Performance of uncoated/coated carbide inserts during MQL (sunflower oil) assisted machining of Inconel 718 superalloy

In the present work, the machinability of difficult-to-cut Inconel 718 aerospace superalloy is studied under vegetable oil-based minimum quantity lubrication (MQL) in consideration with different cutting tool materials. MQL environment is produced by supplying air-oil mist in which biodegradable sunflower oil is used. In comparison with uncoated carbide tool, performances of MT-CVD multi-layered TiCN-Al2O3-TiOCN coated and MT-CVD double-layered TiCN-Al2O3 coated carbide inserts are assessed during longitudinal turning of Inconel 718. Coating materials are characterized by average thickness of individual coating layer, elemental composition and frictional coefficient. With constant feed and depth-of-cut (0.1 mm/rev and 0.25 mm respectively), quantitative responses such as tangential cutting force, tool-tip temperature and width of tool flank wear are considered as machinability assessment criteria under varied cutting speed condition (v = 60, 80, 100 and 130 m/min). Notable reduction in tool-tip temperature (25.6% and 30.4%) and reduction in cutting forces (10.6% and 22.3%) are obtained for coated tool [T1] and coated tool [T2] respectively, when compared to uncoated counterpart. Detailed analysis on tool wear modes is carried out followed by chip's macro/micro-morphology. Apart from chip's micro-morphological parameters, morphologies of chip's back and free surfaces and chip microhardness are studied.