Laser Shock Processing (LSP) is a process of laser treating of a surface with a
pulsed beam of high power density. The process enables hardening of a thin surface layer;
therefore, it is suitable for the improvement of fatigue strength of quality materials. Locally
directed mechanical waves produce a considerably increased dislocation density in the thin
surface layer, which affects the variations of microhardness and residual stresses. The
magnitude and variation of the residual compressive stresses in the surface layer are
favourable, which ensures higher fatigue strength. Laser shock processing (LSP) is more
exacting than conventional shot peening, but it shows certain advantages such as better
control of the surface state, processing of locally limited surfaces and a possibility to
produce different transitions between the processed surface and the non-processed one. LSP
has so far been tested and efficiently applied to various materials, including maraging
steels. Relevant publications often deal with LSP mechanisms and the influence of the
process on the dynamic strength of maraging steel, but less frequently the influence of
individual characteristics such as the microstructure of matrix and of precipitated phases or
residual stresses.
The present paper deals with LSP of 12% Ni maraging steel. The material chosen is
suitable for the production of complex structural parts and dies for die casting, which
require high resistance of the material to thermo-mechanical loads. By means of
measurement of the state before and after LSP, the value of the mean roughness Ra, surface
defects and the variation of residual stresses in the thin surface layer were determined. After
LSP of the surface, the influence of processing parameters such as laser-beam diameter and
pulse density per unit of area was established.
Laser Shock Processing as an Advanced Technique for the Surface and Mechanical Resistance Properties Modification of Bioabsorbable Magnesium Alloys