Study On Tool Wear Mechanism During Precision Cutting Isotropic Pyrolytic Graphite

As a new kind of high performance graphite material, isotropic graphite has a series of advantages, such as low density, good thermal shock resistance, low thermal expansion coefficient, good self-lubrication, low and stable friction coefficient. It has been widely used in precision machinery, shipbuilding, aerospace and other fields. However, due to the high hardness and brittleness of isotropic pyrolytic graphite, it easy to produce chipping, dimples and other processing quality problems during machining, the chips of isotropic pyrolytic graphite with higher abrasive, it will cause severe tool wear in cutting process. These factors have restricted the further popularization and application.This paper aims at tool wear mechanism during cutting isotropic pyrolytic graphite. By using isotropic pyrolytic graphite turning test, analyze the wear morphology and wear process of hard alloy cutting tool, polycrystalline diamond tool and single crystal diamond tool respectively, study the tool wear mechanism. In addition, graphite transfer film formation mechanism during polycrystalline diamond tool cutting isotropic pyrolytic graphite was studied.First, by using hardness indentation test, the hardness of isotropic graphite was analyzed, and the change of isotropic graphite material hardness under different load was studied, the size effect of material hardness value was analyzed.Second, experiments with same cutting parameters and tool geometric parameters turning of isotropic pyrolytic graphite were conducted out using hard alloy cutting tool, polycrystalline diamond tool and single crystal diamond tool respectively. Cutting distance was defined as the only reference amount, tool wear morphology and tool wear process under different cutting distance were observed, and the surface roughness of specimen was detected, comprehensive tool wear morphology, isotropic pyrolysis graphite material characteristics, tool material characteristics and other factors, tool wear mechanism were analyzed.Finally, according to transfer phenomenon during polycrystalline diamond tool cutting isotropic pyrolytic graphite, the formation process and formation mechanism of graphite transfer film were research, the key factors of influence graphite transfer film quality were analyzed, the effects of graphite transfer film on surface machined quality and cutting force were discussed.