OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 The study of the microstructure performed in [22] revealed that it consists of a ferrite-perlite mixture. It contains 81.7 % ferrite and 18.3 % pearlite. According to GOST 8233, the structure rating is 8. The minimum grain size rating is 8, the maximum grain size rating is 13, and the most frequently observed grain size rating on the micrographs is 11. The study of corrosion damage of the investigated samples was carried out on a JEOL 6008A scanning electron microscope (Fig. 2). The corrosion products of the material were removed from the surface before the study. Fig. 2. Structure of sample No. 1 of St3 steel Fig. 1. Microstructure of undeformed St3 steel sample Determination of the geometric parameters of the polished microsection surface was performed on images acquired using a scanning electron microscope (within the scanning area) with AXALIT software [30]. The values of the damage depth distribution were set in the software. Using the color gamut of the image, the depth of the observed damage was determined. Image scaling was performed in AXALIT to allow more accurate measurement results. Themeasurement was performed by delineating the defect contour, after which the software automatically calculated the area in μm². Depth variation was performed along a straight line, with the software counting darker areas of the image as deeper. The graph obtained in this way represents a profilogram of the surface along the selected direction. The constructed graphs determine the dependence of the depth in µm (determined by brightness) on the coordinate of the line position on the sample (µm). The methodology for calculating the depth of corrosion damage is as follows. The values of the corrosion damage depth obtained by measurements along a straight line (profilogram) on the base image surface were used to find the median value. Results and discussion Fig. 3 shows an example of the surface image of the investigated sample No. 2, obtained on a scanning electron microscope and analyzed in AXALIT software. An example of a profilogram is shown in Fig. 4. According to the obtained depth values from several measurements, the median corrosion damage depth values were determined for each sample. Determination of the median corrosion damage depth of the material under study was based on the following considerations: – the sample surface exhibits significant variations in height, even in areas without apparent corrosion damage (variations can reach 45 μm). this is attributed to the fact that the material under investigation is a multiphase system, in which different components react differently to the aggressive environment. furthermore, the grain boundaries are highly heterogeneous due to the high concentration of crystalline defects;
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