrO2(s) composite, a 304L stainless steel powder was studied under oxygen at high temperature. Oxidation tests were performed with thermogravimetry. The so-called jumps method, which involves a sudden change of the temperature, was also applied to propose a kinetic model. Two periods with different rate-determining steps could be distinguished for short (<12 h) and long time experiments (12–20 h). SEM observations of oxidized particles revealed an oxide layer structure similar to that of alloy plates of same composition: during the first ten hours period, the external scale surrounding stainless steel particles was found to be chromium oxide; for the second oxidation period, the outer oxide layer was enriched in iron. Considering the relatively short-term oxidation period, a kinetic model based on an outward growth of chromia from oxidation of Cr in solution in the spherical alloy particles was successfully compared to the experimental mass gain curve. The kp value deduced from this modeling was found to be in agreement with the literature data. The diffusion of interstitial chromium ions is the rate-determining step in agreement with the absence of influence of the oxygen partial pressure.