An Investigation of the Compatibility of Nickel-Based Single Crystal Superalloys with Thermal Barrier Coating Systems

Abstract

The compatibility of a number of nickel-based single crystal superalloys with a thermal barrier coating (TBC) system is examined. An industry-standard yttria-stabilised zirconia (YSZ)-type ceramic was used throughout this work, deposited using electron beam physical vapour deposition at a commercial facility. It is demonstrated that the resistance to spallation during thermal cycling is dependent upon the composition of the superalloy substrate upon which the TBC system is placed -the number of cycles to failure is found to vary by up to a factor of three when identical TBC systems (bond coat, ceramic layer) are employed. Of the three different bond coat systems considered, a platinumdiffused (so-called low-cost bond coat) was found to be consistently better than both low-activity or high-activity platinum aluminide bond coats, but only marginally. The composition of the superalloy substrate is thus shown to be the primary factor in determining TBC life.

Effect of Pre-Oxidation and Thermal Exposure on the Microstructure of Superalloys and Thermal Barrier Coating Systems

“…As illustrated in other studies [85] and as emphasized in this study, substrate selection is paramount. The substrate must have sufficient Al concentration to form a steady state Al 2 O 3 scale [8].…”

“…In work done by Wu et al [85] Pt was electroplated on to single crystal alloys SRR99, CMSX-4, TMS-82+, PWA-1484 and TMS-138A. No diffusion or overlay bond coats were applied.…”