Inconel 617 samples were coated with silicon or silicon oxide SiO
X(0<
X≤2) films by reactive magnetron sputtering method. The coated samples were corrosion-tested in an impure helium environment at 900 and 1 000°C. The impure helium simulates the coolant gas of a high temperature gas cooled reacter now being developed in Japan. The SiO
X(
X<2) films reacted with the substrate alloy, Inconel 617 at elevated temperatures. Silicon in the SiO
X films diffused into the substrate to form the carbide of (Si, Mo)
X C
Y. Nickel and Chromium in the substrate diffused into the SiO
X films to form silicides. The SiO
X(
X<2) films exfoliated appreciably during the corrosion test and hardly protected the substrate against corrosive attack by the impure helium. Rather, SiO
X(
X<2) films enhanced a carburization of Inconel 617 in the impure helium.
On the other hand, the stoichiometric SiO
2 films had an excellelent protective effect in the impure helium at 900 and 1 000°C. However, the protective effect of the SiO
2 film degraded a little at 1 000°C. Inconel 617 was carburized and oxidized internally to form aluminum internal oxide-layer at 1 000°C.
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