Development of Advanced Thermal Barrier Coatings for Severe Environments

Abstract

Air plasma sprayed yttria-stabilized zirconia thermal barrier coatings (TBCs) have been successfully used to extend life of superalloy components in utility gas turbines. GE Power Generation has over ten years of field experience with TBCs on combustor hardware, and over 20,000 hours of field experience with TBCs on turbine nozzles. Despite this promising experience, the full advantage of TBCs can be achieved only when the reliability of the coating approaches that of the superalloy component substrate. Recent work at GE has emphasized characterization of mechanical properties and physical attributes of TBCs to understand better the causes of delamination crack growth and coating spallation. In addition, unique tests to examine the TBC response under conditions simulating severe gas turbine service environments have been developed. Through evaluation of the results from comparative TBC ranking tests, pre-production application experience and field test results, gas turbine design engineers and materials process engineers are rapidly gaining the practical knowledge needed to integrate the TBC into the component design.