Influence of surface hardening by laser irradiation on the loss factor of cast iron

Abstract

Surface hardening by laser irradiation was examined regarding the loss factor, which is the parameter of the vibration-damping characteristics, for flake graphite cast irons and spherical graphite cast irons. The surface of the samples was quenched by changing speed of beam, gas pressure, and beam frequency. It was found that the depth of the hardening region was from 0.12 mm to 1.11 mm, and the hardness of the boundary between the hardening and the nonhardening regions changed suddenly. It was confirmed that the loss factor of the laser hardened specimens increased considerably as compared with that of the as-cast specimens. The internal friction at the vicinity of the boundary between the hardening and the nonhardening regions may be responsible for this result.