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<p>The tribological behaviors and microstructural evolution of weld St37 mild steel fabricated by gas metal arc welding (GMAW) under flat and vertical-up welding positions −subsequently processed by high-pressure torsion (HPT) − were investigated using scanning electron microscopy (SEM), optical microscopy, and transmission electron microscopy (TEM). It was found that HPT sufficiently led to the microstructure evolution and uniform distribution of ultra-fine grains in the sample and improved the mechanical characterization of the welds. Tensile tests revealed that weld samples, regardless of welding position, exhibited lower strength and elongation compared to the base metal. However, weld hardness increased notably compared to the as-received alloy, the HPT-processed samples showed a substantial rise in hardness due to intense grain refinement and increased dislocation density. Tribological analysis showed that HPT-treated samples possessed superior wear resistance relative to those produced by conventional welding methods. This improvement is attributed to stress relief resulting from welding, refined microstructure, and higher hardness induced by HPT. Furthermore, wear analysis indicated a transition in wear mechanism—from adhesive to sliding—caused by surface flattening from local asperity deformation, grain refinement, and the accumulation of submicron wear particles on the worn surfaces.</p>

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Influence of the nano-structuring by high-pressure torsion on the microstructure, mechanical behavior, and tribological properties of mild steel weld samples fabricated by GMAW

  • 期刊论文

  • 发表日期：

    2026年2月3日

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  • Mahmoud Abbasi,
  • Behrouz Bagheri Vanani,
  • Mohammad Reza Mehraban Dehaqani,
  • Melika Mohammadkhah,
  • Sandra Klinge

摘要

The tribological behaviors and microstructural evolution of weld St37 mild steel fabricated by gas metal arc welding (GMAW) under flat and vertical-up welding positions −subsequently processed by high-pressure torsion (HPT) − were investigated using scanning electron microscopy (SEM), optical microscopy, and transmission electron microscopy (TEM). It was found that HPT sufficiently led to the microstructure evolution and uniform distribution of ultra-fine grains in the sample and improved the mechanical characterization of the welds. Tensile tests revealed that weld samples, regardless of welding position, exhibited lower strength and elongation compared to the base metal. However, weld hardness increased notably compared to the as-received alloy, the HPT-processed samples showed a substantial rise in hardness due to intense grain refinement and increased dislocation density. Tribological analysis showed that HPT-treated samples possessed superior wear resistance relative to those produced by conventional welding methods. This improvement is attributed to stress relief resulting from welding, refined microstructure, and higher hardness induced by HPT. Furthermore, wear analysis indicated a transition in wear mechanism—from adhesive to sliding—caused by surface flattening from local asperity deformation, grain refinement, and the accumulation of submicron wear particles on the worn surfaces.