Stage growth of columnar 7YSZ coating prepared by plasma spray-physical vapor deposition

In this research, a multi-stage deposition experiment was designed to prepare 7YSZ coatings by plasma spray-physical vapor deposition (PS-PVD). The microstructure and relevant properties of the coatings at various stages were studied. The results indicated that the growth process of PS-PVD columnar coatings could be divided into three stages. These stages are: (1) stage I, the coating thickness from 0 to 5 μm, a dense coating composing of well-ranged fine columns is formed through absorption, nucleation and growth; (2) stage II, the coating among 5-60 μm, this is the fastest deposition stage, fine columns grow rapidly up to large columns with big gaps in between; (3) stage III, the coating over 60 μm, the typical columnar structures are formed eventually after new column branches growing on large columns. At this stage, the amount and average width of branches in the top of coating would not change with a further increase of spray passes. Based on the experimental results, the stage evolution of columnar 7YSZ coating prepared by PS-PVD was investigated and revealed.