Laser-shock processing of aluminium-coated 55C1 steel in water-confinement regime, characterization and application to high-cycle fatigue behaviour

55C1 steel was irradiated with a high-power neodymium-glass laser with application to induce plastic shock waves within targets, through the expansion of a laser-induced surface plasma. Laser-shock processing experiments were conduced in the plasma-confined regime with water to increase the laser-induced peak stresses. Physical, mechanical and processings aspects were reviewed, such as the characterization of stress waves in coated steels with a VISAR velocimeter system, and the mechanical changes induced in 55Cl in terms of compressive residual stresses or work-hardening levels. With the use of convenient protective coatings, some 7-8 GPa peak stress levels could be achieved which authorized the generation of high compressive residual stress levels (nearly 80% of the compressive yield strength), but preserved the surface integrity from detrimental roughening. Surface modifications performed under different shock conditions were shown to display some 30% increase on the bending fatigue limits of 55C1 at R=0.1.