SURFACE MODIFICATION BY MEANS OF LASER MELTING COMBINED WITH SHOT PEENING - A NOVEL-APPROACH

Among the available laser applications laser surface melting has turned out to be a powerful technique for the production of wear-resistant layers. Despite the advantages of this process, laser surface melting results in tensile stresses which may assist crack propagation. In this paper it will be shown that shot peening can overcome this drawback effectively. It turned out that a preceding laser treatment of an eutectic aluminium-silicon alloy is able to amplify considerably the effectiveness of the shot peening treatment. In particular the maximum attainable hardness and compressive stress increase upon increasing the quench rate, i.e. upon increasing the laser scan velocity. The high concentration of silicon in solid solution turned out to be the main reason for the enhanced mechanical performance, not only directly through solid solution hardening, but also by precipitation hardening and by a higher dislocation density. The latter contribution is affected indirectly by a changed cross slip behaviour.