The effects of cutting environment on surface roughness and tool life in milling of AISI 4340

Abstract In this work, AISI 4340 alloy was machined using PVD tungsten multilayer TiAlN/AlCrN coated carbide inserts under two different cutting environments: cryogenic cooling using liquid nitrogen (LN) and dry cutting condition. The experiments were performed at varying cutting parameters of cutting speed: 200–300 m/min, feed rate: 0.15–0.30 mm/tooth, axial depth of cut: 0.3–0.5 mm, and radial depth of cut: 0.2-0.5 mm. Nine variations in tool life and surface roughness were observed when machining under different machining parameters of AISI 4340 at 32 HRC. The analysis includes the tool life and surface roughness as well as its relationship. Cryogenic LN showed significant improvement towards increasing the tool life to a maximum of 41.7% relative to dry cutting. The experiment showed that the cryogenic application was able to reduce the surface roughness by up to 43.9 % when compared to dry machining. Thus application of cryogenic cooling reduces tool wear, reduces cutting temperature and produces good surface quality which is believed to be the main factor causing an improvement compared to dry cutting.

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