Quality Evaluation of Precision-Shaped Film Cooling Holes Machined on Aerospace Nickel-Based Superalloy Using Femtosecond Laser Trepan Drilling Technique
摘要
Due to the development of the aviation industry, the thrust-to-weight ratio of new aircraft engines keeps increasing. Increasing the turbine inlet temperature is the most efficient method to achieve a high thrust-to-weight percentage. Shaped film cooling holes (FCHs) is the best in today’s highly cooled gas turbine blades. This study uses a femtosecond (fs) laser drilling technique to drill shaped micro-holes. The shaped FCHs contain some initial round entry that acts as the throat section, though not necessarily choked, followed by an expanded diffuser-type exit used to spread the coolant flow laterally or into the surface. Acute angle cylindrical holes of diameter 700 µm and inclination angle 30° from the substrate surface are drilled on 550 µm thick IN718 substrate. According to the material thicknesses, the corresponding drilling scanning strategies are proposed. The entrance and exit of holes are considered elliptical shapes. The influence of different laser processing parameters on hole quality is investigated and discussed in detail. The hole quality regarding the entrance and exit elliptical roundness and taper angle of FCHs has been evaluated. Results revealed that femtosecond laser drilling is an efficient hole-processing method that produces good-quality film cooling holes.