关键词: 镍基单晶高温合金, 高速铣削, 锯齿状切屑, 切屑毛边

Abstract: In order to improve the difficult-to-machine property of DD5 Ni-based single crystal superalloys, a high-speed milling transition criteria and chip edge formation mechanism were proposed with the variable of cutting speed based on adiabatic shear theory and using the method of single factor experiments and FEM simulation. According to the measurement results of the chip sawtooth level and intervals, the chip free surface transforms from lamellar structure to serrated structure when cutting speed reaches 37.7 m/min, which shows the milling has entered into high-speed zone. The stress concentrated on the grooves intersected between the chip side and adiabatic shear band induces the longitudinal crack formation and expansion, which causes the transverse and longitudinal stress distribution variations. Then, the transverse cracks were generated. The longitudinal and transverse crack formation was the main reason of the chip edge generation. With the increasing of milling speed, the chip edge morphology transformed from flat and smooth trapezoid to narrow and defective triangle. Compared with the traditional machining, high-speed cutting is beneficial to the reduction of cutting force, chip edge height and intervals, and restrain the lateral crack expansion at the same time.

Key words: Ni-based single crystal superalloy, high-speed milling, sawtooth chip, chip edge