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<p>The electrical discharge alloying (EDA) process refines the grain structure through an exothermic reaction between nickel and Ti–6Al–4V, generating back pressure that restricts plasma expansion and breaks carbon chains, thereby inducing phase transformations with a crystallographic melt-spun structure. The strain rate interaction between titanium and nickel results in sequential melting followed by rapid cooling beyond the critical temperature, leading to thermoelastic martensitic transformation with a twinned microstructure. The nickel layer on titanium limits excessive material transfer and enhances mechanical performance, evidenced by a reduction in surface roughness to approximately 2&#xa0;µm and an increase in hardness to 845 HV<sub>0.5</sub>—more than twice that of the substrate (275 HV<sub>0.5</sub>). Furthermore, the alloyed surface exhibits significantly reduced specific wear under extreme sub-zero conditions (− 2&#xa0;°C), with values of 1.10 × 10⁻<sup>5</sup> N/mm<sup>2</sup> and a friction coefficient of 0.1, compared to 2.93 × 10⁻<sup>5</sup>&#xa0;N/mm<sup>2</sup> and 0.3 for the substrate. The formation of vapor-filled cavities due to cavitation pressure in the liquid medium contributes to a reduction in liquid pressure, indicating self-lubricating behavior. These results demonstrate the potential of EDA-processed Ni–Ti alloyed surfaces for space technology and low-orbital material applications.</p>

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Electrical Discharge Nickel Alloying on Ti–6Al–4V: Mechanism and Material Processing for Space Application

  • 期刊论文

  • 发表日期：

    2025年12月17日

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  • Ilangovan Arun,
  • Igor Velkavrh,
  • R. Uma Rani,
  • Sivakumar Annamalai,
  • C. Yuvaraj

摘要

The electrical discharge alloying (EDA) process refines the grain structure through an exothermic reaction between nickel and Ti–6Al–4V, generating back pressure that restricts plasma expansion and breaks carbon chains, thereby inducing phase transformations with a crystallographic melt-spun structure. The strain rate interaction between titanium and nickel results in sequential melting followed by rapid cooling beyond the critical temperature, leading to thermoelastic martensitic transformation with a twinned microstructure. The nickel layer on titanium limits excessive material transfer and enhances mechanical performance, evidenced by a reduction in surface roughness to approximately 2 µm and an increase in hardness to 845 HV0.5—more than twice that of the substrate (275 HV0.5). Furthermore, the alloyed surface exhibits significantly reduced specific wear under extreme sub-zero conditions (− 2 °C), with values of 1.10 × 10⁻5 N/mm2 and a friction coefficient of 0.1, compared to 2.93 × 10⁻5 N/mm2 and 0.3 for the substrate. The formation of vapor-filled cavities due to cavitation pressure in the liquid medium contributes to a reduction in liquid pressure, indicating self-lubricating behavior. These results demonstrate the potential of EDA-processed Ni–Ti alloyed surfaces for space technology and low-orbital material applications.