Abstract: This paper presents tool wear and material comparison experiments of turning Ni-based superalloy GH706 with PCBN tools. Based on the characteristics of positions and states of PCBN tool wear,tool wear patterns are defined in a new way,e.g. notch wear on main edge border,chipping of the main cutting edge and flank wear,flank wear on the junction of main and minor cutting edges,minor flank wear and chipping on the minor cutting edge etc. The mechanisms of tool wear were presented according to the properties of PCBN and workpiece materials,and the relationship among tool,workpiece and chips. Also,this paper proposes the variation of tool wear and fracture in the cutting process in order to understand tool failure process. Finally,the relationships of tool wear with the CBN content and the binding agent are made clear through comparing five kinds of PCBN materials,which provides the technology supports for PCBN tool design and application.