Crack repair of hot work tool steel by laser melt processing

Tool steel used in hot work such as die-casting is required to have the res istance to heat checking which results in fine shallow cracking on the part surface. Laser melt processing, which can produce a localized shallow melt ed zone, has been adapted to repair such kind of cracks. However, the melte d zone has a detrimental effect on impact toughness because the laser heati ng may generate hard structures during the processing. In this paper, the e ffect of laser melt processing on repairing cracks was evaluated by means o f the Charpy impact test and fractography. The test results suggested that when this laser melt processing can eliminate an extensive damaged volume t hrough heat treatment after laser melt processing, the impact toughness is able to recover again to the initial state after heat treatment.