Duplex scale formation during high-temperature oxidation of Ni-0.1 wt.% Al alloy

The development of a duplex NiO scale microstructure on a Ni-0.1 wt.% Al alloy at 900°C has been examined, principally using secondary-ion mass spectrometry and analytical transmission electron microscopy. The¹⁸O-tracer distribution following sequential oxidation in¹⁸O₂/¹⁸O₂ showed that the inner NiO layer formed as a result of gaseous-oxygen penetration of the scale. The provision of pathways for oxygen transport as well as the role of Al, Si, and Ce segregation at oxide grain boundaries in influencing the growth rate and spallation behavior of the scale are discussed.