CBN-WC-10Co刀具材料的电火花线切割机理

On Cutting Mechanism of CBN-WC-10Co Composite Cutting Tool Material with WEDM

采用电火花线切割方法对CBN-WC-10Co刀具材料进行了线切割加工实验,利用带能谱分析的扫描电子显微镜(SEM)观察了切割试件截面和表面的显微形貌并进行了成分分析。从微观角度分别研究了CBN颗粒和硬质合金基体的材料去除机理,分析了CBN-WC-10Co刀具材料的电火花线切割热损伤情况。研究结果表明:CBN-WC-10Co刀具材料的电火花线切割材料去除机理主要是通过放电通道产生的高温使材料局部区域熔化或者气化,在放电爆炸力作用下被抛出熔池,同时放电爆炸力使部分CBN颗粒直接从硬质合金基体脱落,形成凹坑;黏结剂金属钴因其导电性好、熔点和沸点低而容易被过量去除,导致WC颗粒因失去支撑结构而从表层脱落,且放电通道内产生的爆炸冲击波也会造成WC边缘局部碎裂。

Traditional machining was unsuitable for CBN- WC- 10Co composite cutting tool mate- rial due to its perfect toughness,high hardness and excellent abrasive resistance. WEI）M was an effec- tive method for the cutting tool material because of the unique advantages. Experiments on WEI）M of CBN - WC - 10Co composite cutting tool material were carried out. The surface properties of WEDM specimens were analyzed by scanning electron microscopy（SEM）. The material removal mechanism and thermal damage of CBN - WC - 10Co were discussed. The study indicates that the material remow al mechanism with WEDM is mainly due to the extremely high temperature generated by the dis- charge channel which makes the local material melt or gasification, and the products are thrown out under the action of discharge explosive force. Meanwhile, the discharge explosive force makes part of CBN particles directly fall off from the cemented carbide and forms pits. Cobalt is easy to over-removal for the good conductivity,low melting point and boiling point, and then WC particles always drop from the surface owing to the losing of the supporting structure. The shock wave generated in the discharge channel can also cause the appearance of the local crack at WC grains edge.