Environmental Degradation of Multiple Principal Component Materials: High Temperature Corrosion II
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Wenjun Cai, Virginia Polytechnic Institute and State University; XiaoXiang Yu, Novelis Inc.; Vilupanur Ravi, California State Polytechnic University Pomona; Christopher Weinberger, Colorado State University; Elizabeth Opila, University of Virginia; Bai Cui, University of Nebraska Lincoln; Mark Weaver, University of Alabama; Bronislava Gorr, Karlsruhe Institute of Technology (KIT); Gerald Frankel, Ohio State University; ShinYoung Kang, Lawrence Livermore National Laboratory; Srujan Rokkam, Advanced Cooling Technologies, Inc.

Monday 2:00 PM
March 20, 2023
Room: Sapphire 410A
Location: Hilton

Session Chair: Xiaoxiang Yu, Novelis Global Research Center; Bronislava Gorr, Karlsruhe Institut für Technologie


2:00 PM  Invited
High Temperature Oxidation of NbTiZr and HfNbTaTiZr RMPEAs: Charlie Brandenburg1; David Beaudry2; Elaf Anber2; Jean-Philippe Couzinie3; Loic Perriere3; Mitra Taheri2; Elizabeth Opila1; 1University of Virginia; 2Johns Hopkins University; 3ICMPE - Institut de Chimie et des Matériaux Paris-Est
    Oxidation mechanisms of refractory multiple principal element alloys (RMPEAs) and methods for mitigating rapid oxidation rates remains a challenge. The oxidation kinetics of equimolar NbTiZr and HfNbTaTiZr were studied by thermogravimetric analysis at 1050°C in 1% oxygen (balance argon). The oxidation kinetics of NbTiZr were non-parabolic but slowed with time, and the sample fully oxidized within the 20-hour TGA experiment. The oxidation kinetics of HfNbTaTiZr were approximately parabolic, and the specific weight gain was significantly less than that of NbTiZr. XRD analysis of the oxide scales revealed TiO2, TiNb2O7, and Zr6Nb2O17 structures in all samples. SEM-EDS of sample cross sections showed initial phase separation of NbTiZr into Nb- and Zr-rich regions, and HfNbTaTiZr into (Nb, Ta) and (Hf, Zr)-rich regions. As oxidation progressed, Ti also precipitated out of solution. Possible explanations for reduced oxidation rates in the HfNbTaTiZr system are explored.

2:20 PM  
Hot Corrosion of TP347H in Coal Ash – an Electrochemical Noise Investigation: Shanshan Hu1; Xingbo Liu1; 1West Virginia University
    Electrochemical noise is adopted to study the corrosion behavior of TP347H at 650 oC – 750 oC in coal ash. The corrosion process is divided into five steps indicated by different characteristic potential noise patterns: direct oxidation, dissolution of protective scale, oxidation, sulfidation and continuous sulfidation. The corrosion product is divided into two layers: an external layer composed of Cr2O3 and Cr3S4 and an inner layer consisting of Fe2O3 and Fe3S4. The corrosion rate shows a maximum value at 700 oC. A further increase of temperature to 750 oC lowers the corrosion rate due to the decomposition of Fe2(SO4)3 to Fe2O3.

2:40 PM  
Intermediate and High-Temperature Oxidation Behavior of an Equiatomic CrTaTi Alloy from 800°C to 1400°C: Noah Welch1; Maria Quintana1; Todd Butler2; Peter Collins1; 1Iowa State University; 2Air Force Research Laboratory, WPAFB
    In some cases, refractory multi principal element alloys (RMPEAs) have been reported to show favorable oxidation resistance at high temperatures (>1000°C). This is due to the concentrated alloying additions, which facilitate the formation of complex oxides that reduce oxidation kinetics compared to simple, deleterious refractory oxides. However, limited work has explored the oxidation behavior of these concentrated alloy systems at intermediate temperatures (600°C-900°C). These regimes can be highly unpredictable due to pesting-like phenomena, oxide volatilization, and thermodynamic shifts in oxide stability. This study explores the oxidation behavior of an equiatomic, two-phase (BCC+Laves) CrTaTi alloy at 800, 1000, 1200, and 1400°C. Thermogravimetric data was collected for 24-hour intermediate and high-temperature tests in air and specific mass change was subsequently measured. Oxidation products and associated kinetics were characterized and compared to other alloy systems and classical oxidation mechanisms.

3:00 PM  Invited
Limitations of Equiatomic Refractory High Entropy Alloys: Role of Reactive Elements in Al-containing HfNbTaTiZr: Elaf Anber1; David Beaudry1; Daniel Foley1; Lavina Backman2; Michael Waters3; Jean Phillippe Couzinie4; James Rondinelli3; Elizabeth Opila2; Mitra Taheri1; 1Johns Hopkins University; 2university of virginia; 3Northwestern University; 4University Paris-Est Créteil (UPEC) - IUT
    Refractory high entropy alloys (RHEAs) hold the promise of superior mechanical properties at high temperatures but are plagued by a lack of oxidation resistance. Efforts to improve the oxidation resistance of RHEAs by adding classical passivating elements, such as Cr and Al, have been unsuccessful, largely due to the presence of reactive elements(REs) (i.e. Zr and Hf) in high concentration. Here, we studied the role of Al additions as a means of improving protective oxide scale formation in a RHEAs, using analytical microscopy and Thermodynamic calculations. Critically, we reveal evidence that the presence of reactive elements (Zr and Hf) in high concentration could act against the formation of a continuous Al2O3 scale by blocking the outward diffusion of Al cation. Controlling the concentrations and species of REs opens an avenue for designing RHEAs that are more resistant to oxidation in high temperature environments.

3:20 PM Break

3:35 PM  Invited
Novel Refractory Metal-based High Entropy Silicide-Borides and their Oxidation at 1100°C: Mathias Galetz1; Anke Ulrich1; Georg Hasemann2; Manja Krüger2; 1DECHEMA-Forschungsinstitut; 2Universität Magdeburg
    The invention and development of new high temperature structural metallic materials that can be employed beyond the paradigm of Ni-based alloys is one of the greatest challenges in materials science and engineering today. Refractory high-entropy silicide-borides (HESB) introduce a new field of high temperature materials by combining metallic high-entropy alloys (HEAs) with intermetallics based on a refractory metal (RM)-silicon-boron alloys, well known from Mo-Si-B alloys. In this work, three different silicon and boron containing alloys (RM-15Si-5B), equiatomic in their four- or five-component refractory metals, were manufactured using arc-melting. These three HESBs with the compositions 20Mo-20V-20Cr-20Ti-15Si-5B, 20Mo-20V-20Nb-20Ti-15Si-5B and 16Mo-16V-16Nb-16Cr-16Ti-15Si-5B were oxidized at 1100°C for 100 h in a TGA. Their scale formation is discussed in comparison to MoSiB alloys.

3:55 PM  
On the High-temperature Oxidation of Complex Concentrated Alloys FeAlCrNixVy: Eliska Jaca1; Peter Minarik1; Stanislav Daniš1; Jozef Veselý1; 1Charles University
    An ongoing call for materials capable of operating at high temperatures has led to the development of numerous structural alloys such as Ni-based superalloys. In recent years, much hope was also put into Complex concentrated alloys – alloys consisting of multiple elements. Our department developed equimolar alloy FeAlCrNiV possessing promising mechanical properties up to 800 °C. We focused on further characterization of its oxidation behavior. A series of FeAlCrNixVy samples was made to examine in detail the effect of vanadium which seems to play a crucial role in the kinetics of the oxidation. Our findings have shown that vanadium, even in a reduced amount, deteriorates oxidation resistance of the material. Presumably, the formation of V2O5 impairs alumina and chromia scale and thus limits the resistance to high-temperature oxidation. Furthermore, the detailed characterization of the formed oxide scale revealed formation of complex oxides and presence of oxides in rare modifications.

4:15 PM  
Tailoring Oxidation Behavior of MPEAs Through Microstructural Modification: Michael Pavel1; Mark Weaver1; 1University of Alabama Tuscaloosa
    Multiple Principal Element Alloys have shown to be possible candidates for replacing nickel- based and other dilute alloy systems in high temperature service environments due to their increased melting temperatures, lower density, and oxidation resistance. Thus far, the bulk of high temperature oxidation research in this field has been performed on either as-cast or homogenized samples with little attention given to microstructural effects on oxygen penetration, specific mass gain, and protective transition time. The goal of this work is to demonstrate the use in engineering unique microstructures through thermal processing to improve oxidation resistance of the equiatomic AlCoCrFeNi alloy. Oxidation studies have been performed under oxygen atmosphere at 900°C and 1000°C via TGA and have been further analyzed using electron microscopy and ex-situ XRD. The design principles learned in this study will prove useful in furthering the oxidation resistance of other MPEAs that may not form protective oxides as readily.

4:35 PM  
Tuning of Hierarchical Oxide Evolution in NbTiZr-based RMPEAs: David Beaudry1; Michael Waters2; Charlotte Brandenburg3; Daniel Foley1; Elaf Anber1; Jean-Philippe Couzinie4; Loic Perriere4; Keith Knipling5; Benjamin Redemann1; Tyrel McQueen1; Elizabeth Opila3; James Rondinelli2; Mitra Taheri1; 1Johns Hopkins University; 2Northwestern University; 3University of Virginia; 4Univ Paris Est Creteil, CNRS, ICMPE; 5U.S. Naval Research Laboratory
    Refractory multi-principal element alloys (RMPEAs) have high specific strength at elevated temperatures, offering an alternative to Ni-based superalloys in high-temperature turbine applications. These alloys often exhibit detrimental oxidation behavior due to their constituent refractory elements. This issue has typically been addressed unsuccessfully by adding conventional passivating elements. Oxygen-induced miscibility gaps and resulting spinodal decomposition cause hierarchical layered transitions from the base metal to the surface oxide. These phase transformations offer an opportunity to tune the diffusion pathways between the surface oxide and base metal. Controlling these microstructures can reduce degradation of the surface oxide by limiting the oxygen that is diffused from the oxide into the bulk alloy. This novel approach to control oxidation resistance of RMPEAs was demonstrated in alloys based upon the NbTiZr system, and was verified through TEM, APT, and Monte Carlo simulations.