Machining of Austenitic Stainless Steel Under Various Cooling-Lubrication Strategies Smita Padhan, Ajay Kumar Behera, and Sudhansu Ranjan Das Abstract

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Discussion of Results
The optical images of carter wear under different machining environments (dry,
compressed air, flooded, MQL) are shown in Fig.
a. In dry as well as compressed air-cooled cutting conditions, due to the weak heat transfer capability of cooling medium, large amount of heat is generated at the interface of tool and workpiece,
which is responsible for the development of thermal stress, which leads to the starting of cracking will on rake face followed by edge chipping. However, due to the surplus availability of coolant at the cutting zone in flooded cooling condition, large amount of heat was taken out from the cutting zone, so it effectively minimizes the carter wear by reducing the generation of thermal stress on the tool rake surface. For
MQL condition, as cutting fluid is applied in jet form to the cutting zone at high pressure, it effectively extracted heat from the cutting zone and resulting decease in thermal stress buildup in cutting tool. Thus, a very less chipping was observed on the tool insert in MQL condition compared to other CL environment. Still some edge chipping was observed in MQL condition. Figure
b shows flank wear on cutting insert indifferent CL methods. Maximum flank wear was observed in dry cutting environment, whereas it was minimum in MQL cutting. Since, coolant is not applied in dry turning the heat generated during cutting is accumulated at cutting region causing rapid increase in cutting temperature. This high temperature promoted the formation of notch due to high thermal stress and adhesion of melted chip to the flank surface of the tool. Due to improper lubrication, chipping and abrasion type of wear are also seen on the flank face of cutting tool. However, in provision for
MQL condition, due to its effective CL capacity, slight edge chipping, negligible adhered material, compact notch, and very smooth abrasion marks were noticed,
whereas compressed air-cooled condition gave better result in comparison to dry cutting condition. Figure
c depicts IR thermography of cutting zone temperature indifferent cooling-lubrication methods using IR thermal imaging camera. Moreover,
d shows the measurement signal images of the cutting temperature under the influence of various CL environments. Maximum temperature was observed in dry cutting environment, whereas it was minimum in MQL condition. The use of coolant reduces the cutting temperature by providing highly effective heat extracting medium as well as lubrication. In addition, the reason of less heat generation in MQL condition is that, here the friction in between the tool-chip is deceased as the contact length

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