Date of Award

3-2-2021

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Cutting fluid, Inconel 718, Liquid nitrogen, Machining, Nano-lubricants, Tribology

Supervisor

Ahmed T. Alpas

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Utilization of cutting fluid incorporating graphene nanoplatelets (GNP) as well as application of liquid nitrogen (LN2) to the cutting area were investigated in drilling and turning of Inconel 718 iron-nickel-based superalloy in order to improve their machinability and reduce the use of mineral-based cutting fluids. The methodology was developed to establish correlations between the tribological properties of the surfaces and the role of interfacial friction on machining properties and understanding the improvements in machining from a microstructural point of view. In addition, response surface methodology (RSM) was employed to systematically optimized the cutting parameters. The results are presented in two parts: In ‎Chapter 3, a cutting fluid (CF) consisting of 70% water and 30% vegetable oil blended with GNPs was used in order to improve drilling performance of Inconel 718 alloy. The results showed that sliding of Inconel 718 workpiece using WC-Co drills with CF containing 54×10-5 wt.% graphene (GCF) reduced the coefficient of friction (COF) between the tool and workpiece surfaces from 0.16 to 0.08 as a result of formation of tribolayers on the sliding surfaces. A Similar tribolayer was observed when drilling under GCF condition which resulted in lower cutting torque and temperature, leading to lower surface roughness and subsurface microstructural deformation compared to conventional flooded and dry conditions. In ‎Chapter 4, turning experiments were conducted on the Inconel 718 using a stream of liquid nitrogen, and the effects of different cutting speed, feed rate and depth of cut values on the response factors, namely flank wear, cutting force and Ra surface roughness were investigated. Cryogenic cutting reduced flank wear compared to dry cutting, to values comparable to wear during flooded cutting. The results revealed that there could be an optimum set of values in which cryogenic cutting can provide a performance equivalent to the flooded cutting. Thus, experiments were designed according to RSM under cryogenic condition. Statistical analyses showed that cutting speed was the most influential parameter on flank wear and cutting force during cryogenic turning and a cutting speed of 81 m/min, a feed rate of 0.06 mm/rev and a depth of cut of 0.63 mm constituted the optimum set of cutting parameters considered in this investigation. Higher cutting speed and feed rate values can be used during the machining process by using a GNP-blended vegetable-based oil to shorten the cutting time, and thus, reduce the usage of cutting fluid for production of each part. Moreover, it was shown that complete omission of cutting fluid during the machining process would be feasible by employing cryogenic cutting. Liquid nitrogen evaporates after contacting the tool and workpiece surfaces leaving no contamination which eliminates the cleaning, recycling, and deposal costs after the machining process.

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