Thermal Barrier Coating Sintering Behavior as a Function of Processing Condition

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.