Micromachining Of Metal And Thermal Barrier Coatings Using A532nm Nanosecond Pulsed Fiber Laser

As the advance of gas turbine engines, turbine entry temperature has been continuouslyenhanced, which demands for high performance thermal barrier coatings and improved coolingarrangement on turbine blades. In recent years, for the purpose of improving film coolingefficiency on a turbine blade while reducing the total volume of cooling air, film cooling holesare designed with three-dimensional shaped diffuser openings. Precise manufacturing of suchshaped hole-openings is a challenge especially when the metal blades are coated with ceramicthermal barrier coating (ZrO2). In this study, a nanosecond pulsed Ytterbium fiber laser is usedto study the physical interactions between pulsed laser beam and ceramic coating and base metalmaterials through modeling and experimental approaches. A numerical model using finitedifference method is established to determine the ablated material volume and dimensionssubjected to a laser beam. Results are compared between simulation and experimentalapproaches. Optimized machining parameters are obtained with the aim of maximum processefficiency with minimum thermal effects such as spatters, microcracks and spallation. Aero-thermal performances of the film cooling holes are characterized by wind tunnel experiments.