Investigation on micro drilling of low carbon NiTi alloy using tungsten carbide micro drill tool

Abstract

The demand for advancements in Functional Materials due to their extensive applications especially on the development of product miniaturization is ever growing. The current study focusses on the influence of micro drilling process parameters such as tool rotational speed (1500, 2000, 2500 rpm), feed rate (0.2, 0.4, 0.6 mm/min) for a constant length of cut (500 μm) with 495 μm diameter drill tool on the low carbon nickel-titanium (NiTi) alloy, augmented with 0.05 wt% carbon. Studies on the selected rotational speeds and 0.05% carbon added NiTi are highly lacking. A blind hole of 500 μm was micro drilled on NiTi alloy using tungsten carbide (WC) micro drill bit. The results have revealed that high-speed machining at 2500 RPM facilitated the production of an accurately drilled hole with a close dimension of 501 μm at a minimum feed rate (0.2 mm/min). Under the same high-speed conditions, an increase in feed rate leads to a larger drill hole diameter due to tool outing losing precision. In addition, the drill tool experiences buckling as the feed rate increases, drill opening with pre-eminent plastic deformation, and shear, ultimately momentous in the formation of metal chips. In terms of machining time, high-speed machining requires less time (0.43 min) to complete the drilling process, whereas slow-speed machining consumes more time (up to 1.78 min). In high-speed machining, the tool edges undergo severe wear, characterized by both adhesion and abrasion. This work introduces optimized procedure to produce micro sized holes through high-speed machining of low-carbon NiTi alloy using a WC drill tool.

Keywords: Micro Drilling, WC Drill Tool, Niti Alloy, Tool Wear, Machining Time