Time-based study of tool wear in dry turning of Ti-6Al-4 V with coated and bare WC-Co tools

Dry machining of Ti-6Al-4 V remains a major challenge due to its low thermal conductivity and high mechanical strength, which accelerate tool wear and deteriorate surface finish. While many studies focus on optimizing cutting parameters, limited research exists on the time-based progression of tool wear and its direct influence on surface quality under constant dry cutting conditions. This study aims to bridge that gap by evaluating the wear behavior and surface finish outcomes of coated and uncoated carbide tools under identical machining parameters. Four CNMG 120408 carbide inserts were examined: (1) bare WC–Co, (2) textured + TiAlN-coated, (3) TiAlN-coated, and (4) bare + TiN-coated tools. Both continuous and discontinuous cutting strategies were employed, with tool wear (flank wear, Vb) and surface roughness measured at fixed intervals of 4 minutes. The results demonstrated a linear increase in wear and surface roughness with time. After 16 minutes of machining, the bare tool reached a flank wear of 203.8 µm, while the TiAlN- and TiN-coated tools exhibited severe wear (~397.3 µm). In contrast, the textured + TiAlN-coated tool maintained flank wear below 200 µm even after 24 minutes, demonstrating enhanced coating adhesion and thermal stability. In contrast, the textured + TiAlN-coated tool maintained flank wear below 200 µm even after 24 minutes, demonstrating enhanced coating adhesion and thermal stability. Among all tools, the textured + TiAlN-coated insert showed the lowest wear progression and nearly 35% better surface quality, attributed to enhanced coating adhesion and thermal resistance. Although the bare + TiN tool initially performed better than the bare + TiAlN insert, EDX analysis revealed early onset of inter-alloy diffusion in the TiN coating. This study emphasizes the importance of surface texturing and advanced coatings in enhancing tool longevity and machining quality, offering valuable insights for sustainable dry machining of titanium alloys.