Warren Arthur Nelson

Phase stability of thermal barrier coatings made from 8 wt.% yttria stabilized zirconia: A technical note

SummaryIn summary, the phase stability in plasma sprayed 8 wt.% PSZ coatings with a porous and cracked microstructure were studied for times of up to 10 000 h at temperatures of 982 °C, 1204 °C, and 1315 °C. The two coatings behaved similarly and exhibited minimal change in the monoclinic content at exposures of 982 °C, while exposures at 1204 °C and 1315 °C resulted in increasing amounts of monoclinic phase versus time; the monoclinic phase reached a maximum of 40% at longer time exposures at the highest temperature as predicted by the phase diagram.

Development of Advanced Thermal Barrier Coatings for Severe Environments

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.Copyright