Use of High-Entropy Alloys
Marcus Young, assistant professor and associate department chair of the undergraduate program in materials science and engineering at the University of North Texas (UNT), and his team investigated a new class of materials known as high-entropy alloys (HEAs) to coat die heads. The project, which was supported by the Forging Industry Association’s FIERF Program, involved laser engineering net shaping (LENS) coating of the die heads with the HEAs and was tested by Rob Mayer and Andy Spires of Queen City Forging Co.
“Nathan Ley, a graduate student in my research group at UNT, performed much of the research with help from Materials Science and Engineering Professor Narendra Dahotre and his graduate student, Sameehan Joshi,” Young said. “The FIERF project provided an excellent opportunity for our students to gain a deeper understanding of how the forging process works, as well as an opportunity to attend two FIA conferences and present their research on this project.”
Young, who has experience working in R&D at ATI Specialty Alloys & Components and other industrial companies like Boeing and Bell Helicopter, was introduced to the FIERF organization by then-UNT Assistant Professor and now Al and Julie Renken Iowa State University Associate Professor Peter Collins.
“The project was a natural fit and really allowed us to connect with the forging industry and help problem-solve some of their ongoing issues and research activities,” Young said.
Breaking it Down
HEAs are a relatively new class of material that exhibit a single phase at room temperature, show superplastic behavior depending on processing and often have phase stability at elevated temperatures. HEAs are near equiatomic alloys composed of five or more elements with no base element and are currently being investigated as replacements for conventional alloys, which have one primary element as a base.
“The motivation behind this project was to repair a damaged H13 steel die head by laser cladding it with an HEA to extend the life of the die head,” Young said. “The joining method involves LENS, which is an additive-manufacturing method involving laser sintering of alloy powders to the surface of the die head.”
The team worked on four primary objectives:
- Down-select from the wide range of HEAs to candidate alloys that show promise given their room-temperature microstructures.
- Produce laboratory-scale specimens of the candidate alloys to evaluate the room-temperature microstructure and elevated-temperature tensile properties, and acquire H13 to serve as a baseline.
- Subject subscale specimens to both long-term isothermal holds and thermal cycling to assess the stability of the microstructure and properties.
- Fabricate an H13 die with at least one HEA inset in the die to assess performance in conjunction with a forging partner (Queen City Forging Co.).
“All of these objectives were completed successfully,” Young said. “The final HEA consisted of Al3.3Co24.2Cr16.1Fe16.1Ni24.2Ti16.1 and ran as a forge punch about twice as long as a normal die head before obtaining the same amount of wear.”
The results from the project are being finalized for publication, and another die head is in the process of being reconditioned with another HEA that is expected to show improved results.