Abstract
Cast stainless steel CF8C-Plus (19wt%Cr/12%Ni) has excellent creep properties, but limited oxidation resistance above 700°C in environments containing H2O. One strategy to improve the alloy oxidation performance is to increase the Cr and Ni concentration. Two new alloys, with, respectively, 21wt%Cr–15wt%Ni and 22wt%Cr–17.5wt%Ni were therefore developed and their long-term oxidation behaviors in humid air were compared with the oxidation behavior of five other cast alloys. At 650°C and 700°C, all the alloys formed internal Cr-rich nodules, and outer nodules or layers rich in Fe and Ni, but they grew a protective Cr-rich inner layer over time. At 750°C, the lower alloyed steels such as CF8C-Plus showed large metal losses, but the two new alloys still exhibited a protective oxidation behavior. The 21Cr–15Ni alloy was severely oxidized in locations at 800°C, but that was not the case for the 22Cr–17.5Ni alloy. Therefore, the two new modified alloys represent a potential operating temperature gain of, respectively, 50°C and 100°C in aggressive environments compared with the CF8C-Plus alloy.
| Original language | English |
|---|---|
| Article number | 55 |
| Journal | Frontiers in Materials |
| Volume | 2 |
| DOIs | |
| State | Published - Aug 13 2015 |
Funding
The authors would like to thank M. Stephens for his help with the oxidation exposures, T. Lowe, H. Longmire, and T. Jordan for the metallography work, and D. Leonard for conducting the microprobe measurements. They want also to acknowledge M. Brady for reviewing the manuscript. This research was sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Advanced Manufacturing Office | |
| Office of Energy Efficiency and Renewable Energy |
Keywords
- CF8C
- Cast steels
- Creep
- Oxidation
- Protective scale
- Water vapor