Modulation-Assisted Drilling of Inconel-718: Multi-variable Optimization Using Response Surface Method

Artikel i vetenskaplig tidskrift, 2025

The effectiveness of film cooling in inconel-718 turbine blades and compressor vanes is primarily regulated by the quality of small holes (< 5 mm) drilled on its periphery. However, as a difficult-to-machine material, the quality of these holes in terms of surface roughness is often compromised when processed using conventional drilling, leading to ineffective cooling and ultimately reducing its service life. In the present study, we have demonstrated the capability of relatively new and sustainable modulation-assisted drilling (MAD) technology to drill superior quality holes in inconel-718. This was achieved by multi-variable optimization of the process parameters, i.e., drill tool diameter (DD), feed rate (FR), and spindle speed (SS), using the response surface method. For this, low-frequency vibrations (frequency, fm < 1000 Hz and amplitude, 2A < 150 µm) were superimposed on the drill tool using the Tribo-MAM® tool holder (patented device of M4 Sciences) during the drilling experiments. The optimal window was obtained by comparing three decisive output factors–drill tool wear, generated thrust force, and the surface roughness of the holes, investigated over a range of input parameters, i.e., DD (1.5, 2.0, 2.5, 3, and 3.5 mm), FR (0.0035, 0.0095, 0.0155, 0.0215, and 0.0275 mm/rev), and SS (2000, 2200, 2400, 2600, and 2800 rpm). In addition, conventional drilling was also performed at the same set of machining parameters to compare the efficacy of MAD. The obtained results showed the reduction of tool wear, thrust force, and surface roughness by 36, 18, and 49%, respectively, during MAD in comparison to its conventional counterpart. This improvement is primarily attributed to the discrete cutting mechanism resulting from the periodic disruption of tool-workpiece contact. This enhances lubrication, thereby facilitating the efficient removal of discrete chips and contributing to a desired lower surface roughness. The overall superior performance of MAD presented in the current study encourages its widespread industrial use towards precision and sustainable manufacturing.