Heredity and variation of hollow structure from powders to coatings through atmospheric plasma spraying

• Hollow structure was partially inherited from hollow spherical powder to coating.
• 3D structure of the pores in the coatings were characterized and counted statistically.
• Four types of pores in the coatings were formed.

The pore structure is of significance to both thermal barrier performance and compliance of plasma-sprayed thermal barrier coatings (TBCs). In order to tune the pore structure of plasma-sprayed TBCs, the heredity and variation of the hollow structure from hollow spherical powders (HOSP) to coatings were investigated. Different plasma arc powers were selected for spraying the ceramic coatings. The recollected powders sprayed into water were examined to reveal the microstructure of the powders after arc heating. The results showed that the HOSP structure of spray powder could be retained after heating in plasma arc. Therefore, these hollow structures could be retained into the coating. As a result, four types of pores were formed in the coating. The porosities of the coatings were decreased with the increase in the arc power. Therefore, low arc powers were more suitable to retain the HOSP structure into the coating.