Measurement of Fracture Toughness of Plasma‐Sprayed Al2O3 Coatings Using a Tapered Double Cantilever Beam Method

Abstract

The fracture toughness of plasma‐sprayed Al2O3 coatings in terms of the critical strain energy release rate GIc was measured using a tapered double cantilever beam (TDCB) approach. The fracture surfaces were examined using a scanning electron microscope (SEM). The measurement yielded the mean GIc values from 13 to 27 J/m2 for the sprayed Al2O3 coatings at different spray distances. These values agree well with those obtained by the conventional double cantilever beam approach. The dependence of the observed GIc on spray distance is consistent with that for the lamellar bonding ratio. These results suggest that the TDCB test is a reliable approach for measuring the GIc of thermal‐spray coatings without the crack‐length measurement.