Effects of cutting fluid with different pressures and jetting paths on machined surface integrity in cutting compacted graphite iron: An experimental study

Abstract

Compacted graphite iron is one of the existing structural materials for automobile engines that is difficult to machine using the conventional machining method. This article focuses on the effects of cutting fluid with different pressures and jetting paths on machined surface integrity in the machining of compacted graphite iron. The machined surface integrity is compared between dry cutting and 6 MPa wet cutting at cutting speeds of 100–500 m/min and the influences of the cutting fluid jetting paths (pouring, 2–6 MPa) along the tool flank face and rake face on the machined surface integrity are evaluated. Microstructure, roughness, work hardening, and residual stresses of the machined surface are also analyzed. The results suggest that cutting fluid can reduce surface defects and improve the machined surface finish. Of note, the roughness reduction effect decreases with an increase in fluid pressure; the roughness Ra of 6 MPa wet cutting with the cutting fluid jetting along the flank face is 0.2–1.56 µm lower than that seen with dry cutting in the cutting speed range of 100–500 m/min. The degree of hardening in 6 MPa wet cutting is 11%–19% lower than in dry cutting, and cutting fluid enhances the formation of residual compressive stress in the machined surface which reaches its maximum at 3 MPa.