Evolution of Lamellar Interface Cracks during Isothermal Cyclic Test of Plasma-Sprayed 8YSZ coating with a columnar structured YSZ interlayer

摘要

The failure of plasma-sprayed thermal barrier coatings (TBC) usually occurs through spalling of ceramic coating. The cracking of YSZ coating parallel to the interface between the bond coat and YSZ during thermal cycling of TBC is primary cause to lead to spalling YSZ coating. With plasma-sprayed YSZ coating with substantial non-bonded lamellar interfaces which are regarded as precracks uniformly distributed in the coating, although it is known that the fracture toughness is proportional to lamellar bonding ratio, it was still not well known how the cracking along lamellar interface occurs during thermal cycles and its relation to failure of coating. Moreover, there was no data which directly relate the cracks in the coating to the lamellar bonding. In this study, the cracks in YSZ coatings were examined after YSZ coatings were subjected to different isothermal cycles till failure of TBC to examine how the cracking is associated to the thermal cycles and failure of TBCs.