Enhanced Machinability of Ti-5553 Alloy from Cryogenic Machining: Comparison with MQL and Flood-cooled Machining and Modeling

摘要

Due to the high performance requirements such as high strength, excellent properties at room and high working temperatures, better resistance to corrosion and fatigue, etc., Ti-5553 alloy has been generally considered as a suitable material to replace Ti-6Al-4 V alloy in the aerospace industry for producing components, such as the advanced structural and landing gear. However, high chemical reactivity causing rapid tool-wear, low thermal conductivity resulting in high temperature and the formation of adiabatic shear bands introducing high dynamic loads and tool vibration during machining of Ti-5553 alloy, have become the primary reasons limiting the application of this near beta-phase titanium alloy. This paper presents the results of a recent machinability study involving cutting forces, surface roughness and tool-wear aimed at improving the machinability of Ti-5553 alloy by using cryogenic machining, and results are compared with those obtained from machining with flood cooling and minimum quantity lubrication (MQL) methods. Up to 30% reduction in the cutting forces could be achieved by cryogenic machining compared with flood cooling and MQL. MQL machining provides better surface roughness as higher ductility could be achieved due to the elevated temperatures. In the case of tool-wear, less nose wear is observed on the tool inserts used in cryogenic machining. Also, a finite element method (FEM) model is developed to simulate the cutting forces from cryogenic machining based on the modified Johnson-Cook flow stress model, and a good agreement is achieved between the experimental and predicted results.