In Fig. 6b, the interface between substrate and coating is shown. As seen, the coating shows good adherence to the substrate without any formation of pores or cracks. It is also noted that no visible bond layer is formed.
When the coating samples soaked at 1050 °C were examined, only NiAl and Al2O3 could be detected by EDS-analysis of the bulk coatings. However, this AM679 time thick bond-layers were formed. For sample IIc, with polished substrate surface, the bond-layer is uniform and about 4–5 μm thick. For the “as-machined” surface, sample IIIc, the bond layer is alleles thinner and not as uniform. See Fig. 7.
Fig. 7. Back-scattered SEM images of substrate (bottom), bond layer (middle) and coating (top) of a) sample IIc with polished substrate surface and b) sample IIIc with “as-machined” substrate surface. Scale bars indicate 2 μm.Figure optionsDownload full-size imageDownload high-quality image (675 K)Download as PowerPoint slide