SHEAR-STRENGTH OF A THERMAL BARRIER COATING PARALLEL TO THE BOND COAT

The static and low cycle fatigue strength of an air plasma sprayed (AP S) partially stabilized zirconia thermal barrier coating (TBC) is expe rimentally evaluated. The shear testing utilized the losipescu shear t est arrangement. Testing was performed parallel to the TBC-substrate i nterface. The TBC testing required an innovative use of steel extensio ns with the TBC bonded between the steel extensions to form the standa rd losipescu specimen shape. The test method appears to have been succ essful. Fracture of the TBC was initiated in shear, although unconstra ined specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength va lues that were measured. Low cycle fatigue failures were obtained at h igh stress levels approaching the ultimate strength of the TBC. The st atic and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material.