Development of High Sintering-Resistant Thermal Barrier Coating Based on the Bridging Behavior of Inter-Lamellar Pores during Thermal Exposure

Inter-lamellar pores in plasma-sprayed thermal barrier coatings (TBCs) play an important role in decreasing the thermal conductivity and stiffness of the coatings. However, during service especially for the new generation TBCs applied under high temperature conditions over 1473K, healing of the inter-lamellar pores becomes significant through the formation of inter-lamellar free surface bridges. It was found that the free surface bridging is resulted from faceting of the free surface within the pores. Under a certain exposure temperature, there exists a critical width for the inter-lamellar pores over which the pore can be free of sintering. The measured critical width is different for different materials and increases with the exposure temperature. With a proposed novel method the ceramic coatings containing the inter-lamellar pores of a width larger than the critical width are fabricated. The results show that such coatings exhibit much higher sintering resistance compared with the traditional coatings.