To investigate the effects of laser peening (LP) on the surface and bending fatigue properties of carburized steel (JIS SCM420), surface roughness
measurements, residual stress measurements, retained austenite measurements, and four–point bending fatigue tests were conducted.
After LP, the compressive residual stress was introduced on the surface, with the effect extending to a depth of more than 1 mm. Due to the high compressive stress,
the bending fatigue strength of LP specimen was 1.46 times higher than that of the as–heat–treated specimen even though the surface roughness was increased by
LP. Notably, the amount of retained austenite was 10.9ÿ at the top surface of LP specimen, and high– density twins were observed in the lath martensite structure.
This can be attributed to high strain rate deformation by LP.