Influence of Processing on Microstructure and Performance of Electron Beam Physical Vapor Deposition (EB-PVD) Thermal Barrier Coatings

Abstract

The paper addresses the effect of processing parameters on microstructure and lifetime of electron beam physical vapor deposition, partially yttria-stabilized zirconia (EB-PVD PYSZ) coatings deposited onto NiCoCrAlY-coated Ni-base superalloys. In particular, the formation of a thermally grown oxide layer, an equi-axed zone, and various columnar arrangements of the highly textured PYSZ layers are discussed with respect to processing conditions. Three different microstructures were cyclically tested at 1100°C. The intermediate columnar structure was superior with respect to cyclic life times to a fine and to a coarse columnar structure which was mainly attributed to differences in the elastic properties. The effect of PYSZ microstructure on hot corrosion behavior of the thermal barrier coating (TBC) system at 950°C is briefly discussed.

The non-destructive and nano-microstructural characterization of thermal-barrier coatings

“…After TBC spallation, the bond coat is directly exposed to high-temperature gas, leading to accelerated degradation of the bond coat and superalloy components. [1][2][3][4]8,9 Since TBC failure frequently involves component failure and unscheduled maintenance of gas turbine engines, it is important that the integrity of TBCs be nondestructively evaluated by examining the characteristics of TBCs including residual stress, thickness and the phase constituents of the TGO, as well as the presence of any insipient damage. Non-destructive evaluation (NDE) of these characteristics can provide critical information regarding the damage/failure modes of TBCs and can be a part of parameters monitored for lifetime management of TBCs and engine operation.…”

Influence of bias voltage and oxygen flow rate on morphology and crystallographic properties of gas flow sputtered zirconia coatings

“…The relation between thermal conductivity and the process-related micro-and nanostructure in EB-PVD YSZ coatings has been thoroughly investigated [12]. However, due to technical limitations, only a few parameters are accessible to alter the resulting microstructure, especially coating temperature and the direction of particle flux (tilting, rotation of the substrate) [12][13][14][15][16].…”

Review on Advanced EB‐PVD Ceramic Topcoats for TBC Applications

“…During high‐temperature loading of zirconia‐based TBCs in service, significant changes to the microstructural features occur quickly. Inter‐columnar sintering of type 1 pores increases the Young's modulus of the ceramic by formation of contact points between the columns and thus lead to stress increase in the ceramic topcoat during service 17,18,22 . The additional elastic energy stored in the ceramic provides further driving force for crack initiation and propagation and promotes spalling of the coating, thereby reducing the favorable strain tolerance of EB‐PVD coatings.…”