Hot corrosion behavior of La₂(Zr_0.7Ce_0.3)₂O₇based coatings prepared by plasma spraying and exposed to molten salts at 1050 °C in air

Abstract

Hot-corrosion performance of plasma sprayed La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 based coatings in contact with Na 2 SO 4 , V 2 O 5 , and Na 2 SO 4 þ V 2 O 5 mixtures (50:50 wt %) were investigated at 1050 8C in air for 12 h. Structural change is found to rank minimal to moderate and to be severe in case of exposures to Na 2 SO 4 , V 2 O 5 , and salt mixture, respectively. The pyrochlore-structured coating on exposure to salt mixture undergoes various chemical reactions and massive phase transitions, resulting in the formation of rare earth vanadates, lanthanum sulphates, and mainly the monoclinic and tetragonal phases of zirconia. Coatings exposed for 12 and 24 h to salt mixture, exhibited almost no difference.

Characterization and oxidation behaviour of nanostructured La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 /YSZ coatings prepared by calcined precursor precipitate plasma spraying

“…As a result, the topcoat in these DCL coatings is a two-phase mixture composed of the lanthanum zirconate with low solubility of Ce 4+ (LZ phase) and an oxide solid solution comprising Zr 4+ , Ce 4+ , and La 3+ (LC phase). The phase mixture results in better thermophysical properties compared to La 2 Zr 2 O 7 [21,22]. The peaks of the LZ phase in Figure 6 are consistent with peaks of the pyrochlore phase.…”

“…As a result, these coatings can enhance the lifetime of the hot sections of the high-temperature gas turbines. Also, La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 /YSZ coatings can be potentially used in very high service temperatures because of their superior thermophysical properties [21,22]. Thus, turbine inlet temperature and its thermal efficiency can be increased in the industrial gas turbines by using the La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 /YSZ coatings.…”

“…Literature data report that the addition of CeO 2 into the La 2 Zr 2 O 7 atomic structure can be effectively improved thermal expansion coefficient. The La-Zr-Ce-O composite composed of La 2 Zr 2 O 7 pyrochlore and La 2 Ce 2 O 7 fluorite phases results in superior thermo-physical properties such as slow sintering rate, lower thermal conduction, and higher thermal expansion coefficient in comparison with La 2 Zr 2 O 7 [21,22]. Although some works have performed to fabricate and characterize the La-Zr-Ce-O composite coatings [22][23][24], but no data has been published in detail to investigate the properties of nanostructured La-Zr-Ce-O composite coatings applied by a new method of plasma spraying of the solid precursor precipitate.…”