Influence of the Supplying Technique of a Sub-Zero Metalworking Fluid on the Performance of Face Turning of Ti-6Al-4V Titanium Alloy

Abstract

Sub-zero metalworking fluids (MWF) are applied above the temperatures commonly used for cryogenic machining, but at temperatures below 0 °C. Both leads to a high cooling effect, resulting in a lower thermal load and eventually less tool wear. The high cooling effect also influences the chip formation, as the tool-chip contact length is reduced due to high thermally induced stresses in the chip which favors chip breaking. In this paper, a through-tool MWF supplying technique is investigated for face turning of Ti-6Al-4V at varied cutting speeds. Regarding the supplying technique, varied supply temperatures of the sub-zero MWF, varied mass flows, and varied nozzle positions are investigated. The process and process results are characterized by the temperature of the tool, process forces, wear parameters as well as the surface roughness. The results show that, besides the supply temperature of the sub-zero MWF and the applied mass flow, the nozzle position has a high influence on the performance of sub-zero MWF. In particular at high cutting speeds and thus high heat impacts, applying high mass flows at low supply temperatures with a combined MWF supply, over both the rake and the flank face, leads to reduced tool temperatures and less tool wear. The shortest tool-chip contact lengths, however, were achieved by means of a MWF supply only over the rake face. This promotes chip breaking.

Keywords: cryogenic machining; cutting tool, fluid, temperature, titanium, turning, wear 1. Introduction 1.1. Machining of Ti-6Al-4V titanium alloy and supplying techniques used in turning processes The machining of Ti-6Al-4V is associated with high mechanical, thermal, and chemical loads on the cutting tool