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<p>High-speed electrical discharge machining (EDM) is a widely utilized non-contact method for creating small holes in nickel-based high-temperature alloys (Ni-based HAs) used in aircraft engines. However, EDM produces a recast layer on the inner walls of these micro-holes, which can adversely affect surface quality and long-term performance in harsh environments. This study examines the microscopic performance of high-speed EDM on Ni-based superalloys, focusing on key factors influencing recast layer thickness (RLT). Results show that increases in electrode diameter and pulse width correlate positively with RLT. Elemental analysis indicates significant enrichment of O, C, and Cu in the recast layer, while Ni, Fe, and S are less prevalent. The recast layer also displays finer grain sizes and more precipitated phases, potentially compromising fatigue life. Surface morphology features flow-shaped bumps and microcracks, predominantly located in pits. Micro-hardness testing reveals a 22.3% increase in hardness in the recast layer (4.77 GPa) compared to the substrate (3.90 GPa). Additionally, the Young's modulus of the substrate (212 GPa) significantly exceeds that of the recast layer (177 GPa), raising concerns about fatigue performance. This analysis offers valuable insights for optimizing high-speed EDM parameters and evaluating the mechanical properties of machined Ni-based superalloys.</p>

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Surface integrity and mechanical analysis of small holes in Nickel-based high temperature alloys machined by high-speed EDM

  • 期刊论文

  • 发表日期：

    2025年5月7日

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  • Yaou Zhang,
  • Hualin Liao,
  • Qiang Gao,
  • Juncheng Lu,
  • Qian Zheng,
  • Xiangjun Yang,
  • Wansheng Zhao

摘要

High-speed electrical discharge machining (EDM) is a widely utilized non-contact method for creating small holes in nickel-based high-temperature alloys (Ni-based HAs) used in aircraft engines. However, EDM produces a recast layer on the inner walls of these micro-holes, which can adversely affect surface quality and long-term performance in harsh environments. This study examines the microscopic performance of high-speed EDM on Ni-based superalloys, focusing on key factors influencing recast layer thickness (RLT). Results show that increases in electrode diameter and pulse width correlate positively with RLT. Elemental analysis indicates significant enrichment of O, C, and Cu in the recast layer, while Ni, Fe, and S are less prevalent. The recast layer also displays finer grain sizes and more precipitated phases, potentially compromising fatigue life. Surface morphology features flow-shaped bumps and microcracks, predominantly located in pits. Micro-hardness testing reveals a 22.3% increase in hardness in the recast layer (4.77 GPa) compared to the substrate (3.90 GPa). Additionally, the Young's modulus of the substrate (212 GPa) significantly exceeds that of the recast layer (177 GPa), raising concerns about fatigue performance. This analysis offers valuable insights for optimizing high-speed EDM parameters and evaluating the mechanical properties of machined Ni-based superalloys.