Review of 'EPMA quantification on the chemical composition of retained austenite in a Fe-Mn-Si-C-based multi-phase steel'

The authors set out method to analyse carbon bearing phase, carbon is complex in that it is affected by contamination as authors note

The authors imply calibration curve and maps necessary, however EPMA has robust matrix corrections correcting for differences between standards and unknowns and options of point or line analysis as well. A calibration curve is obvious choice for carbon given contamination but not necessarily for other elements

The choice of calibration curve for all elements may reflect the choice of element maps without background correction, otherwise a background would need to be measured or calculated if a full matrix correction where applied to the maps, or spot analyses to generate calibration curves for the maps.

The use of calibration curves relies on similarity between standard and unknown as unlike with matrix corrections background and matrix effects are not corrected for.

when considering the calibration curves and affect of current and dwell time, it is normally assumed counts are proportional to current and time, the exception being where there is deadtime or contamination

carbon contamination is an issue as it is present on samples before analysis and can be deposited and eroded. The merit in the authors method seems to be the stage is moving continuously at the same speed over a large area on both standard and unknown and therefore contamination rate should be the same

There has been extensive research on this including Phillipe Pinard PhD thesis and others. Contamination depends on sample preparation and can be reduced using a cold trap, plasma cleaner and heated stage.

skme of the key references are

Yamashita, T., Tanaka, Y., Nagoshi, M. et al.Novel technique to suppress hydrocarbon contamination for high accuracy determination of carbon content in steel by FE-EPMA. Sci Rep6, 29825 (2016). https://doi.org/10.1038/srep29825
 

Augustyn, E., Hallstedt, B., Wietbrock, B., Mayer, J., Schwedt, A. & Richter, S. (2012). Chemical characterisation of scale formation of high manganese steels (Fe-Mn23-C0.6) on the sub-micrometre scale: A challenge for EPMA. IOP Conf Ser: Mater Sci Eng 32, 012001.

Hirsch, P., Kassens, M., Puttmann, M. & Reimer, L. (1994). Contamination in a scanning electron microscope and the influence of specimen cooling. Scanning 16, 101–110.
Pinard, P.T., Schwedt, A., Ramazani, A., Prahl, U. & Richter, S. (2013 a). Characterization of dual-phase steel microstructure by combined submicrometer EBSD and EPMA carbon measurements. Microsc Microanal 19, 996–1006.
http://publications.rwth-aachen.de/record/673259/
Matthews, M., Kearns, S., & Buse, B. (2018). Electron Beam-Induce Carbon Erosion and the Impact on Electron Probe Microanalysis. Microscopy and Microanalysis. https://doi.org/10.1017/S1431927618015398