Metal-glass based composites for novel TBC systems

A new concept of thermal barrier coating (TBC) system is presented, based on a metal-glass composite (MGC). Coatings of metal-glass composite can be deposited by vacuum plasma spraying and slip casting with a subsequent sinter step. In this TBC system the thermal expansion coefficient depends on the metal-glass ratio. It is chosen in such a way that the thermal expansion coefficient of the composite is close to the one of the substrate. This leads to reduced thermal stresses and hence improved thermal cycling life times. Because of the low thermal mismatch, coatings of more than 600 mum thickness can be realized. Another advantage of the gas tight composite coatings is their ability to protect the bondcoat from severe oxidation. Correspondingly, long life times have been found for these TBCs in oxidation tests. Also good results were found during thermal cycling tests. Furthermore some aspects of the microstructure evolution of the composite during heat treatment are described