CCS and Power Systems
Crosscutting Research - Plant Optimization Technologies
Computational and Experimental Development of Novel High Temperature Alloys
Performer: Ames National Laboratory
Project No: FWP-AL-07-360-019
Researchers have determined that a 20 percent molybdenum (Mo)- balance nickel aluminum (NiAl) alloy has promising characteristics with respect to high temperature oxidation resistance. Mo-Ni-Al alloy compositions made via drop casting showed better oxidation resistance than alloys made by liquid phase sintering. Nodular microstructures showed best resistance to cyclic air oxidation exposure. Researchers have also identified which mix of platinum group metals provides best high temperature oxidation resistance in air. Hafnium doped NiAl plus 6-9 percent iridium provided best oxidation resistance at 1150 – 1300 °C compared to other NiAl plus platinum-group metal alloy compositions tested. Additions of iridium and rhodium to NiAl base alloy increased the melting point of the alloy, as predicted by theoretical calculations.
The alloy system design identified based on previous laboratory-scale tests are directionally solidified NiAl-Mo alloy with columnar Mo grains for mechanical strength plus a coating with platinum-group metal additions for high temperature oxidation resistance. Directional solidification and coating experiments were started. These experiments showed that the high temperature (1150-1250 °C) air oxidation resistance of the coating alloy could be improved by decreasing its grain size.