Laser shock peening rounds influencing microstructural and mechanical properties of 300M steel

Laser shock peeing (LSP) was introduced to produce surface gradient structures on 300M steel to improve its performance, service life and related workpiece safety. The influences of LSP rounds on microstructural and mechanical properties were investigated to optimise the LSP processing. Smoother surface, surface nanocystallization, and gradient structure, hardness, compressive residue stress was observed LSP. Strength and plasticity of 300M steel improved significantly due to the surface changes induced by one round of LSP. However, excessive LSP rounds tend to deteriorate the surface roughness and mechanical properties despite increased surface nanocrystallization, hardening zone depth and compressive residual stress.