A comparative study on performance of multilayer coated and uncoated carbide inserts when turning AISI D2 steel under dry environment

The present work deals with a comparative study on flank wear, surface roughness, tool life, volume of chip removal and economical feasibility in turning high carbon high chromium AISI D2 steel with multilayer MTCVD coated TiN/TiCN/Al₂O₃/TiN] and uncoated carbide inserts under dry cutting environment. Higher micro hardness of TiN coated carbide samples (1880 HV) compared to uncoated carbide (1430 HV) is observed and depicts better resistance against abrasion. The low erosion rate was observed in TiN coated insert compared to uncoated carbide. The tool life of TiN coated insert is found to be approximately 30 times higher than the uncoated carbide insert under similar cutting conditions and produced lower surface roughness compared to uncoated carbide insert. The dominant wear mechanism was found to be abrasion and progression of wear was steady using multilayer TiN coated carbide insert. The developed regression model shows high determination coefficient i.e. R² = 0.977 for flank wear and 0.94 for surface roughness and accurately explains the relationship between the responses and the independent variable. The machining cost per part for uncoated carbide insert is found to be 10.5 times higher than the multilayer TiN coated carbide inserts. This indicates 90.5% cost savings using multilayer TiN coated inserts by the adoption of a cutting speed of 200 m/min coupled with a tool feed rate of 0.21 mm/rev and depth of cut of 0.4 mm. Thus, TiN coated carbide tools are capable of reducing machining costs and performs better than uncoated carbide inserts in machining D2 steel.