High-temperature Corrosion of ~ 30 Pct Porous FeCr Stainless Steels in Air: Long-Term Evaluation Up to Breakaway

Abstract

In this work, a long-term (up to 6000 hours) corrosion evaluation of three porous (~ 30 pct of initial porosity) ferritic iron-chromium alloys with different Cr contents (20, 22, and 27 wt pct of Cr) was carried out at 600 °C, 700 °C, 800 °C, and 900 °C in air. Mass gain measurements and SEM analyses revealed that at temperatures above 600 °C, all alloys exhibit breakaway corrosion, whereas at 600 °C, none of the alloys were heavily oxidized even after 6000 hours. Based on the results, the diffusion character of the corrosion of porous chromia-forming alloys was identified. The microstructure changes at high temperatures in porous alloys containing 22 wt pct of Cr were determined in detail by transmission electron microscopy. The proposed prediction model indicated that the lifetimes of the Fe20Cr and Fe22Cr alloys were determined as 1250 hours (± 535 hours) and 1460 hours (± 640 hours), respectively. It is in agreement with the long-term oxidation experiment. For the Fe27Cr alloy, the deviation between predicted and observed lifetimes occurs. The proposed model allows for qualitative estimation of the porous alloys’ lifetime with experimentally validated accuracy.

Long-Term Oxidation Studies on Porous Stainless Steel 430L Substrate Relevant to Its Application in Metal-Supported SOFC

“…However, the porous 430L alloy used in this study did not seem to agree with the conclusions of Tucker et al As shown in Figure 9, although the oxide scale thickness reached about 3 µm at about 300 h, no breakaway oxidation was observed in the micro-morphology (shown in Figures 3-8), and therefore 3 µm cannot be directly used as the failure criterion for the metal-supported SOFC stainless steel substrate in the present experiment. Furthermore, we cannot rule out the feasibility of such a standard due to variations in sintering temperatures, porosities, and oxidation conditions among different alloys [41].…”

“…Koszelow et al investigated the service life of ferrites at different temperatures. They predicted the service life of Fe27Cr in the air at 700 • C to be in the range of 5070 (±2740 h) [20,41,42]. For the porous 430L (~16 wt.% Cr) stainless steel, the weight increase ranges from 1.85 to 2.77 wt.% if all the chromium forms Cr 2 O 3 , and approximately 2.46 to 3.69 wt.% if all the chromium forms Fe/MnCr 2 O 4 spinel.…”

“…A double logarithmic plot (Figure 9b) was created using the oxidized weight gain data, indicating a slope of 0.5 for diffusion-controlled oxidation kinetics [20,41]. The threshold line for a 3 wt.% weight gain when breakaway oxidation occurs has been labeled.…”

Initial stage oxidation corrosion of commercial ferritic stainless steels with different Cr contents at 650 °C for solid oxide fuel cells

“…An adequate original Cr content (i.e. an abundant Cr reservoir) is a necessary condition for the long life of the alloy [ 13 ]. The element diffusion and oxidation kinetics of steel matrix during the long-term working process are usually positively dependent on temperature [ [14] , [15] ].…”