Influence of Feedstock on the Microstructure of Sm₂Zr₂O₇ Thermal Barrier Coatings Deposited by Plasma Spraying

Four Sm₂Zr₂O₇ (SZO) powders with different morphologies were deposited by atmospheric plasma spraying on superalloy substrates using the same spraying parameters. Both the particle size distribution and microstructure of the powders had an important effect on the coating microstructure. SZO thermal barrier coatings (TBCs) deposited using the powder with a narrow particle size distribution showed a better “molten state” and exhibited a higher average bonding strength compared with the SZO TBCs deposited using the powder with a wide particle size distribution. The dense microstructure of the calcined powder sintered at high temperature and of the powder spheroidized by plasma spraying gun (SF) improved the melting capacity of the powders, and the resulting coatings showed a compact microstructure with unique bimodal structures. Furthermore, the SF SZO TBCs presented an excellent “molten state” with a smooth surface and exhibited a high bonding strength of 29.6 ± 0.15 MPa.