Oxidation-sulfidation studies of Fe-Cr-8Ni alloys with 4, 12, and 22 wt. %. Cr were conducted at 750 and 875~ in multicomponent gas mixtures that contained CO ...
Oxidation of Metals, Vol. 12, No. 3, 1977
Oxidation-Sulfidation Behavior of Iron-ChromiumNickel Alloys* M. Danielewski%+ and K. Natesan~
Received September28, 1977
Oxidation-sulfidation studies of Fe-Cr-8Ni alloys with 4, 12, and 22 wt. % Cr were conducted at 750 and 875~ in multicomponent gas mixtures that contained CO, C02, CH4, H2, and H2S. The reaction processes resulted in parabolic kinetics. A chromium concentration in the range 0-12 wt. % in the alloy had a negligible effect on the parabolic rate constant; however, the rate constant for the alloy with 22 wt. % Cr was significantly lower. For a given sulfur partial pressure, the oxygen partial pressures required for the formation of a continuous oxide layer in an Fe-22Cr-8Ni alloy were ~102 to 103 times those calculated for Cr-Cr203 equilibrium at temperatures of 875 and 750~ respectively. KEY WORDS: oxidation; sulfidation; iron-chromium-nickelalloy; thermochemical diagram; parabolic rate constant. INTRODUCTION The principal materials used in elevated-temperature regions of coalgasification and petrochemical processes are iron-base alloys with chromium as a major constituent. The gas environments in these processes are, in general, complex multicomponent mixtures that contain sulfurbearing gases (H2S and SOz) in addition to oxidants (CO2/CO and H 2 0 / H 2 ) . The corrosion behavior of iron-base alloys in such complex environments is strongly influenced by the gas composition and temperature. 1"2 The corrosion rates can be significantly different, depending on the * Work supported by the U.S. Energy Research and Development Administration. ? Materials Science Division, Argonne National Laboratory, Argonne, Illinois. .~On visiting appointment from the Academy of Mining and Metallurgy, Cracow, Poland through a fellowship of the International Atomic Energy Agency. 227 0030-770X/78/0600-0227505.00/0 0 1978 Plenum Publishing Corporation
1 2 3
750
23.9 1.9 0.7
20.2 3.4 0.6
CO
10.0 0.8 0.3
8.9 1,5 0.3
CO a
61.5 96.4 98.3
67.4 94.1 98.5
H2
3.7 0,3 0.1
3.1 0.5 0.1
CH4
Gas composition, vol. %
0.36 0.57 0.58
0.4 0.56 0.58
H2S
2.8 • 10 -2z 1 . 6 x 10 -23 3 . 7 • 10 -24
7.6 x 10 -a ~ 3.6 x 10 -21 2 . 8 x 1 0 22
Poz, atm
3.2 • 10 9 3 . 4 x 10 -9 3 , 2 x 10 -9
2 . 8 x 10 s 3 . 2 • 10 .8 3.2x10 8
Ps2, arm
Reaction potentialsa
0.468 0.180 0.096
0.226 0.181 0.096
ac
~The oxygen partial pressures for F e / F e O e q u i l i b r i u m at 875 a nd 750~ are 1.2 x 10 -17 and 6.7 • 10 -21 atm, respectively. Th e sulfur partial pressures for F e / F e S equilibrium at 875 and 750~ are 5.4 x 10 -9 and 1.2 • 10 -1~ atm, respectively.
1 2 3
Gas identification number
875
Temperature, ~
T a b l e I. R e a c t i o n P ot e nt i a l s E s t a b l i s h e d in Different E x p e r i m e n t a l R u n s
t~
Oxidation-Sulfidation Behavior of Iron-Chromium-Nickel Alloys
229
Table II. Composition of Iron and Iron-Chromium-Nickel Alloys (Concentrations Are in wt.%) Alloy
Cr
Ni
C
Fe Fe-4Cr-8Ni Fe-12Cr-8Ni Fe-22Cr-8Ni
< 0.004 3.89 11.96 21.86
0.012 7.86 7.96 7.92
0.002 0.004 0.003 0.003
N 0.001
