Energy Materials 2017: Materials for Coal-Based Power: Session IV
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

Thursday 8:30 AM
March 2, 2017
Room: 12
Location: San Diego Convention Ctr

Session Chair: Gordon Holcomb, National Energy Technology Laboratory

8:30 AM  Invited
A New Austenitic Heat-Resisting Steel SP2215 for 620-630℃ USC Boiler Tubing Application: Xishan Xie1; 1University of Science and Technology Beijing
    Austenitic steels TP347H, Super304H and HR3C are routinely used for 600℃ USC boiler superheater/reheater application. Recently China has developed 620-630℃ USC power units and needs a new heat-resisting steel to fulfill its requirement. A new developed austenitic steel SP2215 is based on 22Cr-15Ni with 3.5%Cu and also Nb and N for multiphase precipitation (MX, Cu-rich phase, NbCrN) strengthening in Fe-Cr-Ni austenitic matrix and M23C6 carbide precipitation at grain boundaries. This SP2215 new austenitic steel characterizes with high stress-rupture strength (650℃, 105h>135MPa; 700℃, 105h>85MPa) and good corrosion/oxidation resistance. SP2215 new austenitic steel has been put in routine metallurgical process for making tube product, which is recommended to be used as superheater/reheater components for 620-630℃ USC boiler application.

9:10 AM  
Development of Wrought Ni-Cr-Al Alloy with High Temperature Corrosion Resistance: Yoshihiko Koyanagi1; Hiroyuki Takabayashi1; Shigeki Ueta1; 1Daido Steel Co., Ltd.
    Further high temperature corrosion resistance for sulfidation corrosion, vanadium attack and so on is required to materials for boiler applications. Generally, high Cr containing Fe based or Ni based alloys are used in severe corrosion environment. However, the Ni-based alloys containing high Cr content degrade the manufacturability in large scale product because alpha Cr precipitates during hot-working. The manufacturing process of developed DSA760 has been established in large scale production. DSA760 has good high temperature strength due to the Ni3Al gamma prime phase and cellular alpha Cr precipitation, and excellent sulfidation corrosion resistance and vanadium attack resistance compared with conventional wrought Ni-based alloys, such as Alloy718, Alloy625 and Alloy80A.

9:30 AM  Invited
Materials Performance in Supercritical CO2 in Comparison with Atmospheric Pressure CO2 and Supercritical Steam: Gordon Holcomb1; Joseph Tylczak1; Casey Carney2; Ímer Doğan1; 1National Energy Technology Laboratory; 2National Energy Technology Laboratory, AECOM
    To facilitate the selection or development of materials for use in supercritical CO2 (sCO2) power plants, a comparison of the oxidation behavior of austenitic stainless steels and Ni-base alloys in supercritical water (sH2O), sCO2 , and atmospheric pressure CO2 (aCO2) were made. High pressure experiments were conducted at 730◦C/207 bar (sCO2) and 726◦C/208 bar (sH2O). An analysis was made combining these results with literature values. From this analysis it was shown that the oxidation behavior of Ni-base alloys in CO2 did not exhibit much change with pressure. Ni-base alloys in sH2O had an increase in corrosion rate—the log of the parabolic rate constant was approximately proportional to pressure. Fine-grain austenitic stainless steels in sCO2 and sH2O were less protective than at lower pressures as a result of iron oxide nodule formation occurring more frequently at high pressures.

10:10 AM Break

10:30 AM  
Study of Localized Under-coal Ash Deposit Corrosion of Inconel 740 Alloy Using High Temperature Electrochemical Sensor: Naing Naing Aung1; Xingbo Liu1; 1West Virginia University
    Our developed high temperature electrochemical sensor was applied to study localized under-coal ash deposit corrosion (LUDC) behavior of Inconel 740 superalloy. The LUDC process was studied from working electrode surfaces of the sensor that was partially covered by coal ash using the electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) analyses. Three typical potential noise patterns were found to correlate with the prominent stages in the LUDC process. Two characteristic current noise patterns indicate the extents of corrosion. There was a good correlation between the responses of electrochemical test data and the results from corroded surface analysis.

10:50 AM  Invited
Towards Predicting Reactive-element Tolerances in the Compositional Design of Al2O3-scale Forming Alloys and Coatings: B. C. Zhou1; A Ross1; T. Gheno2; X. L. Liu1; G. Lindwall1; B. Gleeson2; Zi-Kui Liu1; 1The Pennsylvania State University; 2University of Pittsburgh
    Al2O3-scale forming alloys and coatings are used extensively for high-temperature applications, including turbine engines. A common method used to improve the oxidation resistance of such systems is to add small amounts of reactive elements, typically Hf, Y, or Zr. However, when too much reactive element is added the beneficial effects are lost and oxidation resistance is severely reduced. In this presentation, our computational and experimental activities are reviewed, i.e. first-principles calculations, CALPHAD modeling, and oxidation experiments of the Ni-Al-Cr-Hf-Y system. The composition and temperature spaces for optimal oxidation resistance are explored computationally for the Hf and Y tolerance without formation of their oxides and intermetallic phases and compared with our new experimental data showing reasonable agreement.