Study of cutting forces and surface integrity in micro drilling of a Ni-based superalloy

Abstract

Accomplishment of good dimensional accuracy and acceptable surface integrity in micro drilling of Ni-based superalloys has always been a challenge. The current study seeks to explore these aspects and correlate the same with spindle speed, feed and forces in micro drilling of Incoloy 825 under flood cooling condition. Spindle speeds of 10,000, 20,000 and 30,000 rpm along with four different feeds of 1, 4, 8, 12 μm/rev were considered in the present work. Thrust force exhibited increasing trend with cutting parameters. The dynamic fluctuation (%) for radial forces was considerably higher compared to that of thrust force. A gradual transition from ploughing to shearing was discernible when feed was increased from 1 to 4 μm/rev. Oversize error was found to be closely related with radial forces. Circumferential deformation layer, white layer and plastic deformation zone at sub-surface region along hoop direction showed distinct relationship with spindle speed and feed. However, spindle speed has more pronounced influence on white layer formation than feed. After careful analysis of results, it was observed that optimal results in the form of superior dimensional accuracy, minimum circumferential damage, burr formation, minimum radial force, and reasonably less value of thrust force were achieved under the feed of 4 μm/rev and spindle speed of 10,000 rpm.