A new internal cooling system for a green tubular channel investigated for tool life in Hastelloy-B3 turning for MQL medium

Sustainable machining in difficult-to-turn material has been aggressively researched in recent days. In this context, the various cooling systems through MQL were developed as sustainable machining. The present study aims to propose and develop a new internal and external cooling system for the tool holder to study its effectiveness during the turning of Hastelloy-B3 (HB-3). Further, the novelty of the proposed design internal design (top and bottom on the insert) is to supply the fluid at the very near end of the cutting edge and the external design (rake and nose side) is to spray the cutting fluid at the bottom of the cutting edge. The proposed design has the modification only on the shim with a micro-milled groove of 2 mm for internal cooling system arrangement with a micro-hole at the bottom of the cutting edge. The proposed design has a copper tube placed in the 2 mm groove to supply a very small quantity of fluid i.e., a small quantity lubrication concept through the MQL system. Coconut oil as a fluid for the tool holder's cooling system under two conditions: external (TD1 Rake Side Spray, TD2 Nose Side Spray) and internal (TD3 Top on Fluid Flow Face, TD4 Bottom on Fluid Flow Face). The experimental results reveal that the TD4 condition improved the tool life by 12.9%, 32.6%, and 43% compared to other conditions. The improvement in tool life is attributed to improved tool-chip contact length by 38% and 28.5% and reduced cutting force by 9.7%. For condition TD4, in-depth surface hardness values of 11% and 17.6% reduced surface integrity. At tensile improvements of 23% and 42% and compressive stress improvements of 19.8% and 36.7% in the same conditions, residual stress was seen. The roughest surface was 21.5% at TD3. Thus, sustainable new cooling systems make other hard-to-turn materials machinable.