LASER SHOCK SURFACE TREATMENT OF Ni-BASED SUPERALLOYS

Abstract

Laser shock surface treatment could be envisaged to harden and induce compressive stresses within materials thus improving their fatigue and fretting-fatigue resistance. Both laser beam optical phenomena and deformation mechanisms are studied for applications of laser shock treatment to Ni-based mono- and polycrystalline superalloys. Deformation microstructure is studied using TEM applied to the monocrystalline superalloys. Macroscopic mechanical phenomena are determined by superficial or in-depth residual stress measurements using X-ray diffraction technique or the incremental hole drilling method. A fairly elementary analytical model involving surface release wave mechanisms is developed to describe the formation of residual stresses. Understanding of these phenomena leads to improving the laser treatment for application to processing of fatigue test specimens by overlapping of impacts.