Comparison of the hot corrosion behavior of the LZ, CSZ and LZ/CSZ composite thermal barrier coating

Abstract

In the present study, the hot corrosion behavior of Air Plasma Spray (APS)-deposited Ceria Stabilized Zirconia-Lanthanum Zirconate (CSZ-LZ) composite thermal barrier coatings (TBCs) was investigated and compared with CSZ and LZ coatings. The hot corrosion tests were conducted at 950 °C in a cyclic mode in the presence of V2O5 + Na2SO4 molten salt mixture. The microstructural aspects were evaluated by energy dispersive spectroscopy (EDS) equipped scanning electron microscopy (SEM) and x-ray diffraction (XRD) methods. The results showed that CSZ, 75CSZ-25LZ, 50CSZ-50LZ, 25CSZ-75LZ and LZ coating systems lasted for 28–30 h, 24–26 h, 22–24 h, 20–22 h, and 18–20 h, respectively. The results revealed an improvement in the hot corrosion resistance of composite coating compared with LZ coating which can be attributed to better coefficient of thermal expansion (CTE) compatibility of composite coatings. The formation of hot corrosion products such as CeVO4, LaVO4, and also tetragonal to monoclinic transformation are the main reasons for the failure of these coatings.