Abstract
Application of cryogenic fluids for efficient heat dissipation is gradually becoming part and parcel of titanium machining. Not much research is done to establish the minimum quantity of a cryogenic fluid required to sustain a machining process with respect to a given material removal rate. This article presents an experimental investigation for quantifying the sustainability of milling a commonly used titanium alloy (Ti–6Al–4V) by varying mass flow rates of two kinds of cryogenic coolants at various levels of cutting speed. The three cooling options tested are dry (no coolant), evaporative cryogenic coolant (liquid nitrogen), and throttle cryogenic coolant (compressed carbon dioxide gas). The milling sustainability is quantified in terms of the following metrics: tool damage, fluid cost, specific cutting energy, work surface roughness, and productivity. Dry milling carried out the at the highest level of cutting speed yielded the worst results regarding tool damage and surface roughness. Likewise, the evaporative coolant applied with the highest flow rate and at the lowest cutting speed was the worst performer with respect to energy consumption. From a holistic perspective, the throttle cryogenic coolant applied at the highest levels of mass flow rate and cutting speed stood out to be the most sustainable option.
Highlights
Titanium alloys are among the most important engineering alloys, which find widespread applications in various engineering sectors
The results showed that the hybridization of the cryogenic fluid and the location of its application have significant effects on the sustainability measures
A high cutting speed and the application of a throttle cryogenic coolant with a high mass flow rate can yield the highest level of sustainability in the milling of titanium alloy
Summary
Titanium alloys are among the most important engineering alloys, which find widespread applications in various engineering sectors. Machining is an inevitable shaping requirement through which the alloys have to pass for their structural applications. Ti–6Al–4V, the most commonly used titanium alloy, is cut with poor machinability [1]. A high rate of heat generation is due to the alloy’s high shear strength, and the accumulation of the heat close to the cutting edge is due to a shorter-than-normal chip-rake interface cause intensification of heat flux around the cutting zones [2]. The intense heat flux accelerates the temperature-dependent modes of tool damage and seriously shortens tool life and dents machining sustainability. It becomes a prime requirement to efficiently dissipate the accumulated heat through the application of an effective coolant
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