High Temperature Corrosion and Degradation of Structural Materials: CO2-rich Environments/Nuclear Reactor Environments
Sponsored by: TMS Corrosion and Environmental Effects Committee
Program Organizers: Kinga Unocic, Oak Ridge National Laboratory; Raul Rebak, GE Global Research; David Shifler, Office of Naval Research; Richard Oleksak, National Energy Technology Laboratory
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 31
Location: MS&T Virtual
Session Chair: Raul Rebak, GE Research, US; Kinga Unocic, ORNL
8:00 AM
Introductory Comments: High-temperature Corrosion and Degradation of Structural Materials: Kinga Unocic1; 1Oak Ridge National Laboratory
Introductory Comments
8:05 AM
Long-term Oxidation Behavior of Chromia-forming Alloys in High-temperature CO2 and Air: Richard Oleksak1; Casey Carney1; Gordon Holcomb1; Omer Dogan1; 1National Energy Technology Laboratory
Future power systems require structural alloys that can survive long-term (>20 years) exposure to high-temperature CO2. Most studies have focused on relatively short exposures, and while this has improved mechanistic understanding of alloy oxidation in CO2, concerns remain for extrapolating short-term results to enable realistic lifetime predictions. In this work, several chromia-forming steels and Ni-based alloys were exposed in 500 h cycles to high purity CO2 at 700 °C and 1 atm for up to 10,000 h. For comparison, the alloys were also exposed to laboratory air at the same conditions. The exposed samples were characterized using a variety of techniques to assess for extent of oxidation and carburization. Most alloys performed well in pure CO2, forming thin, well-adhered chromia scales throughout the duration of the exposure. Surprisingly, the alloys that formed and maintained chromia scales showed no signs of carburization even after 10,000 h.
8:25 AM
Corrosion Study of Stainless Steel 316 with Different Coatings in MgCl2-KCl Heat Transfer Fluid: Yuxiang Peng1; Ramana Reddy1; 1University of Alabama
In the present work, the corrosion behavior of Stainless Steel 316 (SS316) with different coatings in MgCl2-KCl molten salt are investigated based on the long-term dipping corrosion test for 100 h at different temperatures. The coatings used in the present work were S-1 (two layers ), S-2 (Ni-Fe alloy coating), and S-3 (no coating). The corrosion rates were calculated based on the weight-loss, and the rates are 0.60, 2.09, and 3.03 mg/cm2/day for S-1, S-2, and S-3 at 1023 K, respectively. The samples were characterized using SEM - (EDS). The results showed that such coatings could increase the corrosion resistance of SS316 in the MgCl2-KCl molten salt. Such findings to utilize the coatings to protect SS316 alloy and to contain the MgCl2-KCl molten salt in the thermal solar energy system are discussed.
8:45 AM Invited
Exploring Materials Options for sCO2 Applications: Steels to Cermets: Bruce Pint1; Rishi Pillai1; James Keiser1; 1Oak Ridge National Laboratory
Supercritical CO2 (sCO2) is being explored for a wide range of applications from fossil to solar energy. Recent work showed that Ni-based alloys and advanced austenitic steels are compatible with sCO2 at 750°C for 10 kh. For sCO2 cycles to be cost competitive, conventional steels are needed at 450°-650°C. Post-exposure room-temperature ductility is being used as a metric for evaluating compatibility of 9-12%Cr steels and type 316 stainless steels at these temperatures. Recent efforts also have explored revolutionary cycles at up to 1200°C. Subcritical exposures at 1 and 20 bar CO2 found most materials except CVD SiC were rapidly attacked at 1200°C including FeCrAl. NiCrAl-type alloys and other SiO2-forming materials, MoSi2 and MoSiAl, were explored at 1000°C but reaction rates were higher than expected. Traditional cermet matrix candidates, Mo and W, were rapidly attacked under these conditions. Research sponsored by the US DOE, Office of Fossil Energy, Crosscutting Research Program