Water jet guided laser microdrilling of aerospace alloys: Correlation of material properties to process time and quality

The hot section parts in a gas turbine are subject to high working temperatures and mechanical forces. In order to endure the harsh conditions, these parts are generally made of nickel-based superalloys. Furthermore, microholes are drilled on them to help with cooling by allowing the air to pass through. These holes increase the allowable working temperature and service life of the parts as well. Water Jet Guided Laser is a technology that can be conveniently used for microdrilling operations on aerospace jet engine parts. It is a hybrid process, in which a laser beam is coupled with and guided through a thin cylindrical water jet. Pressurized water provides focusing, cooling, and cleaning on the cut region, eliminating undesired side effects of the laser. The technology has many advantages over traditional laser machining, such as consistent focusing, burr-free cutting, minimized tapering, reduced heat affected zone, and recast layer. In this paper, using the Water Jet Guided Laser, variation in process time and quality are studied on different aerospace nickel-based superalloys. The results depend mainly on the thermophysical properties of the processed materials. The experimental results are compared with calculations and correlated to the material properties.