Architecture designs for extending thermal cycling lifetime of suspension plasma sprayed thermal barrier coatings

Abstract Suspension plasma spraying (SPS) as a relatively new spraying technology has great potential on depositing high performance thermal barrier coatings (TBCs). In some cases, however, columnar SPS TBCs show premature failure in thermal cycling test. To explain the reasons of such failure, a failure mechanism for columnar SPS TBCs was proposed in this work. The premature failure of TBCs might be related to the radial stresses in the vicinity of top coat/bond coat interface. These radial stresses were introduced by the thermal misfit and the roughness of bond coat. According to this mechanism, two architecture designs of SPS TBCs were applied to improve the thermal cycling lifetime. One was a double layered top coat design with a lamellar atmospheric plasma sprayed (APS) sub-layer and a columnar SPS top-layer. The other one was a low roughness bond coat design with a columnar SPS top coat deposited on a low roughness bond coat which was grinded before the spraying. With both designs, lifetimes of SPS TBCs were significantly extended. Especially, a lifetime even better than conventional APS TBCs was achieved with the double layered design.