Dynamic spreading of re-melted volcanic ash bead on thermal barrier coatings

Dynamic spreading of 1 mm diameter volcanic ash bead on thermal barrier coatings (TBCs) surfaces and the infiltration and subsurface lateral flow of these melts within TBCs were quantitatively investigated at 1200−1600 °C for 1−10000 min. The spreading areas, infiltration depths and lateral flow distances are controlled by melt viscosity, coating surface roughness and microstructures. The lateral flow along the inter-column of the coating was dramatically accelerated at higher temperature with a diffusion distance of more than 5.3 mm within 1 min at 1600 °C. These findings are critical for understanding the corrosion mechanism of TBC in contaminated environments.