Experimental investigation and modeling of laser surface melting process for AISI 9254 commercially high silicon spring steel

Abstract

Laser surface melting of AISI 9254 commercially high silicon spring steel was performed in this study. A nanosecond pulse laser was used as a heat source to introduce phase transformations in the metal. The effects of average laser power and laser traverse speed on case depth, roughness, and surface/subsurface morphology of laser-irradiated area were examined in this study. It was found that the micro-hardness of work surface significantly increased from 325 HV to 616 HV and the base metal structure of pearlite was transformed to martensite. The use of high laser power together with slow traverse speed can increase the case depth compared to other processing conditions. However, micro-cracks, micro-grooves, poor surface roughness and porosities were apparent at slow laser traverse speed. A predictive model for case depth was also developed in this study, and the predicted results showed a good agreement with the experiment. The findings of this work could bring a further insight into the laser hardening/texturing process and highlight the potential of laser for metal surface modification. In addition, the model proposed in this study could well facilitate the parameter selection and optimization of the laser surface melting process.