Materials for High Temperature Applications: Next Generation Superalloys and Beyond: Superalloys and Beyond: Oxidation and Mechanical Behavior I
Sponsored by: TMS Structural Materials Division, TMS: Refractory Metals Committee
Program Organizers: Govindarajan Muralidharan, Oak Ridge National Laboratory; Martin Heilmaier, KIT Karlsruhe; Benjamin Adam, Oregon State University; Mario Bochiechio, Pratt & Whitney; Katerina Christofidou, University of Sheffield; Eric Lass, University of Tennessee-Knoxville; Jeremy Rame, Naarea; Sallot Pierre, Safran; Akane Suzuki, GE Aerospace Research; Michael Titus, Purdue University
Thursday 8:30 AM
March 18, 2021
Room: RM 8
Location: TMS2021 Virtual
Session Chair: Sallot Pierre, Safran; Martin Heilmaier, KIT Karlsruhe
8:30 AM
Early Stage Oxidation of Ni- and Co-based Superalloys: Novel Insights from Rapid Thermal Annealing (RTA) Experiments: Dorota Kubacka1; Erdmann Spiecker1; 1FAU Erlangen-Nuremberg
Single crystal Ni-base superalloys are commonly used in modern jet engines but approach fundamental performance limits. Potential applications of Co-base superalloys are still limited due to their insufficient oxidation resistance. Early stages of oxidation appear to be crucial for understanding the difference between the oxidation behavior of Ni- and Co-base superalloys. We exploit the potential of a rapid thermal annealing (RTA) furnace in combination with advanced electron microscopy to investigate the early stages of high-temperature oxidation. The RTA furnace allows complex processing recipes including steep temperature profiles and varying atmospheres. We address the first seconds to minutes of oxidation for two model Ni- and Co-base superalloys at 900°C. Our results prove that difference in oxidation behavior can be directly correlated to the two-phase microstructure and the different partitioning of the alloying elements to γ and γ'. These insights can guild the development of new Co-SA with improved oxidation resistance.
8:50 AM
Residual Stress with High Temperature Oxidation of Ni-based Haynes 282 Superalloy: Kuan-Che Lan1; Hsiao-Ming Tung2; 1National Tsing Hua University; 2Institute of Nuclear Energy Research
Nickel-based superalloy Haynes 282 has been considered as one potential candidate material to be applied in advanced ultrasupercritical (AUSC) power system since the good oxidation resistance of this superalloy and stability of the oxidation phase as well as excellent strength at high temperature has been observed in recent years. The integrity of the oxidation layer is crucial to mitigate the oxidation, and this integrity would be altered the by the accumulation of residual stress in the oxide and the superalloy matrix. In this study, and the gravimetric analysis on Haynes 282 has been carried out in the temperature range from 800 to 950 C for 720 hours. Furthermore, the residual stress of oxide phases and the matrix been evaluated using X-ray diffraction method. The effect of residual stress with the high temperature oxidation on evolution of microstructure in this superalloy is discussed.
9:10 AM
Understanding the High-temperature Fatigue Properties of the Novel Fe-Ni-Cr Based Superalloy: Shivakant Shukla1; Govindarajan Muralidharan2; Lawrence Allard2; Jonathan Poplawsky2; 1Oak Ridge National Laboratory; 2ORNL
Increment in the operating temperature of the internal combustion engine has the capacity to increase the fuel efficiency. Hence, there is an ever-growing demand for materials that can be operational at projected temperatures and be economically sustainable. Subsequently, the current study investigates high-temperature fatigue properties of novel Fe-Ni-Cr based superalloy. The wrought alloy was subjected to high cyclic fatigue testing at 800 and 900 °C and the microstructure before and after the fatigue testing was analyzed via SEM, TEM and APT. Increase in γ’ size after high-temperature fatigue testing was observed. Potential crack initiation sites were also evaluated via fractography and EDS analysis. *Research sponsored by the U.S.DOE, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, Propulsion Materials Program under contract DE-AC05-00OR22725 with UT-Battelle, LLC. APT conducted at the ORNL’s Center for Nanophase Materials Sciences (CNMS), a U. S. DOE Office of Science User Facility.
9:30 AM
Low Cycle Fatigue of Single Crystal Co- and CoNi-base Superalloys: The Role of Oxidation Resistance: Sean Murray1; Alice Cervellon1; Jean-Charles Stinville1; Jonathan Cormier2; Tresa Pollock1; 1University Of California, Santa Barbara; 2ISAE-ENSMA & Institut Pprime
γ-containing Co- and CoNi-base superalloys are promising candidate materials for high temperature, high stress applications. The first studies on the low cycle fatigue resistance of single crystal Co-base superalloys revealed that their insufficient oxidation resistance leads to early fatigue failures in air, even with the addition of an aluminide coating. CoNi-base superalloy compositions have a more flexible design space, allowing for alloying additions that promote the formation of protective oxide scales after high temperature exposure such as α-Al2O3. A novel single crystal single crystal superalloy SB-CoNi-10+ has been investigated in the low cycle regime under load-control, R=-1, at T=950 °C in both laboratory air and under high vacuum. Under these conditions, the alloy has LCF rupture life comparable to Ni-base single crystal alloy AM1 in air and has excellent performance under high vacuum. Stress-strain response, fracture surface analysis, and microstructural investigations of the post-mortem specimens will be discussed.
9:50 AM
Concomitant Oxidation-diffusion-creep Processes for Stress Generation and Its Effects in Cyclic Oxidation Behavior: Yanfei Gao1; 1University of Tennessee - Knoxville
Metallic materials under extreme environmental service conditions oftentimes fail from the morphological instability of such layers at the oxide-alloy interface, such as the rumpling of oxide layer and the formation of oxide pegs under thermal cycles. This work suggests that a tensile, biaxial stress arises in the base alloy due to the concomitant oxidation-diffusion-creep processes, which is different from various mechanisms in literature for the growth stress in the oxide layer. Such a stress in the substrate could provide a stabilizing factor that suppresses the rumpling or compositional variation in the oxide layer. But it may also accelerate the formation of oxide pegs under cyclic oxidation conditions. Predictions will be compared to a number of recent experiments for turbine engines and fossil-fuel power plants.
10:10 AM
Effect of Water Species on Formation of Cationic Defects in Yttria-stabilized-Zirconia (YSZ): Amir Saeidi1; Daniel Mumm1; 1University of California, Irvine
Yttria-Stabilized-Zirconia (YSZ) is used as a Thermal Barrier Coating (TBC) in turbine blades in its t' structure. Due to cation diffusion, t-YSZ transforms to yttrium lean tetragonal YSZ (t-YSZ) and yttrium rich cubic YSZ (c-YSZ). This process happens at a higher rate in the presence of water vapor in the system. In this work, we used first-principles Density Functional Theory (DFT) calculations to study the formation energy of cationic defects, V’’’’Zr and (V..OV’’’’Zr)’’ in YSZ at 1800 K, and how water species change those energetics. Our findings show that the formation energy of these defects is lower in c-YSZ in dry and wet conditions. Also, H+ reduces the formation energy of both defects in t-YSZ and c-YSZ structures, and its effect is more significant on (V..OV’’’’Zr)’’.
10:30 AM
Paving the Way Beyond Ni-based Superalloys: Role of Coupled Thermodynamic-kinetic Models: Rishi Pillai1; Bruce Pint1; 1Oak Ridge National Laboratory
Extensive research has been conducted to achieve optimum mechanical properties while simultaneously balancing environmental resistance of Ni-based superalloys. High temperature oxidation behavior of these materials is complex due to the various alloying additions. A widely used solution to improve oxidation resistance of superalloys employed in gas turbines and jet engines is application of overlay and\or diffusion coatings on a suitable base alloy with required long-term mechanical properties. However, this results in chemical compatibility issues due to coating-substrate interactions driven by differences in chemistry.The present work aims to provide mechanistic understanding of the role of alloy composition, time and temperature on the oxidation behavior and material degradation of coated and uncoated Ni-based superalloys. Coupled thermodynamic-kinetic modelling will be combined with advanced microstructural characterization techniques to predict compositional changes, phase transformations and lifetime. Potential strategies for development of next generation superalloys will be discussed based on the obtained results.
10:50 AM Invited
Development of Refractory Metal ‘BCC-superalloys’ Reinforced by Ordered-BCC Intermetallic Precipitates: Alexander Knowles1; 1University of Birmingham
Nuclear fusion, Generation-IV fission reactors and gas turbines demand advanced materials with ever-improved high temperature performance. Refractory metals have exceptionally high melting points >2000°C, far higher than nickel-based fcc-superalloys, <1450°C. However, ordered-intermetallic precipitate reinforcement is not exploited, which is a potent strategy in γ-γ’ fcc-superalloys for strength, creep resistance and ductility. There is great scope for the exploitation of a β-β’ ‘bcc-superalloy’ strategy for bcc refractory metals, and also within compositionally complex alloys (CCAs, or high entropy alloys, HEAs).Design and development of precipitate reinforced refractory metal alloys will be showcased. New design strategies exploit the two-phase field bcc β (Ti) to β’ TiFe, whereby precipitates can be produced within a matrix of β (Mo,Ti) and also β (W,Ti). Such precipitation offers superalloy-like β-β’ microstructures with development focused on: (1) Microstructure control, (2) Properties and deformation behaviour, seeking to demonstrate bcc-superalloys as a new class of high temperature materials.
11:20 AM Invited
Beyond Superalloys: An Efficient Strategy for Assessing Environmental Resistance: Bruce Pint1; 1Oak Ridge National Laboratory
There is considerable interest in new materials with higher temperature capabilities to improve cycle efficiency and thereby reduce fuel consumption and greenhouse gas emissions. The traditional materials development process has been driven by optimizing high temperature mechanical properties. This was a viable strategy for superalloys, which have reasonable oxidation resistance. However, for refractory metals, high entropy alloys and other candidates, embrittlement also is a concern for long-term performance. With or without a coating, it is necessary to quickly and efficiently assess both oxidation rates and post-exposure mechanical properties often with small volumes of material. Using subsize (e.g. 25mm long) dogbone tensile specimens, it is possible to assess both reaction rates in a variety of environments and residual tensile and creep properties after high temperature exposures. Examples will be provided of assessments that include a variety of conventional and experimental alloys in environments simulating turbine exhaust and supercritical CO2.