The Performance of Uncoated Tungsten Carbide Insert in End Milling Titanium Alloy Ti-6Al 4V through Work Piece Preheating

Abstract

Problem statement: Titanium alloys have been used widely in the aerospace, chemical and petroleum industry because of their high specific strength, fracture resistance and superior resistance to corrosion. Titanium alloys have a very high strength-to-weight ratio making them very suitable for aircraft engines and airframe manufacture. Approach: The use of titanium alloys as engine component materials is due to their ability to maintain their high strength at high operating temperatures of the engine. Titanium alloys exhibit exceptional resistance to corrosion, which provides savings on protective coating like paints that will otherwise be used in the case of steel. However, titanium alloys are difficult to machine due to their high temperature strength, low modulus of elasticity, low thermal conductivity and high chemical reactivity. Results: This study presented the investigation of tool life improvement in end-milling of Titanium Alloy Ti-6Al-4V through workpiece preheating. End milling tests were conducted on Vertical Machining Centre with full immersion cutting. Titanium alloy Ti-6Al-4V bar was used as the workpiece. Machining was performed with a 20 mm diameter end-mill tool holder fitted with one uncoated WC-Co carbide inserts. All of the experiments were run under room temperature and preheating condition at 315, 450 and 650°C. Induction heating was utilized during end milling with preheating. Flank wear has been considered as the criterion for tool failure and the wear was measured using a Hisomet II Toolmaker’s microscope. Tests were conducted until an insert rejected when an average flank wear greater than 0.30 mm was recorded. Cutting force and torque measurements were conducted using the Kistler Rotating Cutting Force Dynamometer. Vibration during cutting was captured using an online vibration monitoring system. Scanning Electron Microscope (SEM) was also used to investigate the wear morphology. Conclusion/Recommendation: The results lead to conclusions that workpiece preheating significantly increases the tool life of uncoated WC-Co carbide inserts in end-milling of Titanium Alloy Ti-6Al-4V. An increase in tool life by 325 % was achieved while employing preheating at 650°C compared to the experiment at room temperature.