Abstract
A new test method to evaluate adhesion strength has been proposed, employing a ring type of TBC specimen specifically designed. It was shown by the experiments that a delamination behavior of the top coat was successfully reproduced by the proposed method, associating with a buckling mode; a similar mode observed in actual gas turbine components. It was also shown that the method have many advantages, compared with the traditional methods. One advantage is that the method can not only provide the adhesion strength of the ceramic top coat in terms of energy criteria, but also make us possible to evaluate the behaviors of stable delamination crack propagation and arrest, based on interface fracture mechanic. The other advantage is that the proposed method enables us to assess the effect of residual stress on the adhesion strength in a simulated manner near to the actual components, because the residual stress is built up in the specimen in a multi-axial stress state. Finally it was strongly suggested by the experiments that the chemical bonding between the ceramic top coat and bond coat in the TBC specimen was negligibly small, but a mechanical anchor effect had a chief contribution to the bonding strength.
