Y. Tan, C. Weyant, Stony Brook University, Stony Brook, NY; E. Mari, S. Sampath, S.U.N.Y at Stony Brook, Stony Brook, NY
Thermal barrier coatings continue to provide substantial benefits to gas turbines through efficiency and long-term performance advantages, as well as life extension of superalloy thermo-structural components. Thermal barrier coating systems were prepared on Ni-based superalloy substrates with HVOF-sprayed MCrAlY bond coats and air plasma sprayed yttria-stabilized zirconia top coats. Powders with three different morphologies were used in top coat fabrication: F&C, HOSP, and a special HOSP powder. Thermal conductivity, Young’s modulus and stress state were measured for both the triple-layer system and the free-standing top coat. The coatings were studied in both as-deposited, isothermally aged and thermal cycled conditions to compare the sintering rate of the ceramic top coat with and without constraints from the bond coat and the substrate. The powder morphology effect on the sintering rate was investigated and quantified through mechanical and thermal measurements, which were performed at both ambient and high temperature conditions.
Summary: Thermal barrier coatings continue to be of significant academic and industrial interest due to their important role in energy efficiency. As operating temperature of the engines increases, the porous sprayed coatings are subject to sintering and related stiffening. As such it is of interest to examine how different process conditions are subject to changes with extended exposures at high temperatures. This paper critically addresses this issue through a systematic study of thermal and mechanical measurements. We believe that this is a systematic investigation of its kind and provides a framework not only for input for life prediction of existing coatings but enable development of new materials and processes.
