Proposal of Delamination Life Predication Method of Thermal Barrier Coating Layer under Thermal Cycle Condition

摘要

In this study, thermal cycle tests for thermal barrier coating, which is constructed by 8wt percent Y_2O_3-ZrO_2 as top coating material and NiCrAlY as bond coating, were conducted. It was found that (1) number of cycles to delamination were reduced with the increase of hold time at the maximum temperature in the thermal cycle, (2) debonding was occurred at side of the top coating layer near the interface between the top coating layer and the bond coating layer, and (3) a thermally growth oxidation layer was formed at the interface. The delamination model of thermal barrier coating layer under thermal cycle condition was proposed based on the some life properties of the coating delamination and micro structure observations of cross section of test specimen used in this study. The model is that radial thermal stress at the interface during heating up and down in thermal cycle test and then stress relaxation due to accumulation of creep deformation in the coating layer during holding temperature was cyclically acted at the interface. The delamination damage progresses as the interface crack propagation due to cyclic thermal stress and the acceleration of the crack propagation due to the effect of the thermally growth oxidation layer. The delamination life prediction method of thermal barrier coating was proposed based on the damage model. The proposed method could estimate actual delamination life of thermal barrier coating layer with a good accuracy.