Laser-shock processing effects on surface microstructure and mechanical properties of low carbon steel

The effects of laser-shock processing (LSP) on the microstructure, microhar dness, and residual stress of low carbon steel were studied. Laser-shock pr ocessing was performed using a Nd:glass phosphate laser with approximate to 600 ps pulse width and up to 120 J pulse energy at power densities above 1 0(12) W cm(-2). The effects of shot peening were also studied for compariso n. Laser-shock induced plastic deformation caused the surface to be recesse d by approximate to 1.5 mu m and resulted in extensive formation of disloca tions. Surface hardness increased by up to 80% after the LSP. The microstru cture and mechanical properties were altered up to approximate to 100 mu m in depth. The LSP strengthening effect on low carbon steel was attributed t o the presence of a high dislocation density. Shot peening resulted in a re latively higher compressive residual stress throughout the specimen than di d LSP. (C) 1999 Elsevier Science S.A. All rights reserved.