Thermo-mechanical effects in drilling using metal working fluids and cryogenic cooling and their impact in tool performance

Cryogenic machining opens up new industrial perspectives in difficult-to-cut materials like nickel-based alloys. In particular, drilling is an operation that generates high thermal and mechanical loading to the drill. Therefore, tool performance, hole geometry and surface integrity can be highly affected. The objective of this study is to analyse tool performance during drilling of IN718 using conventional metal working fluids (MWF) and cryogenic cooling conditions, and correlate it with the thermo-mechanical phenomena. This study is conducted with standard coated cemented carbide twist drills, designed to work with MWF. The results show that drill performance under cryogenic cooling is strongly affected by its geometry. The axial force, drilling torque and tool wear/failure are higher under cryogenic cooling when compared to conventional MWF. Therefore, in order to take advantage of the cryogenic machining, new drill design is required, which currently is not available on the market.