Title: Evaluation of the effects of tool geometry on tool wear and surface integrity in the micro drilling process for Inconel 718 alloy
Authors: Muhammad Imran; Paul T. Mativenga; Sathish Kannan
Addresses: Manufacturing and Laser Processing Research Group, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Sackville St, M13 9PL, UK. ' Manufacturing and Laser Processing Research Group, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Sackville St, M13 9PL, UK. ' Manufacturing Technology Group, Wilmore Road, Derby DE24 8BJ, Rolls Royce Plc, UK
Abstract: Mechanical micro machining of nickel-based super alloys is challenging due to limited tool life, but promising in terms of quality of machined component. Despite present advances in micro machining, milling and drilling tool designs still need to be tailored to specific applications. The study reported here investigated the effect of different tool geometry parameters on tool wear and workpiece surface integrity in micro drilling of nickel-based super alloy. For the cutting tests, 0.5 mm diameter twist drills were used to drill through holes on a 2.5 mm plate. Analysis of variance (ANOVA) was used to evaluate the statistical significance of drill point angle and helix angle and their interactions on tool wear and burr size. Burr formation mechanism was investigated supported by material microstructure evaluations. The results show that a complex relationship (interaction) exists between point angle and helix angle which drive tool wear, burr formation and surface and subsurface deformations. An optimum value of 150° point angle and 40° helix angle results in reduced tool wear rate, burr formation and subsurface plastic deformation. The results also show that subsurface deformation is influenced by the size effect. The study defines the significance of tool geometry on the micro drilling performance for nickel-based super alloys.
Keywords: tool geometry; micro drilling; tool wear; burr formation; nickel alloys; micromachining; surface integrity; superalloys; twist drills; burr size; microstructure; plastic deformation; subsurface deformation.
International Journal of Machining and Machinability of Materials, 2012 Vol.11 No.3, pp.244 - 262
Received: 07 Sep 2010
Accepted: 09 Feb 2011
Published online: 23 Aug 2014 *