Chromium vaporization from alumina-forming and aluminized alloys

The Cr vaporization from alumina-forming and aluminized alloys was investigated at temperatures between 800 °C and 1000 °C using the transpiration method. The growth of alumina scale was studied by XRD, SEM/EDX, SNMS and TEM and discussed in the context of Cr vaporization. The experiments show that chromium vaporization from thermally grown alumina scales on alloys is about three orders of magnitude lower than that from pure chromia. The results indicate that Cr vaporization is governed by the content of dissolved Cr in the alumina scale. Bulk diffusion is identified as the major transport mechanism of Cr through the alumina scale. With regard to Cr vaporization as a major reason for long-term degradation in SOFCs the results show that alumina-forming-alloys and aluminized surfaces are promising for application in SOFC components without a current-conducting function.