Process-level Investigation and optimization of MQL-Assisted turning of Nimonic C-263 using coated carbide tools

Abstract

Turning of nickel-based superalloys such as Nimonic C-263 is challenging due to high cutting temperatures, rapid tool wear, and degradation of surface integrity. This study presents a systematic experimental investigation on the influence of lubrication environment (dry, flood, and minimum quantity lubrication–MQL) and tool coating (uncoated, CVD-coated, and PVD-coated carbide tools) on the turning performance of Nimonic C-263. Cutting temperature, cutting force, surface roughness, flank wear, chip morphology, and surface–subsurface integrity were evaluated under controlled machining conditions. The results reveal that dry turning generated severe thermal and tribological loads, resulting in high cutting temperature (~525 °C), poor surface finish (Ra ≈ 1.42 µm), and accelerated flank wear (VB ≈ 0.32 mm). Flood cooling provided only marginal improvement due to limited coolant penetration into the cutting zone. In contrast, MQL significantly enhanced machining performance, particularly when combined with PVD-coated tools, reducing cutting temperature by up to ~45%, flank wear by ~60%, and surface roughness to as low as 0.42 µm. Grey Relational Analysis and MOPSO–TOPSIS optimization identified the MQL–PVD combination at a cutting speed of 124 m/min and feed rate of 0.14 mm/rev as the optimal machining condition. FESEM analysis revealed suppression of white-layer formation (~1 µm) and refined dynamically recrystallized grains under MQL–PVD conditions, indicating improved surface integrity. The findings demonstrate that the synergistic interaction between MQL and PVD coatings establishes a stable and sustainable turning process for Nimonic C-263, offering reduced coolant usage, improved tool life, and enhanced surface quality for aerospace manufacturing applications. This work provides the first integrated assessment of lubrication–tool coating synergy, surface integrity evolution, and multi-objective optimization for CNC turning of Nimonic C-263.