Chip formation mechanism in cryogenic machining of high temperature alloy-Inconel 718 and Ti-47.5Al-2.5V-1.0Cr

Abstract

Inconel 718 and TiAl alloy are typical difficult-to-cut materials for their high cutting temperature, and cryogenic machining is an effective method to solve this problem. In order to reveal the material removal mechanism of these two materials in cryogenic machining, turning tests with different cooling media were designed and carried out. Cryogenic cooling could increase the brittleness of the material, making the material removal mechanism change from ductile removal to brittle removal. Due to the different plasticity of the material and their different sensitivity to temperature, the cooling conditions have slightly different effects on in the change of the removal mechanism of these two materials. By observing the geometric characteristics of chip, the deformation mechanism of the material near the chip free surface area was studied. Besides, the variation of chip root morphology was discussed to reveal the deformation mechanism of the primary deformation zone near the cutting edge. The experimental results showed that cryogenic cooling could change the material removal mechanism, but the sensitivity of different materials to temperature also have a significant influence, and the more sensitive to temperature, the more the material removal mechanism changes. The formation mechanism of serrated chips of Inconel 718 in cryogenic cutting was a combined action of ductile-brittle mixed fracture near the chip free surface and adiabatic shearing near the cutting edge. And the formation mechanism of Ti-47.5Al-2.5V-1.0Cr serrated chips is a combined action of periodic brittle fracture near the chip free surface and ductile-brittle fracture near the cutting edge.