Influence of cooling nozzle orientation on the machinability of TiAl6V4 and 42CrMo4+QT in rough milling

Abstract

High-pressure cutting fluid supply has a major influence on tool wear and chip formation, especially in difficult-to-cut materials, such as titanium alloys and quenched and tempered steels. The titanium alloy TiAl6V4 features high temperature strength, low thermal conductivity and a low E-modulus. Therefore, high mechanical loads and high temperatures occur in the contact zone between work piece and tool, which is the reason why machining of this material is accompanied by high tool wear. In contrast to machining steel, only a low fraction of the generated heat is dissipated by the chip, which thermomechanically accelerates tool wear mechanisms. Machining of quenched and tempered steel on the other hand is characterized by high abrasive wear due to hard particles, because of the martensitic microstructure. The focused high-pressure cutting fluid supply between the emerging chip and the rake face of the tool showed its potential to reduce thermomechanical induced wear mechanisms in many examinations during turning, resulting from the more effective cooling and lubrication of the contact zone. However, engagement conditions in milling differ substantially from turning, which is the reason for the demand of experimental investigations. In this paper, the tool life and chip formation was examined in face milling with indexable inserts and internal cooling channels that were focused to the rake faces of the inserts. The number of cooling nozzles and their orientation were varied. The cutting fluid was supplied internally through the milling tool with a pressure of p = 80 bar and constant volumetric flow rates. The results show major differences in chip morphology and tool wear depending on the number and orientation of the cooling nozzles. Moreover, different wear mechanisms were identified in reliance to the work piece material and the cooling nozzle orientation and number.