Study in drilling of nickel-base superalloy Inconel 718
Date Issued
2005
Date
2005
Author(s)
Chen, Yu-Chieh
DOI
zh-TW
Abstract
The fracture mechanisms and the approaches to prolong the service life of the coated carbide tool in drilling Inconel 718 superalloy are presented. Four fracture stages are identified in this study. The extra friction between the tool-workpiece interfaces results in the abrasion of the coated layer is the major cause of drill fracture. The BUE is formed and subsurface fatigue cracks are initiated and grow sequentially. Eventually the cutting edge near the periphery is damaged. Therefore, long and thick chip forms leading to unstable drilling force and flank wear is worsened as a result.
Drilling experiments with the use of the nano cutting fluid containing the hydrocarbon molecule are conducted. It is found that the service life of the drill is lengthened significantly and drilling force is decreased. EDAX is taken to identify the constituents on the sliding region of chip-tool interface and contacting region between the tool flank and workpiece. It is found that nano particles are deeply adsorbing and may react with the metal surface. A layer forms to avoid the direct contact between the drill and the workpiece. In addition, less friction coefficient for chip flow is obtained on the drill flute region when nano cutting fluid is applied. It is also noted that the use of uncoated carbide drill with nano cutting fluid results in an even better drill life as compare with that resulting from traditional drilling.
The tool holder of a machining center is retrofitted so that a piezoelectric driven ultrasonic vibration oscillator can be integrated to produce axial harmonic vibration during drilling process. The ultrasonic vibration assisted drilling is applied to eliminate the cutting resistance from long chips. Experimental results show that the chip size is reduced, and the variation of torque in drilling becomes smaller. It is also found that there is little improvement in drilling performance when the frequency of the ultrasonic vibration is varied. On the contrary, a drill’s life is greatly increased by controlling the amplitude of the vibration. The frequency of 31.8 KHz and the amplitude of 4μm result in the best drill life and quality of the drilled hole. Concerning drilling efficiency, it is found that by applying ultrasonic vibration assisted drilling, lifting of the drill in conventional drilling of a high aspect ratio hole is not necessary, and saving one-third of the working time is obtained.
Subjects
Inconel 718
鑽削加工
奈米切削液
超音波振動輔助鑽削
drilling
nano cutting fluid
ultrasonic vibration assisted drilling
Type
thesis
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