Introduction Casting

Paul D. Jablonski, Martin Detrois, Jeffrey A. HawkNETL, Battelle

Disclaimer

2019 Crosscutting Annual Review MeetingPittsburgh April 10th, 2019, Pennsylvania

This work was performed in support of the US Department of Energy’sFossil Energy Crosscutting Technology Research Program. TheResearch was executed through the NETL Research and InnovationCenter’s Advanced Alloy Development Field Work Proposal.Research performed by Leidos Research Support Team staff wasconducted under the RSS contract 89243318CFE000003.

This work was funded by the Department of Energy, National Energy Technology Laboratory, an agency of the United States Government, through a supportcontract with Leidos Research Support Team (LRST). Neither the United States Government nor any agency thereof, nor any of their employees, nor LRST, norany of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulnessof any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to anyspecific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply itsendorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein donot necessarily state or reflect those of the United States Government or any agency thereof.

Acknowledgements

Grain Boundary Design Strengthening & Stability

Alternate Concepts Laboratory

1 µm

1 µm

• A modified casting route was developed for commercial alloy 740Hthat leads to a more homogeneous grain size distribution (b)compared to (a) as well as a better repartition of the grain boundarycarbides.

• The modified casting showed improved creep performance ascompared to several conventional castings.

• To date, the Larson-Miller Parameter curve for the modified casting ison track to overlap with the wrought processed material.

Larson-Miller Parameter plot for 5 different conventionalcastings, the modified casting version and the wroughtproduct.

Creep strain vs creep life for variants of a commercial Ni-based superalloy with a conventional aging treatment or aδ aging treatment.

Predicted phase diagram from ThermoCalc showing precipitation ofthe γʹ strengthening phase and the entropy of the γ matrix.

• Precipitation of phases at the grainboundaries to increase their strengthor resistance to shear deformation.

• A δ (delta) aging treatment wasdeveloped for a commercial Ni-basedsuperalloy which resulted in theformation of δ precipitates across thegrain boundaries (grain boundarystitching).

• The aging treatment resulted inimprovements in creep strain and life.

• A Ni-based superalloy was designed with acontrolled γ/γʹ lattice misfit, nano-sized γʹprecipitates and using the entropy concept toobtain a high-entropy γ matrix around theoperating temperature of the alloy.

• The alloys are showing improved strength whencompared to Nimonic 105.

• Investigations aiming at modifying the compositions of commercial Ni-based superalloysto improve their thermo-mechanical properties are conducted using various approaches.

• The γʹ precipitate strengthening phase can be controlled with respect to its size, fractionand stability (coarsening).

• The formation of undesirable phases after extended time at temperature observed inseveral commercial alloys can be minimized as shown in the SEM micrographs below.

• Controlling both strengthening and stability enables the use of the alloys inenvironments requiring higher operating temperatures.

► Yield strength of the ASC alloys compared to commercial alloy Nimonic 105.

NETL utilizes an integrated approach thatleverages computational materialsengineering, manufacturing at scales thatreadily translate to industrial practice andperformance assessment at condition todevelop alloys that can improve theperformance of the existing fleet and enableadvanced fossil energy systems.

Ni-based superalloys are widely used inapplications that require high strength andtoughness at elevated temperatures. Severalapproaches are investigated at NETL toadvance research in Ni-based alloys frommodifications of thermo-mechanical processing,improvement of commercial alloys to thedevelopment of new concepts.

5000h / 800C Exposure; nominal alloy 263 (M0) and modified versions (M1, M2).