Tribological characteristics of SiALON ceramic inserts during sustainable machining of Inconel 625 based on comprehensive chip morphology analysis

The effectiveness of SiALON ceramic inserts during MQL machining of Inconel 625 under different depth of cut (DoC) – 1.00, 1.25, and 1.5 mm - is investigated through tool wear and chip morphology analysis, and compared with dry and flood conditions. Under MQL conditions, the SiALON tools encounter lower wear and edge chipping than both dry and flood conditions for all DoC. The chip serration height, pitch between serrations, adiabatic shear bandwidth (ASB) in the primary as well as the secondary shear zone, and segmentation height on the free surface of the chip are lower for MQL conditions than dry and flood conditions for all DoC. The shear affected zone (SAZ) or transition layer is noticed near the ASB under dry and flood conditions. More transverse shear lines are seen in the vicinity of the ASB under dry and flood conditions for 1.25 mm DoC, indicating a higher degree of plastic deformation. While coarse grains are present near the ASB, the absence of SAZ in the vicinity of the ASB under MQL conditions points to improved cutting zone lubrication and chip removal under MQL. For the first time, the variation in the chip segmentation along the chip width is studied and is also found to be minimal for MQL as compared to dry and flood conditions pointing to the superior penetration capability of MQL deep into the cutting zone.