Hot Corrosion of Lanthanum Zirconate and Partially Stabilized Zirconia Thermal Barrier Coatings

Abstract

The hot corrosion resistance of lanthanum zirconate and 8wt.% yttria-stabilized zirconia coatings produced by thermal spraying for use as thermal barriers on industrial gas turbines or in aerospace applications was evaluated. The two ceramic oxide coatings were exposed for various periods of time at temperatures up to 1000°C to vanadium- and sulfur-containing compounds, species often produced during the combustion of typical fuels used in these applications. Changes in the coatings were studied using a scanning electron microscope to observe the microstructure and x-ray diffraction techniques to analyze the phase composition. The results showed different behaviors for the two materials: the zirconia-based coating being rapidly degraded by the vanadium compounds and resistant to attack by the sulfur materials while the lanthanum zirconate was less damaged by exposure to vanadia but severely attacked in the presence of sulfur-containing species.

Microstructural, mechanical and thermal characteristics of zirconia-based thermal barrier coatings deposited by plasma spraying

“…It has been reported that lanthanum zirconate TBC was more resistant than YSZ one at the attack of V 2 O 5 at 1000 °C: no spallation and no meaningful changes in microstructure occurred. Otherwise, YSZ TBC failed by cracking and spallation [31]. However, when LZ TBC was attached by sulfates at 900 °C, it was rapidly degraded after a few hours, whereas after 360 h YSZ TBC preserved structural integrity and adhesion to the substrate.…”

Lanthanum zirconate based thermal barrier coatings: A review

“…The most typical corrosive chemicals for TBCs in a gas turbine engine include vanadium compounds (V2O5, NaVO3), sulfur-containing compounds (SO2 and sulfate salts such as Na2SO4, MgSO4), and the mixture of them [73,74]. When the APS deposited LZ based TBC was exposed to the single corrosive chemical at high temperature, it was less damaged by the vanadium compounds (at 1000 o C) but severely attacked by the sulfur-containing compounds (at 900 o C).…”

“…In the vanadia environment, many micro-cracks were generated in the 8YSZ coating, and spallation occurred finally. However, the 8YSZ coating showed an excellent resistance to sulfur-containing compounds [73]. In expecting to improve the corrosive resistance from Na2SO4 and V2O5, the LZ coating was deposited using EB-PVD with the addition of Y2O3 [74].…”

Effect of Cu Content on the Structure, and Performance of Substoichiometric Cr–N Coatings

“…The importance of developing coatings with advanced tribological and mechanical properties, and resistance to high-temperature oxidation, is increasing with applications embracing such fields as aeronautics, medicine and automotive industries [1,2]. Most often, in applications, such as machining, casting, or hot-forming, the protective layers are subjected to high-temperature exposure.…”