Carbon uptake and distribution in Spark Plasma Sintering (SPS) processed Sm(Co, Fe, Cu, Zr)z

Spark Plasma Sintering (SPS) rapidly consolidates high-melting point powders between carbon dies, but carbon can pose a risk for many materials. Carbon uptake in SPS and conventional, pressure-less sintered (CS) Sm(Co, Fe, Cu, Zr)z has been analysed using Electron Probe Micro-Analysis (EPMA) to produce high-detail elemental distribution maps. Field's metal was used as mounting material to avoid introducing carbon into the samples. The distribution maps show high surface carbon levels in the SPS-processed Sm(Co, Fe, Cu, Zr)z to a depth of 10 µm. Much less carbon was observed in CS Sm(Co, Fe, Cu, Zr)z. Furthermore, elemental carbon analysis (LECO-C) confirmed carbon was most abundant at the surface in SPS-processed Sm(Co, Fe, Cu, Zr)z but also at higher levels internally, when compared to the CS sample. It is inferred that the carbon contamination is due to the contact between the powder and the graphite die/paper at elevated temperatures during SPS process. The measured levels of carbon in the SPS-processed sample are not expected to significantly impact the magnetic properties of Sm(Co, Fe, Cu, Zr)z. These results may have implications for other powder materials processed by SPS with properties sensitive to carbon.