Parametric Fabrication Technique of High-Temperature Speckle Based on Femtosecond Laser

The service environment of many core components, such as aero-engine blades, tends toward extreme. Characterization of fatigue failure behavior at high-temperatures is an important means of evaluating their structural integrity, in which digital image correlation (DIC) method shows great potential and advantages due to its full-field, noncontact, and high-temperature compatibility. For high-temperature DIC, its accuracy highly depends on the quality of high-temperature speckle, i.e., deformation carrier or sensor, fabricated on specimen surface. Herein, a parametric high-temperature speckle fabrication technique combining high-temperature dual-layer coating and femtosecond laser etching is developed. The heat-resistant black matte paint and white boron nitride paint are successively coated on the specimen surface, then femtosecond laser is used to etch the coated layer, realizing the parametric non-destructive fabrication. Based on high-throughput design and high-temperature static test, the speckle parameters and fabrication processes are optimized. The fabrication quality of optimized speckles is further verified by charactering fatigue crack propagation behavior of nickel-based superalloy GH4169 at 650℃. The speckle maintains good quality without ablative erosion, showing the advantages of parameterization, automation, high quality, and strong universality/repeatability.