No abstract

No abstract

Cryogenic-based machining has been drawing attention for machining hard metals and super alloys such as the titanium alloys due to environmental concerns and growing regulations over pollution. In this study, cryogenic-assisted milling of Ti-6Al-4V has been performed with the preheated workpiece methods to avoid the cryogenic hardening by liquid nitrogen (LN 2 ). Preliminary experiments show an increase in the cutting force due to cooling of the workpiece; therefore, workpiece preheating was adopted to increase the workpiece temperature. Three cutting speeds and three machining environments (dry, cryogenic, and cryogenic plus preheated) were considered in the analysis of tool wear, cutting forces, tool wear morphology, and chip morphology. Soft (Si coating) and hard (CrTiAlN)-coated tools were used in this study. It was observed that the tool life was increased by 50 to 90 % for Si-coated tools and 50 to 55 % for CrTiAlN-coated tools. The tool wear morphology showed that rubbing and chipping were the primary tool wear mechanisms. It is expected that the present work will be useful for improving tool life and reducing the cost of hard metal products. It may also be useful for reducing the ecological problems by conventional cutting fluids.

Titanium alloys are well-known material because of the excellent mechanical/chemical properties, corrosion resistance and light weight. These alloys are widely used in the high performance applications such as; aerospace, aviation, bio-implants, turbine blades etc. Machining is commonly used to create products out of Ti alloys. Despite of good material properties, Ti alloys have low thermal conductivity, poor machinability, burr formation, high machining temperature, tool wear and poor machinability. The tool wear and high machining temperature can be controlled through coolant. Cryogenic fluid (liquid nitrogen) is a common material used as coolant in various machining process. The current work is focused on the modeling of cryogenic machining on titanium alloy (Ti6Al4V). Dry machining and cryogenic machining processes are modeled for the chip formation and cutting forces in 2D. Experimental works have been performed to validate the model based on the cutting forces and chip morphology. It is showed that the model is capturing the process, evident by the cutting forces and the chip morphology. The error in prediction is limited to 18%. Model showed that the cutting forces are increasing in cryogenic machining due to the increased strength of the workpiece at low temperature. Chip formation is well captured by the current model. Shear band width have been captured in dry machining. Chip curling has been captured at dry and cryogenic machining. It is expected that the model can further useful in the selection of cryogenic process parameter, such as, flow rate, application techniques etc.

No abstract