Multiscale mechanism for electromagnetic-assisted diamond imprinting of nickel-based alloy

The micro/nano machining of nickel-based alloys encounters challenges such as springback and subsurface damage, due to their high hardness, low thermal conductivity, and superior wear resistance. Existing additive and subtractive micro/nano machining technologies struggle to fabricate complex microstructured surfaces on nickel-based alloys with high precision and low damage. This study proposes a novel electromagnetic-assisted diamond imprinting (EADI) technology, a non-additive and non-subtractive machining technology, to produce microstructures on nickel-based alloys. It applies high-frequency alternating electromagnetic fields to induce dislocation evolution through Joule heating and electron wind effects in diamond imprinting. A multiscale (micro-meso-macro) electromagnetic field-CPFEM-DDD coupling model is developed to study the generation mechanisms of surface and subsurface in EADI. Traditional diamond imprinting (TDI) and EADI experiments are conducted on GH4169 to verify the developed multiscale model and investigate the influences of electromagnetic parameters on the machining precision of microstructures and evolution of subsurface. The experimental results show that EADI effectively improves the machining precision of microstructures with a maximum reduction of 61.4% in springback compared with TDI. And the depth-dependent effect of springback suppression in EADI increases with the increasing of current density and temperature. Simultaneously, the assistance of electromagnetic field in diamond imprinting not only generates thicker refined-grain layer but also induces lamellar subgrain structures in the subsurface. This study provides a new method for the fabrication of high-precision microstructures and for the control of material properties on nickel-based alloys, as well as a deeper understanding on surface and subsurface generation mechanisms in electromagnetic-assisted machining.