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ODS IRON ALUMINIDS
1. G. Wright, C. G. McKamey, and B. A. Pint
Oak Ridge National Laboratory
P. O. Box 2008
Oak Ridge, TN37831-6156
ABSTRACT
Since oxide dispersion-strengthened (ODS) FeCrAI-based alloys have sufficient creep strength
and good oxidation resistance at the very high temperatures of interest for the primary heat exchanger
in advanced, closed-cycle gas turbine systems, they constitute viable alternative candidates to
ceramics. A major life-limiting factor of these alloys is the ability to continue to form a protective
scale of aluminum oxide, a factor proportional to the total amount of aluminum contained in the alloy.
Fe3 Al has oxidation resistance comparable to that of the FeCrAl-based alloys, and significantly
superior sulfidation resistance. Also, because of its larger reservoir of aluminum, Fe3 Al would be
expected to exhibit longer lifetimes at the temperatures of interest. Since the strengthening effects of
ODS processing are expected to confer similar high-temperature creep properties to those found for
the FeCrAJ-based alloys, ODS-Fe3 Al is considered to have excellent potential for the very high-
temperature heat exchanger application. The program effort on ODS Fe3AI includes examination of
the properties of available ODS-FeCrAl alloys; development of mechanical alloying parameters for
ODS-Fe3Al; determination of the effects of a dispersion of reactive element oxides on the high-
temperature oxidation behavior of Fe3Al; and evaluation of methods for joining them.
INTRODUCTION
There has been a recent increase of interest in advanced cycles that involve indirectly-fired gas
turbines, in which coal- or gas-fired high-temperature heat exchangers are used to heat a working fluid
in a closed system'. In a program conducted as part of the European COST-501 Concerted Action
Project (Round 2, Work Package 4), available alloys based on FeCrAl-Y203 (listed in Table 1) were
evaluated for use in the main heat exchanger in a similar closed-cycle gas turbine
application2,3,4,5,6,7,8,9,10,l1,12. One of the currently available ODS FeCrAI alloys was found to meet
the strength requirements for this application, in which the working fluid at 0.9 MPa (131 psi) flowing
at 5,889 kg/hr (12,955 lb/hr) was to be heated from 800 to 1100*C (1472 to 2012*F) over a tube length
of 4 m (13 ft).
FeCrAl-based alloys have long been regarded as having excellent resistance to high-
temperature oxidation, with reactive metal or reactive metal oxide additions playing some beneficial
role13,14,15. However, much of the information on oxidation behavior was generated from relatively
short-term exposures. In the very high-temperature heat exchanger application, an area of unexpected
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Wright, I. G.; McKamey, C. G. & Pint, B. A. ODS Iron Aluminides, report, July 1, 1995; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc621577/m1/1/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.