Faculty Sponsor's Department:
Nickel based superalloys are a group of materials with excellent high-temperature strength and low-temperature toughness that are, at present, the only suitable material for high-pressure turbine blades used for aero propulsion. However, these superalloys require thermal and oxidation protection at their service temperatures, which is provided via a three-layer thermal barrier coating (TBC). A TBC consists of a low thermal conductivity ceramic, a dense thermally grown oxide (TGO), and an intermetallic bond coat. The role of a bond coat is to provide compatibility between the metallic substrate and the overlying ceramic layers while simultaneously serving as an aluminum source for TGO growth. The current industry standard coating, a β phase platinum-modified nickel aluminide, has poor creep resistance at high temperatures and is susceptible to rumpling, which leads to cracking and spalling of the ceramic layer. γ' based experimental bond coatings with inherently better creep properties have been developed to resist rumpling and therefore increase TBC lifetimes. Using primarily scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) we investigated the effect of furnace cycling at 1163°C on these γ’ based bond coatings with the aim of understanding the impact of chemistry and diffusion on coating behavior and failure mechanisms.