Experimental Investigation Into Micro-Textured Surface Generation by Through-Mask Electrochemical Micromachining
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rimental Investigation Into Micro-Textured Surface Generation by Through-Mask Electrochemical Micromachining S. Mahataa, * and B. Bhattacharyyaa a Production
Engineering Department, Jadavpur University, Kolkata, 700032 India *e-mail: [email protected]
Received July 1, 2019; revised November 14, 2019; accepted November 17, 2019
Abstract—Micro texturing with dimples is one of the most established methods for the enhancement of lubrication and tribological performance. In this work, a novel approach of through-mask electrochemical micromachining is instigated to fabricate high-aspect-ratio circular micro-dimples utilizing a low-cost photoresist (AZ-4903) as mask. Experiments were performed to understand the influence of the applied voltage along with the electrolyte type and concentration on the machining precision and surface characteristics of the generated micro array. The influence of three electrolytes has been studied and it has been experimentally established that 10% NaCl + 10% NaNO3 is favorable during maximization of the depth of the generated microdimples to 39.03 μm whereas undercut is minimized to 15.15 μm by utilizing 20% NaNO3. The surface quality of the generated micro-dimples has been found to be the finest, i.e. 0.062 μm, for the samples machined with 10% NaNO3. Patterned arrays containing micro-dimples having maximum depths of 30 μm, 35 μm, and 40 μm were successfully fabricated over a stainless steel (SS304) substrate by using these electrolytes with considerable accuracy and repeatability. The experiments confirm possibility to obtain high-aspect-ratio micro-dimples with the least degree of undercut using this technique. Further, friction test results were analyzed to figure out the alterations in the frictional coefficient of the micro-dimples with different depths as well as with non-dimpled samples. Keywords: micro-textured array, mask, aspect ratio, dimple geometry, machining accuracy DOI: 10.3103/S1068375520040092
INTRODUCTION Surface areas covered with microstructures possessing high-aspect-ratio finds potential applications in a wide range of fields including heat transfer, adaptive aerodynamics, seal and bearing design, and composite materials. In the last few years, surface texturing has established to be an effective approach in engineering that result in enhancement of wear resistance, frictional coefficient, load capacity, etc. Reserving lubricant is the basic perception of the lubricating mechanism of the surface texture, which includes micro-dimples, micro-grooves, micro-pillars, microprisms, etc. It was experimentally investigated that there is a considerable reduction in the friction with a dimpled surface compared to an un-textured surface [1]. Moreover, the rapid technological development in the field of automobile, space, optics, and micromanufacturing has created intense ruckus for parts with micro-patterns in difficult to machine materials [2, 3]. Nowadays, the patterns of micro-dimples have gained importance since it helps generating hydrodynamic pressure with more comf
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