Abstract
The influence of different amounts of sulphur impurity on the oxidation behaviour of a Ni–10Cr–9Al alloy in air at 1000°C has been investigated. It is indicated by the results that with increasing sulphur content, not only is there a decrease in the scale spalling resistance, but also there is a significant change in the initial growth rate and composition of the scale. Sulphur causes the formation of an inhomogeneous alumina scale by promoting the initial formation of chromia possibly originating from the oxidation of chromium sulphide. It is found that the addition of yttrium is beneficial in reducing both the spalling of the scales and the enhanced scale growth. The influence of the various impurities on the scale spalling characteristics can be correlated with the observed growth mechanisms in the initial stages of oxidation.
MST/929
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