Ultrafast laser fabricated triple-scale micro/nano structured NdYbZr2O7 thermal barrier coatings with molten volcanic ash repellency

Thermal barrier coatings (TBCs) are extensively applied in the hot-section components of engines to enhance their high-temperature resistance. During service, these coatings often suffer from calcium‑magnesium-alumina-silicate (CMAS) corrosion. Inspired by the hydrophobic properties of lotus leaves, we employed ultrafast laser direct writing to fabricate a triple-scale micro-nano grid structure on the TBC surface, aiming to improve its resistance to molten CMAS infiltration. First, the triple-scale structures with varying laser scanning spacings (70, 80, and 90 μm) were fabricated on ceramic bulks. After 10 min of volcanic ash corrosion, the ceramic with a scanning spacing of 70 μm exhibits the largest contact angle (115°). Subsequently, a triple-scale micro-nano structure with a scanning spacing of 70 μm was prepared on the coating surface. Following 10 min of volcanic ash exposure, this structure demonstrates superior performance, with a larger contact angle (116°) and enhances resistance to CMAS penetration compared to the as-sprayed coating (105°). With the extension of corrosion time, the structured coating surface reacts with molten CMAS and forms a reaction layer composed of ZrO₂ and apatite phase, which inhibits further infiltration. The laser-ablated micro-nano structure increases surface roughness, resulting in a higher friction coefficient (0.280) compared to conventional coatings (0.214).