5. Conclusions
Wear behavior of CBN tool in cutting hardened steels is studied. It is found that tool life rises with the increase of cutting speed until a maximum is reached where it starts to decrease. In low speed cutting, abrasion is the main form of wear. When cut- ting speed is increased, a sticking layer is formed and remained on the tool face which protects tool face from wearing. At high cutting speed, the chip is transformed from continuous type to saw-tooth type. Friction force is increased accordingly, and the layer on tool face is abraded gradually. Since diffusion between work and tool materials becomes more severe at high cutting speed, the bond between the hard particles is weakened, and wear on the rake face is increased drastically. Together with the increase of crater wear, flank wear is increased.