K. Almandoz Forcen¹, C. Chalk¹, L. Isern¹, J.R. Nicholls¹, G. Brewster^2
1Cranfield University, Cranfield, United Kingdom
²Rolls-Royce Plc, Derby United Kingdom
Compliant thermal barrier coatings (TBCs) produced via electron beam physical vapour deposition enabled the long-lasting thermal protection of gas turbine components where damage tolerance of the ceramic coating was critical. However, the columnar microstructures produced via EB-PVD, responsible for the coating compliance introduce easy pathways for heat and fluid transport, reducing the effective thermal insulation and resistance to infiltration by molten slags (CMAS ). This work presents the results of series of coating depositions exploring the parameter space. The effect of the substrate temperature and rotation speed were explored and contrasted against the conditions reported in the literature. The coating process was undertaken using the Von Ardenne EBE-150 EB-PVD coater in Cranfield University. The resulting microstructures ranged from columns with periodic porosity features to homogeneously layered coatings, deviating significantly from the standard columnar morphology. The crystallographic phase makeup of the produced coatings was characterized using X-Ray Diffractometry (XRD), and crystalline texture was investigated using Electron Backscattered Diffraction (EBSD). Additionally, the microstructural morphology of the produced coating systems was compared by means of an automated method for column width measurement (CoCo). The obtained results demonstrate the flexibility of the EB-PVD process and the possibility of addressing the durability and performance penalties introduced by the columnar microstructures while maintaining the critical strain compliance of the system.