Thermal Shock Failure Analysis of LaMgAl 11 O 19 Thick Ceramic Coatings Plasma Sprayed with Different Critical Plasma Spraying Parameters

The effect of the critical plasma spraying parameters (CPSPs) on thermal shock resistance of plasma-sprayed LaMgAl 11 O 19 coatings with thickness of 800 μm was investigated. With the CPSPs value decreased from 1.20 to 0.86, thermal cycling lifetime of the LMA coatings increased from 2571 ± 245 to 3394 ± 78 cycles during testing at 900 °C, while it increased from 300 ± 79 to 702 ± 78 cycles during testing at 1100 °C. Based on the simulation results, the normal tensile stress S 11 concentrated along the bond coat/top coat interface was decreased from 788.20 to 533.94 MPa with the decreasing CPSPs during the first cycle, while the normal tensile stress S 22 concentrated at the end of the interface reduced from 310.32 to 74.51 MPa after 10 cycles. As a result, the improvement of thermal shock resistance of coating would be attributed to the combined effects of the decrease in tensile stress S 11 and S 22 , while the stress accumulation and volume shrinkage induced by the recrystallization of amorphous phase were the main factors of coating failure.