Self-healing plasma sprayed ceramic coatings

Self-healing in plasma sprayed MgAl₂O₄ coatings was examined. Self-healing additives consisting of SiC+X (X was anyone of BaO, CaO, ZnO, Y₂O₃,GeO₂, Ta₂O₅, V₂O₅) were characterized using TGA, HT-XRD and Raman Spectroscopy. Based on its reaction temperature, low toxicity and compatibility with neighbouring components, SiC+Y₂O₃ was selected and coatings were developed using vacuum and atmospheric plasma spraying. The coatings revealed healing after thermal treatment at 1000°C in air after 1 hour; 5 hour dwell improved the healing. CTE and electrical resistivity of the coatings decreased as a function of additive content. The Young’s moduli and fracture strength of the coatings were tested by 4-point flexural tests. In addition, a modelling technique was developed that determined the Young’s modulus by comparing the force-displacement curves of a simulated 4-point bending test with experimental ones. Assuming fracture mode I, the principal stress criterion for the ceramic was implemented in a cohesive zone model determining the fracture energy of the ceramic layer. The numerical results showed good consistence with experimental data.