Failure Mechanism of PCBN Tools when Turning Cast Superalloy
Zhang Yinglin;Sun Jianfei;Chen Wuyi;School of Mechanical Engineering and Automation,Beijing University of Aeronautics and Astronautics;
Cutting tests and finite element modeling of PCBN tools when turning cast superalloy K423 A are studied,tool breakage and tool wear behaviors are observed and analyzed. Moreover,failure mechanism of PCBN tools is further investigated from the perspective of stress distribution and temperature contours. Under four different cutting conditions,flaking of tool material and adhesive wear are observed on tool major cutting edge. Under cutting speed of 60 m / min,the PCBN tool is prone to breakage; with the increase in cutting speed,the width of tool wear / breakage on tool minor cutting edge is reduced. The cutting temperature rises as the increase of cutting speed,leading to the reduced workpiece material strength,the reduced cutting tool brittleness and the increased toughness. This is one of the possible causes of damage reduction on minor flank. The modified Mohr criterion is used to analyze the complex stress contours of the PCBN tool,and then the starting position of the tool material failure is inferred.