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The article evaluates and predicts the resistance of plate-like heat exchangers made of 06KhN28MDT alloy (analogous to AISI 904 L steel) to crevice corrosion in model recycled water using the developed mathematical models. The developed mathematical model, based on regression trees, establishes the relationship between the activation potential Ecrev of the studied alloy in a gap with a chloride-containing medium and its chemical composition and structural components. This potential characterizes the resistance of the passive film on the alloy surface to the activating effect of chloride ions in the gap, and the more positive it is, the higher it is. From the analysis of this mathematical model, it was found that the potential of the 06KhN28MDT alloy has the most positive value of 1.685 V, provided that the chromium content is greater than 23.555 and the nickel content is less than 27.595 wt.%. It has been hypothesized that this trend is due to the fact that with such a chromium content in the alloy, its surface consists exclusively of chromium atoms. However, under the same conditions, this potential shifts to the negative side to 1.634 and 1.43 V if the nickel content in the alloy is more than 27.595 wt.%. This is most likely due to the fact that nickel hinders the solid-phase diffusion of chromium atoms into the passive film on the alloy surface. It has been recorded that the potential Ecrev of the 06KhN28MDT alloy shifts strongly to the negative side to 0.378 V if the chromium content is less than 22.26 wt.%, and the volume of titanium sulfides is 0.00535 vol.%. At the same time, it was found that this potential of the alloy has the most negative value of 0.11 V if its mean austenite grain diameter is less than 13.5 μm. This is due to an increase in the length of the alloy austenite grain boundaries and the number of defects structure on its surface, which makes it possible for the chloride-containing medium to contact the base metal through the pores in the passive film on the alloy surface. It has been found that the potential Ecrev of the studied alloy has a sufficiently high positive value of 1.28 V at a Cr content from 23.055 upto 23.555 wt.%. However, it shifts significantly to the negative side to 0.985 V if the Cr content is less than 23.055 and the C content is 0.0485 wt.%. However, with the same chromium content in the alloy, a shift of this potential to the negative side to 0.426923 V was recorded if the C content in the alloy is more than 0.0485 wt.%. It is hypothesized that this is due to a decrease in the ionization over voltage of hydrogen atoms on the carbide phase in the vicinity of titanium nitrides in the alloy, which are intensively released from the austenite solid solution at this C content. Applying the results of the analysis of the developed mathematical model, it is recommended that enterprises producing plate-like heat exchangers from 06KhN28MDT alloy choose melts containing chromium more than 23.6 wt.% Cr and C less than 0.0485 wt.% with a mean austenite grain diameter from 22 upto 31 microns. The quality of the developed mathematical model was evaluated by SSE (sum of square errors) and MSE (mean square error). They were as follows: SSE = 0.6497 and MSE = 0.0130. Additionally, the resistance of the studied alloy to crevice corrosion was evaluated by the limiting potentials, in particular, repassivation Erep, free corrosion Ecor, and Ecrev, which were calculated using the developed mathematical model, which is several orders of magnitude more accurate than the previous one. In particular, the SSE parameters for the potentials Erep, Ecor, and Ecrev of 06KhN28MDT alloy are 0.00003904, 0.00004015, and 0.00009461, respectively. At the same time, its MSE parameters are 0.00000078, 0.00000080, and 0.00000189, respectively. The developed mathematical model is based on a two-layer neural network of direct signal propagation. This model cannot be used to analyze the effect of the parameters of the 06KhN28MDT alloy on the limit potentials in the gap with a chloride-containing medium. However, it is very well suited for assessing and predicting the resistance of plate-like heat exchangers to crevice corrosion in the recycled water of enterprises. To develop these mathematical models, used the parameters of 50 generated melts of this alloy, and the accuracy was verified by experiments using five industrial melts.

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Evaluation and Prediction of Corrosion Behavior of Plate-Like Heat Exchangers Made of 06KhN28MDT Alloy During Their Operation in the Recycled Water of Enterprises

  • 会议论文

  • 发表日期：

    2025年

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  • A. V. Dzhus,
  • O. E. Narivskyi,
  • S. O. Subbotin,
  • G. V. Snizhnoi,
  • D. G. Voskoboinikov

摘要

The article evaluates and predicts the resistance of plate-like heat exchangers made of 06KhN28MDT alloy (analogous to AISI 904 L steel) to crevice corrosion in model recycled water using the developed mathematical models. The developed mathematical model, based on regression trees, establishes the relationship between the activation potential Ecrev of the studied alloy in a gap with a chloride-containing medium and its chemical composition and structural components. This potential characterizes the resistance of the passive film on the alloy surface to the activating effect of chloride ions in the gap, and the more positive it is, the higher it is. From the analysis of this mathematical model, it was found that the potential of the 06KhN28MDT alloy has the most positive value of 1.685 V, provided that the chromium content is greater than 23.555 and the nickel content is less than 27.595 wt.%. It has been hypothesized that this trend is due to the fact that with such a chromium content in the alloy, its surface consists exclusively of chromium atoms. However, under the same conditions, this potential shifts to the negative side to 1.634 and 1.43 V if the nickel content in the alloy is more than 27.595 wt.%. This is most likely due to the fact that nickel hinders the solid-phase diffusion of chromium atoms into the passive film on the alloy surface. It has been recorded that the potential Ecrev of the 06KhN28MDT alloy shifts strongly to the negative side to 0.378 V if the chromium content is less than 22.26 wt.%, and the volume of titanium sulfides is 0.00535 vol.%. At the same time, it was found that this potential of the alloy has the most negative value of 0.11 V if its mean austenite grain diameter is less than 13.5 μm. This is due to an increase in the length of the alloy austenite grain boundaries and the number of defects structure on its surface, which makes it possible for the chloride-containing medium to contact the base metal through the pores in the passive film on the alloy surface. It has been found that the potential Ecrev of the studied alloy has a sufficiently high positive value of 1.28 V at a Cr content from 23.055 upto 23.555 wt.%. However, it shifts significantly to the negative side to 0.985 V if the Cr content is less than 23.055 and the C content is 0.0485 wt.%. However, with the same chromium content in the alloy, a shift of this potential to the negative side to 0.426923 V was recorded if the C content in the alloy is more than 0.0485 wt.%. It is hypothesized that this is due to a decrease in the ionization over voltage of hydrogen atoms on the carbide phase in the vicinity of titanium nitrides in the alloy, which are intensively released from the austenite solid solution at this C content. Applying the results of the analysis of the developed mathematical model, it is recommended that enterprises producing plate-like heat exchangers from 06KhN28MDT alloy choose melts containing chromium more than 23.6 wt.% Cr and C less than 0.0485 wt.% with a mean austenite grain diameter from 22 upto 31 microns. The quality of the developed mathematical model was evaluated by SSE (sum of square errors) and MSE (mean square error). They were as follows: SSE = 0.6497 and MSE = 0.0130. Additionally, the resistance of the studied alloy to crevice corrosion was evaluated by the limiting potentials, in particular, repassivation Erep, free corrosion Ecor, and Ecrev, which were calculated using the developed mathematical model, which is several orders of magnitude more accurate than the previous one. In particular, the SSE parameters for the potentials Erep, Ecor, and Ecrev of 06KhN28MDT alloy are 0.00003904, 0.00004015, and 0.00009461, respectively. At the same time, its MSE parameters are 0.00000078, 0.00000080, and 0.00000189, respectively. The developed mathematical model is based on a two-layer neural network of direct signal propagation. This model cannot be used to analyze the effect of the parameters of the 06KhN28MDT alloy on the limit potentials in the gap with a chloride-containing medium. However, it is very well suited for assessing and predicting the resistance of plate-like heat exchangers to crevice corrosion in the recycled water of enterprises. To develop these mathematical models, used the parameters of 50 generated melts of this alloy, and the accuracy was verified by experiments using five industrial melts.