New developments in thermal barrier coatings (TBC) for gas turbine use

In order to realize high efficient gas turbines there is a strong need for thermal barrier coating systems with a high reliability and a long lifetime under severe operating conditions. At high operating temperatures the metallic bond coat suffers oxidation attack, which can cause the failure of the TBC system. Al₂O₃ diffusion barriers applicated between the bond coat and the top coat can reduce bond coat oxidation. By the improved oxidation resistance of the bond coat the isothermal and thermal cyclic life of TBCs can be increased. Two other problems arise from the weak interface strength bond coat/top coat and the brittle behaviour of the ceramic top coat. New developments are shown which deal with laser contourating of the bond coat to improve the interface strength and which deal with fibre reinforcement of the ceramic to achieve a pseudo-plastic behaviour of the ZrO₂-Y₂O₃ top coat.