Energy Materials 2017: Materials for Coal-Based Power: Session III
Sponsored by: Chinese Society for Metals
Program Organizers: Jeffrey Hawk, U.S. Department of Energy, National Energy Technology Laboratory; Zhengdong Liu, China Iron & Steel Research Institute Group; Sebastien Dryepondt, Oak Ridge National Laboratory

Wednesday 2:00 PM
March 1, 2017
Room: 12
Location: San Diego Convention Ctr

Session Chair: Kyle Rozman, NETL; Richard Oleksak, National Energy Technology Laboratory

2:00 PM  Invited
Developing a Crystal Plasticity Model for Nickel Based Turbine Alloys Based on the Discrete Element Method: Jamie Kruzic1; Agnieszka Truszkowska2; Qin Yu2; Alex Greaney3; Matthew Evans2; 1UNSW Australia; 2Oregon State University; 3University of California, Riverside
    Material failures in demanding turbine applications often occur due to plastic and/or creep deformation leading to the emergence of strain localization, microvoids, and cracks at heterogeneities in the material microstructure. While many traditional deformation modeling approaches have difficulty capturing these emergent phenomena, the discrete element method (DEM) has proven very effective for the simulation of granular materials where heterogeneities are inherent to the microstructure. The DEM framework has the advantage that it naturally captures the heterogeneity and geometric frustration inherent to deformation processes. While DEM has been adapted successfully for modeling the fracture of brittle solids, to date it has not been used for simulating metal deformation. Here we present our progress in reformulating DEM to model the key elastic, plastic, and visco-plastic deformation characteristics of nickel-based superalloys to create an entirely new crystal plasticity modeling methodology well-suited for the incorporation of heterogeneities and simulation of emergent failure mechanisms.

2:30 PM  Invited
Predicting Microstructure-Creep Resistance Correlation in High Temperature Alloys Over Multiple Time Scales: Vikas Tomar1; 1Purdue University
    DoE-NETL is partnering with Purdue University to predict the creep and associated microstructure evolution of tungsten-based refractory alloys. Researchers use grain boundary (GB) diagrams, a new concept, to establish time-dependent creep resistance and associated microstructure evolution of grain boundaries/intergranular films GB/IGF controlled creep as a function of load, environment, and temperature. The goal is to conduct a systematic study that includes the development of a theoretical framework, multiscale modeling, and experimental validation using W-based body-centered-cubic alloys, doped/alloyed with one or two of the following elements: nickel, palladium, cobalt, iron, and copper—typical refractory alloys. Prior work has already established and validated a basic theory for W-based binary and ternary alloys; the study conducted under this project extends this proven work. Based on interface diagrams phase field models are developed to predict long term microstructural evolution. In order to validate the models nanoindentation creep data is used.

3:00 PM  Invited
The SMARTER Project – Science of Multicomponent Alloys: Roadmap for Theoretical and Experimental Research: M. Kramer1; Pratik Ray1; Duane Johnson1; 1Iowa State University
    High entropy alloys (HEA) or near equiatomic alloys (NEAs) have of a high degree of chemical disorder while maintaining high symmetry crystal structures, usually at high temperatures. These disordered alloys have potential for high-T applications such as burners, waterwalls and even turbines however, the long-term stability in harsh combustion environments remains to be explored. We are developing new methodologies to speed the discovery and optimization of these chemically complex alloys and experimental capabilities for assessing their long-term stability. The alloy design and selection involves both theoretical assessments and in situ studies. We are using the DFT Green’s function code, which can handle solid solutions, to address stability and electronic properties of HEA. We will then test optimized alloys for phase stability and oxidation resistance. Initial studies are focused on validation of this approach using Fe-Cr-Al, AlNiFeCrCo and ZrNbHf alloys as model materials using thermogravimetry and in-situ studies on phase stability.

3:30 PM Break

3:50 PM  Invited
Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems: Chen Shen1; Monica Soare1; Pengyang Zhao1; Vipul Gupta1; Shenyan Huang1; Suzuki Akane1; Yunzhi Wang1; 1GE Global Research
    The long-term behavior of an alloy is often not a simple extrapolation from short-term data. Also, it is common in modern turbines that structural parts are manufactured and then welded to form a large component. The additional material heterogeneities introduced by welding processes complicate creep life assessment. To address these challenges, it is necessary to use physical models with experimental investigation to separate individual factors. Welded Haynes 282 has been studied by applying diffusion and precipitation modeling, the compositional variation inherited from welding, and the continuous coarsening of the strengthening γ’ precipitates during creep life with microstructural effects incorporated from mesoscale crystal plasticity and continuum creep modeling. Variability in microstructures after post-weld heat treatment had very small debit to creep rupture strength, while a reduction in rupture ductility was likely attributed to grain boundary phases in the weld zone. This work is supported by DOE under Award Number DE-FE0024027

4:20 PM  Invited
Solid Sate Joining of Creep Strength Enhanced Ferritic Steels: Glenn Grant1; Jens Darsell1; Arun Devaraj1; 1Pacific Northwest National Laboratory
    Creep Strength Enhanced Ferritic (CSEF) Steels show a combination of excellent creep resistance, moderate oxidation resistance, lower cost and improved thermal conductivity over austenitic steels and nickel alloys. The next generation of power plant design will require plant materials to be operated at higher temperature and pressure. A primary problem in the high temperature application of welded CSEF steels is the propensity of the fusion welds in these steels to display a creep life far below the parent material. This has led to inefficient up-gaging in wall thickness and low weld-strength reduction factors in design. This presentation will describe research to show that solid state joining (friction stir welding), can enable higher creep performance when compared to fusion welds. Data will be presented on the weld process, microstructure and creep performance of friction stir welds in P91, P92 and new Boron Nitrogen 9-12 Cr ferritic steels.