Abstract
In this paper, the influences of cutting speed, depth of cut, feed, workpiece hardness (51, 55, 58, 62, and 65 ± 1 HRC), and nose radius on surface integrity in finish dry hard turning (FDHT) of the hardened tool steel AISI D2 by utilizing the polycrystalline cubic boron nitride (PCBN) inserts were experimentally investigated. Experimental results showed that the ploughing effect, serious squeeze, and elastic deformation have more significant on the surface roughness than those black fusion welding materials and side flows, and the surface roughness values are in the range of 0.34–0.86 μm between 150- and 301-m/min cutting speeds and totally attains a surface finish of grinding. The surface roughness is not very sensitive to the depth of cut in the range from 0.10 to 0.25 mm. The “residual cutting” materials, material plastic deformation, and even cohesion in the machined surface and cold welding effect do occur and hence influence on the surface integrity. The tiny grooves, severe plastic flow, and extensive material flows at lower feeds have significant influence on the surface integrity. The subsurface damages produced by the turning process also do occur and become severer at the larger feeds due to the localized stretch, plastic deformation, and even dilacerations of subsurface material induced by the friction from the tool flank face. The thermal softening, serious material side flows, and squeezing have significant effect on surface integrity when FDHT of the hardened tool steel AISI D2 at different hardness levels. And the heat effect is greater than the geometry effect as the nose radius attains a certain value.
Published Version
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