Product Code: ICAL09_C202

Picosecond Laser Machining of Shaped Holes in Thermal Barrier Coated Turbine Blades
Authors:
Carl Druffner, Mound Laser & Photonics Center, Inc.; Miamisburg OH USA
Larry Dosser, Mound Laser & Photonics Center, Inc.; Miamisburg OH USA
William Roquemore, Air Force Research Laboratory; Wright-Patterson Afb OH USA
Sivaram Gogineni, Spectral Energies, LLC; Dayton OH USA
Presented at ICALEO 2009

Increasing the operating temperature of an aircraft engine has the benefit of increasing thrust and fuel efficiency. Maximizing the operating temperature necessitates the addition of Thermal Barrier Coatings (TBC) and the machining of cooling holes and air flow channels in both the TBC and the high strength superalloys out of which the turbine blades are formed. One method of fabrication is a two step process where the holes are drilled in the base blade metal by either laser or electrical discharge machining, then TBC is applied and finally the holes are drilled again to clear out and shape the TBC. Mound Laser & Photonics Center, Inc. has conducted research utilizing the ability of a picosecond laser system to machine shaped holes through both the TBC and underlying superalloy in a single step. The short pulse duration of the picosecond laser allows for fast hole shaping and drilling without inducing spallation in the TBC or generating recast issues encountered with high power, long pulse duration lasers. Data will be presented on the machining of Yttrium Stabilized Zirconium TBC coatings on Hastelloy substrates with both normal and high angle incidence hole drilling, along with hole shaping through test coupons.