A team of scientists at Pacific Northwest National Laboratory (PNNL; Richland, Wash.; www.pnnl.gov) recently unveiled a modified version of the “superalloy” Inconel 617, in which cobalt — a component of the alloy that is also a critical material with significant supply-chain risks — is replaced with manganese, a much more common element with fewer supply-chain challenges. Cobalt mining, mostly done in the Democratic Republic of the Congo, is beset by geopolitical, environmental and human rights challenges, and most refined cobalt comes from China, so there is much interest in reducing the demand for the element, which also is used in some cathode formulations for lithium-ion batteries.
Inconel 617 is a nickel-chromium-cobalt-molybdenum alloy with exceptional high-temperature strength and resistance to oxidation. Seeking to reduce dependence on the critical material cobalt, PNNL scientists started with computer simulations of potential combinations that would allow the cobalt to be substituted while maintaining the mechanical and chemical properties of Inconel 617. After manganese emerged as a possible replacement element for cobalt, the researchers identified a specific concentration of each alloy component that could offer the desired properties.
The material at center is a modified alloy developed by PNNL that may be able to withstand extreme environments while using less critical materials. (Photo by Andrea Starr | PNNL)
Then, using a technique called friction-stir consolidation, the PNNL team fabricated the modified Inconel, known as IN617-M1. In friction-stir consolidation, specialized tools apply mechanical energy and create friction heat, rather than melting the metals. This advanced manufacturing method allows the materials to be “stirred” in a way that enables tailoring of the alloy’s microstructure, PNNL says.
Subsequent studies of IN617-M1’s properties indicate that its hardness, high-temperature stability and oxidative resistance are comparable to those of the conventional cobalt-containing Inconel 617.
The scientists are seeking industry partners to collaborate on next steps, which could include scaling up the material synthesis and demonstrating the use of the alloy in multiple applications, which could include nuclear reactors, PNNL says.