Abstract: The behaviours of residual stresses induced by laser transformation hardening in steel and cast iron are studied. The experimental results show that the residual compressive stresses existed in the laser hardened case are universal phenomena. It is found that great effects have been made on the values of residual stresses with change the laser energy density P/Dbυ, and the affecting trends are also different for the different materials with different prior structure. The formula of residual stress in laser transformation hardened case is inferred, and the experimental results are discussed.

Key words: Cast iron, Laser transformation hardening, Residual stress, Steel