Cryogenic and conventional machining using CVD-coated inserts to improve the surface characteristics of low-carbon steel alloy E350

The present study evaluates the effectiveness of dry and cryogenic machining environments while face milling carbon steel alloy E350, considering the surface integrity (SI) characteristics. The tests are performed using CVD-coated carbide inserts at three levels of cutting speed (150, 225, and 300 m/min), feed (0.05, 0.1, and 0.15 mm/tooth), and depth of cut (0.5, 1.0, and 1.5 mm). The primary SI features, roughness and microhardness, are evaluated. Furthermore, multi-criteria decision-making (MCDM) methods are employed to determine the best conditions for milling E350 alloy. Milling under cryogenic conditions reduced the roughness by 17% while increasing the microhardness by 14%, compared to dry milling conditions. The cutting speed significantly impacted the surface microhardness (92.2%–dry, 95.3%–cryogenic), and the feed had a greater impact on surface roughness (53.3%–dry, 67.5%–cryogenic). Furthermore, X-ray diffraction (XRD) pattern comparison provided more evidence for different levels of work hardening in milled surfaces compared to the polished as-cast material surface. Evaluation based on Distance from Average Solution (EDAS) and Grey Relational Analysis (GRA) methods showed identical outcomes, with optimal milling conditions for improved SI pegged at a cutting speed of 150 m/min, depth of cut of 1.5 mm, and feed of 0.05 mm/teeth.