Mitigating the tribological challenges in machining Ti6Al4V using tool texturing and deep cryogenic treatment techniques

Despite its immense usage in aerospace, automotive, and biomedical applications, the machinability aspects of Ti6Al4V are extremely challenging owing to their poor thermal conductivity, severe chemical affinity and propensity to exacerbate tool wear rates. While traditional lubricants/coolants could help address some of these challenges, concerns regarding insufficient machining zone penetration, toxicity, and disposal hinder their usage. Hence, the present study explores the influence of tool modification through green-sustainable manufacturing techniques, namely tool texturing and Deep Cryogenic Treatment (DCT) to counter the alloy's machinability challenges. Initially, dimple and groove-textured tool patterns were fabricated via micro-discharge machining-assisted drilling and milling operations. The tool inserts were then exposed to Liquid Nitrogen (LN2) vapours for 24 hat-196 degrees C, followed by tempering at 200 degrees C for 2 h. Subsequently, they were used for CNC turning trials at dry-cutting conditions at speeds of 80, 100, and 120 m/min and at constant feed rates and cutting depth of 0.2 mm/rev and 0.5 mm respectively. The results showed the non-treated textured patterns significantly decreased the frictional contacts while substantially improving the chip entrapment at machining interface. However, rapid piling and significant debris agglomeration in the texture patterns exacerbated the sticking-sliding effects at subsequent stages. This contributed to severe crater face depressions, micro-cracks, and chipping phenomena. Nonetheless, DCT significantly enhanced the efficacy of the fabricated textures, owing to precipitation of hard eta phases which improved the hardness, wear resistance, and heat dissipation features. Thus, the probability of chip debris causing significant deteriorations across micro-textures reduced considerably. Consequently, the Tool Chip Contact Lengths (TCCL), flank wear widths, average roughness, and resultant forces decreased substantially by 15 %, 36 %, 27 %, and 19 % for cryogenically treated dimple-textured tools and by 18 %, 45 %, 31 %, and 20 % for cryogenically treated groove-textured tools compared with untreated non-textured tools.