At Queen City Forging, we’re continually looking for new innovations to the forging process, including promising new metallurgies. One such area of research in recent years has been High-Entropy Alloys, or HEAs.
What are High-Entropy Alloys?
Basically, a High-Entropy Alloy is a complex metal matrix in which no one element makes up more than 30% of the alloy’s composition. Such complex compositions do not necessarily produce a complex structure and microstructure, or the accompanied brittleness, but significantly higher mixing entropy from complex compositions can actually simplify structures and microstructures to create new alloys with attractive properties.
HEA Research and Analysis
With virtually limitless elemental combinations, the resulting properties of HEAs are also seemingly infinite. By using computational tools to explore combinations of elements, material scientists have begun to predict HEA microstructures. This analysis vastly narrows down the possibilities and has allowed targeting of desirable mechanical properties such as high abrasion resistance and tensile strength, leading to the development of new HEAs.
Much of this HEA research has been conducted for aerospace/defense and automotive industries, involving organizations such as the National Science Foundation’s Industry-University Cooperative Research Program. Research Centers such as the Center for Advanced Non-Ferrous Structural Alloys (CANFSA), the Advanced Steel Processing and Products Research Center (ASPPRC), and Military Research Laboratories of the Air Force and Army have been exploring the potential of these materials.
QCF Forging Die Research using HEAs
QC Forge first looked at the application of High-Entropy Alloys for improving forging die performance. Along with support from the Forging Industry Association’s Education and Research Foundation (FIERF), HEAs have been applied to working forge dies for discovering if sufficient benefit can be achieved to justify the costs. This has led to collaborative and experimental application of HEA coatings to die substrates using two different methods:
- Laser Enhanced Net Shape (LENS) additive manufacturing for sintered layering of HEA coatings on forging dies
- Specialty welding of layered HEA material on forging dies. For this coating method, QCF has collaborated with other Forging Industry Association (FIA) members and FIERF to provide a more conventional weld application as an alternative to the LENS process.
LENS application of high-entropy metal alloy on an H13 base has proven to be effective in thicknesses of as little as 20 μm. The HEA LENS coating process provides metallurgical bonding to the die substrate material at the coating/substrate interface, resulting in enhanced microhardness and wear resistance that is superior to typical forging die metallurgies.
Initial QCF Test Results and Beyond
Initial test results have shown that coating dies with HEAs can increase die life by as much as 50%. In addition, improved lubricity of certain HEAs have shown the potential for better die ejection performance that could lower scrap rates and improve forging productivity. Further testing may yet reveal higher temperature properties to target more severe service applications. Different HEA combinations may be revealed to provide the best solution for specific challenges to the variety of tool service conditions. HEA recipes are expected to target high-wear areas, locations that experience thermal shock or degradation, or high mechanical strain in different areas of a single forge die. Our next phase of HEA die research is currently in process and will be nearing completion soon. Stay tuned for more test results to come!
It’s very exciting to see advanced material science, born of the latest aerospace technology, bringing about the realization of enhanced forging die properties we've never had before. As we look to other forging process possibilities using High-Entropy Alloys, we can also envision the forging of HEAs for production of lighter weight, high-performance aerospace and automotive parts on the horizon.