Hot Corrosion Behavior of Yttria Stabilized Zirconia and La₂Ce₂C₇ Based Dual Coatings

One of the promising thermal barrier coatings (TBC) options for use above 1250 °C has been La₂Ce₂O₇ (LC). This work explored the role of dual layered ceramic coatings in the top layer of the TBC system that has been prepared using atmospheric plasma spraying (APS). Above the NiCrAlY bond coat, 8 mol.% yttria stabilized zirconia (8YSZ) coating has been deposited with optimized APS parameters. Over the top layer (8YSZ), another layer that comprises composite with LC and 8 wt.% of 8YSZ (spray dried) has been deposited. Investigations into the hot-corrosion behavior of 8YSZ-LC based TBC subjected to Na₂SO₄+V₂O₅ salt at 950 °C for 4 hours. A porous layer made mostly of LaVO₄, CeO₂, CeO_1.66 and YVO₄ was developed on the LC+8wt.% YSZ layer after being subjected to a hot corrosion test in Na₂SO₄+V₂O₅ salt. Dissociation of LC and 8YSZ leads to the formation of new phases, such as CeO_1.66, CeO₂, LaVO₄ and YVO₄ as the corrosion by-products in the extreme environment. The findings indicated that delamination has occurred due to the phase transformation, cavities and cracks in the 8YSZ-LC based TBCs. The molten salt's hot corrosion mechanisms of the 8YSZ-LC based TBC are discussed in detail. Further, the potential use of 8YSZ-LC based dual coatings and scope for the future work have been derived from the current study.