Temperature-stress synergy in molten salt corrosion of 7YSZ thermal barrier coatings: competing mechanisms of infiltration, stabilizer depletion and interfacial degradation

Purpose This study aims to systematically investigate the synergistic effects of molten salt corrosion (75 Wt.% Na2SO4–25 Wt.% NaCl), external stress and high temperatures (1,220/1,260°C) on the degradation mechanisms of 7 Wt.% yttria-stabilized zirconia thermal barrier coatings (TBCs), with the aim of guiding the design of corrosion-resistant coatings for next-generation turbine engines. Design/methodology/approach High-temperature exposure tests under controlled molten salt corrosion and external compressive stress were conducted. Coating damage behavior at 1,220°C and 1,260°C were comparatively analyzed, including stabilizer depletion kinetics, ceramic layer thinning and interfacial damage progression. Findings Through coupled experimental characterization, two distinct degradation pathways are identified: At 1,220°C, molten salt infiltration through vertical cracks drives progressive Y2O3 stabilizer depletion, resulting in 17% ceramic layer thinning over 10 h, whereas continuous Al2O3-rich thermally grown oxide (TGO) temporarily impedes interfacial damage. In contrast, 1,260°C exposure accelerates stabilizer consumption, enabling rapid salt penetration to the TC/BC interface within 10 h, causing > 40% spallation and substrate delamination via CrCl3 vapor-induced stress concentrations. External compressive stress reduces premature ceramic densification, reducing porosity by 66% and restricting salt penetration depth. Mechanochemical coupling alters failure mode dominance – suppressing interfacial cracks through TGO growth retardation while promoting stabilizer depletion-driven thinning. Originality/value These findings reveal critical stress-temperature-corrosion synergies governing TBC degradation, the competition between molten salt diffusion kinetics and TGO reformation capability emerges as the governing factor in lifetime prediction, providing fundamental insights for designing corrosion-resistant coatings under high temperature in next-generation turbine engines.