Cutting performance of CBN tool for the turning of nickel based superalloy (Inconel 718) which is known as one of the difficult to machine materials has been investigated. It was clarified through the microscopic observation of tool-tip after cutting that adhering of the workpiece material to the tool tip occurred and the adhesion affected significantly on the tool life. The type of tool wear varied with cutting speed. Reaction between the workpiece and tool materials was also investigated through a simulated experiment in which both materials were attached with clump and heated up to 1 473 K. Then, the vicinity of the reaction couple was examined carefully by EPMA EDX and AES. Mutual diffusion between the binder phase of the CBN tool and workpiece was observed. Apparently, it could be concluded that such kind of material transfer promoted the tool wear.
