摘要
Thermal barrier coatings(TBCs)suffer from spalling failure resulting from the rapid growth of thermally grown oxides(TGO)on the metallic bond coat.In this study,to achieve the optimal lifetime of TBCs,a lifetime phase diagram was constructed for the entire service of TBCs.Herein,both the thermal mismatch stress during thermal cycling and the TGO growth stress during thermal exposure were considered.First,thickening behavior of the Al_(2)O_(3) scale related to grain size was investigated.Second,transverse delamination failure due to the thermal mismatch stress was analyzed.Third,vertical cracking failure related to early scale growth was explored.Finally,a critical scale grain size of~2.5μm was identified for achieving the optimal lifetime of TBCs.It was experimentally proved that vertical cracking of the Al_(2)O_(3) scale occurred during early oxidation as the scale grain size was larger than~4μm after pre-oxidation.The proposed lifetime phase diagram and critical scale grain size effect serve as novel criteria for the design of next-generation durable TBCs.
基金
the Postdoctoral Innovative Talent Support Program(No.BX2021238)
the National Natural Science Foundation of China(No.51671159)。
