Evaluation of the effects of tool geometry on tool wear and surface integrity in the micro drilling process for Inconel 718 alloy

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.