Abstract:
Titanium alloy, particularly Ti-6Al-4V, is extensively utilized in versatile engineering applications such as aerospace, automobile, biomedical, chemical and other manufacturing industries owing to their enviable and inimitable mechanical properties. But their machinability is usually considered to be poor because of low thermal conductivity, low elastic modulus, high hardness and high chemical reactivity. In the area of manufacturing, any attempt to improve the machinability of such hard-to-machine material is encouraged. Application of cutting fluids can reduce the cutting temperature and friction which heading to prolonged tool life and improved machining performance. But, conventional cutting fluids application techniques are known for being expensive, polluting and a non-sustainable part of modern manufacturing processes. Manufacturing industries are now being forced to implement economical, ecological and sustainable cooling strategies. Minimum Quantity Lubrication (MQL) technique is a modern technique, where a very small amount of coolant/ lubricant is delivered to the cutting zone as a form of a mist which can improve the machinability. However, the performance of MQL should be enhanced when utilized for machining hard-to-machine materials. Optimum selection of MQL delivery system parameters and improved cutting fluid can enhance its performance. Nano-fluid which comprises superior tribological and thermo-physical properties is a promising alternative to MQL fluid. This fluid can effectively improve the cooling and lubrication efficiency of MQL. Moreover, hybrid nanofluid can be a better choice due to its synergistic effects of integrating multiple nanoparticles. Optimization of process parameters, nano-fluid concentration and tool type also helps to achieve the ultimate machining performance.
In this study, a double jet MQL delivery system has been designed and fabricated for delivering mist directly towards the chip-tool and work-tool interfaces in turning Ti-6Al-4V alloy. Hybrid nano-fluid has also been prepared and applied through the MQL technique. The performance of the newly designed double jet MQL system and hybrid nano-fluid-based MQL has been systematically investigated. Double jet MQL combined with hybrid nano-fluid has performed the best compared to dry, single jet MQL with conventional cutting fluid and double jet MQL with conventional cutting fluid. Finally, process parameters have been optimized due to achieve an overall efficient manufacturing system for turning Ti-6Al-4V alloy. This thesis also presents a finite element model of turning Ti-6Al-4V alloy by carbide insert. Based on this model the effects of hybrid nano-fluid-based MQL application on temperature distribution and chip formation were investigated in simulations. The chip-tool interface temperature distribution and chip morphology in simulation show a good agreement with the measured value. This study revealed the promising behavior of nano-fluid-based double jet MQL in turning Ti-6Al-4V alloy by coated and uncoated carbide inserts within a specified range of cutting parameters. Nano-fluid-based MQL has an enormous opportunity to enhance the machinability of Ti-6Al-4V alloy considering environmental issues and should be explored further.
