Thermal Shock Failure Analysis of LaMgAl11O19 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.