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EP39192

Poster Title: Effects of etchant stirring on the surface quality of the metallography sample
Submitted on 07 Sep 2022
Author(s): Ondřej Ambrož, Jan Čermák, Patrik Jozefovič, Šárka Mikmeková
Affiliations: Institute of Scientific Instruments of the Czech Academy of Sciences
This poster was presented at COMAT 2022
Poster Views: 171
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Abstract: Despite its predominantly empirical nature, metallographic etching remains an important sample preparation method that enables microstructural characterization. The poor repeatability is due to the ignorance of etching mechanisms and the human factor, which is mainly associated with the conventional approach. This approach is most commonly practiced by manual immersion of the sample in the etchant. The solution should be gently stirred so that reaction products do not settle on the surface and uneven etching does not occur. Often, stirring is provided by the sample itself or by a magnetic bar. In terms of spatial orientation, etching with the polished surface facing upwards allows the surface to be observed during the process. Some authors recommend etching with the polished surface downwards to minimize the deposition of reaction products. In some cases, a vertical orientation of the sample is recommended to reduce pitting. In this paper, the effect of the etchant stirring method on the surface quality of a metallographic structural steel specimen will be presented. In addition to different etchant stirring methods, different spatial orientations of the sample will also be investigated. To ensure better repeatability and accurate etching time, the samples will be etched using our automated apparatus. The resulting surface of the samples will be analysed using light optical microscopy (LOM) and confocal laser scanning microscopy (CLSM). The development of more reproducible etching methods is essential to obtain accurate microstructure information without artifacts and for advanced quantitative image analysis using deep learning.Summary: Preheating the sample with a hot air gun for 20 s at 100 °C proved to be crucial in optimizing the process. The best results were achieved by stirring with a magnetic bar, moving the sample and orienting the polished surface downwards. Unconventional stirring of the etching fluid by ultrasonication also appears to be very promising. A more objective method for evaluating image quality needs to be developed. It would be preferable to scan larger areas for more representative results.Report abuse »

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