Performance comparison between internally cooled tools and flood cooling during grey cast iron turning

Abstract

High heat generation with the consequent increase in temperature is still a limiting factor for productivity and quality in machining processes, mainly because it strongly affects the tool's life and the quality of the workpiece. Cutting fluids in abundance (CFA), often named flood cooling, is the standard machining cooling technique used industrially. However, CFA poses significant environmental hazards while incurring mounting manufacturing costs. To address this, the current paper focuses on a comprehensive performance evaluation of a novel internally cooled tool (ICT) while machining grey cast iron - GCI. Designed and built in-house, the ICT system can internally circulate the coolant through a specifically modified insert, effectively removing the heat from the interface. The machining tests followed a full factorial Design of Experiment- DoE (23) with two quantitative input variables, the depth of cut (doc) (1.0 and 2.0 mm) and the cutting speed (vc) (100 and 150 m/min) and one qualitative variable, the cutting atmosphere (ICT or CFA). The feed rate was maintained constant at 0.1 mm/rev. The response variables were cutting force, tool wear mechanisms, and surface integrity in terms of roughness, microhardness, and microstructure. The main results indicated that, compared to CFA, ICT increased cutting force by 42 %. ICT also increased peak microhardness by 22 % at 500 μm from the top surface. It also induced grain modification at 4 mm depth, indicating that ICT caused a work-hardening effect in the subsurface. These results were an indication that ICT could effectively take heat away at the cutting zone. Statistical analysis on surface roughness showed that the significant variables were the cutting speed and its interaction with the atmosphere, where increasing the cutting speed was the dominant parameter. ICT reduced the roughness at higher cutting speeds, as opposed to CFA. The predominant wear mechanisms were adhesion and abrasion, along with plastic deformation for both ICT and CFA. Finally, the ICT system showed to be a promising eco-friendly technique with high cooling capacity, presenting some advantages compared to CFA, with similar machining performance.