The Effect of Minimum Quantity Lubrication on Selected Surface Integrity Attributes When Machining Grade 4 Titanium Alloy

This paper presents an experimental investigation on the influence of Minimum Quantity Lubrication (MQL) process parameters on selected aspects of surface integrity when turning grade 4 titanium alloy. MQL process parameters that were varied include the oil flow rate (50-90 ml/h), nozzle distance (20-40 mm), and airflow rate (25-37 l/h). Surface roughness, residual stress state, and cutting forces were evaluated for dry, flood, and MQL turning conditions using the smaller is better grey relation criterion. Grey relation analysis of the results demonstrated that when utilizing MQL, the best surface finish, lowest cutting forces, and largest compressive residual stresses can be obtained for selected MQL parameter sets but not all at once. The results demonstrate that MQL is a viable alternative to either dry or flood cooling during outside turning of grade 4 titanium alloy, and may result in an improved surface integrity state.