Improvement of interface bond strength between ceramic thermal barrier coatings and metallic bond coatings

摘要

We investigated the bond strength of thermal barrier coating (TBC) for turbine blade applications, made by the addition of Ce and Si into the conventional bond coat materials. This study also examined how to form the the thermally grown oxide film at the interface between TBC and bond coat. The following conclusions are drawn: 1) In both aged TBC specimens, thermally grown oxides (TGO) were observed at the interface between TBC top coat and bond coat. However, morphology of oxides for these two TBCs remarkably different. In case of TBC coated with CoNiCrAlY bond coat, a continuous black TGO in SEM image formed at the interface. On the other hand, the TBC coated with CoNiCrAIYCeSi had intermittent black TGO layer. 2) The addition of Ce and Si into the CoNiCrAlY can prevent the adverse effect from NiO and CoO. 3) In case of TBC cpoated with CoNiCrAlY, the mixed oxides formed on the AI_2O_3 layer. On the other hand, in case of TBC coated with CoNiCrAIYCeSi, it seems that the mixed oxide grew into CoNiCrAIYCeSi bond coat. That is, the oxide was interwined with bond coat. 4) As a result of four point bending test, it is clear that TBC coated with CoNiCrAIYCeSi has a stronger bond strength than CoNiCrAlY one has. For the given same strain, TBC coated with CoNiCrAIYCeSi did not produce delamination.