Analysis of void formation in Pt-rich γ-γ’ bond-coatings for TBC system application

Abstract

Pt-rich γ-γ’ bond-coatings for thermal barrier coating systems may lead to detrimental pore formation. An extensive analysis of literature on voids nucleation and growth in the different metallic components of several kinds of TBC systems was performed. The study then focused on Pt-rich γ-γ’ bond-coating/Ni-based superalloy systems employing an original statistical analysis of voids formation and spatial distribution through secondary electron microscopy with focused ion beam sequential cross sectioning and synchrotron X-Ray tomography. It was found that pores at the Pt-rich γ-γ’ bond-coating/superalloy interface form due to the Kirkendall effect, with the highest concentration located at the Pt diffusion front.