Study of failure mode and failure mechanisms on thermal fatigue of plasma sprayed thermal barrier coatings

Thermal fatigue test was conducted to study the failure process and failure mode of the plasma sprayed thermal barrier coating structures. The controlling factors for failure were also analyzed. A viscoplastic constitutive model was introduced for the ceramic coat. Moreover, the thermal fatigue behavior of the coating layer was studied numerically. The analysis indicates that: Mode I crack is easily initiated at the peak position, and mode II crack at above middle position of interfaces when TGO (thermally growth oxides) thickness is 2μm; the extension of transverse crack is dominated by normal stress when TGO thickness is 8μm; high strain energy density is formed within TGO of different thickness. The process and mechanisms of crack coalescence within PS-TBC (plasma sprayed thermal grown oxides) were presented.