Performance analysis of conventional and high-feed turning tools in machining the thermally affected zone after plasma arc cutting of low carbon manganese-alloyed steel

Abstract

The service life of cutting tools significantly affects machining costs. Establishing end-of-life criteria is crucial to mitigate wear effects on part quality, machine integrity, and maximize tool utilization. This is particularly important in machining operations with materials featuring numerous surface defects, as observed in those processed by prior thermal cutting operations, leading to accelerated tool wear rates. This study compares tool life and wear mechanisms in conventional and high-feed turning of low carbon manganese-alloyed steel bushes, previously profiled by plasma thermal cutting. Machinability tests utilized Class P carbide tools with triangular geometry for conventional turning and rhombic geometry for high-feed turning, both coated for enhanced performance. Tool's end-of-life criterion was established per ISO 3685 standard. The machining parameters adopted include a standard cutting depth of 1.5 mm, varying cutting speeds (140, 160, and 200 m/min) and feed rates (0.2; 0.3; 0.4 mm/rev for conventional turning, and 0.5; 0.75; 0.82 mm/rev for high-feed turning). Analysis involved assessing tool wear rates by observing flank wear and analyzing it using scanning electron microscopy and energy-dispersive spectroscopy techniques. Machined surface quality was quantified by roughness measurements. Metallographic characterization of bushes post-cutting indicated thermal cutting effects on the cutting edge's microstructure, microhardness, and residual stress. Machinability test results showed superior wear resistance in the high-feed turning tool (wear rate about 13 % lower). Surface finish evaluation demonstrated that, when isolating the effects of tool geometry and feed rate, the average surface roughness increased at a similar rate with tool wear for both conventional turning and high-feed turning. Identical wear mechanisms were observed: abrasive on the flank and adhesive on the rake face. Thus, the superiority of high-feed turning over conventional turning is established under the evaluated machining conditions.