Investigation of lubrication strategies in Ti6Al4V milling operations

[摘要] There is a growing global demand for titanium. The aircraft industry is the driving forcebehind the demand for titanium. The reason for this is that titanium has attractiveproperties that justify its use both economically and environmentally. Titanium alloyshave superior strength-to-weight ratios. This implies that by substituting componentsmanufactured from other metals in the aircraft with titanium components, a substantialreduction in structural weight can be achieved. From an economical point of view alower mass implies lower fuel consumption. From an environmental point of view lowerfuel consumption implies less harmful greenhouse emissions.Ti6Al4V components are the most widely used titanium alloy products in aircraftcomponents. Ti6Al4V is known as a difficult-to-machine material. This is due to its lowthermal conductivity and small contact area between the tool and the chips causinghigher temperatures to be generated closer to the cutting edge of the insert. This willsubsequently increase the rate at which the cutting tool wears. For this reason relativelylow cutting speeds and feed rates are employed for the machining of Ti6Al4V comparedto the machining of steels. Ti6Al4V is an exceptionally high cost material. The lowcutting speeds and feed rates used in Ti6Al4V machining raises the machining cost ofparts and contributes to an increase in the price of Ti6Al4V parts. By employing highercutting speeds and feed rates machining times on Ti6Al4V products could be decreased,subsequently lowering the price for Ti6Al4V components.An increase in cutting speeds and feed rates will subsequently cause an increase ingenerated cutting temperatures, resulting in an increase in tool wear. This stresses theimportance of controlling the cutting temperature during machining of Ti6Al4V in order toprolong tool life. The focus of this work was to investigate different lubrication strategiesfor polycrystalline diamond (PCD) and tungsten carbide inserts for Ti6Al4V millingoperations in the quest to develop improved feasible cutting parameters.The results of this study showed that flood lubrication should be utilized for PCD inserts,while a 'softer 60 bar high pressure through spindle lubrication worked best for thetungsten carbide inserts. By utilizing these lubrication strategies, cutting speeds of 100 m/min and feeds per tooth of 0.05 mm/rev for both the PCD and tungsten carbide gradescould be attained with satisfactory tool life.

[发布机构] Stellenbosch University