Abstract
Titanium aluminides are one of the most promising materials in aeronautical and automotive applications. However, their low machinability makes the processing of these alloys quite difficult under sustainability conditions, specially without lubrication. The current study focuses on the turning process of the Ti48Al2Cr2Nb gamma titanium aluminide under dry conditions. As far as we are aware, dry cutting is the most sustainable feature, although it has not been traditionally applied on titanium aluminides due to the accelerated tool wear that the material promotes. The main novelty of this work consists of providing a simple solution for reducing the tool wear based on the inclination of the cutting insert, what is evaluated in terms of tool wear and tool life, cutting forces, cutting temperature, surface integrity of the machined part, as well as its microhardness and microstructural effects. The results shown here clearly point out a better performance of the machining process. This fact could be understood if we take into consideration that an increment of the clearance angle from 6.3° to 11.6° and 15° increases the tool life by five and six times, respectively, using efficient cutting speeds, whose values have increased by 50% with respect to the original cutting conditions. This improvement is explained according to the reduction in the cutting temperature and friction forces in the flank face of the tool. In addition, the use of uncoated carbide inserts may lead to a better behaviour than the coated ones, considering the results obtained for a PVD TiAlN + AlCr2O3 coated insert herein researched.
Highlights
Among the materials developed in recent decades, titanium aluminides have been identified as potential candidates for aeronautical and automotive applications [1]
The inclination of the cutting insert, which means a progressive increment of the clearance angle for configurations 2 and 3, helps to reduce the tool–workpiece contact temperature as the friction force reduces in size in the flank zone
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Summary
Among the materials developed in recent decades, titanium aluminides have been identified as potential candidates for aeronautical and automotive applications [1]. Aspinwall et al [10] reported that the turned workpieces show surface smearing, cracks and subsurface lamellae deformation, which is a proven sign of the existence of strain-hardening at high temperatures They found that very low cutting speeds (about 20–25 m/min) were required to perform the process under a stable behaviour condition, and to control tool wear. Anwar et al [19] studied the machinability of an electron-beam-melted γ-TiAl by using standard coated and uncoated carbide inserts for a wide range of cutting speeds, within 40 m/min and 80 m/min They analysed the involved cutting forces, the surface roughness obtained, and the tool wear mechanisms involved and found that the uncoated tool behaved better than the coated one. The analysis was developed for a wide range of cutting speeds within 40–70 m/min, by using an uncoated carbide insert and a coated one with PVD-TiAlN-AlCr2O3
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