Multi-objective optimization using Grey Relational Analysis (GRA) for the high-speed orthogonal turning of heat-treated alloy steelSaimaYaqoobauthorJaharah A.GhaniauthorNabilJouiniauthorAfifah Z.JuriauthorChe Hassan CheHaronauthorThis study concerns the high-speed machining of heat-treated AISI 4340 alloy steel using multi-layer coated carbide tools in dry condition. Taguchi L₁₈ experimental design is selected to accommodate the machining parameters, which includes coated carbide tool type (T=Physical vapor deposition (PVD) and Chemical Vapor Deposition (CVD), cutting speed (V=300-400m/min), feed rate (F=0.05-0.15mm/rev), and depth of cut (DOC=0.1-0.3mm). The study examined how input variables affect tool life and surface roughness using the Taguchi signal-to-noise (S/N) ratio. Additionally, Grey Relation Analysis (GRA), a multi-objective optimization method, was used to identify the best parameter settings for improved machining performance. The results showed that the CVD tool achieved the highest tool life of 14.75 minutes, while the PVD tool delivered the lowest surface roughness of 0.276 µm. Using the GRA method, the optimal machining parameters (T=CVD, V=300 m/min, F=0.05 mm/rev, DOC=0.1 mm) were identified and validated through confirmation tests. ANOVA on the grey relation grade (GRG) revealed that feed rate had the greatest impact on tool life and surface roughness, followed by tool type, cutting speed, and depth of cut. © 2024, Malaysian Tribology Society (Mytribos). All rights reserved.2024Malaysian Tribology Society (Mytribos)Article