Role of initial defects in thermal sprayed coatings evaluated by thermal acoustic emission method and ultrasonic C-scope

Non-destructive evaluations of initial damage and damage mechanism were con ducted in plasma sprayed coating, ZrO2-8 mass % Y2O3/NiCoCrAlY onto stainle ss steel by atmosphere plasma sprayed method by thermal acoustic emission ( AE) method and ultrasonic C-scope, The materials was subjected to thermal s hock cycle. Initial damage generation occurred on colony pores at the ceram ic/bond layer interface, where delamination was generated by the coalescenc e of initial thermal stress damages following damage nucleation The damage mechanism was cracking of the ceramic layers by thermal tensile stress. AE detected the initial defects and the damage, and damage mechanism in accord ing to an analysis of AE location and amplitude with correspondence to ther mal history. Ultrasonic C-scope evaluation provided a high resolution view for damage detection, combining the results of AE location.