Materials for High Temperature Applications: Next Generation Superalloys and Beyond: Superalloys: Alloy Development
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
Monday 8:30 AM
March 15, 2021
Room: RM 8
Location: TMS2021 Virtual
Session Chair: Govindarajan Muralidharan, Oak Ridge National Laboratory; Akane Suzuki, GE Aerospace Research
8:30 AM
Introductory Comments: Materials for High Temperature Applications-Next Generation Superalloys and Beyond: Govindarajan Muralidharan1; 1Oak Ridge National Laboratory
Introductory Comments
8:35 AM Keynote
Next Generation Superalloys and beyond for Aircraft Engine Applications: Deborah Whitis1; 1General Electric Co.
It has been over ninety years since Bedford and Pilling and Merica added small amounts of titanium and aluminum to the by then well-known “80/20” nickel-chromium alloy to create nickel-based superalloys, enabling advancements in the efficiencies of gas turbines and other applications that subject components to high temperatures and corrosive environments. In that time, nickel-based superalloys have continuously improved their high temperature mechanical and environmental properties through improved chemistry, processing, and coatings. Today, GE Aviation employs nickel-based superalloys in a wide variety of applications across our engines for both rotating and structure components, but as operating temperatures continue to climb, other material systems have begun to show promise, including intermetallic-based materials and ceramic matrix composites. Additionally, the tools used to develop these next generation alloys systems have advanced from simple designed experiments to combinatorial thermodynamic and kinetic modeling and machine learning techniques to accelerate the process.
9:15 AM
Compositionally Graded Nanosize Precipitates at Grain Boundaries of Directionally Solidified Nickel Based (GTD444) Superalloy: Richa Gupta1; M.J.N.V. Prasad1; Prita Pant1; 1IIT Bomaby
Minor addition of boron as a grain boundary strengthener improves the creep rupture properties of Ni-based superalloys. However, the existence of boron in the multicomponent system remains questionable. The role of boron in altering the grain boundary chemistry has been investigated in DS GTD444. DS GTD444 is a grade of General Electric (GE) suitable for later stage gas turbine buckets. The samples were characterized extensively by time of flight-secondary ion mass spectrometry (ToF-SIMS), transmission electron microscopy (TEM) in conjunction with energy-dispersive X-ray spectroscopy (EDS). Here we report first time the presence of compositionally graded nanosize boride precipitates in a superalloy system. The investigation suggests that most of boron present at the γ-γ' interface lies along grain boundary in the form of nanosize (~80-90 nm), (Cr, W, and Mo) based metal borides. The presence of borides could indirectly suppress the agglomeration of reported M23C6 carbides at grain boundaries of DS GTD444.
9:35 AM
TROPEA: A Platinum Containing New Generation Nickel-based Superalloy for Single Crystalline Applications: Jeremy Rame1; Satoshi Utada2; Luciana Maria Bortoluci Ormastroni2; Lorena Mataveli Suave3; Edern Menou3; Lucille Després4; Paraskevas Kontis5; Jonathan Cormier6; 1Safran Aircraft Engines; 2Institut Pprime - ISAE-ENSMA / Safran Aicraft Engines; 3Safran Tech; 4Institut Pprime - ISAE-ENSMA / Safran Tech; 5Max Planck Institut für Eisenforschung; 6Institut Pprime - ISAE-ENSMA
Latest developments of nickel-based single crystals superalloys mainly focus on adjusting Re and Ru additions in order to achieve high creep properties at high temperature and a stable microstructure (e.g: CMSX, and TMS alloys series). Following a different strategy, TROPEA has been developed introducing Pt element as a strengthening element for high temperature aircraft engines components. TROPEA exhibits excellent tensile properties (Yield Stress > 2nd or 3rd SX superalloys and ~ 2nd SX superalloys respectively below and above 800°C) and combines high fatigue properties (LCF and VHCF particularly at low temperature) and high creep resistance at temperatures above 1200 °C. These properties make TROPEA a promising SX superalloy for super cooled turbine blade. Otherwise, platinum additions have shown to significantly stabilize gamma prime phase near solvus temperature outlining the potential to design new platinum containing alloys in addition of or as an alternative to rhenium.
9:55 AM
Enhancing the Creep Performance of a Corrosion Resistant Ni-based Superalloy through Grain Boundary Design: Martin Detrois1; Paul Jablonski1; Jeffrey Hawk1; 1National Energy Technology Laboratory
Alloys with a combination of oxidation resistance and high-temperature creep properties are needed for operation in future advanced ultra-supercritical (AUSC) power plants. An approach to satisfy AUSC requirements consists of modifying commercially available alloys, such as Ni-based superalloys originally developed for aerospace application. In this work, the chemistry and aging heat treatment of a corrosion resistant alloy were modified to increase its mechanical performance at temperatures above 700°C. By enabling the precipitation of stable secondary phases along the grain boundaries, the yield stress and ultimate tensile strength were increased. Furthermore, the creep life of the best performing alloy variant was improved by 256% compared to the baseline alloy at the condition of interest. The modified aging treatment increased the creep life and ductility from 40% to 370% and 53% to 550%, respectively and depending on the alloy’s chemistry. The results from 6 alloy variants will be presented and discussed.
10:15 AM
Segregation-assisted Climb of Frank Partial Dislocations: A Novel Planar Fault Formation Mechanism in L12-hardened Superalloys: Malte Lenz1; Erdmann Spiecker1; Mingjian Wu1; 1Institute of Micro- and Nanostructure Research
In this work, we provide the first experimental evidence for the formation of superlattice intrinsic stacking faults (SISF) by climb of Frank partial (FP) dislocations, a mechanism postulated by Kear et al. in the 1970s. The observation was made in a multinary Co-based superalloy after [001] tensile creep (850 °C/400 MPa/4.6%). A high-resolution analysis revealed a formation mechanism where a Lomer-type channel dislocation becomes incorporated into the precipitate phase and then dissociates into a pinned Shockley partial and a climbing Frank partial, according to: a/2[1-10]→a/3[1-1-1]+a/6[1-12]. The FP is driven forward by an osmotic force arising from a vacancy supersaturation and moves counteracting climb force created by external loading. This mechanism is sustainable since FPs act as internal vacancy sinks absorbing vacancies emitted during climb of matrix dislocations. The climb motion of FPs is assisted by segregation of solutes to the dislocation core and SISF, lowering the fault energy.
10:35 AM
Microstructural Evolution under Complex Stress States during Creep of Single Crystal Ni-base Superalloy CMSX-4: Nicolas Karpstein1; Malte Lenz1; Jonathan Cormier2; Erdmann Spiecker1; 1Institute of Micro- and Nanostructure Research; 2Institut Pprime, CNRS-Université de Poitiers-ISAE ENSMA
We have investigated the microstructural evolution in monocrystalline CMSX-4 creep specimens with V-shaped geometry developed and tested in [001] direction (1093 °C) by Caccuri et al. (https://doi.org/10.1016/j.matdes.2017.06.018). The specific shape causes complex tensile and compressive stress states within one specimen. After 5 h, the region under compressive stress is still in a much earlier incubation stage of creep, as evident from extent of rafting and defect activity. Characteristic defect configurations were investigated by TEM on lamellas from specific locations and orientations. On the compressive side, dislocations display a much lower density and more clustered distribution throughout the matrix; interface networks have not yet restructured to more misfit-relieving configurations. In contrast, regions under tensile stress reached a steady-state creep regime with distinct rafting (N-type), which on the compressive side (P-type) is only observed after 24 h. These findings underline the importance of understanding complex stress states arising in superalloy applications.
10:55 AM Invited
On the Crack Growth Retardation under Dwell-fatigue in Nickel Disc Alloys: Hangyue Li1; 1University of Birmingham
Crack growth resistance at high temperatures under dwell-fatigue loading conditions is a high priority property for modern nickel based superalloys for disc applications. Due to a combined influence of cyclic- and time-dependent failure mechanisms, crack growth rates can be largely variable. An unusual crack retardation behaviour, contrasting to fast and continuous crack acceleration, can be obtained under the low to intermediate mechanical driving forces, represented by stress intensity factor range K. This talk provides detailed characterisation undertaken to interpret the underlying mechanisms of such crack growth behaviour in nickel disc alloys. These include a special experimental procedure of sequential block loading between baseline fatigue cycles and dwell-fatigue cycles to obtain crack growth resistance curves, metallographic and fractographic analysis, and FIB-TEM analysis. The role of microstructure, dwell time, on-test overageing, and load history will be discussed.
11:25 AM
Crack Initiation Anisotropy of Ni-based Single-crystal Superalloys in the VHCF Regime: Alice Cervellon1; Chris Torbet1; Tresa Pollock1; 1University Of California Santa Barbara
The influence of the crystal primary orientation on the transition from crack initiation to crack propagation in Ni-base single-crystals superalloys has been studied in the very high cycle fatigue regime. Ni-based SX superalloys solidified in three orientations close to the <001>, <110> and <111> directions have been tested under fully-reversed conditions (R = -1) at 20 kHz and 750°C.Fracture surface observations and longitudinal cuts intercepting the main crack initiation site have been performed in order to characterize the active slip systems for each orientation. When the number of cycles exceeds 10^7 cycles, the topography of the facets is less planar at the vicinity of the crack initiation site and evidences a dominant micro-crack propagation stage in the total fatigue life. The localization of the plastic deformation and the first stages of crack propagation will be detailed for each orientation. The implications on the resultant fatigue life will be discussed.