The Comparison of Effects of Liquid Carbon Dioxide and Conventional Flood Cooling on the Machining Conditions During Milling of Nickel-based Superalloys

Abstract

In this scientific study, the authors have dealt with the slot milling of nickel-based superalloys. These alloys are among the most difficult materials to machine and are widely used in aerospace and energy industries. Due to the properties of the material, slot milling is a particular problem because tool wear happens quickly, and tool breakages are common. When these superalloys are machined, very high temperatures occur in the cutting zone, which cannot leave due to the extremely poor thermal conductivity of the material and will therefore transfer to the edges of the cutting tool, causing it to anneal, break off and fail. So, the researchers initiated a new field of research: cryogenically-assisted machining. In this paper, the authors used two cooling methods, the conventional flood cooling and cryogenic cooling with liquid carbon-dioxide (LCO₂). The effects of these cooling methods were tested focusing on the cutting forces, tool wear, chip morphology and surface roughness of the bottom of the slots. The aim was to determine the best cooling methods for these materials. Based on the results, it can be concluded that, LCO₂ has a negative effect on cutting forces, tool life and surface roughness. It only has a positive effect on chip formation. It can be see that, the lubricating effect has a greater impact on tool life, tool load and surface roughness of the milled slots than cooling.