Abstract

Emerging aerospace and clean energy technologies will subject materials to extreme operating conditions, e.g., severe thermomechanical loads, which drive creep and thermal fatigue, as well as highly reactive environments, which drive chemical attack. To survive in these environments, structural materials rely on protective overlayers, either in the form of oxide layers grown in situ or advanced coatings applied ex situ. Since overlayer durability governs service life and operability, a mechanistic understanding of their failure is critical to safe operation and to develop more robust overlayers which unlock enhanced system-level performance. This talk will highlight strategies to design such failure-resistant protective overlayers by leveraging fundamental mechanics, experiments, and novel multiphysics theories. The first part of the talk will focus on the physics-based modelling of anomalous periodic failure of oxide layers formed on zirconium alloys in nuclear reactors. Failure of the oxide accelerates hydrogen embrittlement and ultimately limits the fuel burn-up in the reactor. By developing a mechanistic model of stresses and integrating it with Turing’s reaction-diffusion theory of pattern formation, the results reveal a stress-driven chemical interaction as the mechanism behind this detrimental anomaly, thus providing guidelines for the design of alloy chemistry against failure. Next part of the talk will focus on a novel ductile phase-reinforced environmental barrier coating (EBC) to mitigate metal fires in reusable staged combustion rocket engines. A key challenge for coatings in rocket engine applications is delamination from thermal shocks during startup and shutdown. Using a combination of experiments and delamination theory, our results show that crack-bridging by an interpenetrating composite architecture imparts sufficient toughness to resist delamination even under the most aggressive thermal transients. Finally, the talk will conclude with a perspective on a chemo-thermo-mechanics framework to guide the development of high-performance alloys and protective coatings for extreme environments.