Thermal cycling behavior of the plasma-sprayed coating of lanthanum hexaaluminate

Amorphous phase is commonly found in plasma-sprayed LaMgAl11O19 coating. In this work, LaMgAl11O19 coatings were deposited by atmospheric plasma spraying with powders synthesized at the temperatures range from 1300 degrees C to 1600 degrees C. The melting degree of the feedstock was influenced by the amount of the second phase LaAlO3 and density of the powders, which was dependent on the synthesis temperature. Therefore, LaMgAl11O19 coatings with different amorphous phase contents and microstructures were produced. Results showed that the lower the amorphous contents, the lower the volume shrinkage of the coating during the recrystallization process and the longer the thermal cycling lifetime. However, when the amorphous contents were in the same level, the thermal cycling lifetime differences of these coatings seemed to be dependent on the grain size. LMA coating sprayed with powders synthesized at 1450 degrees C had relatively low amorphous content and moderate grain size, showing the longest thermal cycling lifetime.