Influence of bondcoat creep and roughness on damage and lifetime of ZrO $_{2}$ TBCs for gas turbines under thermocyclic loads

摘要

As a simplified model system for thermal barrier coatings (TBCs) in gas turbines, Y2O3 partially stabilized ZrO2 TBCs were applied on FeCrAlY substrates. The creep strength of the substrate was varied by using an oxide-dispersion-strengthened (ODS) alloy and a non-ODS alloy with similar chemical composition. Defined interface profiles were produced before coating. Creep properties of the oxide layer between substrate and TBC were varied by either coating the test pieces with nanocrystalline PVD-alumina or with coarser grained naturally grown Al2O3 before plasma spraying the TBC. During thermal cycling (Tmax=1050°C, Tmin=60°C, dwell of 2 hours at Tmax) periodic 2-d interfaces resulted in very low lifetime independent from substrate strength and interface oxide type. With stochastic 3-d interfaces lifetimes up to 900 cycles were reached, especially for the substrate with low creep strength combined with a coarse grained alumina interlayer.