Machining and Characterization of Deep Micro Holes on Super Alloy Processed by Millisecond Pulsed Laser

Abstract

In this study, a series of deep micro holes were machined on thick GH4169 super alloy by the trepan drilling, using a millisecond pulsed laser which equipped to the numerical control processing system. The microstructure of the holes including surface and longitudinal morphologies, diameter, taper, circularity, micro cracks and recast layer were systematically characterized. The surface morphology and the longitudinal section of the drilled holes were observed by Scanning Electron Microscope and 3D Laser Scanning Confocal Microscope. The method of Minimum circumcircle method was employed to evaluate the entrance and exit end circularity. The results showed that the melt and spattering accumulating around the holes decreased with the augment of laser power. The diameter of the entrance showed an increasing tendency with the growing of laser power, but the exit end was not seriously affected by the power. The micro cracks and recast layer could be found obviously, the micro cracks appeared in those zones which thermal stress concentrated, the thickness of recast layer is about 20μm and the taper and circularity were optimized at a laser power of 80-100W.

Study on Ultrasonic Assisted Electrochemical Drill-Grinding of Superalloy

“…However, nickel-based superalloys are hard to machine due to the low thermal conductivity and high temperature strength [4,5], which could cause poor surface quality, serious tool wear, and low productivity in traditional machining [6][7][8]. As for a few non-traditional machining methods, laser machining [9,10] and electrical discharge machining (EDM) [11,12] which based on heat melting usually produce micro cracks, recast layers, and heat affected zones, while electrochemical machining (ECM) [13] could not meet the demands of high precision machining due to stray current corrosion.…”