Advances in Surface Engineering IV: Session I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Surface Engineering Committee
Program Organizers: Arif Mubarok, PPG; Bharat Jasthi, South Dakota School of Mines & Technology; Tushar Borkar, Cleveland State University; Mary Lyn Lim, PPG Industries; Rajeev Gupta, North Carolina State University

Monday 8:30 AM
February 28, 2022
Room: 210C
Location: Anaheim Convention Center

Session Chair: Rajeev Gupta, North Carolina State University

8:30 AM
Atomic Origin of Corrosion Passivation in NiCrAl Alloys: A Density Functional Theory Study: Sainyam Nagar¹; Yashaswini Karanth¹; Vikrant Beura¹; Kiran Solanki¹; ¹Arizona State University
    Atomic origin of oxidation/repassivation, which is crucial to improve corrosion resistance is systematically explored in Ni-Cr-Al alloys using density functional theory. In particular, parameters such as surface adsorption energy, bond length, d-band center, the shape of density of states for alloying elements are evaluated to understand the mechanism involved in the initial stages of the oxidation/repassivation. Oxygen adsorption energy quantifies site preferences for FCC (111), (110), and (100) surfaces for the solid solution of the Ni alloy. The oxygen atom prefers to bond most tightly with Al followed by Cr although adsorption energy depends on the surrounding atomic environment. Valence charge transfer, Bader analysis, and LDOS provide a full picture of the electronic environment upon oxygen atom adsorption and the impact of alloying Cr and Al electronically. It was shown that the role of individual alloying elements is significant in improving overall oxidation/repassivation tendency providing a foundation for higher-scale modeling.

8:50 AM
Fluorine from Bad to Good in the Oxidation Behavior of Metallic Materials: Alexander Donchev¹; Mathias Galetz¹; ¹DECHEMA-Forschungsinstitut
    Fluorine usually deteriorates the oxidation behavior of metallic materials leading to accelerated attack. This is caused by the formation of gaseous compounds which evaporate leading to metal loss. Under distinct conditions i.e., defined fluorine partial pressure at the surface of the component, fluorine can protect metallic components. For example, intermetallic TiAl alloys which usually form a fast-growing non-protective mixed oxide scale reveal protective alumina formation after optimized fluorine treatment. This so-called fluorine effect is based on the exclusive intermediate formation of aluminum fluorides which finally are oxidized to alumina during their outward diffusion through the natural grown oxide scale. In this paper results of high temperature exposure tests of different materials, Ti- and Ni-based, without and with fluorine treatment will be presented and discussed. Several fluorination methods can be applied. This will be explained in the view of the fluorine effect mechanism.

9:10 AM
Microstructural Design via Plasma Variations in Hollow and Planar Cathode Sputtering: Adie Alwen¹; Andrea Hodge¹; ¹University of Southern California
    Thin films enable advanced materials to operate in environments with extreme stresses and derive their material properties from their microstructure and morphology. Increasing control of thin film characteristics, by developing a fundamental understanding of growth mechanisms, expands both functionality and material property space. In this study, the effect of the sputtering plasma and target geometry on film microstructure is investigated. At a fixed working distance, the sputtering glow discharge properties were studied using a Langmuir Probe, as a function of the applied power and Argon gas pressure. The evolution of plasma properties including ion density, electron density, and electron temperature was observed. XRD and SEM characterization of the films deposited at the known plasma conditions reveal changes in texturing, morphology, and microstructure. The influence of plasma properties and cathode geometry on film growth mechanisms is analyzed to create a foundational understanding to design a wide array of sputtered microstructures.

9:30 AM
Ultra-high Temperature Oxidation Protection Coatings: Alloying of Transition Metal Borides: Thomas Glechner¹; Rainer Hahn¹; Ahmed Bahr¹; Tomasz Wojcik¹; Maximilian Weiss²; Jürgen Ramm³; Oliver Hunold³; Szilard Kolozsvári⁴; Helmut Riedl¹; ¹Christian Doppler Laboratory for Surface Engineering of high-performance Components, TU Wien, Austria; ²Institute of Chemical Technologies and Analytics, TU Wien, Austria; ³Oerlikon Surface Solutions AG, Liechtenstein; ⁴Plansee Composite Materials GmbH, Germany
    Surface protection of highly stressed components used in aviation or energy production is of great interest, especially to extend the operation ranges in oxidative environments at extremely high temperatures. Here, transition metal ceramics are a suitable class to resist such conditions. Therefore, we developed alloying strategies, starting from the oxide scale formation of the binary systems – such as HfB2-z, TaB2-z, and WB2-z, which tremendously enhance the oxidation resistance of these coating materials and enable temperature regimes up to 1600 °C. The coating materials were deposited using an unbalanced magnetron sputtering system and consequently oxidized in a DTA/TG setup (using coatings on substrates) to study the oxidation kinetics. We furthermore conducted long-term oxidation tests at 1200 °C for various time periods up to 60 h and applied a broad set of high-resolution characterization techniques (e.g. HR-TEM, APT, SIMS, as well as XRD).