Damage and failure of ceramic coatings bonded on alloy substrates was studied by observing crack evolution in the coating systems under in situ three-point bending tests with corresponding load-displacement curves. A damage and catastrophic failure model on the ceramic coatings was proposed based on our experimental results and the Taylor expansion of the controlling variable. The results indicate that the damage increases with increasing stress and obeys the power-law characteristics with the power exponent of 0.5, and the damage is 1 as the stress reaches the critical point corresponding to the failure of the coating systems. The damage rate increases rapidly when the stress is near the failure point and shows a power law singularity of -0.5. The experimental results of thin, thick, nanostructured, and conventional micrometer-scale microstructured coatings are all in agreement with the predictions based on the model.

This work was supported by the National Basic Research Programs of China (No. 2012CB937500), the NSFC grants of China (Nos. 11372318, 11023001,11432014, and 91216108), and the CAS/SAFEA International Partnership Program for Creative Research Teams.