Sustainability assessment of cutting fluids for flooded approach through a comparative surface integrity evaluation of IN718

Abstract

The surface integrity (SI) of IN718 is affected by the excessive heat generation during the machining operation. While milling of Ni-based superalloys, use of traditional flooded strategy is encouraged though, due to its superior heat dissipating capacity. However, the cutting lubricants that have been conventionally employed during this approach are subjected to several concerns in regard to sustainability. Instead, vegetable ester-based biodegradable oil, as eco-friendly cutting oil, is one of the suggested choices formerly employed with minimum quantity lubrication (MQL). Therefore, this experimental investigation tries to combine the advantages of flooded cooling method with sustainable cutting fluid to review its impact on the SI of IN718 at first. It then focuses on establishing a comparison with conventional wet and dry approaches to characterize the machinability and the SI. The milling was carried out under the 450 Mecagreen vegetable ester-based biodegradable oil-assisted flooded condition, the Hocut WS8065 mineral oil-assisted flooded condition, and the dry condition. The three process variables, cutting speed (ν_c), feed per flute (ƒ_z), and axial depth of cut (a_p) were considered for all the three environments. The SI characteristics such as surface roughness (SR), surface topography, microhardness, microstructural alterations, white layer formation, grain refinement, and residual stresses were considered as the response variables. The experimental exploration is complemented with scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction analysis (XRD).