Thermally grown oxide formation on Ni2Al3 aluminide coating: The effect of nanocrystalline nickel film on oxide scale adhesion

The Ni2Al3 coatings were prepared by aluminizing with and without nanocrystalline (NC) Ni film using the pack cementation process for 5 hat 620 degrees C. After oxidation at 900 degrees C, the results demonstrate that the alumina formed on two Ni2Al3 coatings composed of O-Al2O3 on the basis of investigations of scanning electron microscopy (SEM), x-ray diffraction (XRD) and photo-stimulated luminescence spectroscopy (PSLS). The transmission electron microscopy (TEM) investigations combined with the electron diffraction pattern revealed that a small grain of alpha-Al2O3 nucleated on the Ni2Al3 coating with Ni film at the alumina scale/coating interface. Moreover, the Ni2Al3 coating with Ni film, in comparison to Ni2Al3 coating without Ni film control the size and density of the cavities formation at the scale/coating interface resulted in better adhesion of the alumina scale on aluminide.