Investigation on the process of laser surface melting using two sequential scans

Laser melting as a flexible and economical surface treatment technology is of significant value to industries. Many efforts have been taken on purpose to gain such desired machining goals and reliable service performances; yet, beneficial and efficient melting strategy is still needed. In studies of some other processes such as multi-pass laser cladding, it is found that the preheating effect of a previous scan can contribute to achieve better results like increasing dilution and improving thermal stress status. Hence in this investigation, for laser surface melting with single track, a helpful preheating process is performed by proposing an approach of using two sequential scans and the effects of preheating laser are further clarified. To this end, a three-dimensional non-linear, indirectly coupled thermal–structural model for the sequential combined process is established accounting for temperature dependency of material properties. Then, investigations are carried out to examine temperature and residual stress fields under different preheating laser power and interval distance. The results show that this melting strategy can improve the residual stress distribution state. In addition, a high thermal stress distributes between two scans and the tensile stress component is released by rapid two-time fusions. Besides, the different combinations of preheating parameters take diverse effects on heat-affected and -remelted zone as well as residual stress distribution.