| Abstract Scope |
Delamination of protective thermal or environmental barrier coatings is a critical challenge in the development of next-generation high-temperature systems. Such coatings are typically made from brittle ceramics that easily fracture from thermal stresses under steady-state or transient operating conditions. To overcome this limitation, my group recently developed a ductile phase-toughened environmental barrier coating designed specifically to resist delamination. The coating comprises a borate-based glass-ceramic matrix reinforced with Ni. The Ni reinforcement sinters to the substrate and percolates through the brittle glass-ceramic when the Ni volume fraction exceeds 0.3, in excellent agreement with the percolation theory. Our experiments and analysis show that when the coating forms an interpenetrating structure, the Ni topology guarantees extrinsic toughening via crack bridging, imparting sufficient toughness to resist delamination under even the most aggressive operating conditions. This talk will summarize the processing, structure, and mechanics of these interpenetrating composite coatings. |