High power water jet guided laser drilling of angular holes through nickel superalloy

Abstract

This paper investigates the basic characteristics of water jet guided laser drilling process using a high power laser with a maximum average power of 400 W to drill 0.7 mm diameter angular holes (60° to the surface) through 1.6 mm thick nickel superalloy (resultant hole length of 1.85 mm). Experimental trials were performed using average powers of up to 148 W to understand the effect of different process parameters on the hole quality and cycle time. Process parameters investigated included shielding gas flow rate, water jet pressure, trepanning speed, pulse frequency, and average power. The results found water jet pressure and average power to be significant in controlling the recast layer thickness and drilling cycle time. At higher power and throughput, average recast layer thicknesses of ∼30 μm could be obtained with a cycle time of 3 seconds. This surpasses the quality of holes, which can be produced via state-of-the-art laser drilling techniques without a significant reduction in productivity.