Comparative evaluation of mechanical properties in plasma-sprayed Al2O3 coatings via Vickers indentation and single edge notched beam methods

In this study, Vickers indentation and single edge notched beam (SENB) methods were applied to characterize mechanical properties of Al 2 O 3 ceramic coatings deposited on titanium alloy substrate via atmospheric plasma spraying process at different critical plasma spraying parameters (CPSPs). A comparison was drawn between the fracture toughness values obtained from both techniques. As the CPSP value increased from 0.83 to 1.17, Vickers indentation consistently produced residual compressive stress ranging from -(111.91 ± 1.92) MPa to -(165.65 ± 3.55) MPa, and an increase in fracture toughness from 1.81 ± 0.03 to 2.22 ± 0.02 MPa·m 1/2 . Meanwhile, the fracture toughness yield via SENB method ranges from 0.89 ± 0.05 MPa·m 1/2 to 1.25 ± 0.02 MPa·m 1/2 . Although there were differences in absolute measurements, both methods consistently indicated that higher CPSP is associated with increased fracture toughness. These findings provide a fundamental understanding for the accurate assessment of plasma-sprayed ceramic coating performance. Moreover, the difference on fracture toughness obtained by the two methods was discussed.