Materials Technology for Coal-Conversion Processes Quarterly Report: October-Decemeber 1978 Page: 16
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Task D -- Corrosion Behavior of Materials
1. Corrosion in Gasification Environments (K. Natesan)
The objectives of this program are to (1) develop uniaxial tensile
data on four commercial alloys upon exposure to multicomponent gas environ-
ments, (2) experimentally evaluate the high-temperature corrosion behavior
of iron- and nickel-base alloys in gas environments with a wide range of
oxygen, sulfur, aid carbon p tentials, and (3) develop a systems approach,
based upon available thermodynamic and kinetic information, to evaluate
possible corrosion problems in different coal-conversion processes.
The experimental program to generate uniaxial tensile data on four
iron- and nickel-base alloys upon exposure to multicomponent gas environments
was discussed previously.7 The experimental apparatus and the chemical
composition of the alloys and gas mixtures used in this program were de-
scribed in detail.1 Calculated values for the oxygen and sulfur partial
pressures established by the gas mixtures in different runs have also been
reported.3
During the present quarter, uniaxial tensile specimens, which were
thermally aged for 3.6 Ms (1000 h) at 750, 871, and 982*C, were tensile
tested in vacuum at an initial strain rate of 4.1 x 10-4 s-1. Additional
experiments that involve the exposure of corrosion and uniaxial-tensile
specimens to gas mixture 2B (see Ref. 1) for 3.6 Ms (1000 h) at 750 and
871*C were completed. Also, 3.6-Ms exposures of specimens to gas mixtures
3A and 3B at 982 and 750*C are in progress.
Tensile data for the thermally aged specimens can be compared with
earlier results3 from specimens exposed to mixed-gas environments to de-
termine the changes in the tensile properties due to variations in oxygen
and sulfur partial pressures in the gas environment. Figures 3-6 show the
engineering stress-engineering strain curves for Incoloy 800, Type 310
stainless steel, Inconel 671, and U.S. Steel Alloy 18-18-2, respectively, in
the as-received and thermally aged conditions, and after 3.6-Ms exposure to
gas mixtures with different oxygen, sulfur, and carbon potentials at 750'C.
In general, the results show that the ultimate tensile strength decreases
after exposure to complex gas mixtures when compared with those of the
material (except Inconel 671 alloy) in the as-received and thermally aged
conditions. In the case of Inconel 671, which is a two-phase nickel-base
alloy containing 48 wt.% Cr and 0.35 wt. X Ti, thermal aging of the material
at 750*C has a strong effect on the tensile behavior, as shown in Fig. 5.
Exposure of this alloy to the complex gas mixtures primarily increases the
tensile ductility values, as can be seen from Fig. 5. The load-elongation
data from the tensile tests were also converted to true stress-true strain
curves up to the point of maximum engineering stress by assuming a constant-
volume approximation for the tensile deformation. Figures 7-10 show the
true stress-true strain curves for Incoloy 800, Type 310 stainless steel,
Inconel 671, and U.S. Steel Alloy 18-18-2, respectively, in the as-received
and thermally aged conditions, and after 3.6-Ms exposure to gas mixtures with
different oxygen, sulfur, and carbon potentials at 750*C. In general, the
flow stress of the material decreases after exposure to complex gas mixtures
when compared with those of the material in the as-received and thermally16
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Argonne National Laboratory. Materials Science Division. Materials Technology for Coal-Conversion Processes Quarterly Report: October-Decemeber 1978, report, 1979?; Argonne, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc283206/m1/30/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.