It is well known that a trace amount of sulfur has a detrimental effect on the oxidation performance of conventional alloys，particularly on weakening the adhesion of thermally-grown oxide scales of chromia or alumina．To mitigate or exclude the negative sulfur effect，adding a small amount of rare earth element (such as Y，La，etc) or its oxide is a normal approach proposed．Recently，it was found that alloy nanocrystallization may be additional method to prevent the sulfur effect on oxidation．To futher convince this，two kinds of conventionally coarse-grained(CG)，high sulfur alloys were deliberately prepared；one is high S Fe-base Fe-25Cr-5Al alloys (by mass%) contains 0.26 mass% and 1 mass% S，respectively，the other is a high S Ni-base Ni-25Cr-5Al-1S alloy．Afterward these alloys were nanocrystallized using a magnetron sputtering technique and the oxidation performance of three nanocrystalline(NC) alloys were compared with that of the coarse-grained alloy counterparts．
Both Fe-25Cr-5Al-0.26S and Fe-25Cr-5Al-1S CG alloys precipitated CrS particles；However，the higher S alloy had more precipitates with increased size．The oxidation in air at 1000℃ shows that although the two alloys developed Al2O3 scale，it was less adherent on the higher S alloy．In contrast，the sputtered，Fe-25Cr-5Al-0.26S and Fe-25Cr-5Al-1S NC alloys could form a very adherent chromia scale．
For the Ni-25Cr-5Al-1S CG alloy，large CrS precipitates occurred．Compare with this， sulfur exists as solid atoms in sputtered，NC alloy counterpart．During oxidation at 1000℃，Ni-25Cr-5Al-1S CG alloy formed a scale composed of mixed Al2O3 and Cr2O3．The latter suffered severe spallation during cooling and high S content could be detected on the spallation area．However，Ni-25Cr-5Al-1S NC alloy formed an external Al2O3 scale，which has very good adherence to the substrate．No sulfur was probed at the interface between the scale and the alloy．The results strongly suggested that the alloy nanocrystallization can prevent the negative sulfur effect on oxidation，through increasing the adhesion of the scale developed to the high-S-content-containing alloy substrate．
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