International Journal of Advanced Engineering Application

Optimisation of Turning Parameters for Inconel 718 Superalloy Using Taguchi–Grey Relational Analysis and Response Surface Methodology Under Dry, Flood, and Minimum Quantity Lubrication Conditions

Author(s):Meenakshi Rawat, Bikash Gogoi

Affiliation: Department of Mechanical Engineering, Rungta College of Engineering and Technology, Bhilai, Chhattisgarh, India Department of Mechanical Engineering, Assam Don Bosco University, Guwahati, Assam, India

Page No: 134-140

Volume issue & Publishing Year: Volume 3, Issue 5, May 2026

Journal: International Journal of Advanced Engineering Application (IJAEA)

ISSN NO: 3048-6807

DOI: https://doi.org/10.5281/zenodo.20304361

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Abstract:
Inconel 718, a precipitation-hardened nickel-based superalloy, is extensively employed in gas turbine discs, combustion chambers, aerospace fasteners, and nuclear reactor components owing to its exceptional retention of mechanical properties at elevated temperatures (up to 700°C), outstanding fatigue resistance, and superior corrosion behaviour. These attributes, however, impose severe machinability challenges: high cutting zone temperatures (often exceeding 600°C at practical cutting speeds), rapid tool wear through thermally activated diffusion and adhesion mechanisms, built-up edge (BUE) formation, and pronounced work-hardening of the machined surface that accelerates subsequent tool wear in adjacent cuts. The selection of optimal machining parameters — cutting speed (Vc), feed rate (f), and depth of cut (ap) — and an appropriate cooling-lubrication strategy are therefore critical determinants of process economy and surface quality in Inconel 718 turning. This study presents a comprehensive experimental investigation of Inconel 718 turning using TiAlN-PVD-coated carbide inserts (ISO CNMG 120408) under three lubrication conditions: dry, flood coolant, and Minimum Quantity Lubrication (MQL, 50 mL/hr soybean-based ester oil at 6 bar nozzle pressure). A Taguchi L27 orthogonal array was employed with three levels each of Vc (80, 120, 160 m/min), f (0.05, 0.15, 0.25 mm/rev), and ap (0.5, 1.0, 1.5 mm). Response variables include cutting force Fc, surface roughness Ra, flank wear VBmax, and cutting zone temperature T measured by embedded K-type thermocouple. Grey Relational Analysis (GRA) converts the multi-response optimisation problem to a single grey relational grade. Response Surface Methodology (RSM) using a Box-Behnken design validates the optimal parameter settings and develops predictive regression models for Ra and VBmax. Results demonstrate that MQL reduces Ra by 18.4% and VBmax by 22.1% relative to dry cutting at optimal conditions (Vc = 120 m/min, f = 0.10 mm/rev, ap = 0.5 mm). The Taguchi-GRA optimal combination (Vc = 120 m/min, f = 0.05 mm/rev, ap = 0.5 mm, MQL) simultaneously minimises all four responses, with ANOVA confirming feed rate as the dominant factor for Ra (P-contribution 58.4%) and cutting speed as dominant for VBmax (P-contribution 46.8%).

Keywords: Inconel 718, turning, Taguchi, Grey Relational Analysis, Response Surface Methodology, MQL, surface roughness, tool wear, TiAlN coating, cutting force, machinability

Reference:

• [1] Deng, J. (1989). Introduction to grey system theory. The Journal of Grey System, 1(1), 1–24.
• [2] Ezugwu, E. O., & Wang, Z. M. (1997). Titanium alloys and their machinability — a review. Journal of Materials Processing Technology, 68(3), 262–274.
• [3] Krishnamurthy, G., Ramesh, S., & Jain, V. K. (2018). Machinability of Ti-6Al-4V under ester-based MQL: Tool life and surface integrity. International Journal of Advanced Manufacturing Technology, 94(9–12), 3643–3656.
• [4] Verma, A., & Singh, R. K. (2021). Multi-response optimisation in CNC turning of Inconel 625 using Taguchi-GRA. Journal of the Institution of Engineers (India): Series C, 102(4), 879–891.
• [5] Patel, S. C., Desai, D. A., & Patel, B. C. (2020). RSM-based modelling of surface roughness in CNC turning of EN31 steel. Materials Today: Proceedings, 28(3), 2221–2226.
• [6] Rawat, M., & Arora, G. (2019). Dry and MQL machining of Inconel 718: A comparative study of tool wear and chip morphology. Tribology International, 138, 276–288.
• [7] Gogoi, B., & Bora, B. J. (2022). Performance evaluation of MQL with nanofluids in turning of Inconel 718. Journal of Manufacturing Processes, 74, 182–196.
• [8] Thakur, A., & Gangopadhyay, S. (2016). State-of-the-art in surface integrity in machining of nickel-based super alloys. International Journal of Machine Tools and Manufacture, 100, 25–54.
• [9] Devillez, A., Schneider, F., Dominiak, S., Dudzinski, D., & Larrouquère, D. (2007). Cutting forces and wear in dry machining of Inconel 718 with coated carbide tools. Wear, 262(7–8), 931–942.
• [10] Jawaid, A., Koksal, S., & Sharif, S. (2001). Cutting performance and wear characteristics of PVD coated and uncoated cemented carbide tools in face milling Inconel 718 aerospace alloy. Journal of Materials Processing Technology, 116(1), 2–12.
• [11] Ducros, C., Benevent, V., & Sanchette, F. (2003). Deposition, characterization and machining performance of multilayer PVD coatings on cemented carbide cutting tools. Surface and Coatings Technology, 163–164, 681–688.
• [12] Nouari, M., & Molinari, A. (2005). Experimental verification of a diffusion tool wear model using a 42CrMo4 steel with an uncoated cemented tungsten carbide at various cutting speeds. Wear, 259(7–12), 1151–1159.