Experimental Study on Cutting Ductile Iron with Coated PcBN Inserts
In this paper,a variety of coated PcBN inserts were used to turn test on nodular cast iron QT500-7,and the processing life,wear patterns and mechanism and coating protection mechanisms of uncoated and different coated PcBN inserts were studied.The test results show that the machining life of the coated PcBN insert is improved under the same cutting conditions.The coated PcBN insert with CVD α-Al2O3 has the longest processing life,followed by the PcBN insert coated with PVD TiAlSiN,and then the PcBN insert coated with PVD TiAlN with the shortest processing life.The wear patterns of the PcBN insert mainly include front insert wear,back insert wear,micro-edge breakage and damage.The wear mechanisms include not only mechanical wear but also adhesive wear,diffusion wear,and oxidation wear.These wear mechanisms occur simultaneously and affect each other.As a chemical and thermal barrier,the coating can form an"isolation layer"between the PcBN insert and the workpiece,reducing mechanical wear,diffusion wear,and bonding wear between the insert and the workpiece,and effectively preventing oxidative wear,thereby avoiding premature micro-breakage or breakage of the insert and improving its processing life.
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