Microstructure and mechanical property regulation of plasma-sprayed high-entropy (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 thick coatings

Abstract

The effect of critical plasma spraying parameters (CPSPs) on phase composition, microstructure and mechanical property of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 thick coatings was investigated. After coating deposition, the phase structure of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 was transformed from pyrochlore to fluorite in the coating. When the CPSP value increased from 0.83kW/Lpm to 1.17kW/Lpm, the porosity of as-deposited coating was decreased from (16.46 ± 0.65)% to (6.94 ± 0.44)%. As a result, the elastic modulus of the coating was improved from (59.34 ± 2.39) GPa to (79.19 ± 4.78) GPa, and the corresponding micro-hardness was also increased from (2.59 ± 0.30) GPa to (3.39 ± 0.37) GPa. Consequently, the fracture toughness of as-deposited coating was decreased with the increasing CPSP value, while the corresponding residual stress was obtained to be compressive stress and it increased from -(43.00 ± 1.96) MPa to -(70.42 ± 3.89) MPa, indicating that the lower CPSP value was beneficial to reducing the residual compressive stress, which might be in favor of enhancing thermal shock resistance of coating.