Study On The Cutting Experiments And The Mechanism Of CBN-WC-Co Composite Used For Cutting Tools

cBN-WC-Co composite cutting tool material is fabricated by spark plasma sintering, which perfectly integrates the high hardness of cBN and the good toughness of cemented carbide. But the advantages lead to the difficult of the composite material. Wire electrical discharge machining(WEDM) and laser processing are the modern special processing technology with the characteristics of high precision and good surface quality. They belong to the non-contact processing, and has nothing to do with the processing and mechanical properties of the object. So they are the effective methods processing cBN-WC-Co composite cutting tool materials. In this study, the cutting experiment is conducted by wire electrical discharge machining(WEDM) and laser processing, respectively. The cross profile and surface microstructure of the specimens were analyzed by scanning electron microscopy(SEM) and X-Ray Diffraction(XRD). Based on the results the cutting and damage mechanism are researched. The achievements of this article are as following:(1) Experiments on WEDM of cBN-WC-10 Co composite cutting tool material are carried out. The study indicates that the material removal mechanism with WEDM is mainly due to the extremely high temperature generated by the discharge 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 form 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.(2) Laser cutting of cBN-WC-10 Co composite was carried out using Nd: YAG laser. The cutting characteristics, the micro-harndess and the phase composition of the cut surface and the cross section of the workpiece were observed by scanning electron microscope(SEM), micro hardness tester and x-ray diffractometer(XRD). It is found that higher laser power 100 W has a smoother cut surface with a less heat affected zone in comparison with lower laser power 50 W. There are no micro-cracks in the cross-section for the latter and cBN particles ever if around the cut surface still have a good bonding with WC-Co matrix. The phase transformation from cBN to hBN is observed on the heat affected zone. Micro-hardness on the sub-surface decreases because of the destruction of the binder Co bridging cBN and WC particles, phase transformation of hBN. A discussion is provided to reveal the material removal mechanisms.(3) As a result of the good surface quality, the cBN-WC-10 Co fiber micro blades with cross-sectional dimensions of 0.8×0.8×10mm are fabricated by the WEDM.