Wettability and infiltration of molten CMAS droplet on thermal barrier coatings *

Sand particles ingested into a gas-turbine engine, melt in the combustor and often cause severe structural damage to components in the hot-section especially by depositing and eventually penetrating the thermal barrier coating on the engine components. To investigate the wetting and infiltration dynamics of molten CMAS droplets on the surface of thermal barrier coatings, a Lagrangian approach based on many-body dissipative particle dynamics (mDPD) is employed to simulate the mesoscopic dynamics of highly viscous molten CMAS droplets at a typical operating temperature of 1275 degrees Celsius. The physical system is carefully parameterized to best simulate the multiphase dynamics of molten CMAS droplets with diameters in the range of 10-100 micrometers. The use of an arbitrary boundary condition method in mDPD allows for arbitrary geometries to replicate experimental surfaces of thermal barrier coatings on the gas-turbine components. The apparent contact angles of sessile drops from experiments are used to calibrate the contact angle of a sessile droplet in mDPD by varying the liquid-solid interfacial tension. We simulate the infiltration dynamics of molten CMAS droplets on regularly patterned surfaces with specifically designed surface roughness to quantify the effects of surface heterogeneity on high viscous wetting and infiltration dynamics.