Additive Manufacturing of Iron-Cobalt Alloy for Electric Motors
Date of Award
M.S. in Chemical and Materials Engineering
Department of Chemical and Materials Engineering
Donald A. (Donald Albert) Klosterman, 1966-
Additive Manufacturing (AM) is a rapidly developing field that offers new possibilities for manufacturing with materials that are difficult to process with traditional manufacturing methods. This report will examine the application of selective laser melting in making magnetic cores out of Hiperco 50. The iron-cobalt family of alloys is known to offer the best magnetic properties of all soft magnetic materials but is extremely brittle. Additive manufacturing offers the opportunity to make high quality magnetic cores in unique geometries that traditional manufacturing is unable to replicate. To test the viability of this process three types of test specimens were built out of Hiperco 50 powder to examine key material properties. First 1 cm3 cube specimens were built to measure the density of the final parts, and they were also used to examine the porosity and microstructure. The second type of specimens were tensile bars, built in both vertical and horizontal orientations with respect to the build plate, to examine the mechanical properties of the final parts as well as the impact of build orientation. The final test specimens were magnetic toroids, comprised of cores to be wound with copper magnet wire and tested for magnetic permeability and remanence. Half of these specimens were also subjected to a final magnetic heat treatment cycle, which was the same as the cycle used for traditionally manufactured Hiperco 50 components, in order to determine the change in performance. These AM fabricated specimens showed a 1-5% decrease in density from traditionally manufactured Hiperco 50 parts, with the build parameters being the largest deciding factor of final density and porosity. These parts also had a poorly defined grain structure until subjected to a magnetic heat treatment. After undergoing the recommended heat-treatment, niobium precipitates were observed along the newly defined grain boundaries. However, there was a severe drop in mechanical performance, and a minor increase in magnetic properties. Overall, the magnetic performance of all specimens was considerably worse than traditional Hiperco 50 cores, exhibiting permeabilities orders of magnitude lower than the traditionally manufactured counterparts. The cause for this could be attributed to the porosity of the final specimens, which would disrupt uniform magnetic field lines forming around the toroid with internal fields opposing magnetization. With the high cost per part and poor observed magnetic performance, selective laser melting is not recommended as a replacement for traditional methods without significant further development. The data gathered here indicates that while Hiperco 50 did retain some of its magnetic properties, truly unique geometries must be necessary to make the trade-off in performance worth the performance drop, cost, and time investment to make additive manufacturing a serious consideration.
Materials Science, Electromagnetics, Electromagnetism, Hiperco 50, Additive Manufacturing, Selective Laser Melting, Magnetization, Porosity
Copyright 2021, author.
Smith, Derek Michael, "Additive Manufacturing of Iron-Cobalt Alloy for Electric Motors" (2021). Graduate Theses and Dissertations. 6977.