Integrated Mechanism-Based Framework to Address the CMAS Problem in Gas Turbine Technology
Abstract
ABSTRACT: A research program is proposed to generate the fundamental understanding and quantitative description of the mechanisms that govern deleterious CMAS interactions with oxides of interest in thermal and environmental barrier coatings (T/EBCs), and their implications in durability. The problem is sufficiently complex, owing in part to the stochastic nature of CMAS deposits andlimited relevant information on the properties and behavior of deposits and coating materials, that identification of robust solutions requires a strategy guided by ICME principles. Development of an integrated framework was initiated under a previous grant and the proposed project is intended to continue building its requisite components. It is envisaged that such approach wouldinvolve elements of (i) understanding the composition space of relevant siliceous deposits, (ii) phase equilibria and thermochemistry, (iii) the dynamic processes controlling the infiltration of molten silicates into porous TBC microstructures, and the reaction with dense EBC coatings, (iv) the mechanics governing the response of the system to cyclic thermal gradients, and (v) the processing science needed to implement the emerging engineered materials solutions. The proposed program would address the dynamics of the micro-, meso- and macro-scale processes during CMAS-coating interactions, focusing on the thermochemistry and melt dynamics. An ongoing activity on understanding quantitatively the kinetics of oxide dissolution and itseffects on melt crystallization will be extended to new materials and CMAS compositions. Of particular interest is the interplay between the flow of the silicate melt, not only into TBC segmentations, but also under aerodynamic flows on the overlying melt. The role of melt composition, already proven to be critical in both TBCs and EBCs, will continue to be investigated underthis project, with deposit compositions selected to (i) represent the relevant range of viscosities over the temperatures of interest, (ii) provide a spectrum of intrinsic melting and crystallization behaviors, and (iii) yield insight on the selection of phases resulting from interactions with the T/EBC oxide. The effect of oxide composition will be explored in the context of the MaterialsGenome Tool being developed under Navy project N00014-17-C-2034 (with QuesTek and UMN). Collaborations with other processing groups will also be pursued to explore strategies to enhance T/EBC properties via microstructure, notably the toughness of the coating. The thermo-mechanical response of CMAS-modified systems will be investigated using a unique laser-based gradient test facility developed at UCSB, in combination with computationalmodels developed under Navy project N00014-17-1-2351 (Begley). Research in this area will (i) identify the role of the thermal gradient on the penetration rate over a relevant spectrum of melt viscosities, (ii) ascertain the mechanisms arresting melt penetration, and (iii) determine the conditionsleading to transitions between different delamination modes, and the parameters that lead to minimization of damage for a given coating system and depth of penetration. The program builds upon previous ONR-sponsored work and UCSB facilities that enable the study of CMAS/TBC interactions using a variety of techniques, as well as interactions with other organizations that are addressing different components of the ICME framework. The expectedbenefit to the US Navy is an augmented science base and tools that would enable the development of improved coating materials and life prediction models. Broader benefits include an enhanced scientific foundation for high temperature materials and contributions to the training and diversity of human resources in this important area.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N000141912377
Entities
People
- Carlos G. Levi
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara