Tribology and Materials | Volume 4 | Issue 3 | 2025 | 144-154
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https://doi.org/10.46793/tribomat.2025.015
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Microstructure, hardness and tribological behaviour of plasma nitrided R260 rail steel with different nitrogen and hydrogen gas mixtures
Ahmet Deveci
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Harun Mindivan
Bilecik Şeyh Edebali University, Bilecik, Turkey
Abstract: Railway components are essential parts of
transportation infrastructure, withstanding complex and dynamic loads
during their operational lifespan. This work aims to improve the wear
resistance of railway rails by investigating the correlation between the
microstructure, hardness and tribological behaviour of R260 pearlitic
rail steel. This will be achieved through a twelve-hour plasma nitriding
process at a temperature of 450 °C, using two different N2-H2 gas
mixtures (20 vol. % N2 + 80 vol. % H2 and 80 vol. % N2 + 20 vol. % H2).
The treated surfaces were characterised using light optical microscopy,
scanning electron microscopy, X-ray diffraction and microhardness
testing. The unlubricated tribological behaviour of plasma-nitrided
steel was investigated in a ball-on-flat tribometer at room temperature.
The 20 and 80 vol. % N2 gas mixture led to a biphasic compound layer of
ε-Fe2-3N and γˈ-Fe4N. As the amount of nitrogen in the gas mixture
increased, the total compound layer, surface roughness and surface
residual compressive stress increased. In the tribological tests, the
steel treated with a nitrogen-rich gas mixture (80 vol. % N2) yielded
better results due to the formation of a thicker compound layer, a
deeper case-hardening and higher compressive residual stress within the
nitride layer.
Keywords: pearlitic rail steel, plasma nitriding, compound layer, gas mixture influence, wear.
Received: 08-10-2024, Revised: 09-12-2024, Accepted: 05-01-2025
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license, which allows users to distribute, remix, adapt,
and build upon the material in any medium or format for non-commercial purposes only, and only so long as attribution is given to the creator.
Abstract: Railway components are essential parts of transportation infrastructure, withstanding complex and dynamic loads during their operational lifespan. This work aims to improve the wear resistance of railway rails by investigating the correlation between the microstructure, hardness and tribological behaviour of R260 pearlitic rail steel. This will be achieved through a twelve-hour plasma nitriding process at a temperature of 450 °C, using two different N2-H2 gas mixtures (20 vol. % N2 + 80 vol. % H2 and 80 vol. % N2 + 20 vol. % H2). The treated surfaces were characterised using light optical microscopy, scanning electron microscopy, X-ray diffraction and microhardness testing. The unlubricated tribological behaviour of plasma-nitrided steel was investigated in a ball-on-flat tribometer at room temperature. The 20 and 80 vol. % N2 gas mixture led to a biphasic compound layer of ε-Fe2-3N and γˈ-Fe4N. As the amount of nitrogen in the gas mixture increased, the total compound layer, surface roughness and surface residual compressive stress increased. In the tribological tests, the steel treated with a nitrogen-rich gas mixture (80 vol. % N2) yielded better results due to the formation of a thicker compound layer, a deeper case-hardening and higher compressive residual stress within the nitride layer.
Keywords: pearlitic rail steel, plasma nitriding, compound layer, gas mixture influence, wear.
Received: 08-10-2024, Revised: 09-12-2024, Accepted: 05-01-2025
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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license, which allows users to distribute, remix, adapt, and build upon the material in any medium or format for non-commercial purposes only, and only so long as attribution is given to the creator.