Local Microstructure and Hardness Variation After Pulsed Laser Micromelting on S7 Tool Steel

Laser surface melting is being increasingly used as a method of surface polishing steels and other alloys, but understanding the effect of this process on the microstructure and properties is still incomplete. This work experimentally explores several basic questions about how the surface microstructure and properties of S7 tool steel change during a pulsed laser micromelting (PLμM) process. Evaluations of the microstructure and hardness suggest that diffusion-controlled processes such as melt homogenization and surface back-tempering are relevant during rapid microscale laser melting and that the laser parameters and process planning contribute to determining the final surface hardness. The results also suggest that some influence can be exerted over the final hardness obtained from laser surface melting by changing the processing parameters.