Modeling of laser-tempering process for hyper-eutectoid steels

Laser surface tempering causes reduction in the surface hardness without affecting the bulk material hardness. The tempering behavior can be advantageous in advanced manufacturing processes that require controlled softening of the surface layers of through-hardened high-strength steels. This paper presents a computational phase change kinetics-based model for selecting the laser parameters that temper the surface layers of a through-hardened hyper-eutectoid steel (AISI 52100) over a known depth. First, a three-dimensional analytical thermal model is used to evaluate the temperature field produced in the material due to thermal cycles produced by laser scanning of the surface. The computed temperature histories are then fed to the phase-change model to predict the surface and subsurface hardness for the chosen laser-processing conditions. Microstructural analysis of the laser-treated AISI 52100 workpiece surface is presented for different laser-processing conditions. It is shown that good agreement is achieved between the predicted and measured surface hardness.