Enhanced Superalloys via Mesoscale Engineering

Illinois Institute Of Technology, Chicago IL

Investigators

Abstract

Superalloys are critical structural materials ideally suited for high performance gas turbine applications due their excellent resistance to deformation and environmental degradation at elevated temperatures. Although many of the intrinsic characteristics of superalloys can be attributed to the underlying alloy chemistry, in many instances the properties of these alloys can be enhanced through engineering control of the structure at very fine scales. Because many of the advanced turbine engines now operate at temperatures approaching the limits of existing superalloy capabilities, these engineering techniques can potentially extend the life and impart higher a higher degree of damage tolerance to many of these superalloy structures. This award supports fundamental research to understand how the process parameters employed during metal forming and heating operations effect the development of morphology and fine structure. This research will impact advanced gas turbine technologies for power generation, space exploration, and aerospace/marine propulsion, with significant economic and environmental benefits, such as the reduced fuel consumption, minimization of carbon dioxide and nitrous oxide emissions. The award will also support educational outreach programs at local Chicago high schools and assist in the training and education of US graduate students. This research funded by this award aims to understand the fundamental mechanisms that govern the formation serrated grain boundaries in polycrystalline Ni-based superalloys containing a high proportion of Sigma-3 twin boundaries, and assess their combined effect on grain boundary sliding. The extent and effectiveness of coherent and semi-coherent precipitates to induce grain boundary perturbations will be assessed in two commercial superalloys. In addition, bi-crystal samples possessing controlled misorientations will be fabricated to systematically quantify the effect of grain boundary misorientations on the formation and growth of perturbations. Finally, nano-scale assessments of the compositional and mechanical attributes along the serrated boundaries will be combined with 3D microstructural characterization and in situ strain mapping to quantify the effectiveness of the serrations on grain boundary sliding. These studies will contribute to the development of innovative thermal-mechanical processes that can be effectively used to tailor or engineer the mechanical properties of the alloy though the presence of meso-scale features.