Role of bond coat deposition method in the hot corrosion behavior of CSZ thermal barrier coatings

In this research, a NiCrAlY bond coat was applied using two methods – namely, conventional air plasma spraying (APS) and new spark plasma sintering (SPS) technique – on an Inconel-738 substrate. The ceria-stabilized zirconia (CSZ) topcoat was similar in both samples and deposited using the APS method. The hot corrosion performance of the fabricated thermal barrier coatings (TBCs) was studied at 950°C in a sodium sulfate (Na₂SO₄)–55 wt.% vanadium (V) oxide (V₂O₅) corrosive salt environment. The results showed that the hot corrosion resistance of the coating system with an SPS-processed NiCrAlY bond coat and a CSZ topcoat was much better than that of the conventional TBC sample because the adhesion of the bond coat to the substrate was very good in this sample, and the interface was free of any defects such as cracks and porosities. According to these results, no spallation was observed in the SPS-processed coating up to 38 h, while for the CSZ topcoat with an APS-processed bond coat, spallation occurred after 24 h.