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

Microstructure and Thermal Cycling Behavior of Air Plasma-Sprayed YSZ/LaMgAl11O19 Composite Coatings

“…5(g), only the magnetoplumbite-type LaMA phase with small amount of impurities such as the alumina and one phase cannot be identified have been detected in the as-sprayed LaMA overlay. The detected impurities may be due to the partial decomposition of LaMA oxide during plasma spraying process as reported in our previous work (Ref 15,17) and has been confirmed by elemental analysis in our recent study (Ref 27), which can be expressed by the following equation:…”

Corrosion of lanthanum magnesium hexaaluminate as plasma-sprayed coating and as bulk material when exposed to molten V2O5-containing salt

“…These crystal chemistry characteristics impart the LaMA oxide with very good sintering resistance. [25][26][27][28] Our previous studies have already shown that plasma sprayed LaMA coating exhibited much better thermal cycling performance than YSZ and other new TBC candidate materials [29,30]. These results indicate that LaMA is a good TBC candidate material for higher temperature applications.…”

“…The second shrinkage is probably caused by to -Al 2 O 3 transformation originating from a small amount decomposition of the LaMA during plasma spray[29,30]. After thermal annealing at 1400 o C for 20 h, LaMA coating shows the same thermal expansion behaviour as the sintered LaMA bulk.…”

Study on formation mechanism of YSZ thermal barrier coatings with segmented structure

“…As a molten particle strikes the surface of a solid, it typically spreads out, forming a flat splat and rapidly losing heat to the underlying solid through conduction. A good joining between lamellae is a key for the propagation of segmentation cracks [6][7] . Accordingly, a high heat input to the substrate is one of the most important factors in developing segmentation cracks because high substrate and particle temperature promote the joining of adjacent lamellae.…”

“…When the spraying was performed at a high substrate temperature, the temperature between two adjacent splats could be high enough to lead to a partial remelting of the surface of underlying splats. Thus, the tensile stresses generated in the recently deposited splats will be relaxed by the propagation of microcracks [7] . Following this procedure, the microcracks will finally go through the coating, developing into segmentation cracks, as shown in Fig.…”