Laser surface melting and post-heat treatment of AISI 420 stainless tool steel

摘要

Samples of AISI 420 martensitic stainless tool steel were laser Surface Melted (LSM) using a wide range of processing parameters. The modified layer presents a much higher propotion of retained austentie than a solid state coventionally quenched steel. This fact has a considerable impact on the metallurgical and mechanical properties of the steel and reduces the benefits of LSM. In this work the influence of laser processing conditions on the volume fraction of retained austenite and the structural transformations of the LSM steel during tempering are analyzed. It was found that the proportion of retained austentie increasesw ith increasing scanning speed and decreasing power desnity. The retained austentie can be eliminated by tempering trematment. A secondary hardening peak resulted from tempering at 600 deg C. The scondary hardening temperature ater LSM is 100 deg C higher than the equivalent temperature after conventional quenching (600 deg C and 500 deg C respectively).