Z. Zurek et al., Sulphidation and oxidation of the Ni22Cr10Al1Y alloy in H-2/H2S and SO2 atmospheres at high temperatures, J MATER SCI, 35(3), 2000, pp. 685-692
The Ni22Cr10Al1Y alloy was exposed in H-2/H2S gas mixture under the sulphur
pressure 10(-3) and 1 Pa as well as in SO2 at 1173 and 1273 K. At p(s2) =
1 Pa the sulphidation rate was relatively high and the reaction obeyed the
linear rate law. Under these conditions a nickel/nickel sulphide eutectic w
as formed. At p(s2) = 10(-3) Pa nickel sulphides became unstable and the su
lphidation rate was significantly lower. The reaction obeyed the parabolic
rate law. The oxidation rate of the alloy in SO2 was lower than that in any
of the H-2/H2S atmospheres. The sulphide scales formed during sulphidation
in H-2/H2S had complex microstructures and compositions, with sulphospinel
and sulphide phases being present, e.g. NiCr2S4, Ni3S2, CrxSy. As the temp
erature increased and the sulphur pressure decreased, these phases were rep
laced by the chromium-rich sulphide phase. Various oxides formed during oxi
dation of the alloy in SO2. (C) 2000 Kluwer Academic Publishers.