Characterisation of transient oxide formation on NiCrAlY after heat treatment in vacuum

To better understand transient oxide formation on the surface of standalone NiCrAlY in a vacuum, plasma sprayed NiCrAlY samples were subjected to a series of heat treatments at temperatures ranging from 1000 to 1100°C and for two different holding times. The morphology, composition and type of transient oxide(s) formed after heat treatment were characterised using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction (XRD). All samples exhibited the formation of a top layer of discrete or island like Ni rich oxide in cellular shaped alumina. The alumina layer, although difficult to be detected in cross-section, was very dense and covered most of the coating surface. The transisent oxide formation on the heat treated surfaces was further analysed using XRD and α-Al2O3 was detected on all heat treated samples in addition to NiO and possible spinel. Cr2O3 seemed to be present on the samples heat treated at 1000 and 1050°C but not on the sample heat treated at 1100°C. Increa...