Citation: Anwar, S.; Khan, N.A.; Khan, S.A.; Raza, S.F. One-Step High-Speed Finish Drilling of Inconel 718 Superalloy via Novel Inserts. Processes 2023, 11, 752. https:// doi.org/10.3390/pr11030752 Academic Editors: Jun Zhang, Kuo Liu and Hongguang Liu Received: 31 January 2023 Revised: 25 February 2023 Accepted: 27 February 2023 Published: 3 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). processes Article One-Step High-Speed Finish Drilling of Inconel 718 Superalloy via Novel Inserts Saqib Anwar 1 , Nauman Ahmad Khan 2 , Sarmad Ali Khan 2, * and Syed Farhan Raza 2 1 Industrial Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia 2 Department of Industrial and Manufacturing Engineering, University of Engineering and Technology, Lahore 54890, Pakistan * Correspondence: drsarmad@uet.edu.pk Abstract: Inconel 718 is considered the most widely adopted nickel-based superalloy, and drilling of this alloy is always challenging for researchers. Cemented carbide twist drills have been evaluated in the drilling of this alloy by changing the cutting environment or by varying the tool geometry. In the latter case, the cutting speed has been extended from 30 m/min to 60 m/min when drills are micro-textured or ground. In this study, contrary to cemented carbide twist drills, for the first time, inserts named stepped (central) and peripheral (wiper) are evaluated in the drilling of this alloy. The central insert is designed for balanced forces, while the peripheral is a wiper insert designed for better surface finish. Drilling experiments are conducted in flood cooling conditions with a 12 mm diameter twist drill equipped with novel stepped and wiper inserts at varying cutting speeds (25, 35, and 45 m/min) and feed rates (0.04, 0.06, and 0.08 mm/rev). At a cutting speed (Vc) of 25 m/min and feed rate (f ) of 0.04 mm/rev, 25 holes are drilled with roughness (Ra) values ranging from 0.40 μm to 0.60 μm, which represents a significant increase in the number of holes per drill and improved surface finish over to previous work. The new inserts showed almost three-fold longer tool life compared to a standard drill bit at a higher Vc of 45 m/min and 0.04 mm/rev f with an Ra between 0.22 μm to 0.43 μm, which is deemed acceptable for aerospace applications. In addition, minimal surface and sub-surface defects were observed, eliminating the need for a post-drilling finishing operation; therefore, a one-step drilling operation was achieved. Keywords: one-step drilling; Inconel 718; wiper inserts; central insert; tool life; surface quality 1. Introduction The usage of superalloys in an aerospace turbine engine is almost 50% of the total materials, and nickel alloy (Ni-alloy) shares account for ~40% [1]. Nickel-based superal- loys are the family of metallic alloys that the aerospace manufacturing industries have widely adopted, especially in structural components due to outstanding properties such as resistance to corrosion, fracture toughness, better yield and high-temperature strength. However, this alloy is in a category of difficult-to-machine materials is due to low thermal conductivity and greater susceptibility toward work hardening [2]. Among Ni- alloys, Inconel 718 is still the most widely consumed alloy. Compared to turning and milling, data on the drilling process is limited [3]. So far, conventional drilling methods have been found to be less effective and less productive; therefore, researchers have adopted various techniques to improve the machining efficiency for drilling Inconel 718. Previously, peck drilling [4] and pilot hole-making strategies [5] were also adopted by the researchers, but poor hole quality and low productivity, respectively, were the common problems associated with these approaches. A thorough summary of literature reviews on drilling of Inconel 718 in particular, and the machining of nickel alloys in general, is presented below for context building. Processes 2023, 11, 752. https://doi.org/10.3390/pr11030752 https://www.mdpi.com/journal/processes