Effect of EB-PVD thermal barrier coatings on fracture characteristics of superalloy substrate

Two-layered thermal barrier coatings (TBCs) consisting of NiCoCrAlY bond coating and YSZ (Yttria Stabilized Zirconia) top coating were produced by means of electron beam physical vapor deposition (EB-PVD) onto the substrate of K3 superalloy (involving as-cast and standard heat-treated states). The tensile behavior was evaluated for the specimens with and without TBC. The microstructure changes were analyzed in the preparation and inter mediate heat-treatments of coating. It is found that, due to the deposition of TBC onto the as-cast K3 substrate and inter mediate heat-treatment (vacuum pre-heating and heating treatments), the cast microstructure of the substrate is improved. The heat-treatment can result in a precipitation hardening. The tensile strength of K3 substrate is improved from 800 MPa to 1050 MPa after the TBC deposition, whereas the deposition of TBC has almost no effect on the mechanical behavior of the specimen that is dealt with the pre-heat treatment.