Indentation on YSZ thermal barrier coating layers deposited by electron beam PVD

Abstract

We have deposited an yttria-stabilized zirconia (YSZ) layer consisting of microsized grains on an alumina substrate using electron beam physical vapour deposition (EBPVD). The effects of Y2O3 concentration and the coating microstructures of YSZ on indentation damage are investigated. Different coating microstructures are prepared by varying the substrate temperature during deposition. Hertzian and nanoindentation are used to characterize the damage responses of the YSZ thermal barrier-coated alumina layered systems. The damage and failure behaviours have been investigated in relation to the effects of microstructures formed at various substrate temperatures as well as indentation loads from indentation tests. Elastic modulus, hardness, and stress - strain behaviours are characterized by results of the indentation tests. With increasing substrate temperature during the EBPVD process, the overall grain sizes became coarser with a smaller fraction of weak interfaces between the columns, and became more faceted. This change in microstructure ultimately influences the indentation behaviour. The results according to the use of smaller and larger scaled indenters during Hertzian/nanoindentations were also analyzed.