Owing to heavy dynamic and thermal loads,PCBN tools are seriously w during hard cutting,which largely constrains the improvement of their machining performance.Therein,the chamfered structure of a cutting edge has a notable influence on the tool wear.Thus,a comparative study was carried out on the wear morphology and wear mechanism of PCBN tools with either a variable chamfered edge or an invariable chamfered edge.The results indicate that,for a PCBN tool with a variable chamfered edge,the rake wear area is far from the cutting edge and slowly extends toward it.A shallow large-area crater wear occurs on the rake face,and the flank wear area has a long triangular shape with a smaller wear area and width,and the cutting edge remains in a good state during the cutting process.In contrast,for a PCBN tool with an invariable chamfered edge,a deep small-area crater appears on the rake face,and the wear area is close to the cutting edge and quickly extends toward it.Thus,it is easy for chips to accumulate in the crater,resulting in large-area and high-speed wear on the flank face.In addition,the tool shows a weak wear resistance.In the initial wear stage,the rake wear mechanism of the two cutting tools is a mixture of abrasive,oxidation,and other types of wear,whereas their flank wear mechanism is dominated by abrasive wear.With an aggravation of the tool wear,the oxidation and diffusion wear mechanism are both increasingly strengthened.The rake wear of the cutter with a variable chamfered edge showed an obvious increase in the oxidation and diffusion wear,as did the flank wear of the cutter with an invariable chamfered edge.This study revealed the wear mechanism of the PCBN tool with a variable chamfered edge and provided theoretical and technological support for its popularization and application in the machining of high-hardness materials.