Advancing Current and State-of-the-Art Application of Ni- and Co-based Superalloys: Ni-based Superalloys – Structure & Properties
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Chantal Sudbrack, National Energy Technology Laboratory; Mario Bochiechio, Pratt & Whitney; Kevin Bockenstedt, ATI Specialty Materials; Katerina Christofidou, University of Sheffield; James Coakley, Chromalloy; Martin Detrois, National Energy Technology Laboratory; Laura Dial, Ge Research; Bij-Na Kim; Victoria Miller, University of Florida; Kinga Unocic, Oak Ridge National Laboratory
Tuesday 2:00 PM
February 25, 2020
Room: 11B
Location: San Diego Convention Ctr
Session Chair: Katerina Christofidou, University of Sheffield; James Coakley, University of Miami
2:00 PM Invited
Design Approaches for Advanced High Temperature Structural Materials: Sammy Tin1; 1Illinois Institute of Technology
In many cases, transformational design concepts are often limited by the capabilities of existing engineering materials. This necessitates the need for the development of advanced materials that can serve as enabling technologies that can be used to realize these concepts. For example, the performance, efficiency and emissions of advanced gas turbine engines for power generation and aerospace propulsion is limited by the temperature capability of the structural materials used in the hot section of the engine. In order to meet future requirements for clean power generation and aerospace transportation, innovative materials and processing approaches are required. This talk will discuss some of the advances, challenges and lessons learned associated with developing engineering solutions to overcome these intrinsic limitations and extend the temperature capability of high performance materials used in gas turbine applications.
2:30 PM
On the Effects of Chemistry Variations in New Nickel-based Superalloys for Industrial Gas Turbine Applications: Sabin Sulzer1; Hideyuki Murakami2; Roger Reed1; 1University of Oxford; 2National Institute for Materials Science
Alloys-By-Design (ABD) multi-scale modelling methods have been successfully applied in the past to the design of new superalloys for turbine blades and discs. However, since key input parameters are derived from thermodynamic CALPHAD calculations, the reliability of ABD predictions will depend on commercial parameter databases. This is especially critical for new regions of the alloy design space, such as the one considered here. A set of trial nickel-based superalloys for industrial gas turbine (IGT) blades is investigated, with carefully designed chemistries which isolate the influence of individual additions. Results from an extensive experimental characterization campaign covering SEM, EPMA, EDX, APT, and DSC analyses are compared to CALPHAD predictions and with Monte Carlo simulations for the spatial and temporal evolution of atomic arrangements. Insights gained from this study are used to derive guidelines for optimized IGT alloy design and to gauge the reliability of CALPHAD techniques.
2:50 PM
Effect of Stacking Fault Segregation and Local Phase Transformations on Creep Strength in Ni-base Superalloys: Timothy Smith1; Brian Good1; Tim Gabb1; Bryan Esser2; Ashton Egan2; Laura Evans1; David McComb2; Michael Mills2; 1NASA Glenn Research Center; 2The Ohio State University
In this study, two similar, polycrystalline Ni-based disk superalloys (LSHR and ME3) were creep tested at 760C and 552MPa to approximately 0.3% plastic strain. LSHR consistently displayed superior creep properties at this stress/temperature regime even though the microstructural characteristics between the two alloys were comparable. However, high resolution chemical analysis revealed significant differences between the two alloys among active gamma prime shearing modes. In ME3, Co and Cr segregation and Ni and Al depletion were observed along intrinsic faults - revealing a gamma prime to gamma phase transformation. Conversely in LSHR, W segregation was observed along intrinsic faults. This observation combined with scanning transmission electron microscopy (STEM) simulations confirm an atomic-scale gamma prime-to-D019 χ phase transformation in LSHR. Using experimental observations and density functional theory calculations, a novel local phase transformation strengthening mechanism is proposed that may improve the high temperature creep capabilities of future Ni-base disk alloys.
3:10 PM
Segregation at Planar Defects in Model NiCo-based Superalloys: Sae Matsunaga1; Dongsheng Wen1; Michael Titus1; 1Purdue University
Ni-based superalloys have been widely used for high-temperature applications such as turbine blades for jet propulsion and power plants due to their excellent creep, fatigue, and corrosion resistance. Recently researchers have observed solute segregation at stacking faults, antiphase boundaries, and coherent twin boundaries in both Ni- and Co-based superalloys. Solute segregation to these planar defects has been correlated to high temperature mechanical properties, but the fundamental driving forces and mechanisms of solute segregation is still largely not understood. We hypothesize that the presence of Co provides a driving force for segregation to planar defects. As such, model gamma’-containing Ni-30Co-Al-X (X=Ti, Ta, Nb) alloys have been investigated. Our recent results of high temperature mechanical testing and high-resolution electron microscopy will be presented and compared to first-principles density functional theory calculations. Alloy design strategies for enhancing high temperature mechanical properties in Ni-based superalloys will be discussed.
3:30 PM Break
3:50 PM Invited
Factors Controlling VHCF Life of Ni-based Single Crystal Superalloys: Alice Cervellon1; Luciana Maria Bortoluci Ormastroni1; Satoshi Utada1; Phillipp Kürnsteiner2; Paraskevas Kontis2; Lorena Mataveli Suave3; Samuel Hemery1; Patrick Villechaise1; Jonathan Cormier1; 1ENSMA - Institut Pprime - UPR CNRS 3346; 2Max-Planck-Institut für Eisenforschung GmbH; 3SAFRAN Tech
Service operations of sigle crystalline (SX) blades may lead to fatigue controlled failure mechanisms due to the vibrations introduced by the gas flow in addition to the centrifugal forces. Typical frequencies of vibrations of airfoils are in between 1 and 10 kHz, requiring specific experimental facilities to achieve the very high cycle fatigue (VHCF) domain at high temperature.In this presentation, a critical analysis of the VHCF life sensitivity at 1,000°C/20 kHz to the processing parameters (dendritic chemical homogeneity, casting pore size, introduction of a prior plastic deformation and γ/γ’ microstructure degradation) will be performed using 10 different Ni-based SX alloys. A special attention will be paid in this presentation on the fine scale crack initiation mechanisms. By varying the casting process or the oxidation resistance among the different alloys studied, a map of crack initiation mechanisms in VHCF will finally be proposed for Ni-based SX alloys.
4:20 PM Cancelled
Revisiting Precipitation Hardening in Ni- and Co-based Superalloys: Compositional and Microstructural Effects: Vassili Vorontsov1; Hikmatyar Hasan2; Peter Haynes2; 1University of Strathclyde Glasgow; 2Imperial College London
Classical mathematical models for precipitation hardening in superalloys face various practical limitations when it comes to predictive capability. Modern computational approaches have since made significant advances since and allow dislocation-microstructure interactions to be examined quantitatively in considerably greater detail. Thus, they provide the possibility of developing near complete non-empirical descriptions of strengthening effects that can accelerate the development and optimisation of future superalloys. A discussion is presented on how a universal model for precipitation hardening can be developed for multi-component nickel and cobalt-based superalloys using automated multi-scale methods. A combination of first-principles and phase-field modelling is used to explore compositional and microstructural effects on precipitation hardening mechanisms during yield and primary creep of superalloys. The applicability of the method to optimising the microstructure for a given alloy composition is explored. Finally, the effect of solute diffusion on precipitate shearing during primary creep is also investigated.
4:40 PM
Investigating Deformation Mechanisms in a Coarsening Resistant Ni-base Superalloy with "Compact" γ'-γ" Coprecipitates: Semanti Mukhopadhyay1; Hariharan Sriram1; Richard DiDomizio2; Robert Hayes3; Christopher Zenk1; G.B. Vishwanathan1; Yunzhi Wang1; Michael Mills1; 1Ohio State University; 2GE Global Research Center, USA; 3Materials Testing Inc, USA
There is a constant demand for high temperature turbine disk materials in high-throughput gas turbine wheels at temperatures above 650°C. A novel strategy to ensure superior creep strength in the Ni-base superalloys used in this application is to develop a “compact” coarsening resistant morphology of the strengthening phases-γ′&γ″. The coarsening resistance of this morphology, consisting of a layer of γ″ on all the (001) faces of a cuboidal γ' precipitate, arises from the effectiveness of the γ″ precipitate in blocking Al diffusion flux.The creep properties and consequent deformation mechanisms operative in this IN718-based superalloy developed will be discussed. Results from various high-resolution characterization techniques will be utilized to correlate the manifestation of operative deformation mechanisms across different length scales. An attempt will be made to study the 3D nature of the faults and solute segregation. The experimental findings will be complemented with predictions from a microscopic phase field model.
5:00 PM
Microstructure and Mechanical Properties of a Cast Ni-based Alloy: Govindarajan Muralidharan1; Jonathan Charleston1; Donovan Leonard1; Jim Myers2; 1Oak Ridge National Laboratory; 2MetalTek International
Generation 3 Concentrated Solar Power Systems are being targeted for operating temperatures greater than 700°C. Ni-based alloys such as Haynes®230®, Haynes®282® and IN®740H which have the potential to satisfy the high temperature mechanical property requirements and corrosion resistance are being considered for this application. Components such as piping, valve fittings may be manufactured at a lower cost using a casting process to reduce the overall system cost. This talk will present the effect of casting and subsequent heat-treatment on the microstructure and high temperature tensile properties of Haynes®282® and will compare these with that obtained using traditional wrought processing. This work was supported by the US Department of Energy - Solar Energy Technologies Office Concentrating Solar Thermal Power Program. This research was conducted by Oak Ridge National Laboratory, which is managed by UT Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE).
5:20 PM
Evolution of Microstructure in Net-shape HIP IN718 with Improved Fatigue Performance: Benjamin Georgin1; Victor Samarov2; Hamish Fraser1; 1The Ohio State University; 2LNT
The buy-to-fly ratio of Ni-base alloys can be improved by manufacturing components via net-shape hot isostatic pressing (HIP). Historically, the fatigue performance and high temperature ductility of direct-HIP parts has been inadequate when compared with conventional processing routes. Prior particle boundary (PPB) networks form as a result of oxygen contamination of powder stock and drive fatigue performance in these materials. They serve to pin grain boundaries and provide an easy fracture path for cracks resulting in intergranular failure. Recent studies have shown that direct HIP of high purity IN718 powder stock results in a fully recrystallized microstructure with the PPB network lying within the grain interior, reducing the tendency for crack propagation. The reduced oxygen content in the powders increases the oxide interparticle separation which allows recrystallized nuclei at powder boundaries to bypass the PPB network. Homogeneous strain distributions in the powders promote uniform recrystallization and suppress abnormal grain growth.