High-temperature slow crack growth, fracture toughness and room-temperature deformation behavior of plasma-sprayed ZrO2-8 wt % Y2O3

Elevated-temperature slow crack growth and fracture toughness of the thick thermal barrier coatings of plasma-sprayed ZrO2-8 wt % Y2O3 Were determined in flexure at 800 degrees C in air. The coating material exhibited a high resistance to slow crack growth under constant stress-rate flexural test condition. The value of fracture toughness, K-IC approximate to 1.0 MPa root m, was obtained by a new SEVNB technique, consistent from room temperature to 800 degrees C. The stress-strain curves of the material exhibited a significant nonlinearity and hysteresis both in compression and in tension. This behavior also resulted in distortion of the output wave form in response to the input cyclic loading. The stress-strain relation was slightly dependent both on the number of loading and unloading cycles and on the test rate.