The effect of temperature on the hardness of polycrystalline cubic boron nitride cutting tool materials

Polycrystalline cubic boron nitride (PcBN) cutting tools are used for the machining of ferrous alloys at high speeds and temperatures where the use of diamond is precluded due to graphitisation. To accurately predict the life of these tool materials it is necessary to understand inter alia the deformation and relevant mechanisms that occur at the temperatures and pressures associated with cutting. This paper uses Vickers indentation as a means of assessing the role of cBN content, binder phase and cBN grain size on the mechanical properties of a number of polycrystalline cubic boron nitride materials. It will be shown that as experimental temperatures increase, a change in deformation mechanism occurs in the tool materials, confirming that the indentation method is useful in the identification of such changes.