Abstract
AISI 52100 hardened bearing steel is popular in many industrial applications due to its excellent wear resistance and high strength. Therefore, a high level of surface integrity of the same is the utmost important requirement to enhance fatigue life. Machining of hardened AISI 52100 steel is difficult because severe plastic deformation and generation of high temperature alter the surface metallurgy of the machined component and hamper the tool life. The present investigation includes a comparative analysis of surface integrity of AISI 52100 bearing steel during hard turning under different near-dry environments, namely, dry, Minimum Quantity Cooling and Lubrication (MQCL), Compressed Chilled Air by Vortex Tube (CCAVT), and Hybrid Nanofluid Minimum Quantity Cooling and Lubrication (Hybrid NF-MQCL). Soyabean (a vegetable) oil is used as cutting fluid in MQCL and base fluid in Hybrid NF-MQCL environments. To prepare hybrid nanofluid, two different nanoparticles Al2O3 and MWCNT, are used. The chilled air is generated through a vortex tube. The surface integrity of AISI 52100 steel was studied in terms of microhardness, the thickness of the white layer, surface roughness (Ra), and residual stresses. Higher cutting speed and feed show positive and negative correlation on surface integrity of AISI 52100 steel, respectively. Hybrid nanofluid MQCL exhibits the lowest surface roughness (0.34 μm), microhardness (625 Hv0.1), compressive residual stresses (−168 MPa), and thin white layer (0.9 μm) in contrast, and dry machining shows higher surface roughness, microhardness, tensile residual stress, and thick white layer. In comparison, MQCL and CCAVT are found to be intermediate. It is found that hybrid nanofluid MQCL enhances the overall performance of the machined surface as compared to other near-dry techniques.
Highlights
AISI 52100 is a high quality bearing steel alloy
It is observed that surface roughness is directly proportional to feed. e highest Ra value of 2.4 μm was found in the dry machining environment, whereas the lowest value of 1.2 μm was obtained in Hybrid NF-Minimum Quantity Cooling and Lubrication (MQCL) for feed 0.2 mm/rev. e Hybrid NF-MQCL environment exhibits lower surface roughness as compared to the other cutting environments, as can be seen from Figure 5. e Al2O3 enriched nanofluid is popular in MQCL machining due to its ball-bearing effect, which reduces the coefficient of friction between sliding contact surfaces [22]. e multiwall carbon nanotube (MWCNT) nanoparticle enhances thermal conductivity as well as the fluidity of base fluid [23]
In the case of dry turning, there is direct contact of tool and workpiece, which causes more severe wear (see Figure 6(a)). This high friction causes the generation of high heat generation, which results in a high-temperature rise in the cutting zone. is high heat generation tool may change its shape, which results in an increase in surface roughness in case of a dry environment
Summary
AISI 52100 is a high quality bearing steel alloy. It is a solution treated hardened low alloy steel, which contains high carbon, chromium, and manganese. e hardness is in the range of 55 to 60 HRC. AISI 52100 is a high quality bearing steel alloy It is a solution treated hardened low alloy steel, which contains high carbon, chromium, and manganese. E hardness is in the range of 55 to 60 HRC It shows light tempered martensite, less amount of retained austenite, and primary carbides in the microstructure after hardening. It exhibits improved mechanical properties such as tensile strength, yield strength, high bulk, and shear modulus properties [1]. Many industrial applications such as bearing, gauges, and dead centers require a hardened AISI 52100 to improve their wear resistance. e conventional manufacturing processes of these components are the preparation of blanks using forging or casting, annealing to relieve stresses, rough machining, finish machining, hardening, and finish grinding. ese processes require a long processing time resulting in a reduction of productivity and degraded product quality. us, hard turning with a potential benefit such as shorter setup time, high flexibility, and ability to handle complex geometry is an alternative machining process that replaces the finish machining and finish grinding step for machining of AISI 52100 steel [3]
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