Effect of hBN Solid Lubricant Concentration on Machinability of Titanium (Ti-6Al-4V) Alloy

Abstract

The prime rationale for designers to choose titanium in their designs for aerospace applications is its relative low weight for a given strength level and its relative resistance to high temperature. Excellent biocompatibility makes titanium as ideal material for many biomedical applications. Even though the titanium products are either sintered or cast into required shape, there is a need for machining in order to produce intricate shapes. However machining of titanium alloys poses many serious problems owing to the reactivity of titanium at high cutting temperatures and rapid tool wear. An alternative method to overcome this is by reducing the cutting zone temperature. This can be achieved by the addition of solid lubricants to regular cutting liquids and using it as minimum quantity lubrication (MQL) strategy. In this study, hexagonal boron nitride (hBN) powder with different concentrations (5, 10, 15 wt %) was mixed with water and used as a lubricant. Turning experiments were performed with TiAlN coated Tungsten carbide insert for a constant speed and variable feed rates. For comparison purpose, machining was carried out under dry conditions. Results indicate that the cutting zone temperature reduced drastically on addition of solid lubricant hBN with water. MQL conditions showed that cutting zone temperature decreased by several folds when compared to dry machining. However there was no significant decrease in temperature between 10 and 15 wt% hBN additions which indicates that 10% hBN addition proves to be optimal. This type of machining thereby paves way for sustainable manufacturing.