Titanium and its alloys are widely used in various engineering applications such as aerospace,biomedical and chemical industries due to their excellent combination of high strength-toweightratio and good creep, corrosion and fracture resistance. However, these desirabledesign properties pose a serious challenge to the manufacturing engineers owing to the hightemperatures and stresses generated during the machining of titanium alloys. The extremelylow thermal conductivity of titanium alloys results in concentration of high temperature closeto the tool cutting edge resulting in accelerated thermochemical and mechanical tool wear.Many cooling and lubricating techniques such as high pressure cooling (HPC), minimumquantity lubrication (MQL) and cryogenic machining have been proposed for improving themachinability of titanium alloys. In this study, a hybrid combination of MQL and cryogeniccooling using liquid nitrogen (LN2) is proposed, designed and manufactured as an innovativecooling/lubricating approach for CNC end milling of Ti-6Al-4V titanium alloy. Themachining performance of the new hybrid cooling/lubrication technique is investigated interms of tool wear and surface finish and compared to that of flood cooling, MQL andcryogenic cooling.The proposed hybrid cooling/lubrication technique demonstrated the best machiningperformance among all cooling/lubricating conditions and recorded more the 30 foldincreased tool life over conventional flood cooling. In addition, 28% reduction is surfaceroughness was recorded for hybrid cooling/lubrication method as compared to flood cooling.The improvement in surface roughness was 50% for MQL when compared to flood cooling.The outstanding improvement in tool life with hybrid cooling/lubricating strategies isencouraging for the wide spread of this cooling/ lubricating technique for industrial adoption.
Hybrid Cooling/Lubricating Strategies for Machining Ti-6Al-4V in CNC End Milling
Al-Samarrai, I. (Author). 20 Jun 2018
Student thesis: Doctoral Thesis › PhD