This study deals with the in-situ heat treatment system including quenching and tempering processes using YAG laser In the present report, the tempering conditions were investigated to obtain the adequate hardness. Moreover, a theoretical model based on the diffusion equation was proposed to predict the hardness after laser tempering. Then, it was confirmed that theoretical results were in good agreement with the experimental results obtained from this system. Hence, this model is effective to predict the hardness after laser tempering. Consequently, it was demonstrated that the heat treatment process of the quenching and tempering can be done using YAG laser
