Influence of a High-Pressure Lubricoolant Supply on Thermo-Mechanical Tool Load and Tool Wear Behaviour in the Turning of Aerospace Materials

Abstract

In the field of machining difficult-to-cut materials like titanium or nickel-based alloys, the use of a high-pressure lubricoolant supply may result in a significant increase of productivity and process stability. Due to enhanced cooling and lubrication of the cutting zone and thus reduced thermal tool load, tool wear can be decreased which allows higher applicable cutting speeds. Furthermore, the process stability can be increased as a result of effective chip breaking and chip evacuation. The present paper investigates the effect of high-pressure lubricoolant jets, directed into the tool—chip interface, in a longitudinal turning process with cemented carbide tools. For this type of lubricoolant supply the reduction of the contact length between tool and chip is an important detail. In turning of Inconel 718 and Ti6Al4V, the cutting tool temperature, tool wear, and resulting chip forms as well as the ratio of cutting forces and tool—chip contact area were analysed as a function of the lubricoolant supply pressure and flowrate (up to 300 bar, 55 l/min). To study the effect of the high-pressure lubricoolant supply, reference tests were carried out using conventional flood cooling. The results suggest that the tool temperature can be decreased by almost 25 per cent by the use of a high-pressure lubricoolant supply for both machined workpiece materials. However, due to the different tool wear mechanisms of the presented materials and the change in the specific load on the cutting edge during machining, the resulting tool wear was influenced differently. In the best case, tool wear could be reduced in an order of magnitude of 50 per cent, while in other cases tool wear even increased significantly due to the use of a high-pressure lubricoolant supply.