Sulfur localization in NiPtAl/superalloy systems after high temperature isothermal oxidation

Sulfur distribution and its evolution after isothermal oxidation have been studied using secondary ion mass spectrometry. In this work, the systems consist of a Ni-based single-crystal superalloy with a (Ni,Pt)Al bond coat. Two superalloys are compared: AM1 and MCNG. The latter contains Hf as a reactive element. Isothermal oxidations are performed at 1,100 °C under synthetic air for 1, 10, 50, 500 and 1,000 h. After oxidation, sulfur is detected both in the internal and external zones of the bond coat, at the bond coat/oxide interface and inside the oxide scale. An increase of the sulfur signal with oxidation time is registered at the bond coat/oxide interface for the MCNG-based systems whereas the opposite trend is observed for the AM1-based ones.