Alumina-Forming Austenitic Stainless Steels Strengthened by Laves Phase and MC Carbide Precipitates
- ORNL
- Tokyo Institute of Technology
Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe{sub 2}Nb Laves phase was explored. Fe-20Cr-15Ni-(0-8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 C to 800 C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al{sub 2}O{sub 3} scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of {gamma} (fcc) + {alpha} (bcc) dual phase due to the strong {alpha}-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase {gamma}-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe{sub 2}Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe{sub 2}Nb were of limited benefit to creep resistance due to the solution limit of NbC within the {gamma}-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V{sub 4}C{sub 3} or TiC, higher levels of creep resistance were obtained.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Shared Research Equipment Collaborative Research Center
- Sponsoring Organization:
- USDOE Laboratory Directed Research and Development (LDRD) Program; FE USDOE - Office of Fossil Energy (FE); USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 936279
- Journal Information:
- Metallurgical and Materials Transactions A, Vol. 38A, Issue 11
- Country of Publication:
- United States
- Language:
- English
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