TECHNOLOGY AREA(S): Battlespace, Ground/Sea Vehicles, Materials/Processes

ACQUISITION PROGRAM: Shipboard Gas Turbine Marinization Package for Higher Temperature, Higher Pressure Operations

OBJECTIVE: Utilize literature materials data and research data to develop models/algorithms for machine learning (ML) that will detect data patterns and characteristic trends, learn from the accumulated data, and evolve distinguishing characteristics between calcium-magnesium-alumino-silicate attack (CMAS) and calcium sulfate hot corrosion with and without the influence of sea salt in order to develop resistant coatings to CMAS and calcium sulfate hot corrosion.

DESCRIPTION: Calcium oxide is known to react with chromium contained in MCrAlY (M=Ni, Co) alloys and nickel-based superalloys to form a low-melting (1,100�C) calcium chromate. The reactivity of gamma-NiAl and gamma-Ni-based NiCoCrAlY alloys with CaO at 1,100�C produced multi-layer scales of Al2O3 and calcium aluminates (xCaO�yAl2O3).� Increasing alloy chromium content only enhances corrosion severity. The reaction of two-phase beta-gamma MCrAlY alloys with CaO progressed according to two distinct mechanisms. During the initial stage, formation of a liquid calcium chromate led to the rapid consumption of the Cr-rich gamma-phase. The extent of degradation was particularly important for a single-phase gamma-composition, and was significantly reduced by increasing the alloy beta fraction. In the subsequent stage, a continuous Al2O3 layer was established at the base of the scale, which led to a much lower oxidation rate. Additions of Al2O3 or SiO2 decreased the CaO reactivity due to the formation of aluminates or silicates. CMAS degradation is both thermochemical and thermomechanical to thermal barrier coatings (TBCs). Molten CMAS (1,150-1,240�C) penetrates the TBC pores and freezes a given depthwithin the TBC. Early research also showed that CaSO4 attacked yttria, destabilizing zirconia-based TBCs. Upon cooling, the glass and reaction product phases solidify and the void structure that is utilized to reduce thermal conductivity and provide the strain compliance is lost leading to TBC delamination. Recent advances in computer power, coupled with materials databases and informatics, modeling and simulation, and experimental validation of models will enable accelerated discovery and discrimination of degradation mechanisms leading to the creation and development of new materials for mitigation corrosion. These informatic tools will facilitate Integrated Computational Materials (Science and Engineering) (ICMSE/ICME)) to reliably predict the composition and behavior of new materials. This STTR topic seeks to develop the tools that will allow usage of various open and closed materials data sources to provide more conclusive outcomes for mitigation of degradation of propulsion components. This research would develop algorithms from research of both mechanisms and utilize ML to detect chemical patterns that distinguish between the two corrosion mechanisms and lead to efforts to develop corrosion-resistant coatings.

PHASE I: Search and secure literature that pertains to calcium sulfate hot corrosion and CMAS attack in propulsion systems. Identify key attributes/conditions, variables of each corrosion mechanisms and material (alloy or coating), material system that will help distinguish differences in the two mechanisms, which will help develop experiments to validate and/or modify the models. Insert the literature databases and experimental results into a data analytical program to incorporate ML. Boundary conditions and variables that need to be considered for entry: include the alloy/materials type,� the chemical composition of the alloy, materials, and/or coatings, corrosion and/or oxidation activity, fatigue, interdiffusion resistance, creep resistance to phase transitions, the coefficient of thermal expansion compatibility, durability, stress, temperature stability, etc. Assemble and assess a suite of modeling tools to predict processing outcomes and desirable materials properties. Ensure that the selected modeling tools have a history that the modeling results represent gas turbine field (ship and/or aero) conditions, and provide an accurate mathematical representation of the engineering principles and relationships that predict materials� behavior in Navy ship or aero gas turbines. Create an informatics-based framework that will be able to assess the type and quality of the databases required by ICME and other computational programs that can also work with materials modeling and simulation tools. Develop a Phase II plan.

PHASE II: Using the outline of a framework created in Phase I, expand the informatics-based program to determine the quality of different database sources calcium sulfate hot corrosion and CMAS attack in propulsion systems. Continue experiments performed under the range of field conditions identified during Phase I to further populate the data inputs to the ML framework. Validate or modify models as needed to summarize general mechanistic trends and incorporate the complexity in data using, for example, linear regression and logistic regression focus on attribute relationships. Ensure that the discriminating database program is able to perform nonparametric statistical tests for a rapid section-wise comparison of two or more massive data sets, and repair errors in databases. Ensure that the program provides a means for capturing, sharing, and transforming materials data into a structured format that is amenable to transformation to other formats for use by ICME and other computational programs and modeling and simulation methods. Demonstrate the functionality of this framework to distinguish between calcium sulfate hot corrosion and CMAS attack in propulsion systems with or without the presence of sea salt. Ensure that the framework is able to assist in determining materials resistant to CMAS attack (including overlay/diffusion and thermal barrier coatings (TBCs)). The small business should be working with an engine original equipment manufacturer (OEM) to assist in determining discriminating variables for hot corrosion and CMAS.

PHASE III DUAL USE APPLICATIONS: Engage with the Government and/or public, commercial, company, or professional technical societies that retain materials databases. Interface with a software company that promotes and delivers materials computational programs to explore and develop an integration pathway for the database discriminating program with their software. The outcome of this technology development program will be a commercial suite of informatics-derived tools that can will be able to reliably analyze and discriminate various sources of materials databases to optimize the capability for materials prediction. Transition the material production methodology to a suitable industrial material producer. The ICME code needs to be transitioned to the commercial entity for potential incorporation of a more comprehensive ICME code. Commercialize the material for use in DoD and commercial markets. The commercial aviation industry would benefit from this technology when flying in sand-ingested areas such as the Middle East and would provide some added protection for aircraft against the effects of volcanic ash as there are similarities chemically with CMAS, volcanic ash, and calcium sulfate-induced hot corrosion.

REFERENCES:

1. Cowles, B. Backman, D. and Dutton, R. "Verification and Validation of ICME Methods and Models for Aerospace Applications." Integrating Materials and Manufacturing Innovation, 1, 16 (2012Verification_and_validation_of_ICME_methods_and_models_for_aerospace_applications/fulltext/027a24e00cf2195fcb29fdd0/Verification-and-validation-of-ICME-methods-and-models-for-aerospace-applications.pdf

2. Shifler, D,A, �The Increasing Complexity of Corrosion in Gas Turbines.� 2019 Turbomachinery Technical Conference & Exposition, June 17-21, 2019, Phoenix, AZ. Paper GT2019-90111. https://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2656598

3. Shifler, D.A. and Choi, S.R. �CMAS Effects on Ship Gas-Turbine Components/Materials.� 2018 Turbomachinery Technical Conference & Exposition, June 11-15, 2018, Lillestr�m, Norway. Paper GT2018-75865. https://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2700469

4. Kr�mer, S., Faulhaber, S., Chambers, M., Clarke, D.R., Levi, C.G., Hutchinson, J.W. and Evans, A.G,.� Mechanisms of cracking and delamination within thick thermal barrier systems in aero-engines subject to calcium-magnesium-alumino-silicate (CMAS) penetration� Mater. Sci. Engr. A, 490 (2008).� �

KEYWORDS: CMAS; Hot Corrosion; Calcium Sulfate; Propulsion Materials; Informatics; Machine Learning; Material Databases