Statistical analysis on bonding strength and failure mechanism of plasma-sprayed HA coating with reinforced intermediate layers

Experimental results showed that both of commercial pure titanium (CP-Ti) and yttria-stabilized zirconia (YSZ) intermediate layers significantly enhanced the bonding strength of HACs (one-way ANOVA test, p < 0.05). On the basis of fracture morphologies and bonding strength data fluctuation, the Weibull model provided a powerful statistical analysis for assessing the failure mechanism and the reliability of composite coatings. Plasma-sprayed HACs were reliable materials with a right-shift wear-out failure model (m > 3) of increasing failure rate (IFR). The HA composite coatings remained in tack on the substrate, which represented better reliability and less dissociation for further applications. The measured bonding strength of HACs was a combination of adhesive and cohesive strength of a coating layer. The area fraction of adhesive failure tended to decrease with introducing the reinforced intermediate layer, especially for the HA/YSZ composite coating. The decrease of adhesive failure area fraction represented good interlocking between the coating/substrate interfaces. The knowledge of fracture behaviour in HACs with reinforced intermediate layers will be very helpful for the understanding and prediction of the bonding strength.