Materials for High Temperature Applications: Next Generation Superalloys and Beyond: Poster Session
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee, TMS: Refractory Metals Committee
Program Organizers: Akane Suzuki, GE Global Research; Martin Heilmaier, Karlsruhe Institute of Technology (KIT); Pierre Sallot, Safran Tech; Stephen Coryell, Special Metals Corporation; Joseph Licavoli, NETL - Department of Energy; Govindarajan Muralidharan, Oak Ridge National Laboratory

Monday 6:00 PM
February 27, 2017
Room: Hall B1
Location: San Diego Convention Ctr

F-56: An In-situ Synchrotron X-ray Scattering Study of Microstructural Evolution in a Model Ni-based Alloy: Govindarajan Muralidharan1; Dean Pierce1; Ross Andrews2; Jan Ilavsky2; Saul Lapidus2; 1Oak Ridge National Laboratory; 2Argonne National Laboratory
    There is increasing interest in the use of high performance Ni-based alloys for exhaust valve applications in the next generation, higher efficiency automotive engines at 870oC and higher temperatures. Materials used in this application should not only have sufficient strength and microstructural stability at these temperatures but should be lower in cost than traditional Ni-based superalloys. This talk will present the results from an in-situ Ultra-small-angle(USAXS)/SAXS/WAXS study of γ' evolution in a model Ni-based alloy with lower Ni levels. Implications for the development of alloys for service in exhaust valve applications will be presented. Research sponsored by the U.S.DOE, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under contract DE-AC05-00OR22725 with UT-Battelle, LLC and used resources of the Advanced Photon Source, a U.S.DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

F-57: Long-term Thermal Stability of Nickel-base Superalloys: Alison Wilson1; Mark Hardy2; Howard Stone1; 1University of Cambridge; 2Rolls-Royce plc
    The long-term thermal stability of the nickel-base superalloys used for turbine discs is an issue of increasing importance as the latest alloys designed to meet the requirements of future gas turbine engines contain high refractory element contents and γʹ volume fractions. The formation of topologically close-packed (TCP) phases in such alloys is frequently investigated but little attention has been paid to TCP solvus temperatures. In this study, a series of model alloys with systematic compositional variations have been designed that are unstable with respect to TCP precipitation at 800°C. XRD and SEM have been used to determine the identity, morphology and extent of TCP phases following thermal exposure and the TCP solvus temperatures have been measured using DSC. These measured solvus temperatures have been compared with thermodynamic predictions to assess the accuracy of the predictions. This work was supported by Rolls-Royce plc and EPSRC (EP/H022309/1, EP/H500375/1 & EP/M005607/1).

F-59: Physics-based Creep Model of Ni-based Alloy Welds in High Temperature and Pressure Applications using Crystal Plasticity: Wen Jiang1; Pritam Chakraborty1; Thomas Lillo1; 1Idaho National Laboratory
    The long-term mechanical behavior of thick section welds of Ni-based alloys in high temperature and pressure applications often defines the operational limits and system inspection requirements. In the present work, a dislocation-density based crystal plasticity model is developed to simulate the time-dependent deformation behavior of 740H welds at ultra supercritical conditions. At the operating conditions of interest, dislocation climb and glide has been identified as the dominant mechanisms and is incorporated in the model. The effect of γ’ particles on the creep-rate is modeled by considering their resistance to dislocation motion and the bypassing of the particles by dislocation climb and Orowan looping, as well as the antiphase boundary (APB) shearing of the particles by super-dislocations. Subsequently, several single and polycrystalline simulations are performed to verify the workability of the model and compare the secondary creep rates with available experimental data.

F-61: Physical Simulation of Skin Formation during Investment Casting of Nozzle Guide Vanes Made of Ni-based Superalloys: Mehdi Rahimian1; Srdjan Milenkovic2; Laura Maestro3; Aitor Eguidazu Ruiz De Azua3; Ilchat Sabirov2; 1BCAST, Brunel University London; 2IMDEA Materials Institute; 3Precicast Bilbao Co.
    Development of investment casting process has been a challenge for manufacturers of complex shape parts. Numerous experimental casting trials are typically carried out to determine the optimum casting parameters. Particularly, misruns often occur in the as-cast complex shape parts due to the formation of solid skin by freezing of melt in contact with colder ceramic mould. This work presents a new tool for physical simulation of skin formation during investment casting of Nozzle Guide Vanes (NGVs) made of Mar-M247 Ni-based superalloy. Special ceramic tubes are designed and fabricated from the material used for the manufacturing of ceramic moulds for investment casting. Melting/solidification experiments are carried out via GLEEBLE 3800, where the melt is contained in the ceramic tube, which is heated to the temperature of ceramic mould in investment casting estimated by thermal model. NGVs casting trials are produced, and the outcomes of physical simulation tool are validated against them.

F-62: Surface Tension and Viscosity of the Ni-based Superalloys LEK94 and CMSX-10 Measured by the Oscillating Drop Method on Board a Parabolic Flight: Rainer Wunderlich1; Georg Lohöfer2; Hans Fecht1; 1Ulm University; 2Deutsches Zentrum Luft- und Raumfahrt (DLR)
    The surface tension and the viscosity of the Ni-Based superalloys LEK94 and CMSX-10 were measured by the oscillating drop method in a containerless electromagnetic processing device on board a parabolic flight. Surface oscillations were recorded by 150 and 200 Hz frame rate digital cameras positioned in two perpendicular directions and by the inductive coupling between the oscillating sample surface and the oscillating circuit of the radio-frequency heating and positioning generator. The surface tension as a function of temperature of LEK94 and CMSX-10 was obtained as s(T) = 1.72 - 4.20 x 10-4 (T – 1656 K) Nm-1 and s(T) = 1.71 - 4.23 x 10-4 (T – 1683 K) Nm-1, respectively. The viscosities at the liquidus temperatures as 9.8 and 7.8 mPa.s, respectively. In addition some basic thermophysical properties such as solidus and liquidus temperatures, densities at room temperature and thermal expansion will be reported.

F-63: Mechanism of Eutectic Growth in Directional Solidification of an Al2O3/Y3Al5O12 Crystal: Xu Wang1; Dong Wang1; Jingyang Wang1; Langhong Lou1; Jian Zhang1; 1Institute of Metal Research, Chinese Academy of Sciences
    The single crystal of Al2O3/Y3Al5O12 eutectic was prepared by an optical floating zone furnace. The microstructure evolution during directional solidification was investigated by electron backscattered diffraction and high resolution transition electron microscopy. It was found that interfacial energy played a predominant role in controlling the solidification behavior of the Al2O3/Y3Al5O12 eutectic crystal. Single crystal Al2O3 was obtained in a shorter growth distance than Y3Al5O12 during solidification, and the interfacial relationships of Al2O3 and YAG were parallel when their growth directions were not. The competitive growth behavior of Al2O3/Y3Al5O12 eutectic was well discussed and misfit between the two phases was calculated. A model of the Al2O3/Y3Al5O12 eutectic growth was proposed based on the microstructure evolution. This investigation provided a full understanding of the mechanism of binary Al2O3/Y3Al5O12 eutectic growth, and paved way for the design and preparation of large bulk eutectic ceramics.