Niobium in Superalloys: Pushing Beyond the Limits of 718
Presented by:
Dr. Bill MacDonald
Chief Metallurgist
Berwyn Metals LLC
Abstract:
The development of N07718, often referred to as Alloy 718, is one of the key metallurgical discoveries of the 20th century. The alloy is used in a broad range of applications that require resistance to high temperatures, high pressures, and corrosion. The alloy's success depends on niobium's strengthening effect, which forms Ni3Nb “Gamma Double Prime”, g”, coherent precipitates in the gamma lattice. As with all materials, there are limits to the conditions under which 718 can be applied. The temperature limitation of roughly 650°C is due to the transformation of g” to an embrittling delta phase. For higher temperature applications, superalloys use “Gamma Prime” g’ strengthening that is effective up to 870°C in wrought alloys. This talk will outline the current alloy developments that are underway to push the temperature limits of both 718 and newer g’-strengthened alloys which contain significant Niobium additions. Recent technology advances such as local phase transformation, co-precipitation, and oxide dispersion strengthening that require niobium additions to achieve high performance will be presented. The talk will also outline CBMM's contributions—as the global leader in niobium science, technology, and supply—to collaborative research programs that support these developments, including computational alloy design partnerships and technology outreach to the turbomachinery community.
Bio :
William (Bill) D. MacDonald, PhD, P.E., is a materials consultant with Berwyn Metals LLC with more than 38 years of experience in materials and metallurgical engineering across aerospace, oil and gas, industrial, and automotive markets. He previously served as Director of Technical Sales at Special Metals and TIMET, leading technical and commercial development for nickel and titanium alloys. He holds a PhD in Metallurgy from MIT, where he studied under Professor Thomas W. Eagar, and master’s and bachelor’s degrees in Metallurgical Engineering from Queen’s University. A licensed professional engineer in Pennsylvania and Ontario, he has held leadership roles in ASME, ASTM, API, and NACE/AMPP standards activities. His ASM Houston presentation, “Niobium in Superalloys: Pushing Beyond the Limits of 718,” will explore niobium’s role in strengthening and advancing the temperature capability of next-generation superalloys.
