Thermomechanical behavior of thermal-stress relief type of functionally gradient material evaluated by differential temperature heating using H₂/O₂ combustion flame

The burner heating test for thermomechanical evaluation of functionally gradient material in a laboratory scale has been described. A temperature difference was given by heating the ceramic side with a burner frame and cooling the metal side with water flow. The damage at the specimen surface was monitored with a microscope. A vertical crack formation at the ceramic surface was observed during cooling cycle. The test temperature for the first crack formation was defined as a thermal barrier performance value for the test sample. It has been found that the crack formation temperature is almost constant for the various samples and heating conditions, which indicates strong dependency of the thermal barrier property on the material species. The crack formation mechanism was discussed on the basis of a thermal stress analysis using a finite element method.