Influence of WC–Co cutting tool insert modifications on the machinability of Inconel 718

Abstract

This study examines how controlled microstructural modification of WC–Co cutting tool inserts via WC grain size, sintering temperature, and Nano-Al₂O₃ reinforcement governs the mechanical properties and machining performance during the turning of Inconel 718. Four insert grades were investigated: coarse (2000–3000 nm), medium (1000–2000 nm), and fine (500–1000 nm) WC–8 Co compositions sintered at 1375 °C and 1450 °C, along with a fine-grained WC–Co composite reinforced with 0.5 wt.% Nano-Al₂O₃ processed under identical conditions. Grain refinement increased hardness and wear resistance by limiting the binder mean free path, whereas elevated sintering temperature promoted WC grain coarsening, leading to reduced cutting-edge stability despite improved densification. Among all samples, the fine-grained insert sintered at 1450 °C exhibited the most balanced performance, achieving a hardness of 1676 HV30, fracture toughness of 9.6 MPa·m^1/2, minimum cutting force of 265 N, and extended tool life of 12 min. Nano-Al₂O₃ reinforcement further enhanced fracture toughness (12.2 MPa·m^1/2) via crack deflection and bridging; however, it reduced hardness and accelerated tool wear at higher cutting speeds. Unlike prior studies that typically isolate compositional or processing effects, this work establishes a direct, experimentally validated microstructure–property–machining performance linkage, enabling identification of optimal WC–Co insert architectures for machining high-temperature nickel-based superalloys.