Investigation of CMAS infiltration into EB-PVD Thermal Barrier Coatings

Ronghui Ma, Department of Mechanical Engineering
Timothy Munuhe, Department of Mechanical Engineering

The operation of gas turbines in dusty or ash-laden environments causes them to ingest small siliceous particles that melt inside them. These molten particles, termed CMAS, infiltrate into the thermal barrier coatings (TBCs) of gas turbines that protect the underlying metal from heat and corrosion. This infiltration causes loss of strain tolerance and delamination of the top coat. To develop efficient mitigation strategies, it is crucial to understand CMAS infiltration dynamics into the porous topcoat. We introduce an integrated model, incorporating liquid flow in unsaturated porous structures, transient heat transfer, and temperature-dependent viscosities, to study CMAS droplet spreading dynamics and infiltration through thermal barrier coatings grown by the electron beam physical vapor deposition (EB-PVD) method. Droplet spreading and infiltration are modeled by coupling the lubrication theory for droplet spreading with a level-set method for porous medium infiltration. The effects of different CMAS compositions, temperature gradients across the topcoat, and various coating microstructures are investigated.