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<p>This study conducted turning experiments on γ-TiAl alloy using supercritical carbon dioxide minimum quantity lubrication (scCO₂-MQL) technology, with a comparative analysis of surface and subsurface characteristics under dry turning and scCO₂-MQL assisted turning conditions. The experiments were performed under fixed parameters, employing surface roughness, surface morphology, microstructure, microhardness, and residual stress as evaluation indicators to systematically assess the applicability of scCO₂-MQL in γ-TiAl alloy turning. Experimental results demonstrate that scCO₂-MQL significantly improves surface quality: surface roughness (Sa) was reduced by approximately 74% (from 2.625&#xa0;μm to 0.681&#xa0;μm), while effectively suppressing surface defects such as micro-cracks, tearing, and material adhesion. A white layer was observed under both turning conditions, though it was notably thinner in scCO₂-MQL. Electron backscatter diffraction (EBSD) analysis confirmed that scCO₂-MQL inhibits severe microstructural evolution (including texture formation, grain refinement, and recrystallization) observed in dry turning. Furthermore, while both turning methods induced work hardening effects, scCO₂-MQL reduced surface hardness (from 643 HV to 536 HV) and hardening layer depth (from 418&#xa0;μm to 346&#xa0;μm) compared to dry turning. Notably, no significant difference in hardness was observed among different microstructural zones (white layer, transition zone, and substrate region) under either cooling condition. Residual stress measurements revealed that scCO₂-MQL reduced compressive residual stress by approximately 24%. The investigations indicate that scCO₂-MQL, through the synergistic action of supercritical carbon dioxide and minimal lubrication oil, effectively delivers cooling and lubrication media to the cutting zone, thereby significantly enhancing the surface integrity of γ-TiAl alloys during turning.</p>

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Study on Surface Integrity of γ-TiAl Alloy Machined by scCO₂-MQL Assisted Turning

  • 期刊论文

  • 发表日期：

    2026年4月27日

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  • Baiwei Zhu,
  • Hailang Zhou,
  • Yifan Xu,
  • Hang Sun,
  • Limin Shi,
  • Erliang Liu

摘要

This study conducted turning experiments on γ-TiAl alloy using supercritical carbon dioxide minimum quantity lubrication (scCO₂-MQL) technology, with a comparative analysis of surface and subsurface characteristics under dry turning and scCO₂-MQL assisted turning conditions. The experiments were performed under fixed parameters, employing surface roughness, surface morphology, microstructure, microhardness, and residual stress as evaluation indicators to systematically assess the applicability of scCO₂-MQL in γ-TiAl alloy turning. Experimental results demonstrate that scCO₂-MQL significantly improves surface quality: surface roughness (Sa) was reduced by approximately 74% (from 2.625 μm to 0.681 μm), while effectively suppressing surface defects such as micro-cracks, tearing, and material adhesion. A white layer was observed under both turning conditions, though it was notably thinner in scCO₂-MQL. Electron backscatter diffraction (EBSD) analysis confirmed that scCO₂-MQL inhibits severe microstructural evolution (including texture formation, grain refinement, and recrystallization) observed in dry turning. Furthermore, while both turning methods induced work hardening effects, scCO₂-MQL reduced surface hardness (from 643 HV to 536 HV) and hardening layer depth (from 418 μm to 346 μm) compared to dry turning. Notably, no significant difference in hardness was observed among different microstructural zones (white layer, transition zone, and substrate region) under either cooling condition. Residual stress measurements revealed that scCO₂-MQL reduced compressive residual stress by approximately 24%. The investigations indicate that scCO₂-MQL, through the synergistic action of supercritical carbon dioxide and minimal lubrication oil, effectively delivers cooling and lubrication media to the cutting zone, thereby significantly enhancing the surface integrity of γ-TiAl alloys during turning.