Microstructure and mechanical properties of plasma-sprayed LaMgA111O19 thick ceramic coatings

Abstract

In the research, the effect of different critical plasma spray parameters (CPSP) on the microstructure and mechanical properties of plasma-sprayed LMA coatings with thickness of 797 μm were investigated. As a result, the porosity of coatings was increased from 12.14% to 24.88% with the decrease of CPSP from 1.20 to 0.86, while bonding strength of coatings was obviously reduced from 15.98 ± 0.36 MPa to 4.87 ± 0.7 MPa. Relatively, Young's modulus and hardness of the coatings exhibited a decreasing tendency with the decrease of CPSP. When the CPSP was decreased from 1.20 to 0.97, the residual compressive stress of coating surface varied from −162.10 ± 12.13 MPa to −93.49 ± 3.28 MPa, and that obtained from cross-section was decreased from −116.02 ± 5.92 MPa to −70.68 ± 3.99 MPa. Meanwhile, the fracture toughness of coating was improved from 0.62 ± 0.05MPa⋅m1/2 to 1.34 ± 0.05 MPa⋅m1/2, which was higher than that of cross-section of coating. The microstructure and mechanical properties of LMA thick coatings were strongly dependent on the CPSP.