Study of CMAS wettability, penetration, and degradation behaviors on EB-PVD 8YSZ coatings laser micro-glazed (LMGed) by an ultraviolet picosecond ultrashort pulsed laser

Abstract

CaO-MgO-Al2O3-SiO2 (CMAS) is a primary contributor to the failure of thermal barrier coatings, particularly those with columnar structures fabricated via electron beam physical vapor deposition (EB-PVD). This paper presents the laser micro glazing (LMGing) of EB-PVD using an ultraviolet pulsed ultrashort pulsed laser. With the disappearance of inter-columnar gaps, a smooth LMGed layer with extremely narrow cracks (<0.9 μm in width) were formed on the surface. Employing the sessile-drop method, heat treatment demonstrated that the LMGed layer effectively suppressed the wettability, penetration, and degradation behaviors of CMAS. Compared to the original, the spreading area of CMAS on the LMGed layer was decreased by 48 % (37.8 mm2 → 19.5 mm2), while the contact angle was increased by 116 % (6.2° → 13.4°). Meanwhile, a small amount of CMAS was found in the inter-columnar gaps, while no CMAS aggregated at the bottom. The depth of the corrosion layer at the CMAS-coating interface decreased by 68 % (9.9 μm → 3.2 μm), ensuring the blocking effect of the LMGed layer.