Effects of high-pressure cooling in the flank and rake faces of WC tool on the tool wear mechanism and process conditions in turning of alloy 718

Artikel i vetenskaplig tidskrift, 2019

The exceptional properties of Heat Resistant Super Alloys (HRSA) justify the search for advanced technologies that can improve the capability of machining these materials. One such advanced technology is the application of a coolant at high pressure while machining, a strategic solution known for at least six decades. The aim is to achieve extended tool life, better chip control and improved surface finish. Another aim is to control the temperature in the workpiece/tool interface targeting for optimum cutting conditions. In most of the existing applications with high-pressure coolant media, the nozzles are positioned on the rake face side of the insert and they are directed towards the cutting edge (the high-temperature area). The coolant is applied at high-pressure is to improve the penetration of the cooling media along the cutting edge in the interface between the insert and workpiece material (chip) as well as to increase chip breakability. However, the corresponding infusion of coolant media in the interface between the flank face of the insert and the work material (tertiary shear zone) has been previously only scarcely addressed, as is the combined effect of coolant applications on rake and clearance sides of the insert. The present work addresses the influence of different pressure conditions in (flank: 0, 4 and 8 MPa; rake: 8 and 16 MPa) on maximum flank wear, flank wear area, tool wear mechanism, and overall process performance. Round uncoated inserts are used in a set of face turning experiments, conducted on the widely used HRSA “Alloy 718” and run in two condition tests with respect to cutting speed (45 (low) and 90 (high) m/min). The results show that an increase in rake pressure from 8 to 16 MPa has certainly a positive impact on tool life. Furthermore, at high vc of 90 m/min, cutting edge deterioration: due to an extensive abrasion and crack in the wear zone were the dominant wear mechanism. Nevertheless, the increase in coolant pressure condition to 16 MPa reduced the amount of abrasion on the tool compared to 8 MPa. At the lower cutting speed, no crack or plastic deformation or extensive abrasion were found. When using 8 MPa pressure of coolant media on the flank, the wear was reduced by 20% compared to flood cooling conditions. Application of high-pressure cooling on the flank face has a positive effect on tool life and overall machining performance of Alloy 718.