Thermal cycling behaviors of the plasma sprayed thermal barrier coatings of hexaluminates with magnetoplumbite structure

Hexaluminates with magnetoplumbite structure are important high temperature ceramic materials for thermal barrier coatings (TBCs). Four hexaluminate coatings including NdMgAl11O19 (NdMA), SmMgAl11O19 (SmMA), GdMgAl11O19 (GdMA) and SrAl12O19 (SrHA) were prepared by plasma spraying. During plasma spraying, rare earth (RE) hexaluminates are partially decomposed, resulting in the loss of MgO. For RE hexaluminate coatings, the thermal cycling lifetime decreases with the reduction of RE3+ radius, while SrHA has the shortest lifetime. The random arrangement of the platelet-like hexagonal crystals resulted from the recrystallization during thermal cycling may reduce the bond strength of the coatings and make a large contribution to coatings’ failure. The different thermal cycling behaviors of these coatings seem to be dependent on their recrystallization differences to a large extent.