Innovative Methods for Automated Controlled Removal of Thermal Barrier Coatings (TBCs) and Bondcoats from Turbine Airfoils for Rework and Repair

MLPC will develop a laser ablation method for precise removal of thermal barrier coatings (TBC) from aircraft engine parts. Worn TBC eventually needs to be stripped and replaced from airfoils. Current industry practice is to remove the TBC by grit blast or chemical techniques that lack precision, are labor and waste intensive, and risk part damage. The laser stripping method will use laser ablation, guided by spectroscopic feedback that monitors the composition of the ablation plume, to allow for precise depth removal. The laser method will allow stripping of TBC while leaving the bond layer intact or removal of the bond layer as well without damaging the base metal casting. Additionally, spectroscopy guided laser drilling will be used to demonstrate a method of TBC thickness mapping based on depth measurement of very small pilot holes. The technology will result in process step reduction, elimination of chemical waste, reduction of damage to turbine blades, improved success of reapplication of TBC and reduced need to sacrifice parts to verify quality of replaced TBC. This program has strong collaborative support from an Air Force prime contractor that is providing materials to support the development effort and guidance toward military and commercial transition. BENEFIT: Laser stripping and thickness mapping of TBCs will replace current grit blast and chemical processes. It will increase the precision of removal, eliminate chemical waste, reduce labor input, and improve worker safety. Part damage will be reduced and the need for destructive evaluation of expensive sacrificial parts will be eliminated. The likelihood of infant failure of new TBC coatings will be reduced. All of this, along with enhance the life of engine parts and attendant reduction of life cycle costs for engines and minimization of the down time of platforms during engine overhaul or repair will result in large cost savings for the military with respect to aircraft engines.