Heterogeneous layered structure in thermal barrier coatings by plasma spray-physical vapor deposition

Abstract

The unique columnar structure endows thermal barrier coatings (TBCs) prepared by plasma spray-physical vapor deposition (PS-PVD) with high thermal insulation and long lifetime. However, the coating delamination failure resulting from an intra-column fracture (within a column rather than between columns) is a bottleneck in the solid dust particle impact environment for aero-engine. To clarify the intra-column fracture mechanism, a basic layer deposition model is developed to explore a heterogeneous weak-to-strong layered structure formed by a local transient <i>in-situ</i> deposit temperature. During the PS-PVD, an <i>in-situ</i> deposit surface is continuously updated due to constantly being covered by vapor condensation, showing a transient temperature, which means that the <i>in-situ</i> deposit surface temperature rises sharply in short period of 0.2 s of depositing a thin layer during a single pass. Meanwhile, the increasing temperature of the <i>in-situ</i> deposit surface results in an experimentally observed heterogeneous weak-to-strong structure, showing a continuous transition from a porous weak structure at the bottom region to a dense strong structure at the top region. This structure easily makes the intra-column fracture at the porous weak region. The results shed light on improving TBC lifetime by restraining the intra-column fracture.