Abstract
The use of cutting fluids is commonly considered a necessity while machining Heat Resistant Super Alloys (HRSA). Specifically, cutting fluids applied under high-pressure, which for many decades have been the solution for the most demanding applications. The results might be diverse and vary between applications, but typically leads to improved tool life, enhanced chip breakability, lower temperature in the cutting zone and better surface quality of the finished product. The available high-pressure cutting fluid delivery systems are usually designed with the intention to improve the cutting fluid penetration at the vicinity of the cutting edge on the rake face side of the insert. However, there has been limited interest in investigating high-pressure cutting fluid applied to its flank face. Both specifically and in combination with cutting fluid directed to the rake face. In this study, the focus has been to investigate the chip formation process during the turning of Alloy 718 (Inconel 718). Particularly, for a defined turning operation where high-pressure cutting fluid is applied to the flank side as well as the rake side of an uncoated carbide insert. Several combinations of pressure levels and jet directions were investigated. The corresponding effects on the tool-chip contact zone and chip characteristics were studied for two cutting speeds. The results of the investigation showed a substantial improvement in lowering the tool-chip contact area at a rake pressure of 16 MPa. At which pressure, additional cutting fluid applied to the flank at a moderate pressure of 8 MPa had no dominant effect on chip formation (chip break). However, flank cooling of the cutting zone supports chip segmentation and thus indirectly chip breakability. For cutting fluid applied to the rake side at a more moderate pressure of 8 MPa, more prominent effects on the insert became apparent when additional cutting fluid was applied to the flank side. This was particularly noticeable when cutting fluid was directed towards the flank side of the insert at the same pressure level as the cutting fluid applied towards its rake face. The additional thermal transfer was seen to have a significant effect on the material deformation phenomena in the primary shear zone (lowering shear angle) as well as the sliding and sticking conditions of the tool-chip interface. Based on the evidence from this study, it can be concluded that cutting fluid applied towards the flank side of the insert has a significant impact on the cutting process. In particular, if applied in combination with a rake pressure at a similar level, in this case, 8 MPa.
Highlights
The technological advancement in and around the metal cutting industry has incremented towards better understanding and optimization of its processes
How variations in the applied cutting fluid pressure correlate with the attained Tool Chip Contact-area (TCCarea)
This is primarily achieved by lowering the temperature in the cutting zone, and by boosting the mechanical effects of breaking the chips generated at the rake side of the tool
Summary
The technological advancement in and around the metal cutting industry has incremented towards better understanding and optimization of its processes. One such increment is improved tool utilization, which helps driving manufacturing and production of different materials towards improved sustainability and a reduced environmental footprint. Ufactured from high-performance materials like these are widely used in the turbine’s hot sections. For their ability to retain mechanical and physical properties such as creep and corrosion resistance at elevated temperatures. Despite its long and widespread use, it is still a challenge to machine Alloy 718 at high levels of productivity
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More From: CIRP Journal of Manufacturing Science and Technology
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