The benefits of cryogenic cooling by liquid nitrogen in cutting of titanium alloys have often been evaluated as a comparison\ud to dry machining conditions. However, it is more interesting to quantitatively assess the performance of cryogenic\ud conditioning of the process with respect to standard industrial conditions, that is, with respect to flood emulsion cooling.\ud The technical and scientific literature is scarce and somehow contradictory, especially in terms of cutting forces and\ud coefficient of friction. The aim of this article is to enrich the common base of experimental data, by conducting a comparison\ud of traditional and cryogenic turning of Ti6Al4V in a region of cutting parameters particularly relevant to the\ud aerospace industry, where no previous data are available. This study confirms that cryogenic machining is able to\ud increase the tool life, even with respect to wet cutting. Besides, the results show that not only cutting forces are reduced\ud but also a small, albeit significant, reduction can be achieved in the coefficient of friction at the tool–workpiece interface

Ti-6Al-4 V titanium alloy is a popular material in industrial applications (e.g. aerospace, oil & gas, medical) due to its superior mechanical properties, although its low thermal conductivity and high chemical reactivity with other materials make it a hard-to-cut material. A finite element model (FEM) was developed in the present investigation to simulate dry and cryogenic orthogonal cutting of Ti-6Al-4 V by using TiAlN coated carbide inserts. Numerical prediction of the effect of the superior cryogenic cooling on chip formation, cutting and thrust forces were investigated. The simulations were validated by the comparison with experimental results. The model calibration was performed with experimental data on dry cutting and then the model was used for predicting the cryogenic cooling case. The validated FEM models were used to compare the chip formation in dry cutting and cryogenic cutting in order to point out some differences in terms of chip segmentation frequency and chip thickness and gain additional knowledge

Titanium alloys, mainly because of their poor thermal conductivity, need to be cut at relatively low cutting speeds, with obvious negative consequences on the profitability of machining. An important amount of research has been done in order to increase productivity in titanium machining operations: high performance coatings and innovative technologies to improve insert resistance to wear represent promising solutions. In this work, a highly performing cutting insert (coated with a TiAlN layer obtained by Physical Vapor Deposition (PVD) magnetron sputtering) has been tested against the option of applying a Deep Cryogenic Treatment (DCT), when used for rough turning of aerospace titanium. The effects of the DCT have been experimentally investigated with two different experimental plans at low and high cutting speeds (respectively v(c)<= 50 m/min, v(c)>= 60 m/min). Statistical analyses of the results have been performed. The results show that at low cutting speed, the DCT treatment does not increase the tool life. At higher values of v(c), flank wear vs. time curves of coated tools have been determined, with and without DCT, and they clearly show that cryogenically treated tools present better wear resistance at higher cutting speeds. The wear mechanisms on the rake face and the flank for these two TiAlN coated tools have been analysed using a scanning electron microscope. The adhesion of titanium on the tool surface is lower for a DCT treated insert. The results indicate that the hardening of tools induced by the cryogenic treatment improves their useful life in high rate machining of titanium

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Due to their poor machinability, titanium alloys need to be worked at low cutting speeds to prevent a fast tool failure caused by the very high temperatures that are reached at the tool-chip interface. As demonstrated by previous works by the authors, an improvement of productivity for Titanium alloys can be obtained by adopting cryogenic cooling during the machining operations.The present work shows the features of a toolholder specifically designed for cryogenic adduction in turning operations, following Hong’s design guidelines. The paper compares tool life results between traditional and cryogenic rough turning by adopting Grade 5 titanium as the working material. Rough turning is economically more relevant to the machining industry, especially in the aerospace field where generally a large quantity of rough material has to be removed due to the very high buy-to-fly ratio of aerospace components. A full factorial experimental plan was performed basing on typical rough turning parameters. Machining outputs such as forces, roughness, temperatures, friction coefficients were calculated in order to define statistical differences between cryogenic cooling method using the special toolholder and traditional oil water emulsion cooling system.Furthermore, thanks to tool life results the Taylor’s law for cryogenic and traditional cases was calculated and an hypothetical production scenario for Ti6Al4V parts was analysed. An analytical model to calculate production costs and time was built for both cooling methods. A 4-turrets turning centre was considered and cooling methods and costs per hour of machine tool were taken into account in a cost model. The results show that the benefits in terms of tool life offered by liquid nitrogen cooling allows to improve productivity by adopting higher optimal cutting parameters. This improvement, coupled to an increase of tool life, is very significant and allows not only to reduce time of production but also to cover the major costs of liquid nitrogen and have a slight reduction of machining total costs.