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  1. This paper evaluates the performances of dry, minimum quantity lubrication (MQL), and MQL with nanofluid conditions in turning of the most common titanium (Ti) alloy, Ti-6Al-4 V, in a solution treated and aged (STA) microstructure. In particular, the nanofluid evaluated here is vegetable (rapeseed) oil mixed with small concentrations of exfoliated graphite nanoplatelets (xGnPs). This paper focuses on turning process that imposes a challenging condition to apply the oil or nanofluid droplets directly onto the tribological surfaces of a cutting tool due to the uninterrupted engagement between tool and work material during cutting. A series of turning experiments was conductedmore »with uncoated carbide inserts, while measuring the cutting forces with a dynamometer under the dry, MQL and MQL with nanofluid conditions supplying oil droplets externally from our MQL device. The inserts are retrieved intermittently to measure the progress of flank and crater wear using a confocal microscopy. This preliminary experimental result shows that MQL and in particular MQL with the nanofluid significantly improve the machinability of Ti alloys even in turning process. However, to attain the best performance, the MQL conditions such as nozzle orientation and the concentration of xGnP must be optimized.« less
  2. Titanium alloys typically do not contain hard inclusion phases typically observed in other metallic alloys. However, the characteristic scoring marks and more distinctive micro- and/or macro-chippings are ubiquitously observed on the flank faces of cutting tools in machining titanium alloys, which is the direct evidence of abrasive wear (hard phase(s) in the microstructure abrading and damaging the flank surface). Thus, an important question lies with the nature of the hard phases present in the titanium microstructure. In this work, we present a comprehensive study that examines the microstructural impact on flank wear attained by turning various Ti-6Al-4V bars having distinctmore »microstructures with uncoated carbide inserts. In particular, four samples with elongated, mill-annealed, solution treated & annealed and fully-lamellar microstructures were selected for our turning experiments. After turning each sample, the flank surface of each insert was observed with confocal laser scanning microscopy (CLSM) and analyzed to determine the flank wear behavior in relation to each sample' distinct microstructures. To characterize the microstructure, scanning electron microscopy (SEM) together with Orientation imaging microstructure (OIM) was used to identify and distinguish the phases present in each sample and the content and topography of each phase was correlated to the behavior of flank wear. The flank wear is also affected by the interface conditions such as temperature and pressure, which were estimated using finite element analysis (FEA) models. The temperature dependent abrasion models enable us to estimate the flank wear rate for each microstructure, and are compared with the experimentally measured wear data.« less
  3. Titanium alloys typically do not contain hard inclusion phases typically observed in other metallic alloys. However, the characteristic scoring marks and more distinctive micro- and/or macro-chippings are ubiquitously observed on the flank faces of cutting tools in machining titanium alloys, which is the direct evidence of abrasive wear (hard phase(s) in the microstructure abrading and damaging the flank surface). Thus, an important question lies with the nature of the hard phases present in the titanium microstructure. In this work, we present a comprehensive study that examines the microstructural impact on flank wear attained by turning various Ti-6Al- 4V bars havingmore »distinct microstructures with uncoated carbide inserts. In particular, four samples with elongated, mill-annealed, solution treated & annealed and fully-lamellar microstructures were selected for our turning experiments. After turning each sample, the flank surface of each insert was observed with confocal laser scanning microscopy (CLSM) and analyzed to determine the flank wear behavior in relation to each sample' distinct microstructures. To characterize the microstructure, scanning electron microscopy (SEM) together with Orientation imaging microstructure (OIM) was used to identify and distinguish the phases present in each sample and the content and topography of each phase was correlated to the behavior of flank wear. The flank wear is also affected by the interface conditions such as temperature and pressure, which were estimated using finite element analysis (FEA) models. The temperature dependent abrasion models enable us to estimate the flank wear rate for each microstructure, and are compared with the experimentally measured wear data.« less