High Temperature Corrosion and Degradation of Structural Materials: Refractory Metal Alloys/Modeling and Theory
Sponsored by: TMS Corrosion and Environmental Effects Committee
Program Organizers: Kinga Unocic, Oak Ridge National Laboratory; Raul Rebak, GE Global Research; David Shifler, Office of Naval Research; Richard Oleksak, National Energy Technology Laboratory
Tuesday 2:00 PM
November 3, 2020
Room: Virtual Meeting Room 31
Location: MS&T Virtual
Session Chair: Rishi Pillai, ORNL
2:00 PM Invited
Environmental Resistance and Microstructure Design in Mo-Si-B Alloys: John Perepezko1; 1University of Wisconsin-Madison
The multiphase microstructures in the Mo-Si-B system based upon the Mo5SiB2 (T2) phase with Mo and the Mo3Si phases allow for superior creep strength, in-situ toughening and offer some oxidation resistance. Selected alloying can also be used to develop alternative multiphase microstructures. Since the alloy compositions that exhibit the lowest oxidation rate will most likely not yield optimum mechanical properties, it is important to develop robust and compatible aenvironmental resistant coatings. An effective strategy to address this challenge is based upon a pack cementation kinetic biasing. During oxidation of the (Si+B)-pack alloys, the initial MoSi2 outer layer is consumed by formation of the Mo5Si3 (T1) phase and the underlying T2 and/or boride phase diffusion barrier layer. Any damage to the T1 layer can be recovered from the T2 + MoB layer as a self-healing characteristic. The coating strategy is also applicable to other refractory metals and ceramics.
2:30 PM
Effect of Al Addition on Oxidation Behavior of a New Mo-Si-B Alloy: Longfei Liu1; John Perepezko1; 1University of Wisconsin-Madison
Both isothermal and cyclic oxidation behavior of Mo-6Si-12B-(1, 2, 4, 8)Al samples have been studied. With increase of Al content, isothermal oxidation resistance gets better while cyclic oxidation resistance becomes worse. Mo-6Si-12B-4Al sample oxide layer consist of both Al-doped borosilicate glass phase and mullite phase and has the best overall oxidation performance. Al diffusion rate is two orders bigger than Si in mullite, it explains the high Al sample has best isothermal resistance. Low viscosity of Al-doped borosilicate glass provide self-healing effect which related good cyclic oxidation performance of low Al content samples.
2:50 PM
Elucidating Influence of Alloy Composition, Thermal Cycling and Environment on Oxidation Behavior of Engine Exhaust Valve Materials: Rishi Pillai1; Marie Romedenne1; Allen Haynes1; Bruce Pint1; 1Oak Ridge National Laboratory
Higher temperatures (T>800 °C) are required in heavy duty engines to increase efficiencies. Oxidation induced chemical failure is a key life limiting mechanism at these temperatures. Consequently, various chromia-forming Ni-base alloys (Rene41, H282, Nim80A, Pyromet31V, IN751), combining excellent oxidation resistance and creep strength are being considered as engine exhaust valve materials. In the current work, oxidation behavior of model and commercial NiCr alloys was investigated in dry and wet air under thermal cycling conditions between 800-950°C. Coupled thermodynamic-kinetic modeling was performed to understand the role of alloying elements and predict microstructural evolution.Different growth mechanisms of chromia scales in wet and dry air were observed. Presence of Mn and Si seemed to slightly improve oxidation resistance of the alloys while alloys with higher Ti contents performed poorly, especially at T>850 °C. This research was sponsored by the Department of Energy, Vehicle Technologies Office, Propulsion Materials Program.
3:10 PM
Machine Learning and Data Analytics for Accelerating High-temperature, Corrosion-resistant Materials Design: Xuesong Fan1; Baldur Steingrimsson2; Anand Kulkarni3; Peter Liaw; 1University of Tennessee; 2Imagars LLC; Portland State University; 3Siemens Corporation
We will introduce machine learning (ML) models capable of detecting patterns and characteristic trends, and evolving distinguishing characteristics between calcium-magnesium-alumino-silicate (CMAS) and calcium sulfate (CaSO4) hot corrosion attacks, with and without the influence of sea salt, for the purpose of developing coatings resistant to CMAS and calcium sulfate hot corrosion. To this end, we will present a unified feature list, one that captures inputs and outputs describing both CMAS and calcium sulfate attacks, a joint optimization scheme, for identifying a combination of thermal barrier coating and base alloy with good resistance to both corrosion mechanisms, and canonical component analysis, for evolving the distinguishing characteristics. We recommend selecting a ML or data analysis technique suitable for the application at hand and the data available. We recognize close linkage between the feature data extracted and the underlying physics-based models (refer to our patent application “Machine Learning to Accelerate Alloy Design”, No. 16/782,829).
3:30 PM
Kinetic Modeling of High-temperature Oxidation of Pure Metals by Incorporating Wagner’s Theory into the CALPHAD Approach: Fangzhou Xing1; Sa Ma2; Yu Zhong1; Lijun Zhang2; 1Worcester Polytechnic Institute; 2Central South University
In this work, a variety of experimental tracer diffusivities of ions in nickel and magnesium oxides in the literature were first assessed. Atomic mobilities including bulk and short-circuit diffusion of ions were then obtained by means of the CALPHAD (CALculation of PHAse Diagram) approach. Afterwards, the diffusion-controlled kinetic model of oxidation was developed based on the moving boundary model and Fick’s law coupling with the thermodynamic descriptions of oxides and the Wagner’s theories. A mathematical expression for parabolic rate constant accounting for various diffusive contributions was derived. After that, numerical simulations of growth of oxides during oxidation of pure nickel and magnesium at different temperatures were performed. The simulated results agreed well with experimental data and indicated that the contribution of oxygen diffusion turns to be more essential as temperature decreases in NiO and grain boundary diffusion of Mg cations predominated the high temperature oxidation of pure magnesium.