Product Code: ICAL09_1704

Oxide Formation in Acute Laser Percussion Drilled Holes in Single Crystal Nickel Superalloy
Stephen Leigh, Manchester University; Manchester Great Britain
Kursad Sezer, Manchester University; Manchester Great Britain
Lin Li, Manchester University; Manchester Great Britain
Andrew Pinkerton, -; -
Clive Grafton-Reed, Rolls-Royce Plc; Derby Great Britain
Martyn Cuttell, Rolls-Royce Plc; Derby Great Britain
Presented at ICALEO 2009

One industrial application of laser drilling is the production of cooling holes at acute angles in nickel superalloy single crystal material. However laser drilled holes are inherently associated with metallurgical defects such as recast layers and oxide formations. In previous studies it has been found that using laser parameters to minimise the recast layer increase the oxide layer thickness. In an attempt to better understand the formation of this oxide defect, a comparative study was performed to investigate the effects of drilling angle and peak power on the metallurgy of laser percussion drilled holes in turbine blade material - CMSX-4. Variation of the oxide layer thickness with peak power, drilling angle and hole depth is compared. The location and thickness of the oxide layer is found to be highly dependent on drilling angle with the greatest thickness being observed on the leading edge corner at most acute angle (300). To identify the point at which the oxide defect develops, holes were drilled at a range of pulse numbers and analysed. High speed photography was used to capture visual heat build up with time. Using a novel numerical simulation locations of heat and oxide build up are presented. Experimental and visual heat build up on the leading edge corner is explained by the melt ejection analysis in the model.

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